Histone H3 tail clipping regulates gene expression

Induction of gene expression in yeast and human cells involves changes in histone modifications associated with promoters. Here we identify a histone H3 endopeptidase activity in S. cerevisiae that may regulate these events. The endopeptidase cleaves H3 after alanine 21, generating a histone lacking the first 21 residues and displays a preference for H3 tails carrying repressive modifications. In vivo, the H3 N-terminus is clipped, specifically within the promoter of genes following the induction of transcription. H3 clipping precedes the process of histone eviction seen when genes become fully active. A truncated H3 product is not generated in yeast carrying a mutation of the endopeptidase recognition site (H3 Q(19)L(20)->AA) and the gene induction is defective in these cells. These findings identify clipping of H3 tails as a novel modification of promoter-bound nucleosomes, which may result in the localised clearing of repressive signals during the induction of gene expression.