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 ANKRA2, HDAC4 and HDAC5. Interacts with ARNT; forms a heterodimer with ARNT (PubMed:28904176). Predominantly in the nuclear compartment. First cytoplasmic, translocates into the nuclear compartment upon interaction with ARNT in the cytoplasmic compartment. Highly expressed in testis, lung, ovary, spleen and pancreas. Highly expressed in mononuclear cells (MNCs) from umbilical cord blood. Isoform 3 is highly expressed in lung, kidney, spleen and thymus. Down-regulated malignant tissue from different anatomical origins, including colon, breast, lung, stomach, cervix, and ovary. By 3-methylcholanthrene (3-MC) in MNCs from adults. By the heterodimer AHR/ARNT. The Ala-189 allele may be a susceptibility factor for dioxin-related male infertility. Homozygosity for Ala-189 is observed in azoospermic individuals at higher frequency than in normozoospermic individuals (PubMed:15474075, PubMed:17559847). Might also be associated with susceptibility to and severity of endometriosis. Truncated N-terminus. Extended N-terminus.