MCM1 BINDS TO A TRANSCRIPTIONAL CONTROL ELEMENT IN TYL

Some Ty1 transposable-element insertion mutations of Saccharomyces cerevisiae activate adjacent-gene expression. These Ty1-activated genes are regulated similarly to certain mating genes. This report shows that the MCM1 protein, which binds to several mating genes, also binds to a transcriptional regulatory sequence in Ty1. The binding of MCM1 to Ty1 correlates with the ability of its binding site to function as a component of the Ty1 transcriptional activator. This correlation supports the idea that MCM1 is important for Tyl-activated gene expression. At mating-gene promoters, MCM1 binds with coactivators or repressors such as STE12, alpha1, or alpha2. In contrast, MCM1 binds without these associated DNA-binding proteins at its site in Tyl. This finding suggests that its role in Ty1-mediated transcription is different from that at mating genes.