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p21 binding to PCNA causes G1 and G2 cell cycle arrest in p53-deficient cells
C Cayrol1, M Knibiehler, B Ducommun
1Institut de Pharmacologie et de Biologie Structurale du CNRS Université Paul Sabatier, Toulouse, France.
Abstract:
A unique feature of p21 that distinguishes it from the other cyclin-dependent kinase (CDK) inhibitors is its ability to associate with the proliferating cell nuclear antigen (PCNA), an auxiliary factor for DNA polymerases delta and epsilon. While it is now well established that inhibition of cyclin/CDK complexes by p21 can result in G1 cell cycle arrest, the consequences of p21/PCNA interaction on cell cycle progression have not yet been determined. Here, we show, using a tetracycline-regulated system, that expression of wild-type p21 in p53-deficient DLD1 human colon cancer cells inhibits DNA synthesis and causes G1 and G2 cell cycle arrest. Similar effects are observed in cells expressing p21CDK-, a mutant impaired in the interaction with CDKs, but not in cells expressing p21PCNA-, a mutant deficient for the interaction with PCNA. Analysis of cells treated with a p21-derived PCNA-binding peptide provides additional evidence that the growth inhibitory effects of p21 and p21CDK result from their ability to bind to PCNA. Our results suggest that p21 might inhibit cell cycle progression by two independent mechanisms, inhibition of cyclin/CDK complexes, and inhibition of PCNA function resulting in both G1 and G2 arrest.
Insights
The protein p21 inhibits cell cycle progression through two mechanisms: by blocking cyclin-dependent kinases (CDKs) and by interacting with proliferating cell nuclear antigen (PCNA), impacting DNA synthesis and causing cell cycle arrest.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- p21 is a cyclin-dependent kinase (CDK) inhibitor.
- p21 uniquely binds to proliferating cell nuclear antigen (PCNA), a DNA polymerase auxiliary factor.
- The role of the p21-PCNA interaction in cell cycle progression remains unclear.
Purpose of the Study:
- To investigate the consequences of the p21-PCNA interaction on cell cycle progression.
- To determine the mechanisms by which p21 inhibits cell growth.
Main Methods:
- Utilized a tetracycline-regulated system in p53-deficient DLD1 human colon cancer cells.
- Expressed wild-type p21, a p21 mutant deficient in CDK interaction (p21CDK-), and a p21 mutant deficient in PCNA interaction (p21PCNA-).
- Analyzed the effects of a p21-derived PCNA-binding peptide on cell growth.
Main Results:
- Wild-type p21 and p21CDK- expression inhibited DNA synthesis and induced G1 and G2 cell cycle arrest.
- p21PCNA- expression did not cause significant cell cycle arrest.
- PCNA-binding peptide treatment mimicked the growth inhibitory effects of p21 and p21CDK-.
Conclusions:
- p21 inhibits cell cycle progression via two distinct mechanisms: CDK inhibition and PCNA inhibition.
- PCNA inhibition by p21 contributes to both G1 and G2 cell cycle arrest.
- Targeting the p21-PCNA interaction may offer novel therapeutic strategies for cancer treatment.