Methylation been discovered on a spread of lysine residues in numerous histones: K4 (using the single-letter amino-acid code for lysine), K9, K27, K36 and K79 in histone H3, K20 in histone H4, K59 in the globular area of histone H4 2 and K26 of histone H1B three Several proteins answerable for the methylation of specific residues have been characterised, and all however one in all these contains a SET domain