Lysine Methyltransferases

Lysine methyltransferases, or KMTs, are enzymes that catalyze the transfer of methyl groups from S-adenosylmethionine (SAM) to the lysine residues on histones. Upward of 24 human protein lysine methyltransferases have been described and they belong to the histone methyltransferase group of enzymes, which also includes protein arginine methyltransferases. They are also closely related in biological activity to the DNA methyltransferases.

Histones represent the major protein component of chromatin, around which DNA is coiled within the nucleus. Modification of histone protein by methylation induces chromatin remodeling which in turn alters gene expression. Histone methylation is an integral epigenetic process during development and represents an important mechanism of transcriptional regulation and chromatin remodeling. Dysregulation of histone methylation has been implicated in diseases including cancer.

Histone methylation by KMTs occurs predominantly on lysine residues in histones H3 and H4, and multiple methyl groups may be added to each residue.The epigenetic effects of histone methylation are dependent on the residue undergoing methylation and the degree of methylation. Consequently different types of lysine methylation are associated with different functions in the regulation of gene expression. Lysine methylation can induce both transcriptional activation and silencing.