title: Thr-161 phosphorylation of monomeric Cdc2. Regulation by protein phosphatase 2C in Xenopus oocytes.
abstract: Fully grown Xenopus oocyte is arrested at prophase I of meiosis. Re-entry into meiosis depends on the activation of MPF (M-phase promoting factor or cyclin B.Cdc2 complex), triggered by progesterone. The prophase-arrested oocyte contains a store of Cdc2. Most of the protein is present as a monomer whereas a minor fraction, called pre-MPF, is found to be associated with cyclin B. Activation of Cdc2 depends on two key events: cyclin binding and an activating phosphorylation on Thr-161 residue located in the T-loop. To get new insights into the regulation of Thr-161 phosphorylation of Cdc2, monomeric Cdc2 was isolated from prophase oocytes. Based on its activation upon cyclin addition and detection by an antibody directed specifically against Cdc2 phosphorylated on Thr-161, we show for the first time that the prophase oocyte contains a significant amount of monomeric Cdc2 phosphorylated on Thr-161. PP2C, a Mg2+-dependent phosphatase, negatively controls Thr-161 phosphorylation of Cdc2. The unexpected presence of a population of free Cdc2 already phosphorylated on Thr-161 could contribute to the generation of the Cdc2 kinase activity threshold required to initiate MPF amplification.
authors.affiliation: Laboratoire 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.
authors.forename: Veronique
authors.initials: V
authors.lastname: De Smedt
authors.forename: Robert
authors.initials: R
authors.lastname: Poulhe
authors.forename: Xavier
authors.initials: X
authors.lastname: Cayla
authors.forename: Frederic
authors.initials: F
authors.lastname: Dessauge
authors.forename: Anthi
authors.initials: A
authors.lastname: Karaiskou
authors.forename: Catherine
authors.initials: C
authors.lastname: Jessus
authors.forename: Rene
authors.initials: R
authors.lastname: Ozon
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D042846:CDC2-CDC28 Kinases; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D019925:Cyclin A / Q000494:pharmacology; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D018507:Gene Expression Regulation, Developmental; D015723:Gene Library; D005982:Glutathione Transferase / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D015151:Immunoblotting; D008274:Magnesium / Q000494:pharmacology; D008540:Meiosis; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D054648:Protein Phosphatase 2; D000071636:Protein Phosphatase 2C; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013912:Threonine / Q000737:chemistry*; D029867:Xenopus Proteins; D014982:Xenopus laevis; D000095043:Cyclin-Dependent Kinase-Activating Kinase
chemical_list: D019925:Cyclin A; D018076:DNA, Complementary; D006657:Histones; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D029867:Xenopus Proteins; D013912:Threonine; D005982:Glutathione Transferase; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495891:Cdk2 protein, Xenopus; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; C087358:PTC1 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D000071636:Protein Phosphatase 2C; D008274:Magnesium; D000095043:Cyclin-Dependent Kinase-Activating Kinase