Histone acetylation, not stoichiometry, regulates linker histone binding in S. cerevisiae

Linker histones play a fundamental role in shaping chromatin structure, but how their interaction with chromatin is controlled not well understood. In this study we used a combination of genetic and genomic approaches to explore the regulation of linker histone binding in the yeast, Saccharomyces cerevisiae. Despite the tight correlation between linker-to-core histone ratio and nucleosome repeat length (NRL) observed in many organisms, we found that increasing Hho1 levels did not change the overall NRL in yeast chromatin. While over-expression of Hho1 did not alter nucleosome spacing, it did result in a severe growth defect, which could be rescued by mutations that increased histone acetylation in the cell. Consistent with this, genome-wide analysis of linker histone occupancy revealed an inverse correlation with histone tail acetylation in both yeast and mouse embryonic stem cells. Collectively these results suggest that histone acetylation negatively regulates linker histone binding in S. cerevisiae and other organisms. Sonication-based ChIP-seq for H3 and Hho1