Mediates dioxin toxicity and is involved in regulation of cell growth and differentiation. Represses the transcription activity of AHR by competing with this transcription factor for heterodimer formation with the ARNT and subsequently binding to the xenobiotic response element (XRE) sequence present in the promoter regulatory region of variety of genes. Represses CYP1A1 by binding the XRE sequence and recruiting ANKRA2, HDAC4 and/or HDAC5. Autoregulates its expression by associating with its own XRE site. Interacts with ARNT, ANKRA2, HDAC4 and HDAC5. Interacts with ARNT; forms a heterodimer with ARNT (By similarity). Predominantly in the nuclear compartment. First cytoplasmic, translocates into the nuclear compartment upon interaction with ARNT in the cytoplasmic compartment. By 3MC. Up-regulated by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and beta-naphthoflavone in pituitary.