Phosphoprotein phosphatase 2A dephosphorylates eIF‐4E and does not alter binding to the mRNA cap

FEBS Letters

Bu, Xin¹  Hagedorn, Curt H.¹ 

[1]Departments of Medicine and Cell Biology, Vanderbilt University School of Medicine and the VA Medical Center, Nashville, TN 37232, USA

关键词: mRNA cap binding protein;    eIF-4E;    Phosphoprotein phosphatase 2A;    Okadaic acid;    Hep G2;    Translation;    m7GTP;    7-methylguanosine triphosphate;    eIF;    eukaryotic initiation factor;    EGF;    epidermal growth factor;    PDGF;    platelet-derived growth factor;    TNF-α;    tumor necrosis factor-α;    DTT;    dithiothreitol;    PAGE;    polyacrylamide gel electrophoresis;    PMSF;    phenylmethyl sulfonyl fluoride;    TPA;    phorbol 12-myristate 13-acetate;    IEF;    isoelectric focusing;   

DOI  :  10.1016/0014-5793(92)80200-Z

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The phosphorylation and dephosphorylation of the 25 kDa mRNA cap binding protein eukaryotic initiation factor-4E (eIF-4E) is regulated during different physiologic and pathophysiologic states that include cell growth and the late phase of adenovirus infection. We have found that okadaic acid is much more effective in increasing the phosphorylated fraction of eIF-4E than phorbol 12-myristate 13-acetate in Hep G2 cells. Phosphoprotein phosphatase 2A dephosphorylated eIF-4E isolated from both phorbol 12-myristate 13-acetate- or okadaic acid-treated cells, whereas alkaline and acid phosphatase were relatively ineffective. The ability of purified [³⁵S]eIF-4E isolated from okadaic acid-treated cells to bind mRNA caps was compared to phosphoprotein phosphatase 2A-treated [³⁵S]eIF-4E and found to be no different. This suggests that alternative explanations for the previously observed effects of eIF-4E phosphorylation on protein synthesis must be considered. In addition, our results indicate that the in vivo phosphorylation eIF-4E is not catalyzed solely by protein kinase C.

【 授权许可】

Unknown