A novel role for Nhp6 proteins in histone gene regulation in Saccharomyces cerevisiae

Maintaining a stable and balanced histone pool is of paramount importance for genome stability and fineregulation of DNA replication and transcription. This involves a complex regulatory machinery, exploitingtranscription factors as well as histone chaperones, chromatin remodelers and modifiers. The functionaldetails of this machinery are as yet unclear. Previous studies report histone decrease in mammalianand yeast HMGB family mutants. In this study we find that Nhp6 proteins, the S. cerevisiae HMGB1homologues, control histone gene expression by affecting nucleosome stability at regulative regions ofthe histone clusters. In addition, we observe that histone gene overexpression in the nhp6ab mutantis accompanied by downregulated translation, which in turn is responsible for the histone decreasephenotype. Our observations allow us to incorporate Nhp6 proteins into the large group of chromatinfactors that tightly regulate histone gene expression.