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Cdk2-dependent Inhibition of p21 stability via a C-terminal cyclin-binding motif

Hongyan Zhu1, Linghu Nie, Carl G Maki

  • 1Department of Radiation and Cellular Oncology, Center for Molecular Oncology, University of Chicago, Chicago, IL 60637, USA.

The Journal of Biological Chemistry
|June 21, 2005
PubMed

Insights

Cyclin-dependent kinase 2 (CDK2) activity destabilizes the cell cycle inhibitor p21, promoting its degradation. This process involves phosphorylation of p21 at serine 130 and requires specific binding motifs.

Area of Science:

  • Molecular Biology
  • Cell Cycle Regulation

Background:

  • p21 is a key inhibitor in the Cip/Kip family of cyclin-dependent kinase inhibitors.
  • Previous research suggested Cdk2 activity might degrade p21, but the mechanism remained unclear.

Purpose of the Study:

  • To elucidate the mechanism by which Cdk2 influences p21 stability and degradation.
  • To investigate the roles of specific p21 domains and phosphorylation in this process.

Main Methods:

  • Co-expression of p21 with wild-type and mutant Cdk2/cyclin E.
  • Analysis of p21 stabilization and degradation.
  • In vitro phosphorylation assays.

Main Results:

  • Cdk2 activity, not just binding, destabilizes p21.
  • Phosphorylation of p21 at Ser-130 by active Cdk2 is critical for degradation.
  • Specific cyclin-binding motifs (cy1 and cy2) in p21 are essential for these interactions.

Conclusions:

  • Active Cdk2 destabilizes p21 through phosphorylation at Ser-130, mediated by the cy2 motif.
  • This clarifies a key regulatory pathway controlling p21 levels and cell cycle progression.

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