title: pVHL-independent ubiquitination of HIF1alpha and its stabilization by cobalt ion.
abstract: Recent studies have shown that hypoxia-inducible factor1alpha (HIF1alpha) is ubiquitinated by an E3-ligase complex containing von Hippel-Lindau gene product (pVHL) after which it is targeted for proteasomal degradation. In this study, we showed that HIF1alpha was stabilized in the pVHL-deficient cell line 786-0 treated with a proteasome inhibitor or Co(2+). This suggests that HIF1alpha is also ubiquitinated by a pVHL-independent pathway and that its stability is regulated by Co(2+). Indeed, using the COS cell expression system, we confirmed that HIF1alpha is ubiquitinated at the N-terminal region by a pVHL-independent pathway and that its degradation is inhibited by Co(2+). We also demonstrated that Co(2+) binds to both PAS domains in the N-terminal region of HIF1alpha. These observations imply that the stability of HIF1alpha is regulated by an additional pathway through the cobalt binding of PAS domains.
authors.affiliation: Institute of Molecular Medicine, The University of Texas-Houston Health Science Center, Houston, TX 77030, USA.
authors.forename: Koichi
authors.initials: K
authors.lastname: Kanaya
authors.forename: Tetsu
authors.initials: T
authors.lastname: Kamitani
mesh_terms: D000818:Animals; D019556:COS Cells; D003035:Cobalt / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism; D004795:Enzyme Stability; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008025:Ligases / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein
chemical_list: D004791:Enzyme Inhibitors; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009097:Multienzyme Complexes; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; D003035:Cobalt; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D008025:Ligases; C497446:VHL protein, human