title: Differential responses of two degradation domains of HIF-1alpha to hypoxia and iron deficiency.
abstract: HIF-1alpha is a transcription factor involved in the cellular adaptation to either hypoxia or iron deficiency. In the presence of oxygen and iron, proline residues in two degradation domains are modified by HIF-1-prolyl hydroxylases (PHDs), resulting in ubiquitination and degradation of HIF-1alpha. Since both molecular oxygen and iron are elements required for this hydroxylation process, HIF-1alpha might be unmodified and stable in conditions lacking oxygen or iron. If so, two degradation domains may respond to hypoxia and iron-depletion in the same way. In this study, however, we found two degradation domains to differentially regulate the stability of HIF-1alpha. The C-terminal domain responded to both hypoxia and iron-depletion, but the N-terminal domain to only iron-depletion. The deletion or point-mutation of the C-terminal domain blunted the hypoxic induction of HIF-1alpha. However, PHD-silencing siRNAs revealed that two degradation domains were not regulated by different types of PHDs. Both domains were regulated mainly by PHD2. The further mutational analysis demonstrated that the ARD1-acetylated motif near the C-terminal degradation domain (CDD) modulates the oxygen-dependent regulation of HIF-1alpha. The oxygen-dependent HIF-1alpha regulation requiring both proline hydroxylation and lysine acetylation may be more complicated than the iron-dependent regulation requiring only proline hydroxylation.
authors.affiliation: Department of Pharmacology, Seoul National University College of Medicine, 28, Yongon-dong, Chongno-gu, Seoul 110-799, South Korea.
authors.forename: Kyoung-Hwa
authors.initials: KH
authors.lastname: Lee
authors.forename: Eunjoo
authors.initials: E
authors.lastname: Choi
authors.forename: Yang-Sook
authors.initials: YS
authors.lastname: Chun
authors.forename: Myung-Suk
authors.initials: MS
authors.lastname: Kim
authors.forename: Jong-Wan
authors.initials: JW
authors.lastname: Park
mesh_terms: D002460:Cell Line; D003676:Deferoxamine / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D000090463:Iron Deficiencies; D010100:Oxygen / Q000378:metabolism*; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D017262:Siderophores / Q000378:metabolism
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D034741:RNA, Small Interfering; D017262:Siderophores; D007501:Iron; D003676:Deferoxamine; D010100:Oxygen