A NOVEL MEMBER OF THE RHO-FAMILY OF SMALL GTP-BINDING PROTEINS IS SPECIFICALLY REQUIRED FOR CYTOKINESIS

Several members of the rho/rac family of small GTP-binding proteins ar e known to regulate the distribution of the actin cytoskeleton in vari ous subcellular processes. We describe here a novel me protein, racE, which is specifically required for cytokinesis, an actomyosin-mediated process. The racE gene was isolated in a molecular genetic screen dev ised to isolate genes required for cytokinesis in Dictyostelium. Pheno typic characterization of racE mutants revealed that racE is not essen tial for any other cell motility event, including phagocytosis, chemot axis, capping, or development. Our data provide the first genetic evid ence 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.