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.
Toyoshima-Morimoto
F
F
Department of Biophysics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Taniguchi
E
E
Shinya
N
N
Iwamatsu
A
A
Nishida
E
E
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