Required for activity of histone deacetylase complexes that are responsible for the deacetylation of lysine residues on the N-terminal part of the core histones (H2A, H2B, H3 and H4). Histone deacetylation gives a tag for epigenetic repression and plays an important role in transcriptional regulation, cell cycle progression and developmental events (By similarity). Probable component of some histone deacetylase complex. Belongs to the HDA2/3 family. HDA2 subfamily.