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Thr-161 phosphorylation of monomeric Cdc2. Regulation by protein phosphatase 2C in Xenopus oocytes

Veronique De Smedt1, Robert Poulhe, Xavier Cayla

  • 1Laboratoire de Biologie du Développement, Institut de la Recherche Agronomique/Unité Mixte de Recherche-CNRS 7622, Université Pierre et Marie Curie, Boite 24, 4 Place Jussieu, 75252 Paris cedex 05, France.

The Journal of Biological Chemistry
|May 31, 2002
PubMed

Insights

Prophase-arrested Xenopus oocytes contain monomeric Cdc2 phosphorylated at Thr-161. This finding reveals a novel regulatory mechanism for M-phase promoting factor (MPF) activation, crucial for meiosis re-entry.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Developmental Biology

Background:

  • Xenopus oocytes arrest at prophase I of meiosis.
  • Re-entry into meiosis requires M-phase promoting factor (MPF) activation, triggered by progesterone.
  • MPF is a complex of cyclin B and Cdc2, requiring cyclin binding and Thr-161 phosphorylation for Cdc2 activation.

Purpose of the Study:

  • To investigate the regulation of Thr-161 phosphorylation of Cdc2 in prophase-arrested Xenopus oocytes.
  • To understand the role of monomeric Cdc2 in MPF activation.

Main Methods:

  • Isolation of monomeric Cdc2 from prophase-arrested Xenopus oocytes.
  • Assaying Cdc2 activation upon cyclin addition.
  • Utilizing an antibody specific to Thr-161 phosphorylated Cdc2 for detection.

Main Results:

  • A significant amount of monomeric Cdc2 is phosphorylated on Thr-161 in prophase oocytes.
  • PP2C, a Mg2+-dependent phosphatase, negatively regulates Thr-161 phosphorylation of Cdc2.
  • The presence of phosphorylated monomeric Cdc2 may contribute to initiating MPF amplification.

Conclusions:

  • The prophase oocyte contains a pool of free Cdc2 already phosphorylated at Thr-161.
  • This phosphorylation state of monomeric Cdc2 is regulated by phosphatases like PP2C.
  • This finding offers new insights into the threshold mechanism for MPF activation and meiotic resumption.

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