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Regulation of c‐jun mRNA expression in adult cardiocytes by MAP kinase interacting kinase‐1 (MNK1)
Author(s) -
Spruill Laura S.,
McDermott Paul J.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.06-6245fje
Subject(s) - polysome , eif4e , messenger rna , c jun , microbiology and biotechnology , translational efficiency , kinase , biology , chemistry , translation (biology) , gene , biochemistry , ribosome , rna , transcription factor
Hypertrophic growth of adult myocardium is associated with increased expression of theearly response gene c‐jun . The purpose of this study was to determine whether eukaryotic initiation factor (elF)4E (eIF4E) regulates translational efficiency of c‐jun mRNA as measured by flux into polysomes. Adult feline cardiomyocytes in primary culture were treated with 0.2 µM 12‐O‐tetradecanoylphorbol 13‐acetate (TPA), and c‐jun mRNA was quantified in total, monosome, andpolysome fractions by real‐time polymerase chain reaction. After 1 h, TPA increased total c‐jun mRNA by 10.5‐fold. The corresponding flux into polysomes was significantly lower (5‐fold). Adenoviral‐mediated overexpression of either eIF4E or a nonphosphorylatable mutant (S209/A) did not affect total c‐jun mRNA or its flux between monosomes and polysomes. Similar results were obtained following overexpression of the eIF4E kinase Mnk1. Thus, translational efficiency of c‐jun mRNA was not affected by changes in activity ore amount of eIF4E. In contrast, a kinase‐deficient Mnk1 mutant significantly reduced total c‐jun mRNA from 9.8‐fold to 6.0‐fold while flux between monosomes and polysomes remained constant. The decrease in total c‐jun mRNA resulted from increased decay of c‐jun mRNA incorporated into the polysomes. We conclude that Mnk1 activity stabilizes c‐jun mRNA in polysomes independent of eIF4E phosphorylation. ‐Spruill, L. McDermott, P. Regulation of c‐jun mRNA expression in adult cardiocytes by MAP kinase interacting kinase‐1 (MNK1). FASEB J. 20, E1465‐E1475 (2006)