title: Regulation of Greatwall kinase during Xenopus oocyte maturation.
abstract: Greatwall kinase has been identified as a key element in M phase initiation and maintenance in Drosophila, Xenopus oocytes/eggs, and mammalian cells. In M phase, Greatwall phosphorylates endosulfine and related proteins that bind to and inhibit protein phosphatase 2A/B55, the principal phosphatase for Cdk-phosphorylated substrates. We show that Greatwall binds active PP2A/B55 in G2 phase oocytes but dissociates from it when progesterone-treated oocytes reach M phase. This dissociation does not require Greatwall kinase activity or phosphorylation at T748 in the presumptive T loop of the kinase. A mutant K71M Greatwall, also known as Scant in Drosophila, induces M phase in the absence of progesterone when expressed in oocytes, despite its reduced stability and elevated degradation by the proteasome. M phase induction by Scant Greatwall requires protein synthesis but is not associated with altered binding or release of PP2A/B55 as compared to wild-type Greatwall. However, in vitro studies with Greatwall proteins purified from interphase cells indicate that Scant, but not wild-type Greatwall, has low but detectable activity against endosulfine. These results demonstrate progesterone-dependent regulation of the PP2A/B55-Greatwall interaction during oocyte maturation and suggest that the cognate Scant Greatwall mutation has sufficient constitutive kinase activity to promote M phase in Xenopus oocytes.
authors.affiliation: Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
authors.forename: Tomomi M
authors.initials: TM
authors.lastname: Yamamoto
authors.forename: Kristina
authors.initials: K
authors.lastname: Blake-Hodek
authors.forename: Byron C
authors.initials: BC
authors.lastname: Williams
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Lewellyn
authors.forename: Michael L
authors.initials: ML
authors.lastname: Goldberg
authors.forename: James L
authors.initials: JL
authors.lastname: Maller
mesh_terms: D000818:Animals; D002455:Cell Division; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D005260:Female; D016195:G2 Phase; D036341:Intercellular Signaling Peptides and Proteins; D009154:Mutation; D009865:Oocytes / Q000378:metabolism / Q000502:physiology*; D010455:Peptides / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D011374:Progesterone / Q000378:metabolism; D011485:Protein Binding; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014981:Xenopus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D029867:Xenopus Proteins; C075663:endosulfine; D011374:Progesterone; C544010:MASTL protein, Xenopus; D017346:Protein Serine-Threonine Kinases; D018844:Cyclin-Dependent Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2