This gene encodes a protein that represses aryl hydrocarbon receptor-dependent signaling. The encoded protein competes with the aryl hydrocarbon receptor transcription factor for heterodimerization with the aryl hydrocarbon receptor nuclear translocator protein and binding to xenobiotic response element (XRE) sequence in many genes. This protein is implicated in the regulation of cell growth and differentiation as well as mediating dioxin toxicity. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Nov 2015]