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 (By similarity). Interacts with TP53 (By similarity). Interacts with CUX1/CDP (By similarity). Interacts with HDAC1 (By similarity). Part of a corepressor complex containing BANP, HDAC1, SIN3A, SIN3B, RBL1 and RBL2 (By similarity). Belongs to the BANP/SMAR1 family.