Transcriptional corepressor. May specifically inhibit gene expression when recruited to promoter regions by sequence-specific DNA- binding proteins such as BCL6 and MLLT3. This repression may be mediated at least in part by histone deacetylase activities which can associate with this corepressor. Involved in the repression of TFAP2A; impairs binding of BCL6 and KDM2B to TFAP2A promoter regions. Via repression of TFAP2A acts as a negative regulator of osteo-dentiogenic capacity in adult stem cells; the function implies inhibition of methylation on histone H3 'Lys-4' (H3K4me3) and 'Lys-36' (H3K36me2). {ECO:0000269|PubMed:10898795, ECO:0000269|PubMed:15004558, ECO:0000269|PubMed:18280243, ECO:0000269|PubMed:19578371, ECO:0000269|PubMed:23911289}. This is the function of BCOR (BCL6 corepressor, ENSG00000183337).