FIG. 5.
Roles of histone modifications in the regulation of gene transcription. Methylation of histones, acetylation, or ubiquitination can either activate or repress gene expression, depending on specific histone proteins and the sites of modifications. In general, phosphorylation of histones promotes transcription, DNA repair, and apoptosis. H, histone; K, lysine residue; R, arginine residue.