Histone deacetylases (HDACs) (HDACs)

Histone deacetylases (HDACs) are a family of zinc-dependent enzymes that catalyze the removal of acetyl groups from lysine residues on histones and other nuclear proteins, leading to chromatin condensation and repression of gene transcription. Mammalian HDACs are classified into four groups based on sequence similarity and domain structure: Class I (HDAC1, 2, 3, 8), Class IIa (HDAC4, 5, 7, 9), Class IIb (HDAC6, 10), and Class IV (HDAC11). They are involved in key cellular processes including cell cycle regulation, apoptosis, differentiation, and maintenance of epigenetic state. Aberrant HDAC activity often contributes to pathogenic states including cancer, immune disorders, and neurodegeneration, making them significant therapeutic targets. HDAC inhibitors have emerged as an important class of drugs, modifying gene expression by promoting histone acetylation, with approved indications in certain hematologic cancers and ongoing research in solid tumors, CNS disease, and other chronic conditions. Isoform-specific expression and subcellular localization contribute to their diverse biological functions.

Other names

Histone deacetylase (general family name)Class I HDACs (HDAC1, HDAC2, HDAC3, HDAC8)Class IIa HDACs (HDAC4, HDAC5, HDAC7, HDAC9)Class IIb HDACs (HDAC6, HDAC10)Class IV HDAC (HDAC11)Other species-specific or experimental designations (Hda1, Rpd3 in yeast)

Inhibition of histone deacetylase enzymatic activity: drugs bind to HDAC active sites, preventing removal of acetyl groups from lysines on histones and non-histone proteins. Chromatin relaxation and transcriptional upregulation: increased histone acetylation opens chromatin, enabling expression of genes including those mediating cell cycle arrest, apoptosis, and differentiation. Disruption of protein-protein interactions: inhibition can affect HDAC complex formation and function, modulating signaling and transcription. Induction of DNA damage and cellular stress: some inhibitors trigger DNA damage responses.