Nuclear receptor that binds and is activated by variety of endogenous and xenobiotic compounds. Transcription factor that activates the transcription of multiple genes involved in the metabolism and secretion of potentially harmful xenobiotics, drugs and endogenous compounds. Activated by the antibiotic rifampicin and various plant metabolites, such as hyperforin, guggulipid, colupulone, and isoflavones. Response to specific ligands is species-specific. Activated by naturally occurring steroids, such as pregnenolone and progesterone. Binds to a response element in the promoters of the CYP3A4 and ABCB1/MDR1 genes. Heterodimer with RXR. Interacts with NCOA1. Interacts (via domain NR LBD) with CRY1 and CRY2 in a ligand-dependent manner (By similarity). Expressed in liver, colon and small intestine. Belongs to the nuclear hormone receptor family. NR1 subfamily.