Figure 1: Histone acetylation is regulated by the addition of acetyl-CoA via the opposing actions of histone acetyltransferases (HATs) and histone deacetylases (HDACs) in lysine resides on core histones. This addition of the acetyl group results in a more open, transcriptionally permissive chromatin conformation. Removal of acetyl groups by HDACs leads to a condensed, transcriptionally repressive chromatin conformation. HDACIs inhibit HDAC activity, subsequently altering gene transcription and remodelling chromatin by targeting a number of nonhistone proteins.