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Updated: Nov 7, 2025
In Vitro Analysis of E3 Ubiquitin Ligase Function
Published on: May 14, 2021
Erk1/2 Inactivation-Induced c-Jun Degradation Is Regulated by Protein Phosphatases, UBE2d3, and the C-Terminus of
Weiming Ouyang1, David M Frucht1
1Division of Biotechnology Review and Research II, Office of Biotechnology Products, Office of Pharmaceutical Quality, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD 20993, USA.
Abstract:
Constitutive photomorphogenic 1 (COP1) is the ubiquitin E3 ligase that mediates degradation of c-Jun protein upon Erk1/2 inactivation. It remains unknown how this protein degradation pathway is regulated. In this study, we investigated the roles of protein phosphatases, ubiquitin-conjugating E2 enzymes (UBE2), and an intrinsic motif of c-Jun in regulating this degradation pathway. By using pharmacological inhibitors and/or gene knockdown techniques, we identified protein phosphatase 1 (PP1) and PP2A as the phosphatases and UBE23d as the UBE2 promoting c-Jun degradation, triggered by Erk1/2 inactivation. In addition, we report that the C-terminus of c-Jun protein facilitates its degradation. The addition of a C-terminal tag or deletion of the last four amino acid residues from the C-terminus of c-Jun protects it from degradation under Erk1/2-inactivating conditions. Taken together, this study reveals that the Erk1/2 inactivation-triggered and COP1-mediated c-Jun degradation is extrinsically and intrinsically regulated, providing a new understanding of the mechanisms underlying this protein degradation pathway.
Insights
Constitutive photomorphogenic 1 (COP1) targets c-Jun for degradation upon Erk1/2 inactivation. Protein phosphatase 1 (PP1), PP2A, and UBE23d, along with c-Jun's C-terminus, regulate this COP1-mediated pathway.
Area of Science:
- Molecular Biology
- Cellular Biology
- Biochemistry
Background:
- Constitutive photomorphogenic 1 (COP1) acts as a ubiquitin E3 ligase.
- COP1 mediates c-Jun protein degradation following Erk1/2 inactivation.
- The regulatory mechanisms of this c-Jun degradation pathway are not fully understood.
Purpose of the Study:
- To investigate the roles of protein phosphatases, ubiquitin-conjugating E2 enzymes (UBE2), and c-Jun's intrinsic motif in regulating COP1-mediated c-Jun degradation.
- To elucidate the factors controlling c-Jun protein stability upon Erk1/2 pathway inactivation.
Main Methods:
- Pharmacological inhibition of protein phosphatases.
- Gene knockdown of UBE2 enzymes.
- Analysis of c-Jun C-terminal modifications and deletions.
Main Results:
- Protein phosphatase 1 (PP1) and PP2A were identified as key phosphatases.
- UBE23d was identified as the UBE2 enzyme promoting c-Jun degradation.
- The C-terminus of c-Jun was found to be crucial for its degradation; modifications or deletions protected c-Jun.
Conclusions:
- Erk1/2 inactivation-triggered, COP1-mediated c-Jun degradation is regulated by specific phosphatases (PP1, PP2A) and UBE2 (UBE23d).
- An intrinsic C-terminal motif of c-Jun facilitates its degradation.
- This study provides novel insights into the extrinsic and intrinsic regulation of the c-Jun degradation pathway.
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