Functions as histone acetyltransferase and regulates transcription via chromatin remodeling. Acetylates all four core histones in nucleosomes. Histone acetylation gives an epigenetic tag for transcriptional activation. Mediates cAMP-gene regulation by binding specifically to phosphorylated CREB protein. Also functions as acetyltransferase for nonhistone targets. Acetylates 'Lys-131' of ALX1 and acts as its coactivator in the presence of CREBBP. Acetylates SIRT2 and is proposed to indirectly increase the transcriptional activity of TP53 through acetylation and subsequent attenuation of SIRT2 deacetylase function. Acetylates HDAC1 leading to its inactivation and modulation of transcription. Acts as a TFAP2A-mediated transcriptional coactivator in presence of CITED2. Plays a role as a coactivator of NEUROD1-dependent transcription of the secretin and p21 genes and controls terminal differentiation of cells in the intestinal epithelium. Promotes cardiac myocyte enlargement. Can also mediate transcriptional repression. Binds to and may be involved in the transforming capacity of the adenovirus E1A protein. In case of HIV-1 infection, it is recruited by the viral protein Tat. Regulates Tat's transactivating activity and may help inducing chromatin remodeling of proviral genes. Acetylates FOXO1 and enhances its transcriptional activity.
The FOXO (Forkhead box class O) subgroup of forkhead transcription factors controls the expression of many genes involved in fundamental cellular processes. Until recently, studies conducted on posttranslational modifications of Forkhead proteins were restricted to their phosphorylation. In this report, we show that the coactivator p300 directly acetylates lysines in the carboxyl-terminal region of Foxo1 in vivo and in vitro, and potently stimulates Foxo1-induced transcription of IGF-binding protein-1 in transient transfection experiments. The intrinsic acetyltransferase activity of p300 is required for both activities. Our results suggest that acetylation of Foxo1 by p300 is responsible, at least in part, for its increased transactivation potency, although acetylation of histones cannot be excluded. Insulin, the major negative regulator of Foxo1-stimulated transcription, potently enhances p300 acetylation of Foxo1. Three consensus protein kinase B/Akt phosphorylation sites whose phosphorylation is stimulated by insulin are required for insulin-induced acetylation of Foxo1. In contrast to its importance in regulating the transcriptional activity of Foxo1 in the absence of insulin, acetylation plays only a minor role compared with phosphorylation in insulin inhibition of Foxo1 transcriptional activity.
We describe a role for the transcriptional coactivator p300 in DNA metabolism. p300 formed a complex with flap endonuclease-1 (Fen1) and acetylated Fen1 in vitro. Furthermore, Fen1 acetylation was observed in vivo and was enhanced upon UV treatment of human cells. Remarkably, acetylation of the Fen1 C terminus by p300 significantly reduced Fen1's DNA binding and nuclease activity. Proliferating cell nuclear antigen (PCNA) was able to stimulate both acetylated and unacetylated Fen1 activity to the same extent. Our results identify acetylation as a novel regulatory modification of Fen1 and implicate that p300 is not only a component of the chromatin remodeling machinery but might also play a critical role in regulating DNA metabolic events.
We describe a molecular switch based on the controlled methylation of nucleosome and the transcriptional cofactors, the CREB-binding proteins (CBP)/p300. The CBP/p300 methylation site is localized to an arginine residue that is essential for stabilizing the structure of the KIX domain, which mediates CREB recruitment. Methylation of KIX by coactivator-associated arginine methyltransferase 1 (CARM1) blocks CREB activation by disabling the interaction between KIX and the kinase inducible domain (KID) of CREB. Thus, CARM1 functions as a corepressor in cyclic adenosine monophosphate signaling pathway via its methyltransferase activity while acting as a coactivator for nuclear hormones. These results provide strong in vivo and in vitro evidence that histone methylation plays a key role in hormone-induced gene activation and define cofactor methylation as a new regulatory mechanism in hormone signaling.
Although histone deacetylases (HDACs) are generally viewed as corepressors, we show that HDAC1 serves as a coactivator for the glucocorticoid receptor (GR). Furthermore, a subfraction of cellular HDAC1 is acetylated after association with the GR, and this acetylation event correlates with a decrease in promoter activity. HDAC1 in repressed chromatin is highly acetylated, while the deacetylase found on transcriptionally active chromatin manifests a low level of acetylation. Acetylation of purified HDAC1 inactivates its deacetylase activity, and mutation of the critical acetylation sites abrogates HDAC1 function in vivo. We propose that hormone activation of the receptor leads to progressive acetylation of HDAC1 in vivo, which in turn inhibits the deacetylase activity of the enzyme and prevents a deacetylation event that is required for promoter activation. These findings indicate that HDAC1 is required for the induction of some genes by the GR, and this activator function is dynamically modulated by acetylation.
Histone deacetylases (HDACs) are subdivided into three classes--HDAC I, HDAC II, and Sir2. Sirt proteins are mammalian members of the Sir2 family of NAD+ (nicotinamide adenine dinucleotide)-dependent protein deacetylases. The balance between acetylation and deacetylation of histone and non-histone proteins, regulated by protein acetyltransferases and deacetylases, affects the expression of genes involved in a variety of cellular processes. In addition, HDAC1 is acetylated and regulated by p300, a transcriptional co-activator with protein acetyltransferase activity, suggesting that protein acetyltransferases and deacetylases they control the activities of each other. Although the regulation of HDAC1 by p300 is well characterized, the relationship between Sir2 homologs and p300 is not understood. Here, we report that p300 interacts with Sirt2, a member of the Sir2 family, and triggers the acetylation and subsequent down-regulation of the deacetylation activity of Sirt2, and that the acetylation of Sirt2 by p300 relieves the inhibitory effect of Sirt2 on the transcriptional activity of p53. These observations demonstrate that p300 can inactivate Sirt2 by acetylation and that p300 may regulate the activity of p53 indirectly through Sirt2 in addition to its direct modification of p53.
Transcriptional coactivators that modify histones represent an increasingly important group of regulatory factors, although their ability to modify other factors as well precludes common assumptions that they necessarily act by histone modification. In an extension of previous studies showing a role for acetyltransferase p300/CBP in p53 function, we have used systems reconstituted with recombinant chromatin templates and (co)activators to demonstrate (1) the additional involvement of protein arginine methyltransferases PRMT1 and CARM1 in p53 function; (2) both independent and ordered cooperative functions of p300, PRMT1, and CARM1; and (3) mechanisms that involve direct interactions with p53 and, most importantly, obligatory modifications of corresponding histone substrates. ChIP analyses have confirmed the ordered accumulation of these (and other) coactivators and cognate histone modifications on the GADD45 gene following ectopic p53 expression and/or UV irradiation. These studies thus define diverse cofactor functions, as well as underlying mechanisms involving distinct histone modifications, in p53-dependent gene activation.
The paired-like homeoprotein, Cart1, is involved in skeletal development. We describe here that the general coactivator p300/CBP controls the transcription activity of Cart1 through acetylation of a lysine residue that is highly conserved in other homeoproteins. Acetylation of this residue increases the interaction between p300/CBP and Cart1 and enhances its transcriptional activation. INTRODUCTION: Cart1 encodes a paired-like homeoprotein expressed selectively in chondrocyte lineage during embryonic development. Although its target gene remains unknown, gene disruption studies have revealed that Cart1 plays an important role for craniofacial bone formation as well as limb development by cooperating with another homeoprotein, Alx4. In this report, we study the functional involvement of p300/CBP, coactivators with intrinsic histone acetyltransferase (HAT) activity, in the transcriptional control of Cart1. METHODS: To study the transcription activity of Cart1, a reporter construct containing a putative Cart1 binding site was transiently transfected with the expression vectors of each protein. The interaction between p300/CBP and Cart1 was investigated by glutathione S-transferase (GST) pull-down, yeast two-hybrid, and immunoprecipitation assays. In vitro acetylation assay was performed with the recombinant p300-HAT domain and Cart1 in the presence of acetyl-CoA. RESULTS AND CONCLUSIONS: p300 and CBP stimulate Cart1-dependent transcription activity, and this transactivation is inhibited by E1A and Tax, oncoproteins that suppress the activity of p300/CBP. Cart1 binds to p300 in vivo and in vitro, and this requires the homeodomain of Cart 1 and N-terminal 139 amino acids of p300. Confocal microscopy analysis shows that Cart1 recruits overexpressed and endogenous p300 to a Cart1-specific subnuclear compartment. Cart1 is acetylated in vivo and sodium butyrate and trichostatin A, histone deacetylase inhibitors, markedly enhance the transcription activity of Cart1. Deletion and mutagenesis analysis identifies the 131st lysine that locates immediately adjacent to the homeodomain as a target of p300-HAT, and a point mutation to this residue attenuates the binding affinity to p300 as well as p300-dependent transcription activity. Together, these results indicate that p300/CBP acts as a cotransactivator to Cart1 through a direct interaction and specific lysine acetylation. In addition, because 131st lysine is highly conserved in other types of homeoprotein, this lysine may be a common target for HAT of p300/CBP for these proteins.
The transcriptional co-activators and histone acetyltransferases p300/CREB-binding protein (CBP) interact with CITED2, a transcription factor AP-2 (TFAP2) co-activator. p300/CBP, CITED2, and TFAP2A are essential for normal neural tube and cardiac development. Here we show that p300 and CBP co-activate TFAP2A in the presence of CITED2. TFAP2A transcriptional activity was modestly impaired in p300(+/-) and CBP(+/-) mouse embryonic fibroblasts; this was rescued by ectopic expression of p300/CBP. p300, TFAP2A, and endogenous CITED2 could be co-immunoprecipitated from transfected U2-OS cells indicating that they can interact physically in vivo. CITED2 interacted with the dimerization domain of TFAP2C, which is highly conserved in TFAP2A/B. In mammalian two-hybrid experiments, full-length p300 and TFAP2A interacted only when CITED2 was co-transfected. N-terminal residues of TFAP2A, containing the transactivation domain, are both necessary and sufficient for interaction with p300, and this interaction was independent of CITED2. Consistent with this, N-terminal residues of TFAP2A were required for p300- and CITED2-dependent co-activation. A histone acetyltransferase-deficient p300 mutant (D1399Y) did not co-activate TFAP2A and did not affect the expression or cellular localization of TFAP2A or CITED2. In mammalian two-hybrid experiments p300D1399Y failed to interact with TFAP2A, explaining, at least in part, its failure to function as a co-activator. Our results suggest a model wherein interactions among TFAP2A, CITED2, and p300/CBP are necessary for TFAP2A-mediated transcriptional activation and for normal neural tube and cardiac development.
The transcriptional coactivators p300 and CREB binding protein (CBP) are important regulators of the cell cycle, differentiation, and tumorigenesis. Both p300 and CBP are targeted by viral oncoproteins, are mutated in certain forms of cancer, are phosphorylated in a cell cycle-dependent manner, interact with transcription factors such as p53 and E2F, and can be found complexed with cyclinE-Cdk2 in vivo. Moreover, p300-deficient cells show defects in proliferation. Here we demonstrate that transcriptional activation by both p300 and CBP is stimulated by coexpression of the cyclin-dependent kinase inhibitor p21(WAF/CIP1). Significantly this stimulation is independent of both the inherent histone acetyltransferase (HAT) activity of p300 and CBP and of the previously reported carboxyl-terminal binding site for cyclinE-Cdk2. Rather, we describe a previously uncharacterized transcriptional repression domain (CRD1) within p300. p300 transactivation is stimulated through derepression of CRD1 by p21. Significantly p21 regulation of CRD1 is dependent on the nature of the core promoter. We suggest that CRD1 provides a novel mechanism through which p300 and CBP can switch activities between the promoters of genes that stimulate growth and those that enhance cell cycle arrest.
Genetic studies have demonstrated that the basic helix-loop-helix protein E2A is an essential transcription factor in B lymphocyte lineage commitment and differentiation. However, the mechanism underlying E2A-mediated transcription regulation is not fully understood. Here, we investigated the physical and genetic interactions between E2A and co-activators histone acetyltransferases (HATs) in B cells. Gel filtration analysis of human pre-B cell nuclear extract showed that E2A co-elutes with the HATs p300, CBP, and PCAF. A co-immunoprecipitation assay further demonstrated that a fraction of endogenous E2A proteins is associated with each of the three HATs. We show that these HATs acetylate E2A in vitro, enhance E2A-mediated transcription activity, and promote nuclear retention of E2A proteins. A catalytic mutation of p300 completely abrogates the ability of p300 to acetylate E2A and to promote E2A nuclear retention in 293T cells. A breeding test between E2A heterozygous mice and p300 heterozygous mice demonstrated that these two genes interact for proper B cell development. Collectively, these results suggest that E2A and HATs collaboratively regulate B cell development.
Interacting selectively and non-covalently with an activating transcription factor, any protein whose activity is required to initiate or upregulate transcription.
Evidence
1:
Inferred from Physical InteractionUniProtKB
Recent reports have evidenced a role for MEF2C (myocyte enhancer factor 2C) in myelopoiesis, although the precise functions of this transcription factor are still unclear. We show in the present study that MEF2A and MEF2D, two other MEF2 family members, are expressed in human primary monocytes and in higher amounts in monocyte-derived macrophages. High levels of MEF2A-MEF2D heterodimers are found in macrophage-differentiated HL60 cells. Chromatin immunoprecipitations demonstrate that MEF2A is present on the c-Jun promoter, both in undifferentiated and in macrophage-differentiated cells. Moreover, c-Jun expression is derepressed in undifferentiated cells in the presence of HDAC (histone deacetylase) inhibitor, indicating the importance of chromatin acetylation in this process. We show that MEF2A/D dimers strongly interact with HDAC1, and to a lesser extent with HDAC7 in macrophages, whereas low levels of MEF2A/D-HDAC1 complexes are found in undifferentiated cells or in monocytes. Since trichostatin A does not disrupt MEF2A/D-HDAC1 complexes, we analysed the potential interaction of MEF2A with p300 histone acetyltransferase, whose expression is up-regulated in macrophages. Interestingly, endogenous p300 only associates with MEF2A in differentiated macrophages, indicating that MEF2A/D could activate c-Jun expression in macrophages through a MEF2A/D-p300 activator complex. The targets of MEF2A/D-HDAC1-HDAC7 multimers remain to be identified. Nevertheless, these data highlight for the first time the possible dual roles of MEF2A and MEF2D in human macrophages, as activators or as repressors of gene transcription.
Androgen antagonists or androgen deprivation are the primary therapeutic modalities for the treatment of prostate cancer. Invariably, however, the disease becomes progressive and unresponsive to androgen ablation therapy (hormone refractory). The molecular mechanisms by which androgen antagonists inhibit prostate cancer proliferation are not fully defined. In this study, we identify two molecules which are required for effective prostate cancer cell responsiveness to androgen antagonists. We establish that androgen receptor (AR)-dependent transcriptional suppression by androgen antagonists requires the tumor suppressor prohibitin. This requirement for prohibitin was demonstrated using structurally-distinct androgen antagonists, stable and transient knockdown of prohibitin and transfected and endogenous AR-responsive genes. The SWI-SNF complex core ATPase BRG1, but not its closely-related counterpart ATPase BRM, is required for this repressive action of prohibitin on AR-responsive promoters. Androgen antagonists induce recruitment of prohibitin and BRG1 to endogenous AR-responsive promoters and induce a physical association between AR and prohibitin and BRG1. The recruitment of prohibitin to endogenous AR-responsive promoters is dependent upon antagonist-bound AR. Prohibitin binding in the prostate-specific antigen (PSA) promoter results in the recruitment of BRG1 and the dissociation of p300 from the PSA promoter. These findings suggest that prohibitin may function through BRG1-mediated local chromatin remodeling activity and the removal of p300-mediated acetylation to produce androgen antagonist-mediated transcriptional repression. Furthermore, in addition to its necessary role in AR-mediated transcriptional repression, we demonstrate that prohibitin is required for full and efficient androgen antagonist-mediated growth suppression of prostate cancer cells.
In the canonical Wnt signaling pathway, beta-catenin activates target genes through its interactions with Tcf/Lef-family transcription factors and additional transcriptional coactivators. The crystal structure of ICAT, an inhibitor of beta-catenin-mediated transcription, bound to the armadillo repeat domain of beta-catenin, has been determined. ICAT contains an N-terminal helilical domain that binds to repeats 11 and 12 of beta-catenin, and an extended C-terminal region that binds to repeats 5-10 in a manner similar to that of Tcfs and other beta-catenin ligands. Full-length ICAT dissociates complexes of beta-catenin, Lef-1, and the transcriptional coactivator p300, whereas the helical domain alone selectively blocks binding to p300. The C-terminal armadillo repeats of beta-catenin may be an attractive target for compounds designed to disrupt aberrant beta-catenin-mediated transcription associated with various cancers.
Interacting selectively and non-covalently with chromatin, the network of fibers of DNA, protein, and sometimes RNA, that make up the chromosomes of the eukaryotic nucleus during interphase.
Evidence
1:
Inferred from Mutant PhenotypeUniProtKB
We isolated MED25, which associates with retinoic acid (RA)-bound retinoic acid receptor (RAR) through the C-terminal nuclear hormone receptor (NR) box/LxxLL motif, and increases RAR/RXR-mediated transcription. When tethered to a promoter, MED25 showed intrinsic transcriptional activity in its PTOV domain, which is likely accomplished by direct association with CBP. Reporter assays using dominant negatives of MED25 demonstrated the importance of the N-terminal Mediator-binding and C-terminal domains in CBP and RAR/RXR binding, which affect MED25 activity. Downregulation of MED25 specifically reduced RAR but not thyroid hormone receptor (TR) activity. Stimulation of RAR by MED25 was correlated with enhanced RA cytotoxicity in vivo. Chromatin immunoprecipitation (ChIP) assays revealed the RA-dependent recruitment of MED25 to the RARbeta2 promoter. Recruitment of CBP and TRAP220 was diminished by the overexpression of a MED25 NR box deletion mutant, and by treatment with MED25 siRNA. Time-course ChIP assays indicated that CBP, together with RAR and MED25, is recruited early, whereas TRAP220 is recruited later to the promoter. Our data suggest that MED25, in cooperation with CBP and Mediators through its distinct domains, imposes a selective advantage on RAR/RXR activation.
Interacting selectively and non-covalently with the regulatory region composed of the transcription start site and binding sites for the basal transcription machinery. Binding may occur as a sequence specific interaction or as an interaction observed only once a factor has been recruited to the DNA by other factors.
We isolated MED25, which associates with retinoic acid (RA)-bound retinoic acid receptor (RAR) through the C-terminal nuclear hormone receptor (NR) box/LxxLL motif, and increases RAR/RXR-mediated transcription. When tethered to a promoter, MED25 showed intrinsic transcriptional activity in its PTOV domain, which is likely accomplished by direct association with CBP. Reporter assays using dominant negatives of MED25 demonstrated the importance of the N-terminal Mediator-binding and C-terminal domains in CBP and RAR/RXR binding, which affect MED25 activity. Downregulation of MED25 specifically reduced RAR but not thyroid hormone receptor (TR) activity. Stimulation of RAR by MED25 was correlated with enhanced RA cytotoxicity in vivo. Chromatin immunoprecipitation (ChIP) assays revealed the RA-dependent recruitment of MED25 to the RARbeta2 promoter. Recruitment of CBP and TRAP220 was diminished by the overexpression of a MED25 NR box deletion mutant, and by treatment with MED25 siRNA. Time-course ChIP assays indicated that CBP, together with RAR and MED25, is recruited early, whereas TRAP220 is recruited later to the promoter. Our data suggest that MED25, in cooperation with CBP and Mediators through its distinct domains, imposes a selective advantage on RAR/RXR activation.
The adenovirus E1A and SV40 large-T-antigen oncoproteins bind to members of the p300/CBP transcriptional coactivator family. Binding of p300/CBP is implicated in the transforming mechanisms of E1A and T-antigen oncoproteins. A common region of the T antigen is critical for binding both p300/CBP and the tumour suppressor p53, suggesting a link between the functions of p53 and p300. Here we report that p300/CBP binds to p53 in the absence of viral oncoproteins, and that p300 and p53 colocalize within the nucleus and coexist in a stable DNA-binding complex. Consistent with its ability to bind to p300, E1A disrupted functions mediated by p53. It reduced p53-mediated activation of the p21 and bax promoters, and suppressed p53-induced cell-cycle arrest and apoptosis. We conclude that members of the p300/CBP family are transcriptional adaptors for p53, modulating its checkpoint function in the G1 phase of the cell cycle and its induction of apoptosis. Disruption of p300/p53-dependent growth control may be part of the mechanism by which E1A induces cell transformation. These results help to explain how p53 mediates growth and checkpoint control, and how members of the p300/CBP family affect progression from G1 to the S phase of the cell cycle.
Multiprotein bridging factor (MBF-1) is a cofactor that was first described for its capacity to modulate the activity of fushi tarazu factor 1, a nuclear receptor originally implicated in Drosophila development. Recently, it has been shown that human MBF-1 stimulates the transcriptional activity of steroidogenic factor 1, a human homolog of fushi tarazu factor 1, which is implicated in steroidogenesis. Here we show that this cofactor enhances the transcriptional activity of several nonsteroid nuclear receptors that are implicated in lipid metabolism, i.e. the liver receptor homolog 1, the liver X receptor alpha, and PPARgamma. MBF-1 interacts with distinct domains in these receptors, depending on whether the receptor binds DNA as a monomer or as a heterodimer with RXR. MBF-1 does not possess any of the classical histone modifying activities such as histone acetyl- or methyl transferase activities, linked to chromatin remodeling, but interacts in vitro with the transcription factor IID complex. MBF-1 seems therefore to act as a bridging factor enabling interactions of nuclear receptors with the transcription machinery.
Flap endonuclease 1 (FEN1) and Dna2 endonuclease/helicase (Dna2) sequentially coordinate their nuclease activities for efficient resolution of flap structures that are created during the maturation of Okazaki fragments and repair of DNA damage. Acetylation of FEN1 by p300 inhibits its endonuclease activity, impairing flap cleavage, a seemingly undesirable effect. We now show that p300 also acetylates Dna2, stimulating its 5'-3' endonuclease, the 5'-3' helicase, and DNA-dependent ATPase activities. Furthermore, acetylated Dna2 binds its DNA substrates with higher affinity. Differential regulation of the activities of the two endonucleases by p300 indicates a mechanism in which the acetylase promotes formation of longer flaps in the cell at the same time as ensuring correct processing. Intentional formation of longer flaps mediated by p300 in an active chromatin environment would increase the resynthesis patch size, providing increased opportunity for incorrect nucleotide removal during DNA replication and damaged nucleotide removal during DNA repair. For example, altering the ratio between short and long flap Okazaki fragment processing would be a mechanism for better correction of the error-prone synthesis catalyzed by DNA polymerase alpha.
Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).
Evidence
1:
Inferred from Physical InteractionUniProtKB
We identified and characterized two new ING family genes, p29ING4 and p28ING5,coding for two proteins of 249 and 240 amino acids, respectively. Both p29ING4 and p28ING5 proteins have a plant homeodomain finger motif also found in other ING proteins, and which is common in proteins involved in chromatin remodeling. p29ING4 or p28ING5 overexpression resulted in a diminished colony-forming efficiency, a decreased cell population in S phase, and the induction of apoptosis in a p53-dependent manner. Both p29ING4 and p28ING5 activate the p21/waf1 promoter, and induce p21/WAF1 expression. p29ING4 and p28ING5 enhance p53 acetylation at Lys-382 residues, and physically interact with p300, a member of histone acetyl transferase complexes, and p53 in vivo. These results indicate that p29ING4 and p28ING5 may be significant modulators of p53 function.
Evidence
2:
Inferred from Physical InteractionUniProtKB
The retinoblastoma protein (Rb) regulates both the cell cycle and tissue-specific transcription, by modulating the activity of factors that associate with its A-B and C pockets. In skeletal muscle, Rb has been reported to regulate irreversible cell cycle exit and muscle-specific transcription. To identify factors interacting with Rb in muscle cells, we utilized the yeast two-hybrid system, using the A-B and C pockets of Rb as bait. A novel protein we have designated E1A-like inhibitor of differentiation 1 (EID-1), was the predominant Rb-binding clone isolated. It is preferentially expressed in adult cardiac and skeletal muscle and encodes a 187-amino-acid protein, with a classic Rb-binding motif (LXCXE) in its C terminus. Overexpression of EID-1 in skeletal muscle inhibited tissue-specific transcription. Repression of skeletal muscle-restricted genes was mediated by a block to transactivation by MyoD independent of G(1) exit and, surprisingly, was potentiated by a mutation that prevents EID-1 binding to Rb. Inhibition of MyoD may be explained by EID-1's ability to bind and inhibit p300's histone acetylase activity, an essential MyoD coactivator. Thus, EID-1 binds both Rb and p300 and is a novel repressor of MyoD function.
Evidence
3:
Inferred from Physical InteractionUniProtKB
C/EBP homologous protein (CHOP) is an endoplasmic reticulum stress-inducible protein that plays a critical role in the regulation of programmed cell death; however, the regulation of its function has not been well characterized. We have previously demonstrated that CHOP is regulated by the ubiquitin-proteasome system. In this study, during the process of clarifying the mechanism of the degradation of CHOP, we identified a novel regulation domain of CHOP in its N-terminal portion that is involved in various regulations and functions. The CHOP N-terminal domain is necessary not only for protein degradation but also for its transactivity and interaction with p300. In addition, trichostatin A, a histone deacetylase inhibitor, repressed the degradation of CHOP protein via the N-terminal domain. TRB3, a mammalian tribbles homolog that functions as a repressor of CHOP, also interacted with CHOP via the N-terminal portion and significantly blocked the association of p300 with CHOP. These results suggest that the N-terminal portion of CHOP plays a crucial role in its functional regulation and enable us to identify a novel function of TRB3 as an intracellular antagonist of the p300-binding domain of CHOP.
Evidence
4:
Inferred from Physical InteractionUniProtKB
DNA damage response (DDR) acts as a tumorigenesis barrier, and any defects in the DDR machinery may lead to cancer. SOX4 expression is elevated in many types of tumors; however, its role in DDR is still largely unknown. Here, we show that SOX4, a new DNA damage sensor, is required for the activation of p53 tumor suppressor in response to DNA damage. Notably, SOX4 interacts with and stabilizes p53 protein by blocking Mdm2-mediated p53 ubiquitination and degradation. Furthermore, SOX4 enhances p53 acetylation by interacting with p300/CBP and facilitating p300/CBP/p53 complex formation. In concert with these results, SOX4 promotes cell cycle arrest and apoptosis, and it inhibits tumorigenesis in a p53-dependent manner. Therefore, these findings highlight SOX4 as a potential key factor in regulating DDR-associated cancer.
Evidence
5:
Inferred from Physical InteractionIntAct
Aberrant Skp2 signaling has been implicated as a driving event in tumorigenesis. Although the underlying molecular mechanisms remain elusive, cytoplasmic Skp2 correlates with more aggressive forms of breast and prostate cancers. Here, we report that Skp2 is acetylated by p300 at K68 and K71, which is a process that can be antagonized by the SIRT3 deacetylase. Inactivation of SIRT3 leads to elevated Skp2 acetylation, which leads to increased Skp2 stability through impairment of the Cdh1-mediated proteolysis pathway. As a result, Skp2 oncogenic function is increased, whereby cells expressing an acetylation-mimetic mutant display enhanced cellular proliferation and tumorigenesis in vivo. Moreover, acetylation of Skp2 in the nuclear localization signal (NLS) promotes its cytoplasmic retention, and cytoplasmic Skp2 enhances cellular migration through ubiquitination and destruction of E-cadherin. Thus, our study identifies an acetylation-dependent regulatory mechanism governing Skp2 oncogenic function and provides insight into how cytoplasmic Skp2 controls cellular migration.
Evidence
6:
Inferred from Physical InteractionUniProtKB
Oncogene-induced senescence is a p53-dependent defence mechanism against uncontrolled proliferation. Consequently, many human tumours harbour p53 mutations and others show a dysfunctional p53 pathway, frequently by unknown mechanisms. Here we identify BRD7 (bromodomain-containing 7) as a protein whose inhibition allows full neoplastic transformation in the presence of wild-type p53. In human breast tumours harbouring wild-type, but not mutant, p53 the BRD7 gene locus was frequently deleted and low BRD7 expression was found in a subgroup of tumours. Functionally, BRD7 is required for efficient p53-mediated transcription of a subset of target genes. BRD7 interacts with p53 and p300 and is recruited to target gene promoters, affecting histone acetylation, p53 acetylation and promoter activity. Thus, BRD7 suppresses tumorigenicity by serving as a p53 cofactor required for the efficient induction of p53-dependent oncogene-induced senescence.
Evidence
7:
Inferred from Physical InteractionUniProtKB
Interferon regulatory factor 1 (IRF-1) and p53 control distinct sets of downstream genes; however, these two antioncogenic transcription factors converge to regulate p21 gene expression and to inhibit tumor formation. Here we investigate the mechanism by which IRF-1 and p53 synergize at the p21 promoter and show that stimulation of p21 transcription by IRF-1 does not require its DNA-binding activity but relies on the ability of IRF-1 to bind the coactivator p300 and to stimulate p53-dependent transcription by an allosteric mechanism. Deletion of the p300-binding sites in IRF-1 eliminates the ability of IRF-1 to stimulate p53 acetylation and associated p53 activity. Complementing this, small peptides derived from the IRF-1-p300 interface can bind to p300, stabilize the binding of p300 to DNA-bound p53, stimulate p53 acetylation in trans, and up-regulate p53-dependent activity from the p21 promoter. The nonacetylatable p53 mutant (p53-6KR) cannot be stimulated by IRF-1, further suggesting that p53 acetylation is the mechanism whereby IRF-1 modifies p53 activity. These data expand the core p300-p53 protein LXXLL and PXXP interface by including an IRF-1-p300 interface as an allosteric modifier of DNA-dependent acetylation of p53 at the p21 promoter.
Evidence
8:
Inferred from Physical InteractionUniProtKB
Flap endonuclease 1 (FEN1) and Dna2 endonuclease/helicase (Dna2) sequentially coordinate their nuclease activities for efficient resolution of flap structures that are created during the maturation of Okazaki fragments and repair of DNA damage. Acetylation of FEN1 by p300 inhibits its endonuclease activity, impairing flap cleavage, a seemingly undesirable effect. We now show that p300 also acetylates Dna2, stimulating its 5'-3' endonuclease, the 5'-3' helicase, and DNA-dependent ATPase activities. Furthermore, acetylated Dna2 binds its DNA substrates with higher affinity. Differential regulation of the activities of the two endonucleases by p300 indicates a mechanism in which the acetylase promotes formation of longer flaps in the cell at the same time as ensuring correct processing. Intentional formation of longer flaps mediated by p300 in an active chromatin environment would increase the resynthesis patch size, providing increased opportunity for incorrect nucleotide removal during DNA replication and damaged nucleotide removal during DNA repair. For example, altering the ratio between short and long flap Okazaki fragment processing would be a mechanism for better correction of the error-prone synthesis catalyzed by DNA polymerase alpha.
Evidence
9:
Inferred from Physical InteractionUniProtKB
The lasting effects of neuronal activity on brain development involve calcium-dependent gene expression. Using a strategy called transactivator trap, we cloned a calcium-responsive transactivator called CREST (for calcium-responsive transactivator). CREST is a SYT-related nuclear protein that interacts with adenosine 3',5'-monophosphate (cAMP) response element-binding protein (CREB)-binding protein (CBP) and is expressed in the developing brain. Mice that have a targeted disruption of the crest gene are viable but display defects in cortical and hippocampal dendrite development. Cortical neurons from crest mutant mice are compromised in calcium-dependent dendritic growth. Thus, calcium activation of CREST-mediated transcription helps regulate neuronal morphogenesis.
Evidence
10:
Inferred from Physical InteractionIntAct
In response to a shortage of intracellular energy, mammalian cells reduce energy consumption and induce cell cycle arrest, both of which contribute to cell survival. Here we report that a novel nucleolar pathway involving the energy-dependent nucleolar silencing complex (eNoSC) and Myb-binding protein 1a (MYBBP1A) is implicated in these processes. Namely, in response to glucose starvation, eNoSC suppresses rRNA transcription, which results in a reduction in nucleolar RNA content. As a consequence, MYBBP1A, which is anchored to the nucleolus via RNA, translocates from the nucleolus to the nucleoplasm. The translocated MYBBP1A induces acetylation and accumulation of p53 by enhancing the interaction between p300 and p53, which eventually leads to the cell cycle arrest (or apoptosis). Taken together, our results indicate that the nucleolus works as a sensor that transduces the intracellular energy status into the cell cycle machinery.
Evidence
11:
Inferred from Physical InteractionUniProtKB
Epithelium-specific ETS (ESE)-1 is a prototypic member of a novel subset of the ETS transcription factor family that is predominantly expressed in cells of epithelial origin but can also be induced in other cell types including vascular endothelial and smooth muscle cells in response to inflammatory stimuli. To further define the molecular mechanisms by which the transcriptional activity of ESE-1 is regulated, we have focused our attention on identifying proteins that interact with ESE-1. We have determined that Ku70, Ku86, p300, and CREB-binding protein (CBP) are ESE-1 interacting proteins. The Ku proteins have previously been shown to bind to breaks in DNA where they function to recruit additional proteins that promote DNA repair. Interestingly, Ku70 and Ku 86 negatively regulate the transcriptional activity of ESE-1. Using a series of deletion constructs, we have determined that the Ku proteins bind to the DNA-binding domain of ESE-1. The Ku proteins inhibit the ability of ESE-1 to bind to oligonucleotide probes in gel mobility shift assays. The finding that Ku proteins can interact with other transcription factors and block their function has not been previously demonstrated. In contrast, co-transfection of p300 and CBP with ESE-1 enhances the transcriptional activity of ESE-1. Moreover, the induction of ESE-1 in response to inflammatory cytokine interleukin-1 is associated with a parallel increase of the expression of p300 in vascular endothelial cells, suggesting that in the setting of inflammation, the transcriptional activity of ESE-1 is positively modulated by interaction with the transcriptional co-activator p300. In summary, our results demonstrated that the activity of ESE-1 is positively and negatively modulated by other interacting proteins including Ku70, Ku86, p300, and CBP.
Evidence
12:
Inferred from Physical InteractionUniProtKB
The transcriptional co-activators and histone acetyltransferases p300/CREB-binding protein (CBP) interact with CITED2, a transcription factor AP-2 (TFAP2) co-activator. p300/CBP, CITED2, and TFAP2A are essential for normal neural tube and cardiac development. Here we show that p300 and CBP co-activate TFAP2A in the presence of CITED2. TFAP2A transcriptional activity was modestly impaired in p300(+/-) and CBP(+/-) mouse embryonic fibroblasts; this was rescued by ectopic expression of p300/CBP. p300, TFAP2A, and endogenous CITED2 could be co-immunoprecipitated from transfected U2-OS cells indicating that they can interact physically in vivo. CITED2 interacted with the dimerization domain of TFAP2C, which is highly conserved in TFAP2A/B. In mammalian two-hybrid experiments, full-length p300 and TFAP2A interacted only when CITED2 was co-transfected. N-terminal residues of TFAP2A, containing the transactivation domain, are both necessary and sufficient for interaction with p300, and this interaction was independent of CITED2. Consistent with this, N-terminal residues of TFAP2A were required for p300- and CITED2-dependent co-activation. A histone acetyltransferase-deficient p300 mutant (D1399Y) did not co-activate TFAP2A and did not affect the expression or cellular localization of TFAP2A or CITED2. In mammalian two-hybrid experiments p300D1399Y failed to interact with TFAP2A, explaining, at least in part, its failure to function as a co-activator. Our results suggest a model wherein interactions among TFAP2A, CITED2, and p300/CBP are necessary for TFAP2A-mediated transcriptional activation and for normal neural tube and cardiac development.
Evidence
13:
Inferred from Physical InteractionIntAct
The tumor-suppressor function of p53 relies on its transcriptional activity, which is modulated by post-translational modifications and interactions with regulatory proteins. The prolyl isomerase Pin1 has a central role in transducing phosphorylation of p53 into conformational changes that affect p53 stability and function. We found that Pin1 is required for efficient loading of p53 on target promoters upon stress. In addition, Pin1 is recruited to chromatin by p53 and stimulates binding of the p300 acetyltransferase and consequent p53 acetylation. Accordingly, tumor-associated mutations at Pin1-binding residues within the p53 proline-rich domain hamper acetylation of p53 by p300. After phosphorylation of p53 at Ser46 triggered by cytotoxic stimuli, Pin1 also mediates p53's dissociation from the apoptosis inhibitor iASPP, promoting cell death. In tumors bearing wild-type p53, expression of Pin1 and iASPP are inversely correlated, supporting the clinical relevance of these interactions.
Evidence
14:
Inferred from Physical InteractionUniProtKB
The adenovirus E1A and SV40 large-T-antigen oncoproteins bind to members of the p300/CBP transcriptional coactivator family. Binding of p300/CBP is implicated in the transforming mechanisms of E1A and T-antigen oncoproteins. A common region of the T antigen is critical for binding both p300/CBP and the tumour suppressor p53, suggesting a link between the functions of p53 and p300. Here we report that p300/CBP binds to p53 in the absence of viral oncoproteins, and that p300 and p53 colocalize within the nucleus and coexist in a stable DNA-binding complex. Consistent with its ability to bind to p300, E1A disrupted functions mediated by p53. It reduced p53-mediated activation of the p21 and bax promoters, and suppressed p53-induced cell-cycle arrest and apoptosis. We conclude that members of the p300/CBP family are transcriptional adaptors for p53, modulating its checkpoint function in the G1 phase of the cell cycle and its induction of apoptosis. Disruption of p300/p53-dependent growth control may be part of the mechanism by which E1A induces cell transformation. These results help to explain how p53 mediates growth and checkpoint control, and how members of the p300/CBP family affect progression from G1 to the S phase of the cell cycle.
Evidence
15:
Inferred from Physical InteractionIntAct
Eur. J. Biochem. 267, 6413-6422 (2000)[PubMed:11029584]
The class III POU gene brn-2, encoding the Brn-2/N-Oct-3 transcription factor, is widely expressed in the developing mammalian central nervous system. Brn-2 has also been found to regulate the melanocytic phenotype with N-Oct-3 DNA binding activity elevated in malignant melanoma, however, its mode of action is yet to be defined. The functional role of the Brn-2 transcription factor has been investigated through the analysis of protein-protein interactions it forms with a number of basal and melanocytic transcriptional regulatory proteins. In vivo interactions were tested by gene-cotransfection using the mammalian GAL4-Herpes Simplex viral protein 16 (VP16) two hybrid formation and direct protein binding by in vitro glutathione S-transferase (GST)-pull down assay. The Brn-2 protein was found to homodimerize in vivo with high affinity, using Brn-2 deletion constructs dimer complex formation was found to be dependent on the presence of both the homeodomain and linker regions of the POU-domain. However, the POU-homoedomain was dispensable for the formation of the dimerization interface in one of the partner molecules but not both, when the POU-linker region was removed the ability to interact was lost irrespective of the presence of the homeodomain. Dimerization of Brn-2/N-Oct-3 was also found to occur in DNA binding assays using melanoma cell line nuclear extracts and a recently reported dimer target sequence probe, which may have significant consequences for gene regulation in melanocytic tumours. Low affinity Brn-2 protein contacts have also been found with the basal transcription complex, including TATA binding protein (TBP) and the transcriptional coactivator p300, and with the Sox-10 and Pax-3 transcription factors that are known to play an important role in melanocyte cell formation.
Evidence
16:
Inferred from Physical InteractionUniProtKB
Transforming growth factor-beta (TGF-beta)/Smads regulate a wide variety of biological responses through transcriptional regulation of target genes. Smad3 plays a key role in TGF-beta/Smad-mediated transcriptional responses. Here, we show that the proline-rich linker region of Smad3 contains a transcriptional activation domain. When the linker region is fused to a heterologous DNA-binding domain, it activates transcription. We show that the linker region physically interacts with p300. The adenovirus E1a protein, which binds to p300, inhibits the transcriptional activity of the linker region, and overexpression of p300 can rescue the linker-mediated transcriptional activation. In contrast, an adenovirus E1a mutant, which cannot bind to p300, does not inhibit the linker-mediated transcription. The native Smad3 protein lacking the linker region is unable to mediate TGF-beta transcriptional activation responses, although it can be phosphorylated by the TGF-beta receptor at the C-terminal tail and has a significantly increased ability to form a heteromeric complex with Smad4. We show further that the linker region and the C-terminal domain of Smad3 synergize for transcriptional activation in the presence of TGF-beta. Thus our findings uncover an important function of the Smad3 linker region in Smad-mediated transcriptional control.
Evidence
17:
Inferred from Physical InteractionUniProtKB
Small heterodimer partner (SHP; NR0B2) is an atypical orphan nuclear receptor that lacks a conventional DNA binding domain (DBD) and represses the transcriptional activity of various nuclear receptors. In this study, we examined the novel cross talk between SHP and BETA2/NeuroD, a basic helix-loop-helix transcription factor. In vitro and in vivo protein interaction studies showed that SHP physically interacts with BETA2/NeuroD, but not its heterodimer partner E47. Moreover, confocal microscopic study and immunostaining results demonstrated that SHP colocalized with BETA2 in islets of mouse pancreas. SHP inhibited BETA2/NeuroD-dependent transactivation of an E-box reporter, whereas SHP was unable to repress the E47-mediated transactivation and the E-box mutant reporter activity. In addition, SHP repressed the BETA2-dependent activity of glucokinase and cyclin-dependent kinase inhibitor p21 gene promoters. Gel shift and in vitro protein competition assays indicated that SHP inhibits neither dimerization nor DNA binding of BETA2 and E47. Rather, SHP directly repressed BETA2 transcriptional activity and p300-enhanced BETA2/NeuroD transcriptional activity by inhibiting interaction between BETA2 and coactivator p300. We also showed that C-terminal repression domain within SHP is also required for BETA2 repression. However, inhibition of BETA2 activity was not observed by naturally occurring human SHP mutants that cannot interact with BETA2/NeuroD. Taken together, these results suggest that SHP acts as a novel corepressor for basic helix-loop-helix transcription factor BETA2/NeuroD by competing with coactivator p300 for binding to BETA2/NeuroD and by its direct transcriptional repression function.
Evidence
18:
Inferred from Physical InteractionUniProtKB
In response to DNA damage, p53 undergoes post-translational modifications (including acetylation) that are critical for its transcriptional activity. However, the mechanism by which p53 acetylation is regulated is still unclear. Here, we describe an essential role for HLA-B-associated transcript 3 (Bat3)/Scythe in controlling the acetylation of p53 required for DNA damage responses. Depletion of Bat3 from human and mouse cells markedly impairs p53-mediated transactivation of its target genes Puma and p21. Although DNA damage-induced phosphorylation, stabilization, and nuclear accumulation of p53 are not significantly affected by Bat3 depletion, p53 acetylation is almost completely abolished. Bat3 forms a complex with p300, and an increased amount of Bat3 enhances the recruitment of p53 to p300 and facilitates subsequent p53 acetylation. In contrast, Bat3-depleted cells show reduced p53-p300 complex formation and decreased p53 acetylation. Furthermore, consistent with our in vitro findings, thymocytes from Bat3-deficient mice exhibit reduced induction of puma and p21, and are resistant to DNA damage-induced apoptosis in vivo. Our data indicate that Bat3 is a novel and essential regulator of p53-mediated responses to genotoxic stress, and that Bat3 controls DNA damage-induced acetylation of p53.
Evidence
19:
Inferred from Physical InteractionIntAct
In a yeast two-hybrid screen to identify proteins that bind to the KIX domain of the coactivator p300, we obtained cDNAs encoding nucleosome assembly protein 1 (NAP-1), a 60-kDa histone H2A-H2B shuttling protein that promotes histone deposition. p300 associates preferentially with the H2A-H2B-bound form of NAP-1 rather than with the unbound form of NAP-1. Formation of NAP-1-p300 complexes was found to increase during S phase, suggesting a potential role for p300 in chromatin assembly. In micrococcal nuclease and supercoiling assays, addition of p300 promoted efficient chromatin assembly in vitro in conjunction with NAP-1 and ATP-utilizing chromatin assembly and remodeling factor; this effect was dependent in part on the intrinsic histone acetyltransferase activity of p300. Surprisingly, NAP-1 potently inhibited acetylation of core histones by p300, suggesting that efficient assembly requires acetylation of either NAP-1 or p300 itself. As p300 acted cooperatively with NAP-1 in stimulating transcription from a chromatin template in vitro, our results suggest a dual role of NAP-1-p300 complexes in promoting chromatin assembly and transcriptional activation.
Evidence
20:
Inferred from Physical InteractionIntAct
p68 RNA helicase has been implicated in a variety of processes, including rearrangement of RNA secondary structures, RNA splicing, gene transcription and tumor development, yet its mechanisms of action are not well understood. In this study, we show that p68 is predominantly localized to the cell nucleus, where it partially colocalizes with the transcriptional coactivator p300. Accordingly, p68 and p300, or the paralogous CREB-binding protein (CBP), coimmunoprecipitate. Similarly, p68 and RNA polymerase II (Pol II) are able to interact in vivo. GST pull-down assays confirmed these interactions in vitro, demonstrating that p68 can interact with several domains of CBP, while CBP/p300 bind to amino acids 176-388 of p68 and RNA Pol II binds to the N-terminal 80 amino acids of p68. Furthermore, p68 stimulates transcription mediated by the C-terminal transactivation domain of CBP. p68 is also able to stimulate TPA oncogene responsive unit (TORU) promoter activity, and p300 acts in synergy with p68. On the other hand, suppression of CBP/p300 function by the adenoviral protein E1A abolishes TORU promoter activation by p68. Altogether, our results suggest the existence of a multiprotein complex in which p68 RNA helicase, CBP/p300 and RNA Pol II jointly promote gene expression.
Evidence
21:
Inferred from Physical InteractionUniProtKB
Homeostasis under hypoxic conditions is maintained through a coordinated transcriptional response mediated by the hypoxia-inducible factor (HIF) pathway and requires coactivation by the CBP and p300 transcriptional coactivators. Through a target-based high-throughput screen, we identified chetomin as a disrupter of HIF binding to p300. At a molecular level, chetomin disrupts the structure of the CH1 domain of p300 and precludes its interaction with HIF, thereby attenuating hypoxia-inducible transcription. Systemic administration of chetomin inhibited hypoxia-inducible transcription within tumors and inhibited tumor growth. These results demonstrate a therapeutic window for pharmacological attenuation of HIF activity and further establish the feasibility of disrupting a signal transduction pathway by targeting the function of a transcriptional coactivator with a small molecule.
Evidence
22:
Inferred from Physical InteractionUniProtKB
The ability of p53 to function as a transcription factor is instrumental in facilitating the response to cellular stress, and p300/CBP proteins, which act as coactivators for diverse transcription factors, participate in regulating p53 activity. We report a novel cofactor for p300 that facilitates the p53 response by augmenting p53-dependent transcription and apoptosis. JMY and p300 associate in physiological conditions, and, during the cellular stress response, the p300/JMY complex is recruited to activated p53. The bax gene is efficiently activated by JMY, and protein isoforms that arise through alternative splicing alter the functional outcome of the p53 response. The results provide compelling evidence that the p300/JMY coactivator complex plays a central role in facilitating the p53 response.
Evidence
23:
Inferred from Physical InteractionUniProtKB
We describe a role for the transcriptional coactivator p300 in DNA metabolism. p300 formed a complex with flap endonuclease-1 (Fen1) and acetylated Fen1 in vitro. Furthermore, Fen1 acetylation was observed in vivo and was enhanced upon UV treatment of human cells. Remarkably, acetylation of the Fen1 C terminus by p300 significantly reduced Fen1's DNA binding and nuclease activity. Proliferating cell nuclear antigen (PCNA) was able to stimulate both acetylated and unacetylated Fen1 activity to the same extent. Our results identify acetylation as a novel regulatory modification of Fen1 and implicate that p300 is not only a component of the chromatin remodeling machinery but might also play a critical role in regulating DNA metabolic events.
Evidence
24:
Inferred from Physical InteractionUniProtKB
J. Biol. Chem. 275, 8825-8834 (2000)[PubMed:10722728]
The MSG1 nuclear protein has a strong transcriptional activating activity but does not bind directly to DNA. When cotransfected, MSG1 enhances transcription mediated by the Smad transcription factors in mammalian cells in a manner dependent on ligand-induced Smad hetero-oligomerization. However, the mechanism of this MSG1 effect has been unknown. We now show that MSG1 directly binds to the p300/cAMP-response element-binding protein-binding protein (CBP) transcriptional coactivators, which in turn bind to the Smads, and enhances Smad-mediated transcription in a manner dependent on p300/CBP. The C-terminal transactivating domain of MSG1 is required for binding to p300/CBP and enhancement of Smad-mediated transcription; the viral VP16 transactivating domain could not substitute for it. In the N-terminal region of MSG1, we identified a domain that is necessary and sufficient to direct the specific interaction of MSG1 with Smads. We also found that the Hsc70 heat-shock cognate protein also forms complex with MSG1 in vivo, suppressing both binding of MSG1 to p300/CBP and enhancement of Smad-mediated transcription by MSG1. These results indicate that MSG1 interacts with both the DNA-binding Smad proteins and the p300/CBP coactivators through its N- and C-terminal regions, respectively, and enhances the functional link between Smads and p300/CBP.
Evidence
25:
Inferred from Physical InteractionIntAct
In this study we have investigated hyaluronan (HA)-mediated CD44 (an HA receptor) interactions with p300 (a histone acetyltransferase) and SIRT1 (a histone deacetylase) in human breast tumor cells (MCF-7 cells). Specifically, our results indicate that HA binding to CD44 up-regulates p300 expression and its acetyltransferase activity that, in turn, promotes acetylation of beta-catenin and NFkappaB-p65 leading to activation of beta-catenin-associated T-cell factor/lymphocyte enhancer factor transcriptional co-activation and NFkappaB-specific transcriptional up-regulation, respectively. These changes then cause the expression of the MDR1 (P-glycoprotein/P-gp) gene and the anti-apoptotic gene Bcl-x(L) resulting in chemoresistance in MCF-7 cells. Our data also show that down-regulation of p300, beta-catenin, or NFkappaB-p65 in MCF-7 cells (by transfecting cells with p300-, beta-catenin-, or NFkappaB-p65-specific small interfering RNA) inhibits the HA/CD44-mediated beta-catenin/NFkappaB-p65 acetylation and abrogates the aforementioned transcriptional activities. Subsequently, there is a significant decrease in both MDR1 and Bcl-x(L) gene expression and an enhancement in caspase-3 activity and chemosensitivity in the breast tumor cells. Further analyses indicate that activation of SIRT1 (deacetylase) by resveratrol (a natural antioxidant) induces SIRT1-p300 association and acetyltransferase inactivation, leading to deacetylation of HA/CD44-induced beta-catenin and NFkappaB-p65, inhibition of beta-catenin-T-cell factor/lymphocyte enhancer factor and NFkappaB-specific transcriptional activation, and the impairment of MDR1 and Bcl-x(L) gene expression. All these multiple effects lead to an activation of caspase-3 and a reduction of chemoresistance. Together, these findings suggest that the interactions between HA/CD44-stimulated p300 (acetyltransferase) and resveratrol-activated SIRT1 (deacetylase) play pivotal roles in regulating the balance between cell survival versus apoptosis, and multidrug resistance versus sensitivity in breast tumor cells.
Evidence
26:
Inferred from Physical InteractionUniProtKB
CITED1, a CBP/p300-binding nuclear protein that does not bind directly to DNA, is a transcriptional coregulator. Here, we show evidence that CITED1 functions as a selective coactivator for estrogen-dependent transcription. When transfected, CITED1 enhanced transcriptional activation by the ligand-binding/AF2 domain of both estrogen receptor-alpha (ERalpha) and ERbeta in an estrogen-dependent manner, but it affected transcriptional activities of other nuclear receptors only marginally. CITED1 bound directly to ERalpha in an estrogen-dependent manner through its transactivating domain, and this binding activity was separable from its p300-binding activity. CITED1 was strongly expressed in nulliparous mouse mammary epithelial cells and, when expressed in ER-positive MCF-7 breast cancer cells by transduction, exogenous CITED1 enhanced sensitivity of MCF-7 cells to estrogen, stabilizing the estrogen-dependent interaction between p300 and ERalpha. The estrogen-induced expression of the transforming growth factor-alpha (TGF-alpha) mRNA transcript was enhanced in the CITED1-expressing MCF-7 cells, whereas estrogen-induced expression of the mRNA transcripts for progesterone receptor or pS2 was not affected. Chromatin immunoprecipitation assay revealed that endogenous CITED1 is recruited to the chromosomal TGF-alpha promoter in MCF-7 cells in an estrogen-dependent manner but not to the pS2 promoter. These results suggest that CITED1 may play roles in regulation of estrogen sensitivity in a gene-specific manner.
Evidence
27:
Inferred from Physical InteractionUniProtKB
Forkhead box (Fox)/winged-helix transcription factors regulate multiple aspects of immune responsiveness and Foxp3 is recognized as an essential functional marker of regulatory T cells. Herein we describe downstream signaling pathways targeted by Foxp3 that may negatively impact retroviral pathogenesis. Overexpression of Foxp3 in HEK 293T and purified CD4+ T cells resulted in a dose-dependent and time-dependent decrease in basal levels of nuclear factor-kappaB (NF-kappaB) activation. Deletion of the carboxyl-terminal forkhead (FKH) domain, critical for nuclear localization and DNA-binding activity, abrogated the ability of Foxp3 to suppress NF-kappaB activity in HEK 293T cells, but not in Jurkat or primary human CD4+ T cells. We further demonstrate that Foxp3 suppressed the transcription of two human retroviral promoters (HIV-1 and human T cell lymphotropic virus type I [HTLV-I]) utilizing NF-kappaB-dependent and NF-kappaB-independent mechanisms. Examination of the latter identified the cAMP-responsive element binding protein (CREB) pathway as a target of Foxp3. Finally, comparison of the percent Foxp3+CD4+CD25+ T cells to the HTLV-I proviral load in HTLV-I-infected asymptomatic carriers and patients with HTLV-I-associated myelopathy/tropical spastic paraparesis suggested that high Foxp3 expression is associated with low proviral load and absence of disease. These results suggest an expanded role for Foxp3 in regulating NF-kappaB- and CREB-dependent cellular and viral gene expression.
Evidence
28:
Inferred from Physical InteractionUniProtKB
In a screen to identify factors that regulate the conversion of mesenchyme to epithelium during the early stages of nephrogenesis, it was found that the Smad4-interacting transcriptional cofactor, Cited1, is expressed in the condensed cap mesenchyme surrounding the tip of the ureteric bud (UB), is downregulated after differentiation into epithelia, and has the capacity to block UB branching and epithelial morphogenesis in cultured metanephroi. Cited1 represses Wnt/beta-catenin but activates Smad4-dependent transcription involved in TGF-beta and Bmp signaling. By modifying these pathways, Cited1 may coordinate cellular differentiation and survival signals that regulate nephronic patterning in the metanephros.
Evidence
29:
Inferred from Physical InteractionIntAct
The overexpression of human apurinic/apyrimidinic (AP) endonuclease 1 (APE1/Ref-1), a key enzyme in the DNA base excision repair (BER) pathway, is often associated with tumor cell resistance to various anticancer drugs. In this study, we examined the molecular basis of transcriptional regulatory (nonrepair) function of APE1 in promoting resistance to certain types of drugs. We have recently shown that APE1 stably interacts with Y-box-binding protein 1 (YB-1), and acts as its coactivator for the expression of multidrug resistance gene MDR1, thereby causing drug resistance. In this study, we show, to the best of our knowledge, for the first time that APE1 is stably associated with the basic transcription factor RNA polymerase II (RNA pol II) and the coactivator p300 on the endogenous MDR1 promoter. The depletion of APE1 significantly reduces YB-1-p300 recruitment to the promoter, resulting in reduced RNA pol II loading. Drug-induced APE1 acetylation, which is mediated by p300, enhances formation of acetylated APE1 (AcAPE1)-YB-1-p300 complex on the MDR1 promoter. Enhanced recruitment of this complex increases MDR1 promoter-dependent luciferase activity and its endogenous expression. Using APE1-downregulated cells and cells overexpressing wild-type APE1 or its nonacetylable mutant, we have demonstrated that the loss of APE1's acetylation impaired MDR1 activation and sensitizes the cells to cisplatin or etoposide. We have thus established the basis for APE1's acetylation-dependent regulatory function in inducing MDR1-mediated drug resistance.
Evidence
30:
Inferred from Physical InteractionIntAct
The adenoviral oncoprotein E1A induces progression through the cell cycle by binding to the products of the p300/CBP and retinoblastoma gene families. A new cellular p300/CBP-associated factor (P/CAF) having intrinsic histone acetylase activity has been identified that competes with E1A. Exogenous expression of P/CAF in HeLa cells inhibits cell-cycle progression and counteracts the mitogenic activity of E1A. E1A disturbs the normal cellular interaction between p300/CBP and its associated histone acetylase.
Evidence
31:
Inferred from Physical InteractionIntAct
Neuroendocrine (NE) phenotype, seen in >30% of prostate adenocarcinomas (PCa), and NE prostate tumors are implicated in aggressive prostate cancer. Formation of NE prostate tumors in the TRAMP mouse model was suppressed in mice lacking the ubiquitin ligase Siah2, which regulates HIF-1alpha availability. Cooperation between HIF-1alpha and FoxA2, a transcription factor expressed in NE tissue, promotes recruitment of p300 to transactivate select HIF-regulated genes, Hes6, Sox9, and Jmjd1a. These HIF-regulated genes are highly expressed in metastatic PCa and required for hypoxia-mediated NE phenotype, metastasis in PCa, and the formation of NE tumors. Tissue-specific expression of FoxA2 combined with Siah2-dependent HIF-1alpha availability enables a transcriptional program required for NE prostate tumor development and NE phenotype in PCa.
Evidence
32:
Inferred from Physical InteractionUniProtKB
The paired-like homeoprotein, Cart1, is involved in skeletal development. We describe here that the general coactivator p300/CBP controls the transcription activity of Cart1 through acetylation of a lysine residue that is highly conserved in other homeoproteins. Acetylation of this residue increases the interaction between p300/CBP and Cart1 and enhances its transcriptional activation. INTRODUCTION: Cart1 encodes a paired-like homeoprotein expressed selectively in chondrocyte lineage during embryonic development. Although its target gene remains unknown, gene disruption studies have revealed that Cart1 plays an important role for craniofacial bone formation as well as limb development by cooperating with another homeoprotein, Alx4. In this report, we study the functional involvement of p300/CBP, coactivators with intrinsic histone acetyltransferase (HAT) activity, in the transcriptional control of Cart1. METHODS: To study the transcription activity of Cart1, a reporter construct containing a putative Cart1 binding site was transiently transfected with the expression vectors of each protein. The interaction between p300/CBP and Cart1 was investigated by glutathione S-transferase (GST) pull-down, yeast two-hybrid, and immunoprecipitation assays. In vitro acetylation assay was performed with the recombinant p300-HAT domain and Cart1 in the presence of acetyl-CoA. RESULTS AND CONCLUSIONS: p300 and CBP stimulate Cart1-dependent transcription activity, and this transactivation is inhibited by E1A and Tax, oncoproteins that suppress the activity of p300/CBP. Cart1 binds to p300 in vivo and in vitro, and this requires the homeodomain of Cart 1 and N-terminal 139 amino acids of p300. Confocal microscopy analysis shows that Cart1 recruits overexpressed and endogenous p300 to a Cart1-specific subnuclear compartment. Cart1 is acetylated in vivo and sodium butyrate and trichostatin A, histone deacetylase inhibitors, markedly enhance the transcription activity of Cart1. Deletion and mutagenesis analysis identifies the 131st lysine that locates immediately adjacent to the homeodomain as a target of p300-HAT, and a point mutation to this residue attenuates the binding affinity to p300 as well as p300-dependent transcription activity. Together, these results indicate that p300/CBP acts as a cotransactivator to Cart1 through a direct interaction and specific lysine acetylation. In addition, because 131st lysine is highly conserved in other types of homeoprotein, this lysine may be a common target for HAT of p300/CBP for these proteins.
Evidence
33:
Inferred from Physical InteractionIntAct
The tumour suppressor p53 is a transcriptional regulator whose ability to inhibit cell growth is dependent upon its transactivation function. Here we demonstrate that the transcription factor CBP, which is also implicated in cell proliferation and differentiation, acts as a p53 coactivator and potentiates its transcriptional activity. The amino-terminal activation domain of p53 interacts with the carboxy-terminal portion of the CBP protein both in vitro and in vivo. In transfected SaoS-2 cells, CBP potentiates activation of the mdm-2 gene by p53 and, reciprocally, p53 potentiates activation of a Gal4-responsive target gene by a Gal4(1-147)-CBP(1678-2441) fusion protein. A double point mutation that destroys the transactivation function of p53 also abolishes its binding to CBP and its synergistic function with CBP. The ability of p53 to interact physically and functionally with a coactivator (CBP) that has histone acetyltransferase activity and with components (TAFs) of the general transcription machinery indicates that it may have different functions in a multistep activation pathway.
Evidence
34:
Inferred from Physical InteractionUniProtKB
The basic helix-loop-helix (bHLH) transcription factor family contains key regulators of cellular proliferation and differentiation as well as the suspected oncoproteins Tal1 and Lyl1. Tal1 and Lyl1 are aberrantly over-expressed in leukemia as a result of chromosomal translocations, or other genetic or epigenetic events. Protein-protein and protein-DNA interactions described so far are mediated by their highly homologous bHLH domains, while little is known about the function of other protein domains. Hetero-dimers of Tal1 and Lyl1 with E2A or HEB, decrease the rate of E2A or HEB homo-dimer formation and are poor activators of transcription. In vitro, these hetero-dimers also recognize different binding sites from homo-dimer complexes, which may also lead to inappropriate activation or repression of promoters in vivo. Both mechanisms are thought to contribute to the oncogenic potential of Tal1 and Lyl1. Despite their bHLH structural similarity, accumulating evidence suggests that Tal1 and Lyl1 target different genes. This raises the possibility that domains flanking the bHLH region, which are distinct in the two proteins, may participate in target recognition. Here we report that CREB1, a widely-expressed transcription factor and a suspected oncogene in acute myelogenous leukemia (AML) was identified as a binding partner for Lyl1 but not for Tal1. The interaction between Lyl1 and CREB1 involves the N terminal domain of Lyl1 and the Q2 and KID domains of CREB1. The histone acetyl-transferases p300 and CBP are recruited to these complexes in the absence of CREB1 Ser 133 phosphorylation. In the Id1 promoter, Lyl1 complexes direct transcriptional activation. We also found that in addition to Id1, over-expressed Lyl1 can activate other CREB1 target promoters such as Id3, cyclin D3, Brca1, Btg2 and Egr1. Moreover, approximately 50% of all gene promoters identified by ChIP-chip experiments were jointly occupied by CREB1 and Lyl1, further strengthening the association of Lyl1 with Cre binding sites. Given the newly recognized importance of CREB1 in AML, the ability of Lyl1 to modulate promoter responses to CREB1 suggests that it plays a role in the malignant phenotype by occupying different promoters than Tal1.
Evidence
35:
Inferred from Physical InteractionIntAct
Vascular endothelial growth factors (VEGFs) are crucial regulators of angiogenesis and vasculogenesis. The autocrine VEGF signaling is required for maintaining the homeostasis of vasculature. Dysregulation of angiogenesis is implicated in the development of many human cancers, especially in clear-cell renal cell carcinoma (ccRCC), a highly vascularized tumor. Meanwhile, antiangiogenesis has become a mainstay in the treatment of human cancers. In this study, we analyzed the functional roles of RKTG (Raf Kinase Trapping to Golgi), a negative regulator of mitogen-activated protein kinase (Raf/MEK/ERK) signaling, by sequestration of Raf kinase to the Golgi apparatus, in angiogenesis and ccRCC. Through a series of in vitro and in vivo experiments, we found that RKTG has a negative effect on cell proliferation, migration, sprouting and angiogenesis of endothelial cells. RKTG, by suppressing mitogen-activated protein kinase signaling, negatively regulates the transactivation activity of hypoxia-inducible factor 1α (HIF-1α) by inhibiting formation of HIF-1α/p300 complex and suppressing VEGF transcription, thereby reducing hypoxia-induced VEGF production. The expression level of RKTG is significantly downregulated in clinical ccRCC tumor samples, with an inverse correlation with VEGF expression level. These results highlight the functional roles of RKTG and its regulated Raf/ERK/MEK signaling cascade in angiogenesis and autocrine VEGF signaling. In addition, this study indicates that RKTG is likely implicated in the development of ccRCC through its regulation on angiogenesis.
Evidence
36:
Inferred from Physical InteractionIntAct
The activation of the tumor suppressor p53 facilitates the cellular response to genotoxic stress; however, the p53 response can only be executed if its interaction with its inhibitor Mdm2 is abolished. There have been conflicting reports on the question of whether p53 posttranslational modifications, such as phosphorylation or acetylation, are essential or only play a subtle, fine-tuning role in the p53 response. Thus, it remains unclear whether p53 modification is absolutely required for its activation. We have now identified all major acetylation sites of p53. Although unacetylated p53 retains its ability to induce the p53-Mdm2 feedback loop, loss of acetylation completely abolishes p53-dependent growth arrest and apoptosis. Notably, acetylation of p53 abrogates Mdm2-mediated repression by blocking the recruitment of Mdm2 to p53-responsive promoters, which leads to p53 activation independent of its phosphorylation status. Our study identifies p53 acetylation as an indispensable event that destabilizes the p53-Mdm2 interaction and enables the p53-mediated stress response.
Erratum in:
Cell. 133(7), 1290 (2008 Jun 27)
Evidence
37:
Inferred from Physical InteractionUniProtKB
CITED1 is the founding member of the CITED family of cofactors that are involved in regulating a wide variety of CBP/p300-dependent transcriptional responses. In the present study, we show that the phosphorylation status of CITED1 changes during the cell cycle and affects its transcriptional cofactor activity. Tryptic mapping and mutagenesis studies identified five phosphorylated serine residues in CITED1. Phosphorylation of these residues did not affect CRM1-dependent nuclear export, but did decrease CITED1 binding to p300 and inhibited CITED1-dependent transactivation of Smad4 and p300. These results suggest that CITED1 functions as a cell cycle-dependent transcriptional cofactor whose activity is regulated by phosphorylation.
Evidence
38:
Inferred from Physical InteractionUniProtKB
The FOXO (Forkhead box class O) subgroup of forkhead transcription factors controls the expression of many genes involved in fundamental cellular processes. Until recently, studies conducted on posttranslational modifications of Forkhead proteins were restricted to their phosphorylation. In this report, we show that the coactivator p300 directly acetylates lysines in the carboxyl-terminal region of Foxo1 in vivo and in vitro, and potently stimulates Foxo1-induced transcription of IGF-binding protein-1 in transient transfection experiments. The intrinsic acetyltransferase activity of p300 is required for both activities. Our results suggest that acetylation of Foxo1 by p300 is responsible, at least in part, for its increased transactivation potency, although acetylation of histones cannot be excluded. Insulin, the major negative regulator of Foxo1-stimulated transcription, potently enhances p300 acetylation of Foxo1. Three consensus protein kinase B/Akt phosphorylation sites whose phosphorylation is stimulated by insulin are required for insulin-induced acetylation of Foxo1. In contrast to its importance in regulating the transcriptional activity of Foxo1 in the absence of insulin, acetylation plays only a minor role compared with phosphorylation in insulin inhibition of Foxo1 transcriptional activity.
Evidence
39:
Inferred from Physical InteractionUniProtKB
Recruitment of p300/CBP by the hypoxia-inducible factor, HIF-1, is essential for the transcriptional response to hypoxia and requires an interaction between the p300/CBP CH1 region and HIF-1alpha. A new p300-CH1 interacting protein, p35srj, has been identified and cloned. p35srj is an alternatively spliced isoform of MRG1, a human protein of unknown function. Virtually all endogenous p35srj is bound to p300/CBP in vivo, and it inhibits HIF-1 transactivation by blocking the HIF-1alpha/p300 CH1 interaction. p35srj did not affect transactivation by transcription factors that bind p300/CBP outside the CH1 region. Endogenous p35srj is up-regulated markedly by the HIF-1 activators hypoxia or deferoxamine, suggesting that it could operate in a negative-feedback loop. In keeping with this notion, a p300 CH1 mutant domain, defective in HIF-1 but not p35srj binding, enhanced endogenous HIF-1 function. In hypoxic cells, p35srj may regulate HIF-1 transactivation by controlling access of HIF-1alpha to p300/CBP, and may keep a significant portion of p300/CBP available for interaction with other transcription factors by partially sequestering and functionally compartmentalizing cellular p300/CBP.
Evidence
40:
Inferred from Physical InteractionUniProtKB
The proto-oncoprotein c-Myc functions as a transcriptional regulator that controls different aspects of cell behavior, including proliferation, differentiation, and apoptosis. In addition, Myc proteins have the potential to transform cells and are deregulated in the majority of human cancers. Several Myc-interacting factors have been described that mediate part of Myc's functions in the control of cell behavior. Here, we describe the isolation of a novel 150 kDa protein, designated PARP-10, that interacts with Myc. PARP-10 possesses domains with homology to RNA recognition motifs and to poly(ADP-ribose) polymerases (PARP). Molecular modeling and biochemical analysis define a PARP domain that is capable of ADP-ribosylating PARP-10 itself and core histones, but neither Myc nor Max. PARP-10 is localized to the nuclear and cytoplasmic compartments that is controlled at least in part by a Leu-rich nuclear export sequence (NES). Functionally, PARP-10 inhibits c-Myc- and E1A-mediated cotransformation of rat embryo fibroblasts, a function that is independent of PARP activity but that depends on a functional NES. Together, our findings define a novel PARP enzyme involved in the control of cell proliferation.
Evidence
41:
Inferred from Physical InteractionIntAct
Variations in intracellular levels of p53 regulate many cellular functions and determine tumor susceptibility. Major mechanisms modulating p53 levels include phosphorylation and interaction of p53 with specific ubiquitin ligases that promote its degradation. N-terminal phosphorylation regulates the interaction of p53 with several regulatory molecules. Vaccinia-related kinase 1 (VRK1) is the prototype of a new Ser-Thr kinase family in the human kinome. VRK1 is located in the nucleus outside the nucleolus. Overexpression of VRK1 increases the stability of p53 by a posttranslational mechanism leading to its accumulation by a mechanism independent of the Chk2 kinase. Catalytically inactive VRK1 protein (a K179E mutant) does not induce p53 accumulation. VRK1 phosphorylates human p53 in Thr18 and disrupts p53-Mdm2 interaction in vitro, although a significant decrease in p53 ubiquitination by Mdm2 in vivo was not detected. VRK1 kinase does not phosphorylate Mdm2. VRK1-mediated p53 stabilization was also detected in Mdm2(-/-) cells. VRK1 also has an additive effect with MdmX or p300 to stabilize p53, and p300 coactivation and acetylation of p53 is enhanced by VRK1. The p53 stabilized by VRK1 is transcriptionally active. Suppression of VRK1 expression by specific small interfering RNA provokes several defects in proliferation, situating the protein in the regulation of this process. VRK1 might function as a switch controlling the proteins that interact with p53 and thus modifying its stability and activity. We propose VRK1 as the first step in a new pathway regulating p53 activity during cell proliferation.
Evidence
42:
Inferred from Physical InteractionUniProtKB
Genetic studies have demonstrated that the basic helix-loop-helix protein E2A is an essential transcription factor in B lymphocyte lineage commitment and differentiation. However, the mechanism underlying E2A-mediated transcription regulation is not fully understood. Here, we investigated the physical and genetic interactions between E2A and co-activators histone acetyltransferases (HATs) in B cells. Gel filtration analysis of human pre-B cell nuclear extract showed that E2A co-elutes with the HATs p300, CBP, and PCAF. A co-immunoprecipitation assay further demonstrated that a fraction of endogenous E2A proteins is associated with each of the three HATs. We show that these HATs acetylate E2A in vitro, enhance E2A-mediated transcription activity, and promote nuclear retention of E2A proteins. A catalytic mutation of p300 completely abrogates the ability of p300 to acetylate E2A and to promote E2A nuclear retention in 293T cells. A breeding test between E2A heterozygous mice and p300 heterozygous mice demonstrated that these two genes interact for proper B cell development. Collectively, these results suggest that E2A and HATs collaboratively regulate B cell development.
Evidence
43:
Inferred from Physical InteractionIntAct
The SIR2 family of nicotinamide adenosine dinucleotide (NAD)-dependent deacetylases modulates diverse biological functions in different species, including longevity, apoptosis, cell cycle exit, and cellular differentiation. SIRT1, the closest mammalian ortholog of the yeast SIR2 (silent information regulator 2) gene, represses several transcription factors, including p53, NFkappaB and forkhead proteins. The p300 protein serves as a rate-limiting transcriptional cointegrator of diverse transcription factors either to activate or to repress transcription through modular subdomains. Herein, SIRT1 physically interacted with and repressed p300 transactivation, requiring the NAD-dependent deacetylase activity of SIRT1. SIRT1 repression involved the CRD1 transcriptional repression domain of p300. Two residues within the CRD1 domain (Lys-1020 and Lys-1024) were required for SIRT1 repression and served as substrates for SIRT1 deacetylation. These residues also serve as acceptor lysines for modification by the ubiquitin-like SUMO protein. The SUMO-specific protease SSP3 relieved SIRT1 repression of p300. SSP3 antagonism of SIRT1 required the SUMO-deconjugating function of SSP3. Thus, p300 serves as a deacetylase substrate for SIRT1 through a conserved SUMO consensus motif. Because p300 is a limiting transcriptional cofactor, deacetylation and repression of p300 by SIRT1 may serve an important integration point during metabolism and cellular differentiation.
Interacting selectively and non-covalently with an RNA polymerase II transcription activating factor, a protein involved in positive regulation of transcription.
Evidence
1:
Inferred from Physical InteractionBHF-UCL
OBJECTIVE: The transcription factor early growth response (EGR)-1 has been implicated as a key vascular phenotypic switch through its control of inducible transcription. EGR-1 autoregulation, and histone modification in the EGR-1 promoter, represent key mechanisms in EGR-1 control, but have not been explored. METHODS AND RESULTS: We demonstrate that EGR-1 regulates its own transcription and that this involves histone H3 phosphorylation and acetylation. EGR-1 transactivates its promoter in smooth muscle cells exposed to interleukin (IL) 1beta through a novel cis-acting element (-211/-203). PD98059, which inhibits mitogen-activated protein kinase kinase/extracellular regulated kinase (MEK/ERK) attenuates IL-1beta-inducible phosphorylation of extracellular signal-regulated kinase 1/2 and mitogen and stress-activated protein kinases 1/2; and reduces levels of phosphorylated and acetylated histone H3. Histone deacetylase inhibition enhances EGR-1 transcription in response to cytokine. Conversely, suppression of histone modification with mitogen and stress-activated protein kinase 1/2 short interfering RNA, or the histone H3 acetyltransferase inhibitor Garcinol, inhibits IL-1beta-inducible EGR-1 transcription. EGR-1 interacts with the acetyltransferase p300. Acetylated H3 and phosphorylated H3 are enriched at the promoter of EGR-1; and EGR-1 is enriched at the promoters of tissue factor and plasminogen activator inhibitor 1 in response to IL-1beta, and attenuated by PD98059, Garcinol, and mitogen and stress-activated protein kinase 1/2 short interfering RNA. CONCLUSIONS: IL-1beta induction of EGR-1 transcription involves histone H3 phosphorylation, acetylation, and autoregulation by EGR-1.
Interacting selectively and non-covalently with a activating transcription factor and also with the basal transcription machinery in order to increase the frequency, rate or extent of transcription. Cofactors generally do not bind DNA, but rather mediate protein-protein interactions between activating transcription factors and the basal transcription machinery.
Genetic studies have demonstrated that the basic helix-loop-helix protein E2A is an essential transcription factor in B lymphocyte lineage commitment and differentiation. However, the mechanism underlying E2A-mediated transcription regulation is not fully understood. Here, we investigated the physical and genetic interactions between E2A and co-activators histone acetyltransferases (HATs) in B cells. Gel filtration analysis of human pre-B cell nuclear extract showed that E2A co-elutes with the HATs p300, CBP, and PCAF. A co-immunoprecipitation assay further demonstrated that a fraction of endogenous E2A proteins is associated with each of the three HATs. We show that these HATs acetylate E2A in vitro, enhance E2A-mediated transcription activity, and promote nuclear retention of E2A proteins. A catalytic mutation of p300 completely abrogates the ability of p300 to acetylate E2A and to promote E2A nuclear retention in 293T cells. A breeding test between E2A heterozygous mice and p300 heterozygous mice demonstrated that these two genes interact for proper B cell development. Collectively, these results suggest that E2A and HATs collaboratively regulate B cell development.
The paired-like homeoprotein, Cart1, is involved in skeletal development. We describe here that the general coactivator p300/CBP controls the transcription activity of Cart1 through acetylation of a lysine residue that is highly conserved in other homeoproteins. Acetylation of this residue increases the interaction between p300/CBP and Cart1 and enhances its transcriptional activation. INTRODUCTION: Cart1 encodes a paired-like homeoprotein expressed selectively in chondrocyte lineage during embryonic development. Although its target gene remains unknown, gene disruption studies have revealed that Cart1 plays an important role for craniofacial bone formation as well as limb development by cooperating with another homeoprotein, Alx4. In this report, we study the functional involvement of p300/CBP, coactivators with intrinsic histone acetyltransferase (HAT) activity, in the transcriptional control of Cart1. METHODS: To study the transcription activity of Cart1, a reporter construct containing a putative Cart1 binding site was transiently transfected with the expression vectors of each protein. The interaction between p300/CBP and Cart1 was investigated by glutathione S-transferase (GST) pull-down, yeast two-hybrid, and immunoprecipitation assays. In vitro acetylation assay was performed with the recombinant p300-HAT domain and Cart1 in the presence of acetyl-CoA. RESULTS AND CONCLUSIONS: p300 and CBP stimulate Cart1-dependent transcription activity, and this transactivation is inhibited by E1A and Tax, oncoproteins that suppress the activity of p300/CBP. Cart1 binds to p300 in vivo and in vitro, and this requires the homeodomain of Cart 1 and N-terminal 139 amino acids of p300. Confocal microscopy analysis shows that Cart1 recruits overexpressed and endogenous p300 to a Cart1-specific subnuclear compartment. Cart1 is acetylated in vivo and sodium butyrate and trichostatin A, histone deacetylase inhibitors, markedly enhance the transcription activity of Cart1. Deletion and mutagenesis analysis identifies the 131st lysine that locates immediately adjacent to the homeodomain as a target of p300-HAT, and a point mutation to this residue attenuates the binding affinity to p300 as well as p300-dependent transcription activity. Together, these results indicate that p300/CBP acts as a cotransactivator to Cart1 through a direct interaction and specific lysine acetylation. In addition, because 131st lysine is highly conserved in other types of homeoprotein, this lysine may be a common target for HAT of p300/CBP for these proteins.
The transcriptional co-activators and histone acetyltransferases p300/CREB-binding protein (CBP) interact with CITED2, a transcription factor AP-2 (TFAP2) co-activator. p300/CBP, CITED2, and TFAP2A are essential for normal neural tube and cardiac development. Here we show that p300 and CBP co-activate TFAP2A in the presence of CITED2. TFAP2A transcriptional activity was modestly impaired in p300(+/-) and CBP(+/-) mouse embryonic fibroblasts; this was rescued by ectopic expression of p300/CBP. p300, TFAP2A, and endogenous CITED2 could be co-immunoprecipitated from transfected U2-OS cells indicating that they can interact physically in vivo. CITED2 interacted with the dimerization domain of TFAP2C, which is highly conserved in TFAP2A/B. In mammalian two-hybrid experiments, full-length p300 and TFAP2A interacted only when CITED2 was co-transfected. N-terminal residues of TFAP2A, containing the transactivation domain, are both necessary and sufficient for interaction with p300, and this interaction was independent of CITED2. Consistent with this, N-terminal residues of TFAP2A were required for p300- and CITED2-dependent co-activation. A histone acetyltransferase-deficient p300 mutant (D1399Y) did not co-activate TFAP2A and did not affect the expression or cellular localization of TFAP2A or CITED2. In mammalian two-hybrid experiments p300D1399Y failed to interact with TFAP2A, explaining, at least in part, its failure to function as a co-activator. Our results suggest a model wherein interactions among TFAP2A, CITED2, and p300/CBP are necessary for TFAP2A-mediated transcriptional activation and for normal neural tube and cardiac development.
Androgen antagonists or androgen deprivation are the primary therapeutic modalities for the treatment of prostate cancer. Invariably, however, the disease becomes progressive and unresponsive to androgen ablation therapy (hormone refractory). The molecular mechanisms by which androgen antagonists inhibit prostate cancer proliferation are not fully defined. In this study, we identify two molecules which are required for effective prostate cancer cell responsiveness to androgen antagonists. We establish that androgen receptor (AR)-dependent transcriptional suppression by androgen antagonists requires the tumor suppressor prohibitin. This requirement for prohibitin was demonstrated using structurally-distinct androgen antagonists, stable and transient knockdown of prohibitin and transfected and endogenous AR-responsive genes. The SWI-SNF complex core ATPase BRG1, but not its closely-related counterpart ATPase BRM, is required for this repressive action of prohibitin on AR-responsive promoters. Androgen antagonists induce recruitment of prohibitin and BRG1 to endogenous AR-responsive promoters and induce a physical association between AR and prohibitin and BRG1. The recruitment of prohibitin to endogenous AR-responsive promoters is dependent upon antagonist-bound AR. Prohibitin binding in the prostate-specific antigen (PSA) promoter results in the recruitment of BRG1 and the dissociation of p300 from the PSA promoter. These findings suggest that prohibitin may function through BRG1-mediated local chromatin remodeling activity and the removal of p300-mediated acetylation to produce androgen antagonist-mediated transcriptional repression. Furthermore, in addition to its necessary role in AR-mediated transcriptional repression, we demonstrate that prohibitin is required for full and efficient androgen antagonist-mediated growth suppression of prostate cancer cells.
Tat is a critical viral transactivator essential for human immunodeficiency virus (HIV) gene expression. Activation involves binding to an RNA stem-loop structure and recruitment of the positive transcription elongation factor b. Tat also induces the remodeling of a single nucleosome in the HIV promoter. However, the mechanism of this remodeling has remained unclear. Knockdown of INI-1 and BRG-1, two components of the SWI/SNF chromatin-remodeling complex, suppressed Tat-mediated transactivation. Cells lacking INI-1 (G401 and MON) or BRG-1 (C33A) exhibited defective transactivation by Tat that was restored upon INI-1 and BRG-1 expression, respectively. Tat was co-immunoprecipitated with several SWI/SNF subunits, including INI-1, BRG-1, and beta-actin. The SWI/SNF complex interacted with the integrated HIV promoter in a Tat-dependent manner. We also found that INI-1 and BRG-1 synergized with the p300 acetyltransferase to activate the HIV promoter. This synergism depended on the acetyltransferase activity of p300 and on Tat Lys(50) and Lys(51). In conclusion, Tat-mediated activation of the HIV promoter requires the SWI/SNF complex in synergy with the coactivator p300.
Homeostasis under hypoxic conditions is maintained through a coordinated transcriptional response mediated by the hypoxia-inducible factor (HIF) pathway and requires coactivation by the CBP and p300 transcriptional coactivators. Through a target-based high-throughput screen, we identified chetomin as a disrupter of HIF binding to p300. At a molecular level, chetomin disrupts the structure of the CH1 domain of p300 and precludes its interaction with HIF, thereby attenuating hypoxia-inducible transcription. Systemic administration of chetomin inhibited hypoxia-inducible transcription within tumors and inhibited tumor growth. These results demonstrate a therapeutic window for pharmacological attenuation of HIF activity and further establish the feasibility of disrupting a signal transduction pathway by targeting the function of a transcriptional coactivator with a small molecule.
Evidence
2:
Inferred from Physical InteractionUniProtKB
The human CYP11A1 gene is expressed specifically in steroidogenic tissues and encodes cytochrome P450scc, which catalyzes the first step in steroid synthesis. A region of the 5'-flanking DNA of the gene from nucleotides -155 to -131 (-155/-131) is shown to activate transcription in steroidogenic human placental JEG-3 (1) and adrenal NCI-H295 cells. Using this region of the gene as probe, a cDNA clone of 4.4 kilobase pairs was isolated by screening JEG-3 cell and human placental cDNA expression libraries. The open reading frame encodes three zinc fingers of the C(2)H(2) subtype, and separate regions rich in glutamate, proline, and glutamine, which are indicative of a DNA-binding protein involved in gene transcription. Expression of the cDNA in vitro and in HeLa cells yields a protein of 132 kDa, which concurs with the predicted size. Northern blot analysis demonstrate expression of two TReP-132 transcripts of 4.4 and 7.5 kilobase pairs in the thymus, adrenal cortex, and testis; and expression is also found in the steroidogenic JEG-3, NCI-H295, and MCF-7 cell lines. Immunocytochemistry analysis demonstrates localization of the HA-tagged TReP-132 protein in the nucleus. The expression of exogenous TReP-132 in HeLa cells was demonstrated to interact with the -155/-131 region in bandshift analysis. Transfection of the cDNA in placental JEG-3 and adrenal NCI-H295 cells increases expression of a reporter construct controlled by the P450scc gene 5'-flanking region from nucleotides -1676 to +49. Moreover, a chimeric protein generated by fusion of TReP-132 with the Gal4 DNA-binding domain was able to significantly increase promoter activity of a reporter construct via Gal4-binding sites upstream of the E1b minimal promoter. Coexpression of CREB-binding protein (CBP)/p300 with TReP-132 has an additive effect on promoter activity, and the proteins were demonstrated to interact physically. Thus, these results together indicate the isolation of a novel zinc-finger transcriptional regulating protein of 132 kDa (TReP-132) involved in the regulation of P450scc gene expression.
Evidence
3:
Inferred from Physical InteractionUniProtKB
The adenoviral oncoprotein E1A induces progression through the cell cycle by binding to the products of the p300/CBP and retinoblastoma gene families. A new cellular p300/CBP-associated factor (P/CAF) having intrinsic histone acetylase activity has been identified that competes with E1A. Exogenous expression of P/CAF in HeLa cells inhibits cell-cycle progression and counteracts the mitogenic activity of E1A. E1A disturbs the normal cellular interaction between p300/CBP and its associated histone acetylase.
In response to DNA damage, p53 undergoes post-translational modifications (including acetylation) that are critical for its transcriptional activity. However, the mechanism by which p53 acetylation is regulated is still unclear. Here, we describe an essential role for HLA-B-associated transcript 3 (Bat3)/Scythe in controlling the acetylation of p53 required for DNA damage responses. Depletion of Bat3 from human and mouse cells markedly impairs p53-mediated transactivation of its target genes Puma and p21. Although DNA damage-induced phosphorylation, stabilization, and nuclear accumulation of p53 are not significantly affected by Bat3 depletion, p53 acetylation is almost completely abolished. Bat3 forms a complex with p300, and an increased amount of Bat3 enhances the recruitment of p53 to p300 and facilitates subsequent p53 acetylation. In contrast, Bat3-depleted cells show reduced p53-p300 complex formation and decreased p53 acetylation. Furthermore, consistent with our in vitro findings, thymocytes from Bat3-deficient mice exhibit reduced induction of puma and p21, and are resistant to DNA damage-induced apoptosis in vivo. Our data indicate that Bat3 is a novel and essential regulator of p53-mediated responses to genotoxic stress, and that Bat3 controls DNA damage-induced acetylation of p53.
A programmed cell death process which begins when a cell receives an internal (e.g. DNA damage) or external signal (e.g. an extracellular death ligand), and proceeds through a series of biochemical events (signaling pathways) which typically lead to rounding-up of the cell, retraction of pseudopodes, reduction of cellular volume (pyknosis), chromatin condensation, nuclear fragmentation (karyorrhexis), plasma membrane blebbing and fragmentation of the cell into apoptotic bodies. The process ends when the cell has died. The process is divided into a signaling pathway phase, and an execution phase, which is triggered by the former.
Evidence
1:
Inferred from Mutant PhenotypeUniProtKB
The adenovirus E1A and SV40 large-T-antigen oncoproteins bind to members of the p300/CBP transcriptional coactivator family. Binding of p300/CBP is implicated in the transforming mechanisms of E1A and T-antigen oncoproteins. A common region of the T antigen is critical for binding both p300/CBP and the tumour suppressor p53, suggesting a link between the functions of p53 and p300. Here we report that p300/CBP binds to p53 in the absence of viral oncoproteins, and that p300 and p53 colocalize within the nucleus and coexist in a stable DNA-binding complex. Consistent with its ability to bind to p300, E1A disrupted functions mediated by p53. It reduced p53-mediated activation of the p21 and bax promoters, and suppressed p53-induced cell-cycle arrest and apoptosis. We conclude that members of the p300/CBP family are transcriptional adaptors for p53, modulating its checkpoint function in the G1 phase of the cell cycle and its induction of apoptosis. Disruption of p300/p53-dependent growth control may be part of the mechanism by which E1A induces cell transformation. These results help to explain how p53 mediates growth and checkpoint control, and how members of the p300/CBP family affect progression from G1 to the S phase of the cell cycle.
The progression of biochemical and morphological phases and events that occur in a cell during successive cell replication or nuclear replication events. Canonically, the cell cycle comprises the replication and segregation of genetic material followed by the division of the cell, but in endocycles or syncytial cells nuclear replication or nuclear division may not be followed by cell division.
The process whose specific outcome is the progression of the heart over time, from its formation to the mature structure. The heart is a hollow, muscular organ, which, by contracting rhythmically, keeps up the circulation of the blood.
Chromatin modification is considered to be a fundamental mechanism of regulating gene expression to generate coordinated responses to environmental changes, however, whether it could be directly regulated by signals mediated by G protein-coupled receptors (GPCRs), the largest surface receptor family, is not known. Here, we show that stimulation of delta-opioid receptor, a member of the GPCR family, induces nuclear translocation of beta-arrestin 1 (betaarr1), which was previously known as a cytosolic regulator and scaffold of GPCR signaling. In response to receptor activation, betaarr1 translocates to the nucleus and is selectively enriched at specific promoters such as that of p27 and c-fos, where it facilitates the recruitment of histone acetyltransferase p300, resulting in enhanced local histone H4 acetylation and transcription of these genes. Our results reveal a novel function of betaarr1 as a cytoplasm-nucleus messenger in GPCR signaling and elucidate an epigenetic mechanism for direct GPCR signaling from cell membrane to the nucleus through signal-dependent histone modification.
In response to DNA damage, p53 undergoes post-translational modifications (including acetylation) that are critical for its transcriptional activity. However, the mechanism by which p53 acetylation is regulated is still unclear. Here, we describe an essential role for HLA-B-associated transcript 3 (Bat3)/Scythe in controlling the acetylation of p53 required for DNA damage responses. Depletion of Bat3 from human and mouse cells markedly impairs p53-mediated transactivation of its target genes Puma and p21. Although DNA damage-induced phosphorylation, stabilization, and nuclear accumulation of p53 are not significantly affected by Bat3 depletion, p53 acetylation is almost completely abolished. Bat3 forms a complex with p300, and an increased amount of Bat3 enhances the recruitment of p53 to p300 and facilitates subsequent p53 acetylation. In contrast, Bat3-depleted cells show reduced p53-p300 complex formation and decreased p53 acetylation. Furthermore, consistent with our in vitro findings, thymocytes from Bat3-deficient mice exhibit reduced induction of puma and p21, and are resistant to DNA damage-induced apoptosis in vivo. Our data indicate that Bat3 is a novel and essential regulator of p53-mediated responses to genotoxic stress, and that Bat3 controls DNA damage-induced acetylation of p53.
Intrinsic apoptotic signaling pathway in response to DNA damage by p53 class mediatordefinition[GO:0042771]
A series of molecular signals in which an intracellular signal is conveyed to trigger the apoptotic death of a cell. The pathway is induced by the cell cycle regulator phosphoprotein p53, or an equivalent protein, in response to the detection of DNA damage, and ends when the execution phase of apoptosis is triggered.
In response to DNA damage, p53 undergoes post-translational modifications (including acetylation) that are critical for its transcriptional activity. However, the mechanism by which p53 acetylation is regulated is still unclear. Here, we describe an essential role for HLA-B-associated transcript 3 (Bat3)/Scythe in controlling the acetylation of p53 required for DNA damage responses. Depletion of Bat3 from human and mouse cells markedly impairs p53-mediated transactivation of its target genes Puma and p21. Although DNA damage-induced phosphorylation, stabilization, and nuclear accumulation of p53 are not significantly affected by Bat3 depletion, p53 acetylation is almost completely abolished. Bat3 forms a complex with p300, and an increased amount of Bat3 enhances the recruitment of p53 to p300 and facilitates subsequent p53 acetylation. In contrast, Bat3-depleted cells show reduced p53-p300 complex formation and decreased p53 acetylation. Furthermore, consistent with our in vitro findings, thymocytes from Bat3-deficient mice exhibit reduced induction of puma and p21, and are resistant to DNA damage-induced apoptosis in vivo. Our data indicate that Bat3 is a novel and essential regulator of p53-mediated responses to genotoxic stress, and that Bat3 controls DNA damage-induced acetylation of p53.
The process whose specific outcome is the progression of the lung over time, from its formation to the mature structure. In all air-breathing vertebrates the lungs are developed from the ventral wall of the oesophagus as a pouch which divides into two sacs. In amphibians and many reptiles the lungs retain very nearly this primitive sac-like character, but in the higher forms the connection with the esophagus becomes elongated into the windpipe and the inner walls of the sacs become more and more divided, until, in the mammals, the air spaces become minutely divided into tubes ending in small air cells, in the walls of which the blood circulates in a fine network of capillaries. In mammals the lungs are more or less divided into lobes, and each lung occupies a separate cavity in the thorax.
Genetic studies have demonstrated that the basic helix-loop-helix protein E2A is an essential transcription factor in B lymphocyte lineage commitment and differentiation. However, the mechanism underlying E2A-mediated transcription regulation is not fully understood. Here, we investigated the physical and genetic interactions between E2A and co-activators histone acetyltransferases (HATs) in B cells. Gel filtration analysis of human pre-B cell nuclear extract showed that E2A co-elutes with the HATs p300, CBP, and PCAF. A co-immunoprecipitation assay further demonstrated that a fraction of endogenous E2A proteins is associated with each of the three HATs. We show that these HATs acetylate E2A in vitro, enhance E2A-mediated transcription activity, and promote nuclear retention of E2A proteins. A catalytic mutation of p300 completely abrogates the ability of p300 to acetylate E2A and to promote E2A nuclear retention in 293T cells. A breeding test between E2A heterozygous mice and p300 heterozygous mice demonstrated that these two genes interact for proper B cell development. Collectively, these results suggest that E2A and HATs collaboratively regulate B cell development.
The transcriptional coactivators p300 and CREB binding protein (CBP) are important regulators of the cell cycle, differentiation, and tumorigenesis. Both p300 and CBP are targeted by viral oncoproteins, are mutated in certain forms of cancer, are phosphorylated in a cell cycle-dependent manner, interact with transcription factors such as p53 and E2F, and can be found complexed with cyclinE-Cdk2 in vivo. Moreover, p300-deficient cells show defects in proliferation. Here we demonstrate that transcriptional activation by both p300 and CBP is stimulated by coexpression of the cyclin-dependent kinase inhibitor p21(WAF/CIP1). Significantly this stimulation is independent of both the inherent histone acetyltransferase (HAT) activity of p300 and CBP and of the previously reported carboxyl-terminal binding site for cyclinE-Cdk2. Rather, we describe a previously uncharacterized transcriptional repression domain (CRD1) within p300. p300 transactivation is stimulated through derepression of CRD1 by p21. Significantly p21 regulation of CRD1 is dependent on the nature of the core promoter. We suggest that CRD1 provides a novel mechanism through which p300 and CBP can switch activities between the promoters of genes that stimulate growth and those that enhance cell cycle arrest.
The cytokines LIF (leukemia inhibitory factor) and BMP2 (bone morphogenetic protein-2) signal through different receptors and transcription factors, namely STATs (signal transducers and activators of transcription) and Smads. LIF and BMP2 were found to act in synergy on primary fetal neural progenitor cells to induce astrocytes. The transcriptional coactivator p300 interacts physically with STAT3 at its amino terminus in a cytokine stimulation-independent manner, and with Smad1 at its carboxyl terminus in a cytokine stimulation-dependent manner. The formation of a complex between STAT3 and Smad1, bridged by p300, is involved in the cooperative signaling of LIF and BMP2 and the subsequent induction of astrocytes from neural progenitors.
Morphogenesis of an organ. An organ is defined as a tissue or set of tissues that work together to perform a specific function or functions. Morphogenesis is the process in which anatomical structures are generated and organized. Organs are commonly observed as visibly distinct structures, but may also exist as loosely associated clusters of cells that work together to perform a specific function or functions.
Any process is which a host organism activates or increases the frequency, rate or extent of viral transcription, the synthesis of either RNA on a template of DNA or DNA on a template of RNA.
Tat is a critical viral transactivator essential for human immunodeficiency virus (HIV) gene expression. Activation involves binding to an RNA stem-loop structure and recruitment of the positive transcription elongation factor b. Tat also induces the remodeling of a single nucleosome in the HIV promoter. However, the mechanism of this remodeling has remained unclear. Knockdown of INI-1 and BRG-1, two components of the SWI/SNF chromatin-remodeling complex, suppressed Tat-mediated transactivation. Cells lacking INI-1 (G401 and MON) or BRG-1 (C33A) exhibited defective transactivation by Tat that was restored upon INI-1 and BRG-1 expression, respectively. Tat was co-immunoprecipitated with several SWI/SNF subunits, including INI-1, BRG-1, and beta-actin. The SWI/SNF complex interacted with the integrated HIV promoter in a Tat-dependent manner. We also found that INI-1 and BRG-1 synergized with the p300 acetyltransferase to activate the HIV promoter. This synergism depended on the acetyltransferase activity of p300 and on Tat Lys(50) and Lys(51). In conclusion, Tat-mediated activation of the HIV promoter requires the SWI/SNF complex in synergy with the coactivator p300.
Any process that activates or increases the frequency, rate or extent of protein binding.
IEAOrtholog Compara
Positive regulation of sequence-specific DNA binding transcription factor activitydefinition[GO:0051091]
Any process that activates or increases the frequency, rate or extent of activity of a transcription factor, any factor involved in the initiation or regulation of transcription.
The ability of p53 to function as a transcription factor is instrumental in facilitating the response to cellular stress, and p300/CBP proteins, which act as coactivators for diverse transcription factors, participate in regulating p53 activity. We report a novel cofactor for p300 that facilitates the p53 response by augmenting p53-dependent transcription and apoptosis. JMY and p300 associate in physiological conditions, and, during the cellular stress response, the p300/JMY complex is recruited to activated p53. The bax gene is efficiently activated by JMY, and protein isoforms that arise through alternative splicing alter the functional outcome of the p53 response. The results provide compelling evidence that the p300/JMY coactivator complex plays a central role in facilitating the p53 response.
The transcriptional co-activators and histone acetyltransferases p300/CREB-binding protein (CBP) interact with CITED2, a transcription factor AP-2 (TFAP2) co-activator. p300/CBP, CITED2, and TFAP2A are essential for normal neural tube and cardiac development. Here we show that p300 and CBP co-activate TFAP2A in the presence of CITED2. TFAP2A transcriptional activity was modestly impaired in p300(+/-) and CBP(+/-) mouse embryonic fibroblasts; this was rescued by ectopic expression of p300/CBP. p300, TFAP2A, and endogenous CITED2 could be co-immunoprecipitated from transfected U2-OS cells indicating that they can interact physically in vivo. CITED2 interacted with the dimerization domain of TFAP2C, which is highly conserved in TFAP2A/B. In mammalian two-hybrid experiments, full-length p300 and TFAP2A interacted only when CITED2 was co-transfected. N-terminal residues of TFAP2A, containing the transactivation domain, are both necessary and sufficient for interaction with p300, and this interaction was independent of CITED2. Consistent with this, N-terminal residues of TFAP2A were required for p300- and CITED2-dependent co-activation. A histone acetyltransferase-deficient p300 mutant (D1399Y) did not co-activate TFAP2A and did not affect the expression or cellular localization of TFAP2A or CITED2. In mammalian two-hybrid experiments p300D1399Y failed to interact with TFAP2A, explaining, at least in part, its failure to function as a co-activator. Our results suggest a model wherein interactions among TFAP2A, CITED2, and p300/CBP are necessary for TFAP2A-mediated transcriptional activation and for normal neural tube and cardiac development.
Evidence
2:
Inferred from Mutant PhenotypeUniProtKB
Chromatin modification is considered to be a fundamental mechanism of regulating gene expression to generate coordinated responses to environmental changes, however, whether it could be directly regulated by signals mediated by G protein-coupled receptors (GPCRs), the largest surface receptor family, is not known. Here, we show that stimulation of delta-opioid receptor, a member of the GPCR family, induces nuclear translocation of beta-arrestin 1 (betaarr1), which was previously known as a cytosolic regulator and scaffold of GPCR signaling. In response to receptor activation, betaarr1 translocates to the nucleus and is selectively enriched at specific promoters such as that of p27 and c-fos, where it facilitates the recruitment of histone acetyltransferase p300, resulting in enhanced local histone H4 acetylation and transcription of these genes. Our results reveal a novel function of betaarr1 as a cytoplasm-nucleus messenger in GPCR signaling and elucidate an epigenetic mechanism for direct GPCR signaling from cell membrane to the nucleus through signal-dependent histone modification.
Androgen antagonists or androgen deprivation are the primary therapeutic modalities for the treatment of prostate cancer. Invariably, however, the disease becomes progressive and unresponsive to androgen ablation therapy (hormone refractory). The molecular mechanisms by which androgen antagonists inhibit prostate cancer proliferation are not fully defined. In this study, we identify two molecules which are required for effective prostate cancer cell responsiveness to androgen antagonists. We establish that androgen receptor (AR)-dependent transcriptional suppression by androgen antagonists requires the tumor suppressor prohibitin. This requirement for prohibitin was demonstrated using structurally-distinct androgen antagonists, stable and transient knockdown of prohibitin and transfected and endogenous AR-responsive genes. The SWI-SNF complex core ATPase BRG1, but not its closely-related counterpart ATPase BRM, is required for this repressive action of prohibitin on AR-responsive promoters. Androgen antagonists induce recruitment of prohibitin and BRG1 to endogenous AR-responsive promoters and induce a physical association between AR and prohibitin and BRG1. The recruitment of prohibitin to endogenous AR-responsive promoters is dependent upon antagonist-bound AR. Prohibitin binding in the prostate-specific antigen (PSA) promoter results in the recruitment of BRG1 and the dissociation of p300 from the PSA promoter. These findings suggest that prohibitin may function through BRG1-mediated local chromatin remodeling activity and the removal of p300-mediated acetylation to produce androgen antagonist-mediated transcriptional repression. Furthermore, in addition to its necessary role in AR-mediated transcriptional repression, we demonstrate that prohibitin is required for full and efficient androgen antagonist-mediated growth suppression of prostate cancer cells.
Homeostasis under hypoxic conditions is maintained through a coordinated transcriptional response mediated by the hypoxia-inducible factor (HIF) pathway and requires coactivation by the CBP and p300 transcriptional coactivators. Through a target-based high-throughput screen, we identified chetomin as a disrupter of HIF binding to p300. At a molecular level, chetomin disrupts the structure of the CH1 domain of p300 and precludes its interaction with HIF, thereby attenuating hypoxia-inducible transcription. Systemic administration of chetomin inhibited hypoxia-inducible transcription within tumors and inhibited tumor growth. These results demonstrate a therapeutic window for pharmacological attenuation of HIF activity and further establish the feasibility of disrupting a signal transduction pathway by targeting the function of a transcriptional coactivator with a small molecule.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of stimulus by an estrogen, C18 steroid hormones that can stimulate the development of female sexual characteristics.
CITED1, a CBP/p300-binding nuclear protein that does not bind directly to DNA, is a transcriptional coregulator. Here, we show evidence that CITED1 functions as a selective coactivator for estrogen-dependent transcription. When transfected, CITED1 enhanced transcriptional activation by the ligand-binding/AF2 domain of both estrogen receptor-alpha (ERalpha) and ERbeta in an estrogen-dependent manner, but it affected transcriptional activities of other nuclear receptors only marginally. CITED1 bound directly to ERalpha in an estrogen-dependent manner through its transactivating domain, and this binding activity was separable from its p300-binding activity. CITED1 was strongly expressed in nulliparous mouse mammary epithelial cells and, when expressed in ER-positive MCF-7 breast cancer cells by transduction, exogenous CITED1 enhanced sensitivity of MCF-7 cells to estrogen, stabilizing the estrogen-dependent interaction between p300 and ERalpha. The estrogen-induced expression of the transforming growth factor-alpha (TGF-alpha) mRNA transcript was enhanced in the CITED1-expressing MCF-7 cells, whereas estrogen-induced expression of the mRNA transcripts for progesterone receptor or pS2 was not affected. Chromatin immunoprecipitation assay revealed that endogenous CITED1 is recruited to the chromosomal TGF-alpha promoter in MCF-7 cells in an estrogen-dependent manner but not to the pS2 promoter. These results suggest that CITED1 may play roles in regulation of estrogen sensitivity in a gene-specific manner.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a stimulus indicating lowered oxygen tension. Hypoxia, defined as a decline in O2 levels below normoxic levels of 20.8 - 20.95%, results in metabolic adaptation at both the cellular and organismal level.
Homeostasis under hypoxic conditions is maintained through a coordinated transcriptional response mediated by the hypoxia-inducible factor (HIF) pathway and requires coactivation by the CBP and p300 transcriptional coactivators. Through a target-based high-throughput screen, we identified chetomin as a disrupter of HIF binding to p300. At a molecular level, chetomin disrupts the structure of the CH1 domain of p300 and precludes its interaction with HIF, thereby attenuating hypoxia-inducible transcription. Systemic administration of chetomin inhibited hypoxia-inducible transcription within tumors and inhibited tumor growth. These results demonstrate a therapeutic window for pharmacological attenuation of HIF activity and further establish the feasibility of disrupting a signal transduction pathway by targeting the function of a transcriptional coactivator with a small molecule.
Recruitment of p300/CBP by the hypoxia-inducible factor, HIF-1, is essential for the transcriptional response to hypoxia and requires an interaction between the p300/CBP CH1 region and HIF-1alpha. A new p300-CH1 interacting protein, p35srj, has been identified and cloned. p35srj is an alternatively spliced isoform of MRG1, a human protein of unknown function. Virtually all endogenous p35srj is bound to p300/CBP in vivo, and it inhibits HIF-1 transactivation by blocking the HIF-1alpha/p300 CH1 interaction. p35srj did not affect transactivation by transcription factors that bind p300/CBP outside the CH1 region. Endogenous p35srj is up-regulated markedly by the HIF-1 activators hypoxia or deferoxamine, suggesting that it could operate in a negative-feedback loop. In keeping with this notion, a p300 CH1 mutant domain, defective in HIF-1 but not p35srj binding, enhanced endogenous HIF-1 function. In hypoxic cells, p35srj may regulate HIF-1 transactivation by controlling access of HIF-1alpha to p300/CBP, and may keep a significant portion of p300/CBP available for interaction with other transcription factors by partially sequestering and functionally compartmentalizing cellular p300/CBP.
The developmental sequence of events leading to the formation of adult muscle that occurs in the anima. In vertebrate skeletal muscle the main events are: the fusion of myoblasts to form myotubes that increase in size by further fusion to them of myoblasts, the formation of myofibrils within their cytoplasm and the establishment of functional neuromuscular junctions with motor neurons. At this stage they can be regarded as mature muscle fibers.
p300/CBP is a transcriptional adaptor that integrates signals from many sequence-specific activators via direct interactions. Various cellular and viral factors target p300/CBP to modulate transcription and/or cell cycle progression. One such factor, the cellular p300/CBP associated factor (PCAF), possesses intrinsic histone acetyltransferase activity. Here, we demonstrate that p300/CBP is not only a transcriptional adaptor but also a histone acetyltransferase. p300/CBP represents a novel class of acetyltransferases in that it does not have the conserved motif found among various other acetyltransferases. p300/CBP acetylates all four core histones in nucleosomes. These observations suggest that p300/CBP acetylates nucleosomes in concert with PCAF.
Protein involved in the complex series of events by which the cell duplicates its contents and divides into two. The eukaryotic cell cycle can be divided in four phases termed G1 (first gap period), S (synthesis, phase during which the DNA is replicated), G2 (second gap period) and M (mitosis). The prokaryotic cell cycle typically involves a period of growth followed by DNA replication, partition of chromosomes, formation of septum and division into two similar or identical daughter cells.
Viral protein involved in a direct and specific interaction with a host macromolecule. Viruses interact with many cellular pathways to achieve their replication cycle. Entry into the host cell, transport to the viral replication sites or viral budding are all steps that require interaction between the host and the virus. Additionally, the evasion from the host immune response requires a lot of viral proteins to associate with and inhibit cellular proteins with antiviral functions.
Protein involved in the transfer of genetic information from DNA to messenger RNA (mRNA) by DNA-directed RNA polymerase. In the case of some RNA viruses, protein involved in the transfer of genetic information from RNA to messenger RNA (mRNA) by RNA-directed RNA polymerase.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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