title: Expression of the human aryl hydrocarbon receptor complex in yeast. Activation of transcription by indole compounds.
abstract: The human aryl hydrocarbon receptor (AHR) and aryl hydrocarbon receptor nuclear translocator protein (ARNT) were coexpressed in the yeast Saccharomyces cerevisiae to create a system for the study of this heterodimeric transcription factor. Specific transcriptional activation mediated by AHR/ARNT heterodimer, which is a functional indicator of receptor expression, was assessed by beta-galactosidase activity produced from a reporter plasmid. Yeast expressing AHR and ARNT displayed constitutive transcriptional activity that was not augmented by addition of AHR agonists in strains that required exogenous tryptophan for viability. In contrast, strains with an intact pathway for tryptophan biosynthesis responded to AHR agonists and had lower levels of background beta-galactosidase activity. Hexachlorobenzene, benzo(a)pyrene, and beta-naphthoflavone were effective AHR agonists in the yeast system, and had EC50 values of 200, 40, and 20 nM, respectively, for beta-galactosidase activity induction. Tryptophan, indole, indole acetic acid, and tryptamine activated transcription in yeast coexpressing AHR and ARNT (EC50 values approximately 300 microM). Indole-3-carbinol was an exceptionally potent AHR agonist (EC50 approximately 10 microM) in yeast. This yeast system is useful for the study of AHR/ARNT protein complexes, and may be generally applicable to the investigation of other multiprotein complexes.
authors.affiliation: Department of Environmental Health Sciences and Center for Bioenvironmental Research, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana 70112, USA. rellim@mailhost.tcs.tulane.edu
authors.forename: C A
authors.initials: CA
authors.lastname: Miller
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins; D017930:Genes, Reporter; D005838:Genotype; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D018336:Receptors, Aryl Hydrocarbon / Q000096:biosynthesis* / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: C497396:ARNT protein, human; D000975:Antioxidants; D004268:DNA-Binding Proteins; D007211:Indoles; D018336:Receptors, Aryl Hydrocarbon; D014157:Transcription Factors; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; C016517:indole-3-carbinol; D019363:Cytochrome P-450 CYP1A1