THE ROLE OF FAR1P IN LINKING THE HETEROTRIMERIC G-PROTEIN TO POLARITYESTABLISHMENT PROTEINS DURING YEAST MATING

Heterotrimeric guanosine triphosphate (GTP)-binding proteins (G protei ns) determine tissue and cell polarity in a variety of organisms. In y east, cells orient polarized growth toward the mating partner along a pheromone gradient by a mechanism that requires Far1p and Cdc24p. Far1 p bound G beta gamma and interacted with polarity establishment protei ns, which organize the actin cytoskeleton. Cells containing mutated Fa r1p unable to bind G beta gamma or polarity establishment proteins wer e defective for orienting growth toward their mating partner. In respo nse to pheromones, Far1p moves from the nucleus to the cytoplasm, Thus , Far1p functions as an adaptor that recruits polarity establishment p roteins to the site of extracellular signaling marked by G beta gamma to polarize assembly of the cytoskeleton in a morphogenetic gradient.