| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Regular Article |
a Research Institute for the Biology of Farm Animals, 18146 Dummerstorf-Rostock, Germany
b Institute of Artificial Insemination, BVN 91413 Neustadt/Aisch, Germany
c Institute of Animal Physiology and Genetics, 277 21 Libechov, Czech Republic
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 protein kinases are involved in these events; namely, cdc2 kinase and mitogen-activated protein (MAP) kinase, because the inhibition of these kinases arrest mammalian oocytes in the germinal vesicle (GV) stage. We show that during meiotic maturation of bovine oocytes, the translation initiation factor, eIF4E (the cap binding protein), gradually becomes phosphorylated. This substantial phosphorylation begins at the time of germinal vesicle breakdown (GVBD) and continues to the metaphase II stage. The onset of eIF4E phosphorylation occurs in parallel with a significant increase in overall protein synthesis. However, although eIF4E is nearly fully phosphorylated in metaphase II oocytes, protein synthesis reaches only basal levels at this stage, similar to that of prophase I oocytes, in which the factor remains unphosphorylated. We present evidence that a specific repressor of eIF4E, the binding protein 4E-BP1, is present and could be involved in preventing eIF4E function in metaphase II stage oocytes. Recently, two protein kinases, called Mnk1 and Mnk2, have been identified in somatic cells as eIF4E kinases, both of which are substrates of MAP kinase in vivo. In bovine oocytes, a specific inhibitor of cdk kinases, butyrolactone I, arrests oocytes in GV stage and prevents activation of both cdc2 and MAP kinase. Under these conditions, the phosphorylation of eIF4E is also blocked, and its function in initiation of translation is impaired. In contrast, PD 098059, a specific inhibitor of the MAP kinase activation pathway, which inhibits the MAP kinase kinase, called MEK function, leads only to a postponed GVBD, and a delay in MAP kinase and eIF4E phosphorylation. These results indicate that in bovine oocytes, 1) MAP kinase activation is only partially dependent on MEK kinase, 2) MAP kinase is involved in eIF4E phosphorylation, and 3) the abundance of fully phosphorylated eIF4E does not necessarily directly stimulate protein synthesis. A possible MEK kinase-independent pathway of MAP kinase phosphorylation and the role of 4E-BP1 in repressing translation in metaphase II oocytes are discussed.
1 This work was supported by Deutsche Forschungsgemeinschaft To 178/2-1 as part of the bilateral program of German/Czech scientific cooperation (436 TES 113/28/0), by GACR 301/00/0781 of the Czech Republic, and by the Karl-Eibel Stiftung. F.M.S is a KAAD fellow.
2 Correspondence: Wolfgang Tomek, Department of Reproductive Biology, Research Institute for the Biology of Farm Animals, 18196 Dummerstorf, Germany. FAX: 49 38208 6 87 52; tomek{at}fbn-dummerstorf.de
This article has been cited by other articles:
|
|
 |
|
  H. Torner, N. Ghanem, C. Ambros, M. Holker, W. Tomek, C. Phatsara, H. Alm, M.-A. Sirard, W. Kanitz, K. Schellander, et al. Molecular and subcellular characterisation of oocytes screened for their developmental competence based on glucose-6-phosphate dehydrogenase activity Reproduction, February 1, 2008; 135(2): 197 - 212. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. M. Rowlett, C. A. Chrestensen, M. Nyce, M. G. Harp, J. W. Pelo, F. Cominelli, P. B. Ernst, T. T. Pizarro, T. W. Sturgill, and M. T. Worthington MNK kinases regulate multiple TLR pathways and innate proinflammatory cytokines in macrophages Am J Physiol Gastrointest Liver Physiol, February 1, 2008; 294(2): G452 - G459. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Uzbekova, Y. Arlot-Bonnemains, J. Dupont, R. Dalbies-Tran, P. Papillier, S. Pennetier, A. Thelie, C. Perreau, P. Mermillod, C. Prigent, et al. Spatio-Temporal Expression Patterns of Aurora Kinases A, B, and C and Cytoplasmic Polyadenylation-Element-Binding Protein in Bovine Oocytes During Meiotic Maturation Biol Reprod, February 1, 2008; 78(2): 218 - 233. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Vanselow, W. Yang, J. Herrmann, H. Zerbe, H.-J. Schuberth, W. Petzl, W. Tomek, and H.-M. Seyfert DNA-remethylation around a STAT5-binding enhancer in the {alpha}S1-casein promoter is associated with abrupt shutdown of {alpha}S1-casein synthesis during acute mastitis J. Mol. Endocrinol., December 1, 2006; 37(3): 463 - 477. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Tomek and T. Smiljakovic Activation of Akt (protein kinase B) stimulates metaphase I to metaphase II transition in bovine oocytes Reproduction, October 1, 2005; 130(4): 423 - 430. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. S. Lequarre, J. M Traverso, J. Marchandise, and I. Donnay Poly(A) RNA Is Reduced by Half During Bovine Oocyte Maturation but Increases when Meiotic Arrest Is Maintained with CDK Inhibitors Biol Reprod, August 1, 2004; 71(2): 425 - 431. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Miyoshi, S. J. Rzucidlo, S. L. Pratt, and S. L. Stice Improvements in Cloning Efficiencies May Be Possible by Increasing Uniformity in Recipient Oocytes and Donor Cells Biol Reprod, April 1, 2003; 68(4): 1079 - 1086. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
