Immediate-early gene. Plays an important role in embryonic development as well as in cellular growth and proliferation; its long-term silencing affects cell survival and cell cycle distribution as well as decreases CDK1 activity correlated with reduced phosphorylation of CDK1. Plays a role as a positive regulator of the sonic hedgehog pathway, acting downstream of PTCH1.
The SIL gene was discovered at the site of a cancer-associated interstitial deletion in which its promoter assumed the regulation of a second gene, SCL. The human SIL gene encodes a 1287-amino acid cytosolic protein that has been found to be highly conserved in the mouse. SIL is expressed in proliferating cells and is down-regulated when cellular proliferation ceases because of serum starvation, contact inhibition, or induction of terminal differentiation. SIL is induced within 1 h of stimulation by 20% serum in growth-arrested 3T3 cells. This induction is independent of protein synthesis because "superinduction" is observed in the presence of the protein synthesis inhibitor cyclohexamide. Thus, SIL is an immediate-early gene. Upon release from serum starvation of 3T3 fibroblasts, SIL mRNA and protein levels display a biphasic pattern during the first cell cycle. In contrast, in exponentially growing EL4 lymphoblasts, SIL mRNA is stable throughout the cell cycle, whereas SIL protein accumulates into G2 phase and then falls precipitously at the completion of the cell cycle. This pattern of cell cycle expression suggests that SIL may play an important role in cellular growth and proliferation.
SIL is an immediate-early gene that is essential for embryonic development and is implicated in T-cell leukemia-associated translocations. We now show that the Sil protein is hyperphosphorylated during mitosis or in cells blocked at prometaphase by microtubule inhibitors. Cell cycle-dependent phosphorylation of Sil is required for its interaction with Pin1, a regulator of mitosis. Point mutation of the seven (S/T)P sites between amino acids 567 and 760 reduces mitotic phosphorylation of Sil, Pin1 binding, and spindle checkpoint duration. When a phosphorylation site mutant Sil is stably expressed, the duration of the spindle checkpoint is shortened in cells challenged with taxol or nocodazole, and the cells revert to a G2-like state. This event is associated with the downregulation of the kinase activity of the Cdc2/cyclin B1 complex and the dephosphorylation of the threonine 161 on the Cdc2 subunit. Sil downregulation by plasmid-mediated RNA interference limited the ability of cells to activate the spindle checkpoint and correlated with a reduction of Cdc2/cyclin B1 activity and phosphorylation on T161 on the Cdc2 subunit. These data suggest that a critical region of Sil is required to mediate the presentation of Cdc2 activity during spindle checkpoint arrest.
The human SIL gene is disrupted by a site-specific interstitial deletion in 25% of children with T-cell acute lymphoblastic leukemia. Since transcriptionally active genes are prone to recombination events, the recurrent nature of this lesion suggests that the SIL gene product is transcriptionally active in the cell type that undergoes this interstitial deletion and that the SIL gene product may play a role in normal lymphoid development. To facilitate studies of SIL gene function, we have cloned and characterized a murine SIL gene. The predicted murine SIL protein is 75% identical to the human gene, with good homology throughout the open reading frame. An in vitro translated SIL cDNA generated a protein slightly larger than the predicted 139-kDa protein. Although a prior report detected SIL mRNA expression exclusively in hematopoietic tissues, a sensitive RT-PCR assay demonstrated SIL expression to be ubiquitous, detectable in all tissues examined. Since the RT-PCR assay suggested that SIL mRNA expression was higher in rapidly proliferating tissues, we assayed SIL mRNA expression using a murine erythroleukemia model of terminal differentiation and found it to be dramatically decreased in conjunction with terminal differentiation. These studies demonstrate that the human SIL gene product is quite well conserved in rodents and suggest that the SIL gene product may play a role in cell proliferation.
The establishment of an organism's body plan or part of an organism with respect to the left and right halves. The pattern can either be symmetric, such that the halves are mirror images, or asymmetric where the pattern deviates from this symmetry.
The process whose specific outcome is the progression of the forebrain over time, from its formation to the mature structure. The forebrain is the anterior of the three primary divisions of the developing chordate brain or the corresponding part of the adult brain (in vertebrates, includes especially the cerebral hemispheres, the thalamus, and the hypothalamus and especially in higher vertebrates is the main control center for sensory and associative information processing, visceral functions, and voluntary motor functions).
The characteristic morphogenetic movements where the primitive heart tube loops asymmetrically. This looping brings the primitive heart chambers into alignment preceding their future integration.
The process whose specific outcome is the progression of the embryo in the uterus over time, from formation of the zygote in the oviduct, to birth. An example of this process is found in Mus musculus.
The process whose specific outcome is the progression of the neural tube over time, from its formation to the mature structure. The mature structure of the neural tube exists when the tube has been segmented into the forebrain, midbrain, hindbrain and spinal cord regions. In addition neural crest has budded away from the epithelium.
The process whose specific outcome is the progression of the notochord over time, from its formation to the mature structure. The notochord is a mesoderm-derived structure located ventral of the developing nerve cord. In vertebrates, the notochord serves as a core around which other mesodermal cells form the vertebrae. In the most primitive chordates, which lack vertebrae, the notochord persists as a substitute for a vertebral column.
Protein involved in development, the process whereby a multicellular organism develops from its early immature forms, e.g., zygote, larva, embryo, into an adult.
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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