Abstract
Several members of the rho/rac family of small GTP-binding proteins are known to regulate the distribution of the actin cytoskeleton in various subcellular processes. We describe here a novel rac protein, racE, which is specifically required for cytokinesis, an actomyosin-mediated process. The racE gene was isolated in a molecular genetic screen devised to isolate genes required for cytokinesis in Dictyostelium. Phenotypic characterization of racE mutants revealed that racE is not essential for any other cell motility event, including phagocytosis, chemotaxis, capping, or development. Our data provide the first genetic evidence for the essential requirement of a rho-like protein, specifically in cytokinesis, and suggest a role for these proteins in coordinating cytokinesis with the mitotic events of the cell cycle.
Highlights
Several members of the rho/rac family of small GTP-binding proteins are known to regulate the distribution of the actin cytoskeleton in various subcellular processes
Our screen was based on the phenotype of Dictyostelium strains deficient for myosin II, a protein known to be essential for cytokinesis (De Lozanne and Spudich, 1987; Knecht and Loomis, 1987)
When analyzed by Southern blot analysis with a specific probe for the Dictyostelium myosin II heavy chain gene, we found that two of the four mutant cell lines (28IF8 and 53PF1) contained a plasmid insertion within the mhcA locus
Summary
Several members of the rho/rac family of small GTP-binding proteins are known to regulate the distribution of the actin cytoskeleton in various subcellular processes. Our data provide the first genetic evidence for the essential requirement of a rho-like protein, in cytokinesis, and suggest a role for these proteins in coordinating cytokinesis with the mitotic events of the cell cycle. Much is understood about how cells achieve proper cytoplasmic division In animal cells, this involves the formation of an equatorial contractile ring that consists largely of actin and myosin and constricts to divide the cell into two (Satterwhite and Pollard, 1992). This involves the formation of an equatorial contractile ring that consists largely of actin and myosin and constricts to divide the cell into two (Satterwhite and Pollard, 1992) It is not understood how these proteins localize to the equator of the cell at the appropriate time and in the correct orientation.
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