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10:24

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The role of Dbf4/Drf1-dependent kinase Cdc7 in DNA-damage checkpoint control

Toshiya Tsuji1, Eric Lau, Gary G Chiang

  • 1The Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.

Molecular Cell
|December 30, 2008
PubMed

Insights

The Cdc7 kinase complex (Ddk) is not inhibited by DNA-damage checkpoints. Instead, Ddk actively regulates these checkpoints, promoting DNA replication recovery during S-phase.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • DNA Replication

Background:

  • The S-phase checkpoint machinery typically inhibits DNA replication upon DNA damage.
  • Cdc7 kinase complex (Ddk) was believed to be inactivated by this checkpoint.

Purpose of the Study:

  • To investigate the role of Ddk during the DNA-damage-induced S-phase checkpoint.
  • To determine if Ddk activity is inhibited by checkpoint signaling.

Main Methods:

  • Experiments were conducted using Xenopus egg extracts and mammalian (HeLa) cells.
  • Ddk activity was assessed through complex formation, chromatin association, and kinase assays.
  • The effect of Ddk on checkpoint signaling was evaluated by adding purified Ddk or overexpressing Dbf4.

Main Results:

  • Ddk complex formation, chromatin association, and kinase activity remain active during the DNA-damage S-phase checkpoint.
  • Ddk addition or Dbf4 overexpression downregulates ATR-Chk1 signaling.
  • This downregulation overrides the DNA replication and cell-cycle progression inhibition caused by DNA-damaging agents.

Conclusions:

  • Ddk functions as an upstream regulator of S-phase checkpoint signaling, not a target of inhibition.
  • Ddk attenuates checkpoint signaling and promotes DNA replication reinitiation during checkpoint recovery.

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