title: RNA-binding proteins HuR and PTB promote the translation of hypoxia-inducible factor 1alpha.
abstract: The levels of hypoxia-inducible factor 1alpha (HIF-1alpha) are tightly controlled. Here, we investigated the posttranscriptional regulation of HIF-1alpha expression in human cervical carcinoma HeLa cells responding to the hypoxia mimetic CoCl(2). Undetectable in untreated cells, HIF-1alpha levels increased dramatically in CoCl(2)-treated cells, while HIF-1alpha mRNA levels were unchanged. HIF-1alpha translation was potently elevated by CoCl(2) treatment, as determined by de novo translation analysis and by monitoring the polysomal association of HIF-1alpha mRNA. An internal ribosome entry site in the HIF-1alpha 5' untranslated region (UTR) was found to enhance translation constitutively, but it did not further induce translation in response to CoCl(2) treatment. Instead, we postulated that RNA-binding proteins HuR and PTB, previously shown to bind HIF-1alpha mRNA, participated in its translational upregulation after CoCl(2) treatment. Indeed, both RNA-binding proteins were found to bind HIF-1alpha mRNA in a CoCl(2)-inducible manner as assessed by immunoprecipitation of endogenous ribonucleoprotein complexes. Using a chimeric reporter, polypyrimidine tract-binding protein (PTB) was found to bind the HIF-1alpha 3'UTR, while HuR associated principally with the 5'UTR. Lowering PTB expression or HuR expression using RNA interference reduced HIF-1alpha translation and expression levels but not HIF-1alpha mRNA abundance. Conversely, HIF-1alpha expression and translation in response to CoCl(2) were markedly elevated after HuR overexpression. We propose that HuR and PTB jointly upregulate HIF-1alpha translation in response to CoCl(2).
authors.affiliation: LCMB, NIA, NIH, 5600 Nathan Shock Dr., Baltimore, MD 21224, USA.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Galbán
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kuwano
authors.forename: Rudolf
authors.initials: R
authors.lastname: Pullmann
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Martindale
authors.forename: Hyeon Ho
authors.initials: HH
authors.lastname: Kim
authors.forename: Ashish
authors.initials: A
authors.lastname: Lal
authors.forename: Kotb
authors.initials: K
authors.lastname: Abdelmohsen
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Yang
authors.forename: Youngjun
authors.initials: Y
authors.lastname: Dang
authors.forename: Jun O
authors.initials: JO
authors.lastname: Liu
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Lewis
authors.forename: Martin
authors.initials: M
authors.lastname: Holcik
authors.forename: Myriam
authors.initials: M
authors.lastname: Gorospe
mesh_terms: D000954:Antigens, Surface / Q000235:genetics / Q000378:metabolism*; D015687:Cell Hypoxia / Q000187:drug effects; D045744:Cell Line, Tumor; D003035:Cobalt / Q000494:pharmacology; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D038941:Polypyrimidine Tract-Binding Protein / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D014176:Protein Biosynthesis / Q000187:drug effects; D021381:Protein Transport; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D000954:Antigens, Surface; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; C098770:ELAVL1 protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D038941:Polypyrimidine Tract-Binding Protein; D003035:Cobalt; C018021:cobaltous chloride