Histone methylation versus histone acetylation: new insights into epigenetic regulation

Post-translational addition of methyl groups to the aminoterminal tails of histone proteins was discovered more than three decades ago. Only now, howe ver, is the biological significance of lysine and arginine methylation of h istone 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 biologi cal processes ranging from transcriptional regulation to epigenetic silenci ng via heterochromatin assembly. Taken together, these new findings suggest that histone methylation may provide a stable genomic imprint that may ser ve to regulate gene expression as well as other epigenetic phenomena.