Controls V(D)J recombination during T-cell development by repressing T-cell receptor (TCR) beta enhancer function. Binds to scaffold/matrix attachment region beta (S/MARbeta), an ATC-rich DNA sequence located upstream of the TCR beta enhancer. Represses cyclin D1 transcription by recruiting HDAC1 to its promoter, thereby diminishing H3K9ac, H3S10ph and H4K8ac levels. Promotes TP53 activation, which causes cell cycle arrest and inhibits tumor growth (PubMed:12494467). Interacts with TP53 (PubMed:12494467). Interacts with CUX1/CDP (PubMed:15371550). Interacts with HDAC1 (PubMed:16166625). Part of a corepressor complex containing BANP, HDAC1, SIN3A, SIN3B, RBL1 and RBL2 (PubMed:16166625). Highly expressed in heart, spleen, and thymus. Isoform 1 is highly expressed in kidney, brain and testis. Isoform 3 is highly expressed in kidney and lung. Belongs to the BANP/SMAR1 family. Interaction with TP35 was reported to promotes TP53 'Ser-15' phosphorylation and nuclear accumulation causing cell cycle arrest and inhibition of tumor growth (PubMed:15701641). However, the publication has been retracted due to image duplication and manipulation. Interaction with TP35 has been confirmed by other studies (PubMed:12494467). The nuclear locatization has been confirmed by other studies (PubMed:10940556, PubMed:12494467, PubMed:15371550, PubMed:16166625).