The small GTPase superfamily, which includes the Ras, Rho/Rac, Rab, Arf and Ran subfamilies, serves as a signal transducer to regulate cell proliferation and differentiation, actin cytoskeleton, membrane trafficking, and nuclear transport. Here, we identify novel GTPases (human Gie1 and Gie2) that form a distinct subfamily of the small GTPases in terms of their sequences and intracellular function. Gie stands for 'novel GTPase indispensable for equal segregation of chromosomes', and this subfamily is conserved in multicellular organisms. Expression of dominant-negative Gie mutants in mammalian cells or knockdown of Gie transcripts using RNA interference in Drosophila S2 cells induced abnormal morphology in the chromosome segregation. Gie protein has ability to bind to tubulin and localizes with microtubules on the spindle mid-zone in late mitosis. Furthermore, overexpression of Gie mutants that lack putative effector domains but have tubulin-binding ability induced micronucleus formation. Thus, this is the first report showing that a small GTPase subfamily capable of associating with microtubules might be involved in chromosome segregation.
Small GTPases of the Arf and Rab families play key roles in the function of subcellular organelles. Each GTPase is usually found on only one compartment and, hence, they confer organelle specificity to many intracellular processes. However, there has so far been little evidence for specific GTPases present on lysosomes. Here, we report that two closely related human Arf-like GTPases, Arl8a and Arl8b (also known as Arl10b/c and Gie1/2), localise to lysosomes in mammalian cells, with the single homologue in Drosophila cells having a similar location. Conventionally, membrane binding of Arf and Arl proteins is mediated by both an N-terminal myristoyl group and an N-terminal amphipathic helix that is inserted into the lipid bilayer upon activation of the GTPase. Arl8a and Arl8b do not have N-terminal myristoylation sites, and we find that Arl8b is instead N-terminally acetylated, and an acetylated methionine is necessary for its lysosomal localization. Overexpression of Arl8a or Arl8b results in a microtubule-dependent redistribution of lysosomes towards the cell periphery. Live cell imaging shows that lysosomes move more frequently both toward and away from the cell periphery, suggesting a role for Arl8a and Arl8b as positive regulators of lysosomal transport.
The small GTPase superfamily, which includes the Ras, Rho/Rac, Rab, Arf and Ran subfamilies, serves as a signal transducer to regulate cell proliferation and differentiation, actin cytoskeleton, membrane trafficking, and nuclear transport. Here, we identify novel GTPases (human Gie1 and Gie2) that form a distinct subfamily of the small GTPases in terms of their sequences and intracellular function. Gie stands for 'novel GTPase indispensable for equal segregation of chromosomes', and this subfamily is conserved in multicellular organisms. Expression of dominant-negative Gie mutants in mammalian cells or knockdown of Gie transcripts using RNA interference in Drosophila S2 cells induced abnormal morphology in the chromosome segregation. Gie protein has ability to bind to tubulin and localizes with microtubules on the spindle mid-zone in late mitosis. Furthermore, overexpression of Gie mutants that lack putative effector domains but have tubulin-binding ability induced micronucleus formation. Thus, this is the first report showing that a small GTPase subfamily capable of associating with microtubules might be involved in chromosome segregation.
The small GTPase superfamily, which includes the Ras, Rho/Rac, Rab, Arf and Ran subfamilies, serves as a signal transducer to regulate cell proliferation and differentiation, actin cytoskeleton, membrane trafficking, and nuclear transport. Here, we identify novel GTPases (human Gie1 and Gie2) that form a distinct subfamily of the small GTPases in terms of their sequences and intracellular function. Gie stands for 'novel GTPase indispensable for equal segregation of chromosomes', and this subfamily is conserved in multicellular organisms. Expression of dominant-negative Gie mutants in mammalian cells or knockdown of Gie transcripts using RNA interference in Drosophila S2 cells induced abnormal morphology in the chromosome segregation. Gie protein has ability to bind to tubulin and localizes with microtubules on the spindle mid-zone in late mitosis. Furthermore, overexpression of Gie mutants that lack putative effector domains but have tubulin-binding ability induced micronucleus formation. Thus, this is the first report showing that a small GTPase subfamily capable of associating with microtubules might be involved in chromosome segregation.
The small GTPase superfamily, which includes the Ras, Rho/Rac, Rab, Arf and Ran subfamilies, serves as a signal transducer to regulate cell proliferation and differentiation, actin cytoskeleton, membrane trafficking, and nuclear transport. Here, we identify novel GTPases (human Gie1 and Gie2) that form a distinct subfamily of the small GTPases in terms of their sequences and intracellular function. Gie stands for 'novel GTPase indispensable for equal segregation of chromosomes', and this subfamily is conserved in multicellular organisms. Expression of dominant-negative Gie mutants in mammalian cells or knockdown of Gie transcripts using RNA interference in Drosophila S2 cells induced abnormal morphology in the chromosome segregation. Gie protein has ability to bind to tubulin and localizes with microtubules on the spindle mid-zone in late mitosis. Furthermore, overexpression of Gie mutants that lack putative effector domains but have tubulin-binding ability induced micronucleus formation. Thus, this is the first report showing that a small GTPase subfamily capable of associating with microtubules might be involved in chromosome segregation.
The small GTPase superfamily, which includes the Ras, Rho/Rac, Rab, Arf and Ran subfamilies, serves as a signal transducer to regulate cell proliferation and differentiation, actin cytoskeleton, membrane trafficking, and nuclear transport. Here, we identify novel GTPases (human Gie1 and Gie2) that form a distinct subfamily of the small GTPases in terms of their sequences and intracellular function. Gie stands for 'novel GTPase indispensable for equal segregation of chromosomes', and this subfamily is conserved in multicellular organisms. Expression of dominant-negative Gie mutants in mammalian cells or knockdown of Gie transcripts using RNA interference in Drosophila S2 cells induced abnormal morphology in the chromosome segregation. Gie protein has ability to bind to tubulin and localizes with microtubules on the spindle mid-zone in late mitosis. Furthermore, overexpression of Gie mutants that lack putative effector domains but have tubulin-binding ability induced micronucleus formation. Thus, this is the first report showing that a small GTPase subfamily capable of associating with microtubules might be involved in chromosome segregation.
The small GTPase superfamily, which includes the Ras, Rho/Rac, Rab, Arf and Ran subfamilies, serves as a signal transducer to regulate cell proliferation and differentiation, actin cytoskeleton, membrane trafficking, and nuclear transport. Here, we identify novel GTPases (human Gie1 and Gie2) that form a distinct subfamily of the small GTPases in terms of their sequences and intracellular function. Gie stands for 'novel GTPase indispensable for equal segregation of chromosomes', and this subfamily is conserved in multicellular organisms. Expression of dominant-negative Gie mutants in mammalian cells or knockdown of Gie transcripts using RNA interference in Drosophila S2 cells induced abnormal morphology in the chromosome segregation. Gie protein has ability to bind to tubulin and localizes with microtubules on the spindle mid-zone in late mitosis. Furthermore, overexpression of Gie mutants that lack putative effector domains but have tubulin-binding ability induced micronucleus formation. Thus, this is the first report showing that a small GTPase subfamily capable of associating with microtubules might be involved in chromosome segregation.
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 in which genetic material, in the form of chromosomes, is organized into specific structures and then physically separated and apportioned to two or more sets. In eukaryotes, chromosome segregation begins with the alignment of chromosomes at the metaphase plate, includes chromosome separation, and ends when chromosomes have completed movement to the spindle poles.
Evidence
1:
Inferred from Mutant PhenotypeUniProtKB
Transcriptional repression plays an essential role in many aspects of metazoan development. Drosophila hairy is a primary pair-rule gene encoding a basic helix-loop-helix class transcriptional repressor that is required for proper segmentation. Previous characterization of Hairy-binding proteins has implicated two different classes of histone deacetylase as mediators of Hairy repression. Here, we present the characterization of a novel Hairy-interacting protein (dTopors) that binds specifically to the basic region of Hairy, but does not affect the ability of Hairy to bind DNA. By reducing the gene dose of dtopors, we demonstrate that it acts genetically as an antagonist of Hairy-mediated transcriptional repression. Consistent with this genetic interaction, we show that that recombinant dTopors protein possesses ubiquitin-protein isopeptide ligase activity in vitro and that dTopors mediates Hairy polyubiquitination and can lead to Hairy degradation. This work provides the first evidence that regulated proteolysis of Hairy is required for correct segmentation.
The small GTPase superfamily, which includes the Ras, Rho/Rac, Rab, Arf and Ran subfamilies, serves as a signal transducer to regulate cell proliferation and differentiation, actin cytoskeleton, membrane trafficking, and nuclear transport. Here, we identify novel GTPases (human Gie1 and Gie2) that form a distinct subfamily of the small GTPases in terms of their sequences and intracellular function. Gie stands for 'novel GTPase indispensable for equal segregation of chromosomes', and this subfamily is conserved in multicellular organisms. Expression of dominant-negative Gie mutants in mammalian cells or knockdown of Gie transcripts using RNA interference in Drosophila S2 cells induced abnormal morphology in the chromosome segregation. Gie protein has ability to bind to tubulin and localizes with microtubules on the spindle mid-zone in late mitosis. Furthermore, overexpression of Gie mutants that lack putative effector domains but have tubulin-binding ability induced micronucleus formation. Thus, this is the first report showing that a small GTPase subfamily capable of associating with microtubules might be involved in chromosome segregation.
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.
Protein involved in the separation of one cell into two daughter cells. In eukaryotic cells, cell division includes the nuclear division (mitosis) and the subsequent cytoplasmic division (cytokinesis).
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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