Figure 3

Cdk1 restricts the pheromone response pathway to the G1 phase of the cell cycle. (A), when pheromone is detected by the receptor during G1 phase (when Cdk1 activity is low), a signaling cascade that is mostly mediated by the βγ subunit of the heterotrimeric G protein prevents entry into S phase, polarizes the actin cytoskeleton towards the face of the cell with the highest pheromone concentration, and activates transcriptional programs. (B), binding of pheromone to the receptor outside of the G1 phase - when Cdk1 is active - does not trigger the pheromone signaling pathway because it is disconnected from its downstream components by Cdk1-mediated phosphorylation of Ste5, Ste20 and Far1. See text for details.