Pim-1 protein expression is regulated by its 5'-untranslated region and translation initiation factor elF-4E.
Expression of Pim-1, an oncogenic serine/threonine kinase, is highly regulated at the transcriptional, posttranscriptional, and posttranslational levels. Here, we report that expression of Pim-1 kinase is additionally regulated at the translational level. Pim-1 protein expression did not increase in Hut-78 lymphocytes in response to PMA1/ionomycin stimulation despite approximately 20-fold increases in mRNA levels, suggesting that translation was repressed. Sequence analysis of the 5'-untranslated region (UTR) indicated a long (400 nucleotide), 76% G + C-rich region, characteristics known to inhibit translation. Deletion of the 5'-UTR of pim-1 increased translation of the Pim-1 protein approximately 10-fold in vitro in reticulocyte lysates and approximately 1.6-fold in vivo in NIH-3T3 cells. When full-length 5'-UTR-containing pim-1 cDNA constructs were transfected into NIH-3T3 cells overexpressing eukaryotic translation initiation factor 4E (eIF-4E), approximately 6-fold higher levels of Pim-1 protein were produced, as compared to that produced in control NIH-3T3 cells. Moreover, eIF-4E overexpression had little effect in the absence of the 5'-UTR, suggesting that it relieved 5'-UTR-mediated inhibition of Pim-1 expression.
Hoover
D S
DS
Department of Genetics and Cell Biology, Washington State University, Pullman 99164-4233, USA.
Wingett
D G
DG
Zhang
J
J
Reeves
R
R
Magnuson
N S
NS
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D039561:Eukaryotic Initiation Factor-4E; D006801:Humans; D008715:Methionine / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009550:Nigericin / Q000031:analogs & derivatives / Q000494:pharmacology; D009690:Nucleic Acid Conformation; D010448:Peptide Initiation Factors / Q000096:biosynthesis / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D051573:Proto-Oncogene Proteins c-pim-1; D012333:RNA, Messenger / Q000032:analysis / Q000502:physiology*; D012156:Reticulocytes / Q000378:metabolism; D017423:Sequence Analysis, RNA; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives / Q000494:pharmacology; D014158:Transcription, Genetic; D014162:Transfection; D001616:beta-Galactosidase / Q000032:analysis
D039561:Eukaryotic Initiation Factor-4E; D010448:Peptide Initiation Factors; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; C016658:phorbolol myristate acetate; C012410:lonomycin; D008715:Methionine; C496634:PIM1 protein, human; C496636:Pim1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D051573:Proto-Oncogene Proteins c-pim-1; D001616:beta-Galactosidase; D013755:Tetradecanoylphorbol Acetate; D009550:Nigericin