Background
The ε-amino lysine acetylation of proteins is an important reversible modification controlling protein activity. The amino-terminal tails of core histones undergo lysine acetylation in multiple sites, termed as “histone code”. Lysine acetylation in core histones occurs in response to various stimuli and plays vital roles in the regulation of many cellular processes including chromatin dynamics, DNA transcription, cell cycle progression, apoptosis, differentiation and nuclear import. In most species, 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. More than 20 histone acetyltransferases (HATs) and 18 histone deacetylases (HDACs) have been identified to date, while the mechanistic details of substrate selection and site specificity of these enzymes remain unclear. The regulation of histone lysine acetylation status is impaired in cancers and other diseases. Therefore, enzymes regulating histone lysine acetylation have become promising targets for anti-cancer drugs.