Novel aspects of pheromone-induced cell-cycle arrest in yeast.

Saccharomyces cerevisiae responds to pheromones by arresting cell-cycle progression at the G1/S boundary. This arrest has been shown to require the activation by phosphorylation of Far1, a cyclin-dependent kinase inhibitor. Arrest resembling pheromone-induced arrest can be triggered by high levels of Ste12, the pheromone-responsive transcriptional activator. In the present study, cell-cycle arrest induced by high levels of Ste12 is characterized. This arrest occurs predominately at the G1/S boundary and is independent of Far1 and upstream components of the pheromone response pathway. Since Ste12 is a transcriptional activator, it is proposed that cell-cycle arrest in response to high levels of Ste12 is due to transcription of a Ste12-dependent arrest factor regulated primarily, but not necessarily exclusively, at the level of transcription. The data presented here suggest that a novel component has a role in arrest in response to pheromone.