Regulation of Translation During In Vitro Maturation of Bovine Oocytes: The Role of MAP Kinase, eIF4E (Cap Binding Protein) Phosphorylation, and eIF4E-BP1

摘要: Meiotic maturation of mammalian oocytes (transition from prophase I to metaphase II) is accompanied by complex changes in the protein phosphorylation pattern. At least two major kinases are involved these events; namely, cdc2 kinase and mitogen-activated (MAP) kinase, because inhibition arrest germinal vesicle (GV) stage. We show that during meiotic bovine oocytes, translation initiation factor, eIF4E (the cap binding protein), gradually becomes phosphorylated. This substantial begins at time breakdown (GVBD) continues II The onset occurs parallel with a significant increase overall synthesis. However, although nearly fully phosphorylated synthesis reaches only basal levels this stage, similar which factor remains unphosphorylated. present evidence specific repressor eIF4E, 4E-BP1, could be preventing function stage oocytes. Recently, kinases, called Mnk1 Mnk2, have been identified somatic cells as both substrates MAP vivo. In inhibitor cdk butyrolactone I, arrests GV prevents activation kinase. Under conditions, also blocked, its impaired. contrast, PD 098059, pathway, inhibits MEK function, leads postponed GVBD, delay phosphorylation. These results indicate 1) partially dependent on 2) phosphorylation, 3) abundance does not necessarily directly stimulate A possible kinase-independent pathway role 4E-BP1 repressing discussed.