A novel chk1-dependent G1/M checkpoint in fission yeast

J Cell Sci. 2002 Sep 15;115(Pt 18):3609-18. doi: 10.1242/jcs.00004.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • CDC2 Protein Kinase / genetics
  • CDC2 Protein Kinase / metabolism
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cells, Cultured
  • Checkpoint Kinase 1
  • Checkpoint Kinase 2
  • DNA Replication / physiology
  • G1 Phase / genetics*
  • Genes, cdc / physiology*
  • Mitosis / genetics*
  • Mutation / genetics
  • Nuclear Proteins*
  • Phosphorylation
  • Protein Kinases / genetics
  • Protein Kinases / metabolism*
  • Protein-Serine-Threonine Kinases*
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / metabolism
  • Schizosaccharomyces / genetics
  • Schizosaccharomyces / metabolism*
  • Schizosaccharomyces pombe Proteins / genetics
  • Schizosaccharomyces pombe Proteins / metabolism
  • Spores, Fungal / genetics
  • Spores, Fungal / radiation effects


  • Cell Cycle Proteins
  • Nuclear Proteins
  • Rum1 protein, S pombe
  • Schizosaccharomyces pombe Proteins
  • srw1 protein, S pombe
  • Protein Kinases
  • wee1 protein, S pombe
  • Checkpoint Kinase 2
  • Protein-Tyrosine Kinases
  • Cds1 protein, S pombe
  • Checkpoint Kinase 1
  • Chk1 protein, S pombe
  • Protein-Serine-Threonine Kinases
  • CDC2 Protein Kinase
  • cdc2 protein, S pombe