Histone deacetylase (HDAC) class I and class II (HDAC class I and II)

Histone deacetylase class I and II enzymes are zinc-dependent hydrolases that remove acetyl groups from lysine residues on histones and other proteins, leading to chromatin condensation and transcriptional repression. Class I HDACs (HDAC1, HDAC2, HDAC3, HDAC8) are nuclear and generally exhibit strong deacetylase activity. Class II HDACs (HDAC4, 5, 6, 7, 9, 10) shuttle between nucleus and cytoplasm and often participate in broader signaling processes; class IIa HDACs are typically enzymatically weak unless complexed with other proteins. Both groups help control cell cycle, metabolism, apoptosis, and stress responses, and are frequently dysregulated in diseases, especially cancer, where HDACs promote tumor growth and survival. Pharmacological inhibition of HDACs alters chromatin structure and gene expression, providing the rationale for HDAC inhibitors as anticancer therapies.

Other names

HDACsHistone deacetylase familyClassical HDACs (when referring to class I and II/IV)

HDAC inhibitors bind to the catalytic site and block deacetylation, causing histone hyperacetylation, chromatin relaxation, and transcriptional activation of silenced genes (often triggering cell cycle arrest, differentiation, and apoptosis in tumor cells).