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. 2004 Apr;131(7):1543-52.
doi: 10.1242/dev.01050. Epub 2004 Feb 25.

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

Anthi Karaiskou  1 , Anne-Claire Leprêtre, Golbahar Pahlavan, David Du Pasquier, René Ozon, Catherine Jessus
Affiliations

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

Anthi Karaiskou et al. Development. 2004 Apr.

Erratum in

Abstract

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.

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