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.
Synnes
Marianne
M
Department of Cell Biology, Institute for Cancer Research, Montebello, 0310 Oslo, Norway.
Nilssen
Esben A
EA
Boye
Erik
E
Grallert
Beáta
B
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