Deubiquitylation and stabilization of p21 by USP11 is critical for cell-cycle progression and DNA damage responses

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• p21^WAF1/CIP1 is a key cyclin-dependent kinase inhibitor regulating cell-cycle progression and cell fate.
• Protein stability of p21 is tightly controlled by ubiquitylation and subsequent degradation via E3 ubiquitin ligase complexes.
• The recycling or stabilization mechanisms for ubiquitylated p21 remain largely uncharacterized.

Purpose of the Study:

• To identify deubiquitylases that regulate p21 stability.
• To elucidate the role of USP11 in the deubiquitylation and stabilization of p21.
• To investigate the functional consequences of the USP11-p21 interaction on cell-cycle control and DNA damage response.

Main Methods:

• Co-immunoprecipitation assays to demonstrate USP11 binding to p21.
• In vitro deubiquitylation assays to confirm USP11 activity on p21.
• Western blotting to assess p21 protein levels following USP11 manipulation.
• Cell cycle analysis (e.g., flow cytometry) to evaluate cell-cycle progression.
• DNA damage induction followed by checkpoint analysis.
• In vivo tumorigenesis assays.

Main Results:

• USP11 directly binds to p21 in the nucleus and functions as a deubiquitylase, removing polyubiquitin chains.
• USP11 stabilizes p21 protein by counteracting degradation mediated by SCF^SKP2, CRL4^CDT2, and APC/C^CDC20.
• Loss of USP11 leads to p21 destabilization, premature G1/S transition, and abrogated DNA damage-induced checkpoints (G2).
• USP11 depletion results in increased apoptosis following DNA damage and impaired p21 accumulation.
• USP11-mediated p21 stabilization inhibits cell proliferation and tumorigenesis in vivo.

Conclusions:

• USP11 is a critical deubiquitylase that stabilizes p21 protein, thereby regulating cell-cycle progression.
• The USP11-p21 axis plays a vital role in maintaining genomic stability by controlling DNA damage responses.
• Targeting the USP11-p21 interaction could offer therapeutic strategies for cancer treatment by modulating cell proliferation.