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. Histone deacetylases act via the formation of large multiprotein complexes. Forms transcriptional repressor complexes by associating with MAD; SIN3; YY1 and N-COR. Interacts in the late S-phase of DNA-replication with DNMT1 in the other transcriptional repressor complex composed of DNMT1; DMAP1; PCNA; CAF1. Deacetylates TSHZ3 and regulates its transcriptional repressor activity. Component of a RCOR/GFI/KDM1A/HDAC complex that suppresses; via histone deacetylase (HDAC) recruitment; a number of genes implicated in multilineage blood cell development. May be involved in the transcriptional repression of circadian target genes; such as PER1; mediated by CRY1 through histone deacetylation. Involved in MTA1-mediated transcriptional corepression of TFF1 and CDKN1A. {ECO:0000269|PubMed:19343227; ECO:0000269|PubMed:21965678}.