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First published online 25 February 2004
doi: 10.1242/dev.01050

This Article Figures Only Full Text Full Text (PDF) All Versions of this Article: dev.01050v1 131/7/1543    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in Development Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Karaiskou, A. Articles by Jessus, C. Search for Related Content PubMed PubMed Citation Articles by Karaiskou, A. Articles by Jessus, C.

Polo-like kinase confers MPF autoamplification competence to growing Xenopus oocytes

Laboratoire de Biologie du Développement, UMR-CNRS 7622, Equipe `Biologie de l'ovocyte', Université Pierre et Marie Curie, boîte 24, 4 place Jussieu, 75252 Paris cedex 05, France

^* Author for correspondence (e-mail: jessus{at}ccr.jussieu.fr)

Accepted 16 December 2003

During oogenesis, the Xenopus oocyte is blocked in prophase of meiosis I. It becomes competent to resume meiosis in response to progesterone at the end of its growing period (stage VI of oogenesis). Stage IV oocytes contain a store of inactive pre-MPF (Tyr15-phosphorylated Cdc2 bound to cyclin B2); the Cdc25 phosphatase that catalyzes Tyr15 dephosphorylation of Cdc2 is also present. However, the positive feedback loop that allows MPF autoamplification is not functional at this stage of oocyte growth. We report that when cyclin B is overexpressed in stage IV oocytes, MPF autoamplification does not occur and the newly formed cyclin B-Cdc2 complexes are inactivated by Tyr15 phosphorylation, indicating that Myt1 kinase remains active and that Cdc25 is prevented to be activated. Plx1 kinase (or polo-like kinase), which is required for Cdc25 activation and MPF autoamplification in full grown oocytes is not expressed at the protein level in small stage IV oocytes. In order to determine if Plx1 could be the missing regulator that prevents MPF autoamplification, polo kinase was overexpressed in stage IV oocytes. Under these conditions, the MPF-positive feedback loop was restored. Moreover, we show that acquisition of autoamplification competence does not require the Mos/MAPK pathway.

Key words: Cdc2, Cyclin, Cdc25, Plx1, Xenopus oocyte

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