Methylation of particular histone lysine residues serves as a post-translational epigenetic modification that controls the expression of genes by serving as ‘markers’ for the recruitment of particular complexes that direct the organization of chromatin. Methylation been discovered on a range of lysine residues in various 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 3 A number of proteins accountable for the methylation of specific residues have been characterized, and all but considered one of these contains a SET area