title: Attenuation of HIF-1 DNA-binding activity limits hypoxia-inducible endothelin-1 expression.
abstract: Hypoxia-inducible factors (HIFs) locate to HIF-binding sites (HBSs) within the hypoxia-response elements (HREs) of oxygen-regulated genes. Whereas HIF-1alpha is expressed ubiquitously, HIF-2alpha is found primarily in the endothelium, similar to endothelin-1 (ET-1) and fms-like tyrosine kinase 1 (Flt-1), the expression of which is controlled by HREs. We identified an unique sequence alteration in both ET-1 and Flt-1 HBSs not found in other HIF-1 target genes, implying that these HBSs might cause binding of HIF-2 rather than HIF-1. However, electrophoretic mobility shift assays showed HIF-1 and HIF-2 DNA complex formation with the unique ET-1 HBS to be about equal. Both DNA-binding and hypoxic activation of reporter genes using the ET-1 HBS was decreased compared with transferrin and erythropoietin HBSs. The Flt-1 HBS was non-functional when assayed in isolation, suggesting that additional factors are required for hypoxic up-regulation via the reported Flt-1 HRE. Interestingly, HIF-1 activity could be restored fully by point-mutating the ET-1 (but not the Flt-1) HBS, suggesting that the wild-type ET-1 HBS attenuated the full hypoxic response known from other oxygen-regulated genes. Such a mechanism might serve to limit the expression of this potent vasoconstrictor in hypoxia.
authors.affiliation: Institute of Physiology, University of Zürich-Irchel, 8057 Zürich, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Camenisch
authors.forename: D M
authors.initials: DM
authors.lastname: Stroka
authors.forename: M
authors.initials: M
authors.lastname: Gassmann
authors.forename: R H
authors.initials: RH
authors.lastname: Wenger
mesh_terms: D001483:Base Sequence / Q000235:genetics; D051792:Basic Helix-Loop-Helix Proteins; D001665:Binding Sites / Q000235:genetics; D001667:Binding, Competitive; D015687:Cell Hypoxia / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D019332:Endothelin-1 / Q000235:genetics / Q000378:metabolism*; D004921:Erythropoietin / Q000378:metabolism; D015870:Gene Expression; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D014176:Protein Biosynthesis; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000502:physiology; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured; D040281:Vascular Endothelial Growth Factor Receptor-1; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D019332:Endothelin-1; D004921:Erythropoietin; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D020794:Receptor Protein-Tyrosine Kinases; D015534:Trans-Activators; D014157:Transcription Factors; D040281:Vascular Endothelial Growth Factor Receptor-1; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human