Histone deacetylase that catalyzes the deacetylation of lysine residues on the N-terminal part of the core histones (H2A, H2B, H3 and H4) (PubMed:10748112, PubMed:10922473, PubMed:10926844, PubMed:14701748, PubMed:28497810). Histone deacetylation gives a tag for epigenetic repression and plays an important role in transcriptional regulation, cell cycle progression and developmental events (PubMed:10748112, PubMed:10922473, PubMed:10926844, PubMed:14701748). Histone deacetylases act via the formation of large multiprotein complexes (PubMed:10748112, PubMed:10922473, PubMed:10926844, PubMed:14701748). Also involved in the deacetylation of cohesin complex protein SMC3 regulating release of cohesin complexes from chromatin (PubMed:22885700). May play a role in smooth muscle cell contractility (PubMed:15772115). In addition to protein deacetylase activity, also has protein-lysine deacylase activity: acts as a protein decrotonylase by mediating decrotonylation ((2E)-butenoyl) of histones (PubMed:28497810).