May be a transcriptional coactivator of the nuclear receptor ESR1 required to induce the expression of a subset of estradiol target genes, such as CCND1, MYC and E2F1. May play a role in the recruitment or occupancy of CREBBP at some ESR1 target gene promoters. May be required for histone hyperacetylation. Involved in the estrogen-induced cell proliferation and cell cycle progression of breast cancer cells. ATP + H2O = ADP + H(+) + phosphate Interacts with ESR1 and NCOA3 and these interactions are enhanced by estradiol. Interacts with acetylated lysine residues on histone H1.4, H2A, H2B and H3 (in vitro). Highly expressed in estrogen receptor positive breast tumors and in osteosarcoma tumors. Up-regulated in breast, uterus, colon, ovary, and stomach tumors. Induced in breast cancer cells overexpressing NCOA3 or treated with estrogen. Down-regulated in 5-fluorouracil-resistant derivatives of the colon cancer cell line HCT 116. Dubious isoform. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the AAA ATPase family. Contaminating sequence. Sequence of unknown origin in the N-terminal part (676-679).