The gene encoding human retinoic acid-receptor-related orphan receptor alpha is a target for hypoxia-inducible factor 1.
Retinoic acid-receptor-related orphan receptor (ROR) alpha is a nuclear receptor involved in many pathophysiological processes such as cerebellar ataxia, inflammation, atherosclerosis and angiogenesis. In the present study we first demonstrate that hypoxia increases the amount of Rora transcripts in a wide panel of cell lines derived from diverse tissues. In addition, we identified a functional promoter sequence upstream of the first exon of the human Rora gene, spanning -487 and -45 from the translation initiation site of RORalpha1. When cloned in a luciferase reporter vector, this sequence allowed the efficient transcription of the luciferase gene in several cell lines. Interestingly, the activity of the Rora promoter was enhanced by hypoxia in HepG2 human hepatoma cells, and this effect was dependent on an HRE (hypoxia response element) spanning from -229 to -225. Using electrophoretic-mobility-shift assays, we showed that HIF-1 (hypoxia-inducible factor 1), which plays a key role in the transcriptional response to hypoxia, bound to this HRE. Overexpression of HIF-1alpha increased the activity of the Rora promoter through the HRE. Overexpression of a dominant-negative form of HIF-1alpha producing transcriptionally inactive HIF-1alpha/HIF-1beta dimers abolished hypoxic activation of the Rora promoter. This indicated that HIF-1 is involved in the response of RORalpha to hypoxia. Taken together, our data reveal Rora as a new HIF-1 target gene. This illustrates, at the molecular level, the existence of cross-talk between signalling pathways mediated by HIF-1 and those mediated by nuclear receptors.
Centre National de La Recherche Scientifique UPR9078, IRNEM (Institut fédératif de recherche Necker Enfants-Malades), Faculté de Médecine Necker-Enfants Malades, 156 rue de Vaugirard, 75015 Paris, Cédex 15, France.
Caroline
C
Chauvet
Brigitte
B
Bois-Joyeux
Edurne
E
Berra
Jacques
J
Pouyssegur
Jean-Louis
JL
Danan
D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000737:chemistry / Q000378:metabolism; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics*; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008113:Liver Neoplasms / Q000737:chemistry / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics*; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D016716:PC12 Cells / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics*
D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; C497444:Hif1a protein, rat; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; C539738:RORA protein, human; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D015534:Trans-Activators; D014157:Transcription Factors