Yeast STE7, STE11, and STE12 genes are required for expression of cell-type-specific genes.

Cell type specialization in yeast haploids involves the mutually exclusive expression of one of two sets of genes, the a-specific and alpha-specific genes. We demonstrated that the products of the STE7, STE11, and STE12 genes were required for the expression of both gene sets. RNA levels transcribed from these gene sets were significantly decreased but not abolished in haploids containing a null mutation in the STE7, STE11, or STE12 gene. Transcript levels from the a- and alpha-specific gene sets were not further reduced in strains harboring mutations in all three STE genes, suggesting that STE7, STE11, and STE12 are required for the same aspect of transcription. We further showed that the requirement for these products was not the same for each member of a particular gene set. However, for any given a- or alpha-specific gene, the effect on RNA levels of any of the three ste mutations was similar.