Polo-like kinase 1 phosphorylates cyclin B1 and targets it to the nucleus during prophase.
In vertebrate cells, the nuclear entry of Cdc2-cyclin B1 (MPF) during prophase is thought to be essential for the induction and coordination of M-phase events. Phosphorylation of cyclin B1 is central to its nuclear translocation, but the kinases that are responsible remain unknown. Here we have purified a protein kinase from Xenopus M-phase extracts that phosphorylates a crucial serine residue (S147) in the middle of the nuclear export signal sequence of cyclin B1. We have identified this kinase as Plx1 (ref. 16), a Xenopus homologue of Polo-like kinase (Plk)-1. During cell-cycle progression in HeLa cells, a change in the kinase activity of endogenous Plk1 toward S147 and/or S133 correlates with a kinase activity in the cell extracts. An anti-Plk1 antibody depletes the M-phase extracts of the kinase activity toward S147 and/or S133. An anti-phospho-S147 antibody reacts specifically with cyclin B1 only during G2/M phase. A mutant cyclin B1 in which S133 and S147 are replaced by alanines remains in the cytoplasm, whereas wild-type cyclin B1 accumulates in the nucleus during prophase. Co-expression of constitutively active Plk1 stimulates nuclear entry of cyclin B1. Our results indicate that Plk1 may be involved in targeting MPF to the nucleus during prophase.
Department of Biophysics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
F
F
Toyoshima-Morimoto
E
E
Taniguchi
N
N
Shinya
A
A
Iwamatsu
E
E
Nishida
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism*; D019926:Cyclin B / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D056744:Cyclin B1; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D048728:MAP Kinase Kinase Kinase 1; D008938:Mitosis; D009154:Mutation; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation; D011233:Precipitin Tests; D011418:Prophase; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism; D021381:Protein Transport; D011518:Proto-Oncogene Proteins; D014981:Xenopus; D029867:Xenopus Proteins; D000097869:Polo-Like Kinase 1
D015107:4-Butyrolactone; D002070:Butadienes; D016203:CDC2 Protein Kinase; D018797:Cell Cycle Proteins; D019926:Cyclin B; D056744:Cyclin B1; D004791:Enzyme Inhibitors; D048728:MAP Kinase Kinase Kinase 1; D009570:Nitriles; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D029867:Xenopus Proteins; D000097869:Polo-Like Kinase 1; C534699:CCNB1 protein, human; C113580:U 0126; C082868:butyrolactone I; C101085:Plk1 protein, Xenopus; C482576:MAP3K1 protein, human