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). Homodimer; mediated by the coiled coil domain. Interacts with CCNA2 and MTA1. Interacts with NFKB1 NF-kappa-B subunit. Component of the CENPA-CAD complex, composed of CENPI, CENPK, CENPL, CENPO, CENPP, CENPQ, CENPR and CENPS. The CENPA-CAD complex interacts with the CENPA-NAC complex, at least composed of CENPA, CENPC, CENPH, CENPM, CENPN, CENPT and CENPU (By similarity). Interacts with TASOR (By similarity). The DD1 domain (also called RepD1 domain) mediates the corepressor function and is essential in the triggering of apoptosis. Contains one Leu-Xaa-Xaa-Leu-Leu (LXXLL) motif, a motif known to be important for the association with nuclear receptors. Contains one Leu-Xaa-Xaa-Ile-Leu (LXXIL) motif, which is essential for the association with nuclear receptors.