Histone Acetyl Transferases
Overview
HATs or histone acetyltransferases, are enzymes that play a role in transcription activation, and are known to function in multi-subunit complexes of two main types; GNAT and MYST. They work by acetylating lysine amino acids on histone proteins. The positive charge of the lysine once acetylated, (the enzyme transfers an acetyl group from acetyl-CoA), is neutralised. This is important as it reduces the affinity between the histone and DNA, as it is negatively charged, which makes the DNA more accessible to other transcription factors[1]. However, this does not produce enough acetylation to impact chromatin structure so in addition to this the conformation change also produces protein-protein interaction domains called bromodomains. These bromodomains promote transcription as Bdf1 binds acetylated H4, and therefore recruits TFIID a subunit (TAFII250) of which also binds to the acetylated H4.
History
In the 1960s a correlation between acetylation and transcription was discovered. The first HAT was shown to be homologous to GCN5 in yeast, which was a monumental discovery as GCN5 was already known to function as a transcriptional activator[2].