Histone Deacetylase

Histone deacetylases (HDACs) are a family of enzymes that remove acetyl groups from the ε-N-acetyl lysine residues on histone and non-histone proteins. This enzymatic activity leads to chromatin condensation and transcriptional repression, playing a central role in the regulation of gene expression, cell cycle progression, development, and disease states such as cancer. There are 18 known HDAC enzymes divided into four classes based on sequence homology and cofactor dependency: Class I (HDAC1, HDAC2, HDAC3, HDAC8), Class II (HDAC4, HDAC5, HDAC6, HDAC7, HDAC9, HDAC10), Class III (SIRT1–SIRT7), and Class IV (HDAC11).

HDAC inhibitors bind to the active site of HDAC enzymes, preventing the removal of acetyl groups from histone and non-histone proteins. This leads to increased acetylation, chromatin relaxation, and altered gene expression, often resulting in cell cycle arrest or apoptosis, particularly in cancer cells.