title: Oxygen- and dioxin-regulated gene expression in mouse hepatoma cells.
abstract: The discovery that the oxygen-regulated transcription factor HIF-1 alpha and the dioxin receptor AhR share the common heterodimerization partner ARNT (HIF-1 beta) raised the question whether a cross-talk between oxygen and dioxin signal transduction pathways exists. To answer this question we investigated an ARNT-deficient mutant cell line (Hepa1C4), which has lost its capability of responding to dioxin. The results demonstrate that the presence of ARNT is indispensable for hypoxia-inducible HIF-1 DNA binding as well as for oxygen-regulated reporter gene activity mediated by the EPO 3' hypoxia response element (HRE). Hypoxic induction of the vascular endothelial growth factor (VEGF) gene, however, was only partially abrogated in Hepa1C4 cells, suggesting that HIF-1-independent oxygen signaling pathways might exist. We further studied HIF-1 and AhR/ARNT DNA binding activity as well as the regulation of oxygen- and xenobiotic-responsive genes by treating mouse Hepa1 hepatoma cells with hypoxia and/or the dioxin analogue ICZ. Hypoxia-inducible VEGF expression was found to be independent of ICZ-treatment, whereas ICZ-inducible cytochrome P-450IA1 expression was slightly reduced by hypoxic treatment of the cells. Interestingly, the enhancer function of a xenobiotic response element (XRE) linked to a reporter gene was induced by hypoxia, but expression of a HRE-containing reporter gene was not affected by ICZ treatment.
authors.affiliation: Institute of Physiology, University of Zürich-Irchel, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Gassmann
authors.forename: I
authors.initials: I
authors.lastname: Kvietikova
authors.forename: A
authors.initials: A
authors.lastname: Rolfs
authors.forename: R H
authors.initials: RH
authors.lastname: Wenger
mesh_terms: D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D015687:Cell Hypoxia / Q000235:genetics; D004273:DNA, Neoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004147:Dioxins / Q000633:toxicity*; D016228:Endothelial Growth Factors / Q000235:genetics; D005634:Fructose-Bisphosphate Aldolase / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D017930:Genes, Reporter / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008114:Liver Neoplasms, Experimental / Q000235:genetics* / Q000378:metabolism*; D008156:Luciferases / Q000235:genetics; D008222:Lymphokines / Q000235:genetics; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors / Q000235:genetics; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: C497396:ARNT protein, human; C497397:Arnt protein, mouse; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D004147:Dioxins; D016228:Endothelial Growth Factors; C497442:HIF1A protein, human; C497443:Hif1a protein, mouse; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008222:Lymphokines; D009687:Nuclear Proteins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D008156:Luciferases; D005634:Fructose-Bisphosphate Aldolase; D010100:Oxygen