Histone methyltransferase

Histone methyltransferases (HMT) are enzymes, histone-lysine N-methyltransferase and histone-arginine N-methyltransferase, which catalyze the transfer of one to three methyl groups from the cofactor S-Adenosyl methionine to lysine and arginine residues of histone proteins. These proteins often contain an SET (Su(var)3-9, Enhancer of Zeste, Trithorax) domain, however the recently discovered HMT Dot1 lacks the characteristic SET domain.

Histone methylation serves in epigenetic gene regulation. Methylated histones bind DNA more tightly, which inhibits transcription.