title: Distinct regulators for Plk1 activation in starfish meiotic and early embryonic cycles.
abstract: The Polo-like kinase, Plk, has multiple roles in regulating mitosis. In particular, Plk1 has been postulated to function as a trigger kinase that phosphorylates and activates Cdc25C prior to the activation of cyclin B-Cdc2 and thereby initiates its activation. However, the upstream regulation of Plk1 activation remains unclear. Here we have studied the interplay between Plk1 and Cdc2 through meiotic and early embryonic cycles in starfish. Distinct kinases, cyclin B-Cdc2, MAPK along with cyclin B- and/or cyclin A-Cdc2 and cyclin A-Cdc2, were unique upstream regulators for Plk1 activation at meiosis I, meiosis II and embryonic M-phase, respectively, indicating that Plk1 is not the trigger kinase at meiotic reinitiation. When Plk1 was required for cyclin B-Cdc2 activation, the action of Plk1 was mediated primarily through suppression of Myt1 rather than through activation of Cdc25. We propose that Plk1 can be activated by either cyclin A- or cyclin B-Cdc2, and its primary target is Myt1.
authors.affiliation: Laboratory of Cell and Developmental Biology, Graduate School of Bioscience, Tokyo Institute of Technology, Nagatsuta, Midoriku, Yokohama 226-8501, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Okano-Uchida
authors.forename: Eiichi
authors.initials: E
authors.lastname: Okumura
authors.forename: Motoko
authors.initials: M
authors.lastname: Iwashita
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yoshida
authors.forename: Kazunori
authors.initials: K
authors.lastname: Tachibana
authors.forename: Takeo
authors.initials: T
authors.lastname: Kishimoto
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000502:physiology; D018797:Cell Cycle Proteins; D002455:Cell Division; D019926:Cyclin B / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D008540:Meiosis; D011494:Protein Kinases / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D013215:Starfish / Q000166:cytology / Q000196:embryology*; D000097869:Polo-Like Kinase 1
chemical_list: D016203:CDC2 Protein Kinase; D018797:Cell Cycle Proteins; D019926:Cyclin B; D018076:DNA, Complementary; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000097869:Polo-Like Kinase 1