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 lysine to form ε-N-acetyl lysine.

Histone acetylation is generally linked to transcriptional activation. These are generally associated with euchromatin. Initially, 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. More recently, it has emerged 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.

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)