Histone acetylation and histone deacetylation involve the addition or removal of an acetyl group on lysine residues in the N-terminal tail and on the surface of the nucelosome core of histone proteins. Acetylated and deacetylated histones are considered epigenetic tags within chromatin by relaxing (euchromatin) or tightening (heterochromatin) chromatin structure, subsequently increasing or decreasing gene transcription levels.
Histone acetylation, including histone H3 and histone H4, is involved in the regulation of chromatin structure and the recruitment of transcription factors to gene promoters. Quantifying total levels of acetylated histone or levels at specific lysines will help to elucidate epigenetic regulation of gene activation, and contribute to the development of HAT or HDAC-targeted drugs.
Histone acetyltransferases (HAT) are enzymes that play a critical role in transcriptional regulation of genes, and directly correspond to transcription by selectively acetylating the epsilon-amino groups of lysines located near the amino termini of core histone proteins. Abnormal gene silencing by reduced HAT activity has been linked to the pathogenesis of many diseases, particularly cancer. Determining the activity of HATs and the potency of their inhibitors contributes to drug discovery and the development of anti-cancer agents, as well as a better understanding of gene transcription.
Histone deacetylases (HDACs), also known as lysine deacetylases (KDACs), are a class of enzymes that remove acetyl groups on a histone, thereby involving the regulation of DNA expression. HDACs are also tightly involved in cell cycle regulation, cell proliferation, and in the development of human cancer.