RNA-binding proteins HuR and PTB promote the translation of hypoxia-inducible factor 1alpha.
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).
Galbán
Stefanie
S
LCMB, NIA, NIH, 5600 Nathan Shock Dr., Baltimore, MD 21224, USA.
Kuwano
Yuki
Y
Pullmann
Rudolf
R
Martindale
Jennifer L
JL
Kim
Hyeon Ho
HH
Lal
Ashish
A
Abdelmohsen
Kotb
K
Yang
Xiaoling
X
Dang
Youngjun
Y
Liu
Jun O
JO
Lewis
Stephen M
SM
Holcik
Martin
M
Gorospe
Myriam
M
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
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