1MJ9

ESA1 Histone acyl transferase is able to catalyse the acylation of histone proteins at specific lysine residues, using acetyl coA as the acyl donor for the reaction. Acylation of histone proteins is important in the regulatation of DNA transcription, as it causes the chromasones to condense and become inaccessible to the enzymes required for unwinding and unzipping the DNA. As a result study of the mechanism by which acylation occurs is of interest to geneticists, and opens the possibility of manipulation of gene expression by designing activators or inhibitors of the enzymes catalysing the process.

Histone acyl transferases in eukaryotes show much sequence homology, and can consequently be assigned to a superfamily (HAT). However, the mechanism of reaction has been previously thought to be not the same where the MYST subfamily, of which ESA1 is a representative, have an acylated enzyme intermediate in the reaction mechanism. Despite this, it has been proposed more recently ESA1 when in complex with two accessory proteins does in fact work proceed with direct attack from the target lysine residue on the acetyl-COA. It has been suggested the catalytic mechanism may reflect the enzyme's physiological surroundings.