Cyclin B synthesis and rapamycin-sensitive regulation of protein synthesis during starfish oocyte meiotic divisions |
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Authors: | Lapasset Laure Pradet-Balade Bérengère Vergé Valérie Lozano Jean-Claude Oulhen Nathalie Cormier Patrick Peaucellier Gérard |
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Affiliation: | UPMC Univ Paris 06, Laboratoire Arago, Banyuls-sur-Mer, France. |
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Abstract: | Translation of cyclin mRNAs represents an important event for proper meiotic maturation and post-fertilization mitoses in many species. Translational control of cyclin B mRNA has been described to be achieved through two separate but related mechanisms: translational repression and polyadenylation. In this paper, we evaluated the contribution of global translational regulation by the cap-dependent translation repressor 4E-BP (eukaryotic initiation factor 4E-binding protein) on the cyclin B protein synthesis during meiotic maturation of the starfish oocytes. We used the immunosupressant drug rapamycin, a strong inhibitor of cap-dependent translation, to check for the involvement of this protein synthesis during this physiological process. Rapamycin was found to prevent dissociation of 4E-BP from the initiation factor eIF4E and to suppress correlatively a burst of global protein synthesis occurring at the G2/M transition. The drug had no effect on first meiotic division but defects in meiotic spindle formation prevented second polar body emission, demonstrating that a rapamycin-sensitive pathway is involved in this mechanism. While rapamycin affected the global protein synthesis, the drug altered neither the specific translation of cyclin B mRNA nor the expression of the Mos protein. The expression of these two proteins was correlated with the phosphorylation and the dissociation of the cytoplasmic polyadenylation element-binding protein from eIF4E. |
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Keywords: | cyclin B translation eIF4E 4E‐BP CPEB rapamycin meiosis starfish oocytes |
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