Nuclear receptor coactivator that directly binds nuclear receptors and stimulates the transcriptional activities in a hormone-dependent fashion. Coactivates expression in an agonist- and AF2-dependent manner. Involved in the coactivation of different nuclear receptors, such as for steroids (GR and ERs), retinoids (RARs and RXRs), thyroid hormone (TRs), vitamin D3 (VDR) and prostanoids (PPARs). Probably functions as a general coactivator, rather than just a nuclear receptor coactivator. May also be involved in the coactivation of the NF-kappa-B pathway. May coactivate expression via a remodeling of chromatin and its interaction with histone acetyltransferase proteins. Monomer and homodimer. Interacts with RBM39 (By similarity). Interacts in vitro with the basal transcription factors GTF2A and TBP, suggesting an autonomous transactivation function. Interacts with NCOA1, CRSP3, RBM14, the histone acetyltransferases EP300 and CREBBP, and with the methyltransferases NCOA6IP and PRMT2/HRMT1L1. Component of the MLL2/3 complex (also named ASCOM complex), at least composed of KMT2D/MLL2 or KMT2C/MLL3, ASH2L, RBBP5, WDR5, NCOA6, DPY30, KDM6A, PAXIP1/PTIP, PAGR1 and alpha- and beta-tubulin. Interacts with ZNF335; may enhance ligand-dependent transcriptional activation by nuclear hormone receptors. Ubiquitous. Highly expressed in brain, prostate, testis and ovary; weakly expressed in lung, thymus and small intestine. Contains two Leu-Xaa-Xaa-Leu-Leu (LXXLL) motifs. Only motif 1 is essential for the association with nuclear receptors, while adjacent Ser-884 displays selectivity for nuclear receptors. Phosphorylated by PRKDC. Phosphorylation on Ser-884 leads to a strong decrease in binding to ESR1 and ESR2. Frequently amplified or overexpressed in colon, breast and lung cancers. Extended N-terminus.