Involved in the functional recruitment of the Sin3-histone deacetylase complex (HDAC) to a specific subset of N-CoR corepressor complexes. Capable of transcription repression by N-CoR. Active in deacetylating core histone octamers (when in a complex) but inactive in deacetylating nucleosomal histones. (Microbial infection) Involved in transcriptional repression of HHV-1 genes TK and gC. Component of the histone deacetylase complex that includes at least SIN3A, HDAC1 and HDAC2 (By similarity). Found in a complex composed of at least SINHCAF, SIN3A, HDAC1, SAP30, RBBP4, OGT and TET1 (By similarity). Interacts with HDAC1 (PubMed:9651585). Interacts with SIN3A, SIN3B, HDAC2, RBBP4 and NCOR1 (By similarity). Interacts with SAMSN1 (By similarity). Interacts with HCFC1 (PubMed:12670868). Interacts with SAP30BP (PubMed:15496587). Expressed in all tissues tested with highest levels in pancreas, ovary, PBL, spleen and thymus; lowest levels in brain, placenta, lung and kidney. Belongs to the SAP30 family.