Evidence that the ATR/Chk1 pathway maintains normal replication fork progression during unperturbed S phase

Cell Cycle. 2006 Oct;5(19):2203-9. doi: 10.4161/cc.5.19.3256. Epub 2006 Oct 1.


If cells are treated with DNA damaging agents or inhibitors that interfere with ongoing DNA replication, the intra-S and S/M checkpoints delay progression through S phase and mitotic entry, respectively, to allow time for DNA repair and replication restart. In vertebrates, these checkpoint responses to replication blocks are largely mediated by the sensor kinase ATR and its major downstream effector kinase Chk1. Increasing evidence suggests that the ATR pathway is also vital in the absence of exogenous stresses, i.e., during "unperturbed" replication. Both ATR and Chk1 are essential proteins in vertebrates, and lack of components of the ATR/Chk1 pathway can result in impaired replication and spontaneous DNA damage. Here we give an overview of how the ATR/Chk1 pathway responds to exogenously blocked replication and then describe evidence for roles of this pathway during replication in an unperturbed S phase.

Publication types

  • Review

MeSH terms

  • Animals
  • Ataxia Telangiectasia Mutated Proteins
  • Cell Cycle Proteins / metabolism*
  • Checkpoint Kinase 1
  • DNA Repair
  • DNA Replication*
  • Humans
  • Protein Kinases / metabolism*
  • Protein Serine-Threonine Kinases / metabolism*
  • S Phase*
  • Signal Transduction


  • Cell Cycle Proteins
  • Protein Kinases
  • Atr protein, mouse
  • ATR protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • CHEK1 protein, human
  • Checkpoint Kinase 1
  • Chek1 protein, mouse
  • Protein Serine-Threonine Kinases