Histone deacetylase that catalyzes 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. Histone deacetylases act via the formation of large multiprotein complexes. Also involved in the deacetylation of cohesin complex protein SMC3 regulating release of cohesin complexes from chromatin. May play a role in smooth muscle cell contractility. In addition to protein deacetylase activity, also has protein-lysine deacylase activity: acts as a protein decrotonylase by mediating decrotonylation ((2E)-butenoyl) of histones. H2O + N(6)-acetyl-L-lysyl-[histone] = acetate + L-lysyl-[histone] H2O + N(6)-acetyl-L-lysyl-[protein] = acetate + L-lysyl-[protein] H2O + N(6)-(2E)-butenoyl-L-lysyl-[protein] = (2E)-2-butenoate + L-lysyl-[protein] Binds 1 divalent metal cation per subunit. Its activity is inhibited by trichostatin A (TSA) and butyrate, 2 well known histone deacetylase inhibitors. Interacts with CBFA2T3. Interacts with phosphorylated SMG5/EST1B; this interaction protects SMG5 from ubiquitin-mediated degradation. Associates with alpha-SMA (smooth muscle alpha-actin) (By similarity). Excluded from the nucleoli. Found in the cytoplasm of cells showing smooth muscle differentiation. Phosphorylated by PKA on serine 39. Phosphorylation reduces deacetylase activity observed preferentially on histones H3 and H4 (By similarity). Belongs to the histone deacetylase family. HD type 1 subfamily.