Transcription coregulator that can have both coactivator and corepressor functions. Involved in the coactivation of nuclear receptors for retinoid X (RXRs) and thyroid hormone (TRs) in a ligand-dependent fashion. In contrast; it does not coactivate nuclear receptors for retinoic acid; vitamin D; progesterone receptor; nor glucocorticoid. Acts as a coactivator for estrogen receptor alpha. Acts as a transcriptional corepressor via its interaction with the NFKB1 NF-kappa-B subunit; possibly by interfering with the transactivation domain of NFKB1. Induces apoptosis in breast cancer cells; but not in other cancer cells; via a caspase-2 mediated pathway that involves mitochondrial membrane permeabilization but does not require other caspases. May also act as an inhibitor of cyclin A-associated kinase. Also acts a component of the CENPA-CAD (nucleosome distal) complex; a complex recruited to centromeres which is involved in assembly of kinetochore proteins; mitotic progression and chromosome segregation. May be involved in incorporation of newly synthesized CENPA into centromeres via its interaction with the CENPA-NAC complex (By similarity). {ECO:0000250}.