The changes that occur during the mating response include arrest in G1 and induction of transcription of specific genes. We have shown previously that inappropriate expression of the a-factor receptor gene (STE3) in MATa cells confers resistance to pheromone-mediated cell cycle arrest. Pheromone binding results in the activation of several protein kinases (Ste20p, Ste11p, Ste7p, Fus3p and Kss1p) and phosphorylation of cell cycle inhibitors such as Far1p. In MATa cells expressing STE3, transient activation of the signaling pathway occurs, as measured by Far1p phosphorylation, activation of Fus3p and transcriptional activation of mating specific genes. These results indicate that inappropriate expression of the receptor causes a late inactivation of the mating pathway, and that sustained activation is required for cell cycle arrest. Epistasis experiments suggest that receptor-mediated inhibition affects a step between the G protein and Ste11p. Accumulating evidence indicates that cell cycle regulators play an important role in facilitating the mating response. For example, G1 arrest is required for optimal signaling. The participation of the G1 cyclins in the mutant phenotype was analyzed. The signaling response was also followed in non-G1 arrested cells. The results obtained suggest that Ste3p-mediated inactivation does not appear to act through cell cycle regulators but rather involves the participation of mating specific components.