A novel chk1-dependent G1/M checkpoint in fission yeast.
Fission yeast cells with a temperature-sensitive Orp1 protein, a component of the origin recognition complex, cannot perform DNA replication at the restrictive temperature. Seventy percent of orp1-4 cells arrest with a 1C DNA content, whereas 30% proceed to mitosis ('cut'). The arrest depends upon the checkpoint Rad proteins and, surprisingly, the Chk1 protein, which is thought to act only from late S phase. The arrested cells maintain a 1C DNA content, as judged by flow cytometry, and the early origin ars3001 has not been initiated, as judged by 2D gel analysis. We show that in G1-arrested orp1-4 cells, Wee1 phosphorylates and inactivates Cdc2. Activation of Chk1 occurs earlier than Cdc2 phosphorylation, indicating a novel role for Chk1, namely to induce and/or maintain Cdc2 phosphorylation upon checkpoint activation in G1. We also show that commitment to cutting occurs already in early G1 phase.
Department of Cell Biology, Institute for Cancer Research, Montebello, 0310 Oslo, Norway.
Marianne
M
Synnes
Esben A
EA
Nilssen
Erik
E
Boye
Beáta
B
Grallert
D016203:CDC2 Protein Kinase / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D004261:DNA Replication / Q000502:physiology; D016193:G1 Phase / Q000235:genetics*; D018816:Genes, cdc / Q000502:physiology*; D008938:Mitosis / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism; D013172:Spores, Fungal / Q000235:genetics / Q000528:radiation effects
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C086077:Rum1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; C113000:srw1 protein, S pombe; D011494:Protein Kinases; C068689:wee1 protein, S pombe; D064447:Checkpoint Kinase 2; D011505:Protein-Tyrosine Kinases; C578636:Cds1 protein, S pombe; D000071877:Checkpoint Kinase 1; C000605873:Chk1 protein, S pombe; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; C469447:cdc2 protein, S pombe