BNI1P, A YEAST FORMIN LINKING CDC42P AND THE ACTIN CYTOSKELETON DURING POLARIZED MORPHOGENESIS

The Saccharomyces cerevisiae BNI1 gene product (Bni1p) is a member of the formin family of proteins, which participate in cell polarization, cytokinesis, and vertebrate limb formation. During mating pheromone r esponse, bni1 mutants showed defects both in polarized morphogenesis a nd in reorganization of the underlying actin cytoskeleton, In two-hybr id experiments, Bni1p formed complexes, with the activated form of the Rho-related guanosine triphosphatase Cdc42p, with actin, and with two actin-associated proteins, profilin and Bud6p (Aip3p). Both Bni1p and Bud6p (like Cdc42p and actin) localized to the tips of mating project ions. Bni1p may function as a Cdc42p target that links the pheromone r esponse pathway to the actin cytoskeleton.