Identification of mRNAs that continue to associate with polysomes during hypoxia.
Tumors must adapt to the hypoxic environment in order to grow beyond a benign microscopic mass. In addition to transcriptional activation mediated by HIF-1alpha, hypoxia has also been reported to inhibit translation. The degree of translational inhibition is dependent on the duration as well as the severity of the hypoxic insult. Anoxia (<0.02% O(2)) seems to have a more rapid and dramatic effect on translation as compared to hypoxia. We show here that prolonged hypoxia dramatically and reversibly inhibits translation in PC-3 cells. We also found that mTOR is inactivated and eIF-2alpha is phosphorylated during hypoxic treatment but only the eIF-2alpha phosphorylation correlates with the translational repression. We further used polysome analysis and microarray technology to analyze the impact of this translational repression on gene expression. We found that 33 mRNAs were refractory to this translational repression and that there was no correlation between mRNA induction and the ability to recruit ribosomes during hypoxia. We also found that ribosomal protein encoding mRNAs are more sensitive to this translational repression as compared to the majority of mRNAs. Although other reports have analyzed the effect of translation inhibition on gene expression under anoxic conditions, we believe that this is the first report in hypoxic cells. Our results show that the translational repression that occurs during hypoxia does impact gene expression in the highly transformed prostate cancer cell line, PC-3.
Thomas
Jeff D
JD
Department of Pathology and Laboratory Medicine, Drexel University College of Medicine, Philadelphia, PA 19341, USA.
Johannes
Gregg J
GJ
D018797:Cell Cycle Proteins / Q000378:metabolism; D015687:Cell Hypoxia / Q000235:genetics; D015536:Down-Regulation; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism; D011132:Polyribosomes / Q000378:metabolism*; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000302:isolation & purification* / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000235:genetics; D058570:TOR Serine-Threonine Kinases; D014407:Tumor Cells, Cultured; D000099259:N-myc Downstream-Regulated Gene 1 Protein
D018797:Cell Cycle Proteins; D015852:Eukaryotic Initiation Factor-2; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D047908:Intracellular Signaling Peptides and Proteins; D020781:Matrix Metalloproteinase 1; D011494:Protein Kinases; D012333:RNA, Messenger; D012269:Ribosomal Proteins; D058570:TOR Serine-Threonine Kinases; D000099259:N-myc Downstream-Regulated Gene 1 Protein; C497442:HIF1A protein, human; C546842:MTOR protein, human