HIF prolyl-hydroxylase 2 is the key oxygen sensor setting low steady-state levels of HIF-1alpha in normoxia.
Hypoxia-inducible factor (HIF), a transcriptional complex conserved from Caenorhabditis elegans to vertebrates, plays a pivotal role in cellular adaptation to low oxygen availability. In normoxia, the HIF-alpha subunits are targeted for destruction by prolyl hydroxylation, a specific modification that provides recognition for the E3 ubiquitin ligase complex containing the von Hippel-Lindau tumour suppressor protein (pVHL). Three HIF prolyl-hydroxylases (PHD1, 2 and 3) were identified recently in mammals and shown to hydroxylate HIF-alpha subunits. Here we show that specific 'silencing' of PHD2 with short interfering RNAs is sufficient to stabilize and activate HIF-1alpha in normoxia in all the human cells investigated. 'Silencing' of PHD1 and PHD3 has no effect on the stability of HIF-1alpha either in normoxia or upon re-oxygenation of cells briefly exposed to hypoxia. We therefore conclude that, in vivo, PHDs have distinct assigned functions, PHD2 being the critical oxygen sensor setting the low steady-state levels of HIF-1alpha in normoxia. Interestingly, PHD2 is upregulated by hypoxia, providing an HIF-1-dependent auto-regulatory mechanism driven by the oxygen tension.
Berra
Edurne
E
Institute of Signaling, Developmental Biology and Cancer Research, CNRS UMR 6543, Centre Antoine Lacassagne, 33 Avenue Valombrose, 06189 Nice, France. berra@unice.fr
Benizri
Emmanuel
E
Ginouvès
Amandine
A
Volmat
Véronique
V
Roux
Danièle
D
Pouysségur
Jacques
J
D001692:Biological Transport; D015687:Cell Hypoxia; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D006900:Hydroxylation; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D017874:Immediate-Early Proteins; D007527:Isoenzymes / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D011393:Procollagen-Proline Dioxygenase / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D017874:Immediate-Early Proteins; D007527:Isoenzymes; D009687:Nuclear Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D014157:Transcription Factors; C490190:EGLN1 protein, human; D011393:Procollagen-Proline Dioxygenase; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D010100:Oxygen