p42/p44 mitogen-activated protein kinases phosphorylate hypoxia-inducible factor 1alpha (HIF-1alpha) and enhance the transcriptional activity of HIF-1.
Hypoxia-inducible factor-1 (HIF-1) controls the expression of a number of genes such as vascular endothelial growth factor and erythropoietin in low oxygen conditions. However, the molecular mechanisms that underlie the activation of the limiting subunit, HIF-1alpha, are still poorly resolved. Results showing that endogenous HIF-1alpha migrated 12 kDa higher than in vitro translated protein led us to evaluate the possible role of phosphorylation on this phenomenon. We report here that HIF-1alpha is strongly phosphorylated in vivo and that phosphorylation is responsible for the marked differences in the migration pattern of HIF-1alpha. In vitro, HIF-1alpha is phosphorylated by p42 and p44 mitogen-activated protein kinases (MAPKs) and not by p38 MAPK or c-Jun N-terminal kinase. Interestingly, p42/p44 MAPK stoichiometrically phosphorylate HIF-1alpha in vitro, as judged by a complete upper shift of HIF-1alpha. More importantly, we demonstrate that activation of the p42/p44 MAPK pathway in quiescent cells induced the phosphorylation and shift of HIF-1alpha, which was abrogated in presence of the MEK inhibitor, PD 98059. Finally, we found that in a vascular endothelial growth factor promoter mutated at sites previously shown to be MAPK-sensitive (SP1/AP2-88-66 site), p42/p44 MAPK activation is sufficient to promote the transcriptional activity of HIF-1. This interaction between HIF-1alpha and p42/p44 MAPK suggests a cooperation between hypoxic and growth factor signals that ultimately leads to the increase in HIF-1-mediated gene expression.
Richard
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Institute of Signaling, Developmental Biology and Cancer Research, UMR CNRS 6543, Centre Antoine Lacassagne, 33 Avenue Valombrose, 06189 Nice, France. drichard@unice.fr
Berra
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Gothié
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Roux
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Pouysségur
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D000818:Animals; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D014157:Transcription Factors; D015533:Transcriptional Activation / Q000235:genetics*
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D014157:Transcription Factors; D004958:Estradiol; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one