title: Ligand-dependent interaction of the aryl hydrocarbon receptor with a novel immunophilin homolog in vivo.
abstract: In an effort to identify regulators of aryl hydrocarbon receptor (AHR) signaling, we have employed the yeast two-hybrid system to screen for human proteins that interact in a ligand-dependent manner with the AHR. After screening 1.4 x 10(6) clones from a human B cell library, two distinct clones were identified that associated specifically with the liganded receptor. No clones were identified that interacted preferentially with the unliganded AHR. One of the ligand-dependent clones, ARA9, encodes a novel 330-amino acid protein with regions of amino acid sequence similarity to the 52-kDa FK506-binding protein known to be associated with the glucocorticoid receptor. Yeast two-hybrid experiments with ARA9 demonstrated a strong interaction with the AHR that is enhanced 11-fold in the presence of the ligand beta-naphthoflavone. In vitro experiments using proteins generated in reticulocyte lysates confirmed this interaction and indicated that ARA9 can be co-immunoprecipitated with the AHR using antisera raised specifically for either the AHR or the 90-kDa heat shock protein. The observation that ARA9 has a high affinity for both the 90-kDa heat shock protein-associated and ligand-activated forms of the AHR suggests that ARA9 is a component of the AHR-signaling pathway in vivo.
authors.affiliation: McArdle Laboratory for Cancer Research, University of Wisconsin Medical School, Madison, Wisconsin 53706-1599, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Carver
authors.forename: C A
authors.initials: CA
authors.lastname: Bradfield
mesh_terms: D000595:Amino Acid Sequence; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D001402:B-Lymphocytes / Q000378:metabolism; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011485:Protein Binding; D011506:Proteins; D016601:RNA-Binding Proteins; D018336:Receptors, Aryl Hydrocarbon / Q000819:agonists / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D022021:Tacrolimus Binding Proteins; D014157:Transcription Factors / Q000378:metabolism
chemical_list: C497396:ARNT protein, human; D002352:Carrier Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; C114207:IVNS1ABP protein, human; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D009687:Nuclear Proteins; D011506:Proteins; D016601:RNA-Binding Proteins; D018336:Receptors, Aryl Hydrocarbon; D014157:Transcription Factors; C103265:aryl hydrocarbon receptor-interacting protein; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D022021:Tacrolimus Binding Proteins