STE12 AND MCM1 REGULATE CELL CYCLE-DEPENDENT TRANSCRIPTION OF FAR1

The transcripts of many genes involved in Saccharomyces cerevisiae mat ing were found to fluctuate during the cell cycle. In the absence of a functional Ste12 transcription factor, both the levels and the cell c ycle pattern of expression of these genes were affected, FUS1 and AGA1 levels, which are maximally expressed only in G(1)-phase cells, were strongly reduced in sfe12(-) cells, The cell cycle transcription patte rn for FAR1 was changed in ste12(-) cells: the gene was still signific antly expressed in G,IM, but transcript levels were strongly reduced i n G(1) phase, resulting in a lack of Far1 protein accumulation, G(2)/M transcription of FAX1 was dependent on the transcription factor Mcm1, and expression of a gene with Mcm1 fused to a strong transcriptional activation domain resulted in increased levels of FAR1 transcription, The pattern of cell cycle-regulated transcription of FAR1 could involv e combinatorial control by Ste12 and Mcm1. Forced G(1) expression of F AR1 from the GAL1 promoter restored the ability to arrest in response to pheromone in ste12(-) cells, This indicates that transcription of F AR1 in the G(1) phase is essential for accumulation of the protein and for pheromone-induced cell cycle arrest.