The role of nucleosome positioning in repression by the yeast α2/Mcm1p repressor

In Saccharomyces cerevisiae, cc2/Mcm1p represses a-cell specific genes. Previous studies indicated that repression by oc2/Mcm1p is associated with organization of positioned nucleosomes in promoters of a-cell specific genes such as STE6 and BAR1. Here, we examined the role of nucleosome positioning in repression of STE6-lacZ by a2/Mcm1 p. We showed that insertion of an A34 sequence, which is shown to disrupt an array of positioned nucleosomes, affects STE6-lacZ expression. Furthermore, artificial recruitment of TBP is facilitated by the insertion of A 34 to derepress STE6-lacZ expression. These findings support the model that nucleosome positioning plays a regulatory role in repression by a2/Mcm1p.