Histone methylation versus histone acetylation: new insights into epigenetic regulation.

Post-translational addition of methyl groups to the amino-terminal tails of histone proteins was discovered more than three decades ago. Only now, however, is the biological significance of lysine and arginine methylation of histone tails being elucidated. Recent findings indicate that methylation of certain core histones is catalyzed by a family of conserved proteins known as the histone methyltransferases (HMTs). New evidence suggests that site-specific methylation, catalyzed by HMTs, is associated with various biological processes ranging from transcriptional regulation to epigenetic silencing via heterochromatin assembly. Taken together, these new findings suggest that histone methylation may provide a stable genomic imprint that may serve to regulate gene expression as well as other epigenetic phenomena.