Figure2. Histone modifications
Histone modifications mainly include histone acetylation and histone methylation. HDACs and HATs are necessary enzymes for histone acetylation. HATs catalyze the reversible acetylation reaction at the ε-amino group of lysine residues. Meanwhile, HDACs can remove acetyl groups silencing the transcriptional activity of genes and leading to chromatin condensation. Histone methylation is catalyzed by HMTs, which occurs mainly on lysine (K) and arginine (R) residues. Key enzymes of histone methylation involved in HMTs and KDMs. Lysine methylation occurs in mono-, di-, and tri-states, whereas arginine methylation only occurs in mono-and di-states. Histone H3 methylation occurs at lysine residues K4, K9, K27, K36, and K79 and histone H4 methylation occurs at lysine residues K20.