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.
Probst
M R
MR
Laboratory of Structural Biology and Molecular Medicine, School of Medicine, University of California, Los Angeles 90024.
Reisz-Porszasz
S
S
Agbunag
R V
RV
Ong
M S
MS
Hankinson
O
O
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