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Activation of the DNA damage checkpoint in mutants defective in DNA replication initiation

Ling Yin1, Alexandra Monica Locovei, Gennaro D'Urso

  • 1Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, FL 33101, USA.

Molecular Biology of the Cell
|August 1, 2008
PubMed

Insights

Replication initiation defects in fission yeast activate the Chk1 DNA damage checkpoint, not the Cds1 intra-S phase checkpoint. Mrc1 protein supports viability independently of Cds1 activation in these mutants.

Area of Science:

  • Cellular biology
  • Molecular genetics
  • DNA replication

Background:

  • DNA replication requires precise initiation and elongation.
  • Replication stress activates checkpoints like intra-S phase (Cds1) and DNA damage (Chk1).
  • Distinct checkpoints respond to replication elongation blocks versus initiation defects.

Purpose of the Study:

  • Investigate the checkpoint response to defects in DNA replication initiation.
  • Characterize the role of Chk1 and Cds1 kinases in replication initiation mutants.
  • Determine the function of Mrc1 in replication initiation-defective mutants.

Main Methods:

  • Utilized fission yeast (Schizosaccharomyces pombe) as a model system.
  • Generated and analyzed mutants defective in DNA replication initiation.
  • Assessed kinase activation (Cds1, Chk1) and mutant viability.

Main Results:

  • Replication initiation defects activate the Chk1 kinase-dependent DNA damage checkpoint, independent of the Cds1 intra-S phase checkpoint.
  • This Chk1-dependent, Cds1-independent phenotype was termed 'rid' (replication initiation defective).
  • Mrc1 protein is essential for rid mutant viability, independent of its role in Cds1 activation.

Conclusions:

  • DNA replication initiation defects trigger a distinct checkpoint pathway involving Chk1.
  • Mrc1 plays a crucial, checkpoint-independent role in maintaining cell viability when DNA replication initiation is compromised.

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