COOPERATIVE INTERACTION OF S-POMBE PROTEINS REQUIRED FOR MATING AND MORPHOGENESIS

We isolated two S. pombe genes, scd1 and scd2, that are required for n ormal morphology and mating. scd1 and scd1 are homologous to CDC24 and BEM1, respectively, of S. cerevisiae. Epistasis analyses indicate tha t scd2 and rest converge upon scd1, which, in turn, interacts with cdc 42sp, a RHO-like GTPase. Studies with the yeast two-hybrid system indi cate that scd2 forms complexes with both scd1 and cdc42sp. Furthermore , biochemical studies indicate that the interaction between scd1 and s cd2 is direct. The yeast two-hybrid data further suggest that scd1, sc d2, cdc42sp, and ras1, in its GTP-bound state, act cooperatively to fo rm a protein complex.