Nuclear receptor that binds and is activated by a 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, endogenous compounds and drugs. Response to specific ligands is species-specific, due to differences in the ligand-binding domain. 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 (By similarity). Heterodimer with RXRA (By similarity). Interacts with NCOA1 (By similarity). Interacts (via domain NR LBD) with CRY1 and CRY2 in a ligand-dependent manner (By similarity). Belongs to the nuclear hormone receptor family. NR1 subfamily.