Methylation been discovered on a variety of lysine residues in varied histones: K4 (utilizing the one-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 Several proteins answerable for the methylation of particular residues have been characterized, and all however one among these contains a SET domain