The Ah receptor, bHLH/PAS transcription factor, upon binding of an agonist such as 2,3,7,8-tetrachlorodibenzo-p-dioxin translocates into the nucleus and heterodimerizes with the transcription factor ARNT. The Ahreceptor/ARNT heterodimer binds to dioxin-responsive elements and alters expression of a number of genes including; CYP1A1, CYP1A2, CYP1B1, and NAD(P)H quinone oxidoreductase. The inactive form of the Ah receptor exists in the cytoplasm as a tetrameric complex composed of the ligand binding subunit, a dimer of the 90-kDa heat shock protein, and X-associated protein 2 (also refered to as AIP or ARA9).
Contributor: Dr. Gary Pedrew
REFERENCES: Meyer, B.K., and Perdew, G.H. (1999) Biochemistry 38, 8907-8917. Whitlock, J.P., Jr. (1999) Annu. Rev. Pharmacol. 39, 103-25.
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