Background
Histone post-translational modifications (PTMs) are key mechanisms of epigenetics that modulate chromatin structures, termed as “histone code”. The PTMs on histone including acetylation, methylation, phosphorylation and novel acylations directly affect the accessibility of chromatin to transcription factors and other epigenetic regulators, altering genome stability, gene transcription, etc. Histone acetylation occurs primarily at multiple lysine residues on the amino-terminal of core histones, in response to various stimuli and plays vital roles in the regulation of gene expression, DNA damage repair, chromatin dynamics, etc. Mostly, histone H2A is primarily acetylated at Lys5, 9, 15, and 36; H2B is primarily acetylated at Lys5, 12, 15,16, and 20. Histone
H3 is primarily acetylated at Lys4, 9, 14, 18, 23, 27, 56, and 79. Histone H4 is primarily acetylated at Lys5, 8, 12, 16, and 20. Histone acetyltransferases (HATs) and histone deacetylases (HDACs) are major regulating factors.