Bni1p, a Yeast Formin Linking Cdc42p and the Actin Cytoskeleton During Polarized Morphogenesis

TLDR

Bni1p is a formin protein that participates in cell polarization and cytokinesis. The study investigates whether Bni1p links Cdc42p signaling to the actin cytoskeleton during pheromone response. Bni1p mutants display impaired polarized morphogenesis and actin reorganization, and Bni1p interacts with activated Cdc42p, actin, profilin, and Bud6p, localizing to mating projection tips.

Abstract

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 response, bni1 mutants showed defects both in polarized morphogenesis and in reorganization of the underlying actin cytoskeleton. In two-hybrid 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 projections. Bni1p may function as a Cdc42p target that links the pheromone response pathway to the actin cytoskeleton.