Gene expression during acute and prolonged hypoxia is regulated by distinct mechanisms of translational control.
Hypoxia has recently been shown to activate the endoplasmic reticulum kinase PERK, leading to phosphorylation of eIF2alpha and inhibition of mRNA translation initiation. Using a quantitative assay, we show that this inhibition exhibits a biphasic response mediated through two distinct pathways. The first occurs rapidly, reaching a maximum at 1-2 h and is due to phosphorylation of eIF2alpha. Continued hypoxic exposure activates a second, eIF2alpha-independent pathway that maintains repression of translation. This phase is characterized by disruption of eIF4F and sequestration of eIF4E by its inhibitor 4E-BP1 and transporter 4E-T. Quantitative RT-PCR analysis of polysomal RNA indicates that the translation efficiency of individual genes varies widely during hypoxia. Furthermore, the translation efficiency of individual genes is dynamic, changing dramatically during hypoxic exposure due to the initial phosphorylation and subsequent dephosphorylation of eIF2alpha. Together, our data indicate that acute and prolonged hypoxia regulates mRNA translation through distinct mechanisms, each with important contributions to hypoxic gene expression.
Koritzinsky
Marianne
M
Department of Radiation Oncology (Maastro), GROW Research Institute, University of Maastricht, The Netherlands.
Magagnin
Michaël G
MG
van den Beucken
Twan
T
Seigneuric
Renaud
R
Savelkouls
Kim
K
Dostie
Josée
J
Pyronnet
Stéphane
S
Kaufman
Randal J
RJ
Weppler
Sherry A
SA
Voncken
Jan Willem
JW
Lambin
Philippe
P
Koumenis
Constantinos
C
Sonenberg
Nahum
N
Wouters
Bradly G
BG
D048868:Adaptor Proteins, Signal Transducing; D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000502:physiology*; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D039562:Eukaryotic Initiation Factor-4F / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D000860:Hypoxia / Q000235:genetics*; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011132:Polyribosomes / Q000235:genetics; D014176:Protein Biosynthesis; D012313:RNA / Q000032:analysis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; C411571:EIF4ENIF1 protein, human; D015852:Eukaryotic Initiation Factor-2; D039561:Eukaryotic Initiation Factor-4E; D039562:Eukaryotic Initiation Factor-4F; D029543:Nucleocytoplasmic Transport Proteins; D010750:Phosphoproteins; D012313:RNA