Genetically encoding N(epsilon)-methyl-L-lysine in recombinant histones

Lysine methylation is an important post-translational modification of histone proteins that defines epigenetic status and controls heterochromatin formation, X-chromosome inactivation, genome imprinting, DNA repair, and transcriptional regulation. Despite considerable efforts by chemical biologists to synthesize modified histones for use in deciphering the molecular role of methylation in these phenomena, no general method exists to synthesize proteins bearing quantitative site-specific methylation. Here we demonstrate a general method for the quantitative installation of N(epsilon)-methyl-L-lysine at defined positions in recombinant histones and demonstrate the use of this method for investigating the methylation dependent binding of HP1 to full length histone H3 monomethylated on K9 (H3K9me1). This strategy will find wide application in defining the molecular mechanisms by which histone methylation orchestrates cellular phenomena.