Plays a role in transcriptional repression by promoting histone deacetylase activity, leading to deacetylation of histone H3 (PubMed:21221920). Acts as a regulator of pre-mRNA splicing by facilitating assembly of the cyclin-L-CDK11 cyclin-dependent protein kinase complex, thereby promoting phosphorylation of SF3B1 (PubMed:38059508). May be involved in the regulation of beta-2- microglobulin genes (By similarity). {ECO:0000250|UniProtKB:Q02614, ECO:0000269|PubMed:21221920, ECO:0000269|PubMed:38059508}. (Microbial infection) Involved in transcriptional repression of HHV-1 genes TK and gC. . This is the function of ENSG00000161526 (SAP30BP, SAP30 binding protein).