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ATP-dependent activation of p21WAF1/CIP1-associated Cdk2 by Cdc6

Qiuming Kan1, Shigeki Jinno, Hanako Yamamoto

  • 1Department of Biochemistry and Molecular Biology, Graduate School and Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.

Proceedings of the National Academy of Sciences of the United States of America
|March 22, 2008
PubMed

Insights

Cdc6 protein reactivates cyclin-dependent kinase 2 (Cdk2) to advance cell cycle progression after DNA damage, revealing a new role for Cdc6 in S-phase control.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • DNA damage in mid-S phase causes prolonged cell cycle arrest.
  • This arrest persists after checkpoint signals fade due to p53-induced p21.
  • p21 inhibits cyclin-dependent kinase 2 (Cdk2), preventing S-phase reinitiation.

Purpose of the Study:

  • To investigate the role of Cdc6 in overcoming prolonged S-phase arrest.
  • To determine if Cdc6 can reactivate Cdk2 in the presence of p21.
  • To elucidate the mechanism by which Cdc6 influences S-phase progression.

Main Methods:

  • Enforced expression of Cdc6 in damaged cells.
  • In vitro kinase assays using purified Cdc6 and p21-associated Cdk2.
  • Site-directed mutagenesis of Cdc6 to assess ATPase and cyclin-binding activity.

Main Results:

  • Enforced Cdc6 expression accelerated recovery from S-phase arrest and Cdk2 reactivation.
  • Cdc6 activated p21-associated Cdk2 in an ATP-dependent manner in vitro.
  • Cdc6 mutants defective in ATPase or cyclin binding failed to rescue S-phase progression and Cdk2 activity in vivo.

Conclusions:

  • Cdc6 possesses a novel function in activating Cdk2.
  • Cdc6's ATPase and cyclin-binding activities are crucial for its role in S-phase recovery.
  • This study redefines Cdc6's function in mammalian cell S-phase control.

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