Translational regulation of the mammalian growth-related protein P23: involvement of eIF-4E.
Synthesis of the mammalian growth-related protein P23 is rapidly induced after serum stimulation of mouse fibroblasts and Ehrlich ascites tumour cells. This induction occurs at the translational level. Growth-induction leads also to an increase in phosphorylation of the rate-limiting initiation factor eIF-4E. Here, we present the following evidence indicating the involvement of eIF-4E in the regulation of P23 synthesis: 1) P23 synthesis is induced by the same mitogenic stimuli which lead to enhanced eIF-4E phosphorylation. 2) Upon heat shock treatment of Ehrlich ascites cells (which results in immediate dephosphorylation and concomitant inactivation of eIF-4E), P23 synthesis is rapidly shut off. 3) In control NIH 3T3 cells, P23 synthesis is readily induced by growth stimulation. This response is strongly diminished in cells overexpressing eIF-4E, and the basal level of P23 synthesis is elevated in these cells. Overexpression of a nonfunctional mutant of eIF-4E diminishes the basal level of P23 synthesis as well as the serum-response of the cells with respect to P23 induction. 4) Cells transformed by overexpression of the ras or src genes in which eIF-4E is highly phosphorylated do not show any inducibility of P23 synthesis. 5) HeLa cells expressing antisense RNA of eIF-4E, have reduced levels of eIF-4E/F and show reduced rates of growth and protein synthesis. In these cells the total amount of P23 protein is about 50% compared with control cells. The results suggest that P23 is one of the gene products, the synthesis of which is regulated by eIF-4E activity.
Bommer
U A
UA
Division of Biochemistry, St. George's Hospital Medical School, University of London, UK.
Lazaris-Karatzas
A
A
De Benedetti
A
A
Nürnberg
P
P
Benndorf
R
R
Bielka
H
H
Sonenberg
N
N
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D014408:Biomarkers, Tumor; D015153:Blotting, Western; D003994:Bucladesine / Q000494:pharmacology; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D002455:Cell Division; D004815:Epidermal Growth Factor / Q000494:pharmacology; D039561:Eukaryotic Initiation Factor-4E; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006133:Growth Substances / Q000032:analysis / Q000096:biosynthesis*; D006367:HeLa Cells; D006358:Hot Temperature; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D008715:Methionine / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000032:analysis / Q000096:biosynthesis*; D010448:Peptide Initiation Factors / Q000096:biosynthesis / Q000378:metabolism*; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects; D011817:Rabbits / Q000276:immunology; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D013462:Sulfur Radioisotopes; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured; D000090324:Tumor Protein, Translationally-Controlled 1
D000906:Antibodies; D014408:Biomarkers, Tumor; D039561:Eukaryotic Initiation Factor-4E; D006133:Growth Substances; D007328:Insulin; D009363:Neoplasm Proteins; D010448:Peptide Initiation Factors; D010455:Peptides; D011994:Recombinant Proteins; D013462:Sulfur Radioisotopes; D000090324:Tumor Protein, Translationally-Controlled 1; D004815:Epidermal Growth Factor; D003994:Bucladesine; D008715:Methionine; D013755:Tetradecanoylphorbol Acetate