Histone acetyltransferase

Histone acetyltransferases (HAT) are enzymes that acetylate conserved lysine amino acids on histone proteins by transferring an acetyl group from acetyl CoA to form ε-N-acetyl lysine.

In general, histone acetylation is linked to transcriptional activation and associated with euchromatin. When it was first discovered, it was thought that acetylation of lysine neutralizes the positive charge normally present, thus reducing affinity between histone and (negatively charged) DNA, which renders DNA more accessible to transcription factors. Research has emerged, since, to show that lysine acetylation and other posttranslational modifications of histones generate binding sites for specific protein–protein interaction domains, such as the acetyl-lysine-binding bromodomain. Histone acetyltransferases can also acetylate non-histone proteins, such as transcription factors and nuclear receptors to facilitate gene expression.

Examples
Human proteins that possess histone acetyltransferase catalytic activity include:


 * CREBBP, CDY1, CDY2, CDYL1, CLOCK
 * ELP3, EP300
 * HAT1
 * KAT2A, KAT2B, KAT5
 * MYST1, MYST2, MYST3, MYST4
 * NCOA1, NCOA3, NCOAT
 * TF3C4

Interaction with HDACs
Histone acetyltransferases (HATs) and histone deacetylases (HDACs) are recruited to their target promoters through a physical interaction with a sequence-specific transcription factor (TF). They usually function within a multimolecular complex ('enzymatic complex'), in which the other subunits are necessary for them to modify nucleosomes around the binding site. These enzymes can also modify factors other than histones (protein X).