Requirement of Hos2 histone deacetylase for gene activity in yeast.

Histone deacetylases, typified by class I Rpd3 in the yeast Saccharomyces cerevisiae, have historically been associated with gene repression. We now demonstrate that Hos2, another member of the class I family, binds to the coding regions of genes primarily during gene activation, when it specifically deacetylates the lysines in H3 and H4 histone tails. Moreover, Hos2 is preferentially associated with genes of high activity genome-wide. We also show that Hos2 and an associated factor, Set3, are necessary for efficient transcription. Therefore, our data indicate that, in contrast to other class I histone deacetylases, Hos2 is directly required for gene activation.