DGAP1, A HOMOLOG OF RASGTPASE ACTIVATING PROTEINS THAT CONTROLS GROWTH, CYTOKINESIS, AND DEVELOPMENT IN DICTYOSTELIUM-DISCOIDEUM

A protein accumulated in the cortical region of Dictyostelium discoide um cells proved to be a homologue of GTPase activating proteins that a re responsible for the inactivation of ras in yeast and man. Eliminati on of this protein, DGAP1, by gene replacement resulted in an increase d rate of growth of D, discoideum cells on bacterial lawns, and in the formation of aberrant, multi-tipped fruiting bodies, Overexpression o f DGAP1 caused the cells to become multi-nucleated since chromosome se gregation during mitosis was not reliably followed by cleavage of the cells, These results suggest that in D. discoideum, ras or a related s mall GTP-binding protein is involved in regulating growth based on the phagocytosis of bacteria, and in coupling activities of the cell cort ex to the organization of spindle and asters in mitotic cells.