title: Activity of hypoxia-inducible factor 2alpha is regulated by association with the NF-kappaB essential modulator.
abstract: The hypoxia-inducible factors 1alpha (HIF-1alpha) and 2alpha (HIF-2alpha) are key regulators of the transcriptional response to low oxygen and are closely related in domain architecture, DNA binding, and activation mechanisms. Despite these similarities, targeted disruption of the HIF-alpha genes in mice results in distinctly different phenotypes demonstrating nonredundancy of function, although the underlying mechanisms remain unclear. Here we report on the novel and specific interaction of HIF-2alpha, but not HIF-1alpha, with the NF-kappaB essential modulator (NEMO) using immunoprecipitation, mammalian two-hybrid, and in vitro protein interaction assays. Reporter gene assays demonstrate that this interaction specifically enhances normoxic HIF-2alpha transcriptional activity, independently of the HIF-2alpha transactivation domain, consistent with a model by which NEMO aids CBP/p300 recruitment to HIF-2alpha. In contrast, HIF-2alpha overexpression does not alter NF-kappaB signaling, suggesting that the functional consequence of the HIF-2alpha/NEMO interaction is limited to the HIF pathway. The specificity of NEMO for HIF-2alpha represents one of the few known differential protein-protein interactions between the HIF-alpha proteins, which has important implications for the activity of HIF-2alpha and is also the first postulated NF-kappaB-independent role for NEMO.
authors.affiliation: School of Molecular and Biomedical Science and the Centre for the Molecular Genetics of Development, University of Adelaide, Adelaide, South Australia, 5005, Australia.
authors.forename: Cameron P
authors.initials: CP
authors.lastname: Bracken
authors.forename: Murray L
authors.initials: ML
authors.lastname: Whitelaw
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Peet
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D002460:Cell Line; D050881:E1A-Associated p300 Protein; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D051550:I-kappa B Kinase; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D050881:E1A-Associated p300 Protein; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D051550:I-kappa B Kinase; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D017346:Protein Serine-Threonine Kinases; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human; C494361:Ep300 protein, mouse; C496559:CHUK protein, human; C496564:Chuk protein, mouse; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse