Histone deacetylase (HDAC) proteins play an important role in gene expression by governing
the acetylation state of lysine residues located on the amino-terminal tails of histone proteins
(Fig. 1). Histones comprise nucleosomes, which are the basic packaging units of chromosomes.
1 By binding to genomic DNA, the accessibility of genes to transcriptional proteins is altered
by histone lysine acetylation. As a result, HDAC proteins are generally associated with
repression of transcription and reduced gene expression (for a review of HDAC proteins,
histone acetylation, and transcription, see ref. 2