Hypoxia-inducible transcription factor-1 (HIF-1) plays a decisive role in cell survival and adaptation to hypoxic stress by controlling the expression of genes involved in oxygen homeostasis. HIF-1 activity is fine-tuned through specific post-translational modifications of its essential HIF-1α subunit. Among these modifications, phosphorylation is important for HIF-1 transcriptional activity. Studies have shown that the mitogen-activated protein kinases, p42/p44 MAPKs, directly phosphorylate HIF-1α and increase HIF-1-mediated transcription. Pin1, a peptidyl-prolyl cis/trans isomerase, targets a number of proteins containing a phosphorylated Ser/Thr-Pro motif. Pin1 isomerization causes a change in target protein conformation which can modify their activity. Here, we identify Pin1 as an important HIF-1α partner. Immunoprecipitation and pull-down studies show that Pin1 interacts with HIF-1α. We demonstrate that the interaction between Pin1 and HIF-1α is regulated through p42/p44 MAPK pathway activation. By performing proteolysis studies, our results indicate that Pin1 catalytic activity generates a conformational change in HIF-1α. Finally, our work shows that Pin1 is required for gene-specific HIF-1 transcriptional activity. Our results indicate that the prolyl isomerase Pin1 regulates HIF-1 transcriptional activity by interacting with HIF-1α and promoting conformational changes in a p42/p44 MAPK phosphorylation-dependent manner.
1649 - 1656
Centre de recherche du CHU de Québec, L'Hôtel-Dieu de Québec, Department of Molecular Biology, Medical Biochemistry and Pathology, Université Laval, Québec, QC G1R 3S3, Canada.
Cell Line, Hela Cells, Animals, Humans, Mice, Peptidylprolyl Isomerase, Mitogen-Activated Protein Kinase 1, Mitogen-Activated Protein Kinase 3, RNA, Small Interfering, Transcription, Genetic, RNA Interference, Phosphorylation, Hypoxia-Inducible Factor 1, alpha Subunit, Protein Interaction Domains and Motifs, HEK293 Cells, NIMA-Interacting Peptidylprolyl Isomerase