Activation of the DNA damage checkpoint in mutants defective in DNA replication initiation.
In the fission yeast, Schizosaccharomyces pombe, blocks to DNA replication elongation trigger the intra-S phase checkpoint that leads to the activation of the Cds1 kinase. Cds1 is required to both prevent premature entry into mitosis and to stabilize paused replication forks. Interestingly, although Cds1 is essential to maintain the viability of mutants defective in DNA replication elongation, mutants defective in DNA replication initiation require the Chk1 kinase. This suggests that defects in DNA replication initiation can lead to activation of the DNA damage checkpoint independent of the intra-S phase checkpoint. This might result from reduced origin firing that leads to an increase in replication fork stalling or replication fork collapse that activates the G2 DNA damage checkpoint. We refer to the Chk1-dependent, Cds1-independent phenotype as the rid phenotype (for replication initiation defective). Chk1 is active in rid mutants, and rid mutant viability is dependent on the DNA damage checkpoint, and surprisingly Mrc1, a protein required for activation of Cds1. Mutations in Mrc1 that prevent activation of Cds1 have no effect on its ability to support rid mutant viability, suggesting that Mrc1 has a checkpoint-independent role in maintaining the viability of mutants defective in DNA replication initiation.
Yin
Ling
L
Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, FL 33101, USA.
Locovei
Alexandra Monica
AM
D'Urso
Gennaro
G
D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D002470:Cell Survival; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D016195:G2 Phase; D008954:Models, Biological; D009154:Mutation; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012568:Schizosaccharomyces / Q000235:genetics* / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics* / Q000378:metabolism
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C533276:MRC1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; C499635:Swi3 protein, S pombe; C513096:swi1 protein, S pombe; D064447:Checkpoint Kinase 2; C578636:Cds1 protein, S pombe; D017346:Protein Serine-Threonine Kinases