Role of the aryl hydrocarbon receptor nuclear translocator protein in aryl hydrocarbon (dioxin) receptor action.
Immunoprecipitation experiments performed on cytosolic extracts of the mouse hepatoma cell line Hepa-1c1c7 (Hepa-1) confirm that the 9-S, unliganded, cytosolic aryl hydrocarbon (Ah) receptor complex contains the 90-kDa heat shock protein and the Ah receptor protein but reveal that it does not contain the Ah receptor nuclear translocator (ARNT) protein. These experiments confirm that the 6-S liganded form of the receptor identified in nuclear extracts of cells treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) contains the Ah receptor protein and ARNT but not the 90-kDa heat shock protein. The 6-S liganded Ah receptor complex activates transcription of the CYP1A1 gene via its binding to upstream xenobiotic-responsive elements (XREs). Treatment of cytosolic extracts of Hepa-1 cells with TCDD in vitro transforms the Ah receptor complex to the XRE-binding state. No such transformation occurs in a C- mutant deficient in ARNT activity. When in vitro synthesized ARNT was added concomitantly with TCDD to C- cytosolic extracts, it associated with the Ah receptor and restored Ah receptor-dependent XRE-binding activity to the extracts. Covalent cross-linking experiments in nuclear extracts of Hepa-1 and human LS180 cells treated with TCDD in vivo demonstrate that both ARNT and the Ah receptor bind directly to the XRE core sequence.
Laboratory of Structural Biology and Molecular Medicine, School of Medicine, University of California, Los Angeles 90024.
M R
MR
Probst
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S
Reisz-Porszasz
R V
RV
Agbunag
M S
MS
Ong
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O
Hankinson
D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D001483:Base Sequence; D001692:Biological Transport / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays
C497396:ARNT protein, human; C497397:Arnt protein, mouse; D004268:DNA-Binding Proteins; D000072317:Polychlorinated Dibenzodioxins; D011506:Proteins; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug; D014157:Transcription Factors; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator