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. {ECO:0000250|UniProtKB:O88574, ECO:0000269|PubMed:9651585}. (Microbial infection) Involved in transcriptional repression of HHV-1 genes TK and gC. . This is the function of SAP30 (Sin3A associated protein 30, ENSG00000164105).