These tails are topic to several post-translational covalent modifications, including acetylation, phosphorylation, ubiquitination, sumoylation and methylation (reviewed in 1 ). Methylation been discovered on a variety of lysine residues in numerous histones: K4 (utilizing the only-letter amino-acid code for lysine), K9, K27, K36 and K79 in histone H3, K20 in histone H4, K59 in the globular domain of histone H4 2 and K26 of histone H1B three A number of proteins responsible for the methylation of particular residues have been characterized, and all but one in every of these accommodates a SET domain