title: Purification and cloning of a protein kinase that phosphorylates and activates the polo-like kinase Plx1.
abstract: The Xenopus polo-like kinase 1 (Plx1) is essential during mitosis for the activation of Cdc25C, for spindle assembly, and for cyclin B degradation. Polo-like kinases from various organisms are activated by phosphorylation by an unidentified protein kinase. A protein kinase, polo-like kinase kinase 1 or xPlkk1, that phosphorylates and activates Plx1 in vitro was purified to near homogeneity and cloned. Phosphopeptide mapping of Plx1 phosphorylated in vitro by recombinant xPlkk1 or in progesterone-treated oocytes indicates that xPlkk1 may activate Plx1 in vivo. The xPlkk1 protein itself was also activated by phosphorylation on serine and threonine residues, and the kinetics of activation of xPlkk1 in vivo closely paralleled the activation of Plx1. Moreover, microinjection of xPlkk1 into Xenopus oocytes accelerated the timing of activation of Plx1 and the transition from G2 to M phase of the cell cycle. These results define a protein kinase cascade that regulates several events of mitosis.
authors.affiliation: Howard Hughes Medical Institute and Department of Pharmacology, University of Colorado School of Medicine, Denver, Colorado 80262, USA.
authors.forename: Y W
authors.initials: YW
authors.lastname: Qian
authors.forename: E
authors.initials: E
authors.lastname: Erikson
authors.forename: J L
authors.initials: JL
authors.lastname: Maller
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D018797:Cell Cycle Proteins; D003001:Cloning, Molecular; D004789:Enzyme Activation; D008938:Mitosis; D008969:Molecular Sequence Data; D019319:Okadaic Acid / Q000494:pharmacology; D009865:Oocytes / Q000201:enzymology; D010449:Peptide Mapping; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D011374:Progesterone / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014981:Xenopus; D029867:Xenopus Proteins; D000097869:Polo-Like Kinase 1
chemical_list: D000255:Adenosine Triphosphate; D018797:Cell Cycle Proteins; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases; D011374:Progesterone; D017346:Protein Serine-Threonine Kinases; D011993:Recombinant Fusion Proteins; D029867:Xenopus Proteins; C115856:stk10-a protein, Xenopus; C101085:Plk1 protein, Xenopus; D000097869:Polo-Like Kinase 1