Formin a shmoo

Mate selection, yeast style, consists of polarizing and projecting in the right direction. Matheos et al. (page 99) define a new step in this polarization dance—a step that may link the extracellular yeast pheromone signal to the intracellular establishment of polarized actin cables.

The proposed link involves phosphorylation of Bni1p, a cable-generating formin protein, by Fus3p, a MAP kinase. Fus3p got its name because cells lacking this kinase could not fuse during mating. Sure enough, activated Fus3p was long ago found to lead to transcription of fusion genes. Then Fus3p was found to help arrest the cell cycle of mating cells. But replacement of both of these functions did not restore fusion to cells lacking Fus3p.

Now Matheos et al. find that Fus3p is also needed for polarization of the cell and localization of...