Cyclin B synthesis and rapamycin-sensitive regulation of protein synthesis during starfish oocyte meiotic divisions.
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.
Lapasset
Laure
L
UPMC Univ Paris 06, Laboratoire Arago, Banyuls-sur-Mer, France.
Pradet-Balade
Bérengère
B
Vergé
Valérie
V
Lozano
Jean-Claude
JC
Oulhen
Nathalie
N
Cormier
Patrick
P
Peaucellier
Gérard
G
D000818:Animals; D019926:Cyclin B / Q000096:biosynthesis*; D039561:Eukaryotic Initiation Factor-4E / Q000037:antagonists & inhibitors / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology*; D008540:Meiosis / Q000187:drug effects / Q000502:physiology*; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects / Q000502:physiology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D020123:Sirolimus / Q000494:pharmacology*; D013215:Starfish / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D019926:Cyclin B; D039561:Eukaryotic Initiation Factor-4E; D011500:Protein Synthesis Inhibitors; D020123:Sirolimus