Related Experiment Video
Updated: May 21, 2026
The Cell-based L-Glutathione Protection Assays to Study Endocytosis and Recycling of Plasma Membrane Proteins
Published on: December 13, 2013
Epidermal growth factor receptor protects proliferating cell nuclear antigen from cullin 4A protein-mediated
Yuan-Hung Lo1, Po-Chun Ho, Shao-Chun Wang
1Department of Cancer and Cell Biology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0521, USA.
Abstract:
Proliferating cell nuclear antigen (PCNA) is an essential component for DNA synthesis upon growth stimulation. It has been shown that phosphorylation of PCNA at Tyr-211 by the EGF receptor (EGFR) protects PCNA from polyubiquitylation and degradation, whereas blocking phosphorylation induces ubiquitylation-mediated degradation of the chromatin-bound, but not the -unbound, PCNA, and suppresses cell proliferation. However, the ubiquitin E3 ligase linking growth signaling to the proteolysis of PCNA and the underlying regulatory mechanism remain to be identified. Here we show that, in the absence of Tyr-211 phosphorylation, PCNA is subject to polyubiquitylation at Lys-164 by the CUL4A E3 ligase, resulting in the degradation of PCNA. Mutation of Lys-164 to arginine prevents PCNA ubiquitylation and rescues the degradation of the K164R/Y211F PCNA double mutant. Activation of EGFR inhibits the interaction of PCNA with CUL4A, whereas inhibition of EGFR leads to increased CUL4A-PCNA interaction and CUL4A-dependent ubiquitin-mediated degradation of PCNA. Substitution of endogenous PCNA with the Y211F mutant PCNA conveys enhanced sensitization to EGFR inhibition. Our findings identify CUL4A as the ubiquitin ligase linking the down-regulation of cell surface receptor tyrosine kinase to the nuclear DNA replication machinery in cancer cells.
Insights
Proliferating cell nuclear antigen (PCNA) is degraded by CUL4A E3 ligase when not phosphorylated. This links EGFR signaling to DNA replication, impacting cancer cell proliferation and sensitivity to EGFR inhibitors.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Proliferating cell nuclear antigen (PCNA) is crucial for DNA synthesis.
- EGF receptor (EGFR) phosphorylation of PCNA at Tyr-211 prevents its degradation.
- The E3 ligase responsible for PCNA degradation upon growth signaling remains unidentified.
Purpose of the Study:
- Identify the ubiquitin E3 ligase that targets PCNA for degradation.
- Elucidate the regulatory mechanism linking growth signaling to PCNA proteolysis.
- Investigate the role of PCNA ubiquitylation in cancer cell response to EGFR inhibition.
Main Methods:
- Investigated PCNA ubiquitylation and degradation in response to EGFR signaling.
- Utilized site-directed mutagenesis (K164R, Y211F) to study PCNA ubiquitylation.
- Assessed the interaction between PCNA and CUL4A E3 ligase.
- Evaluated the effect of PCNA mutations on sensitivity to EGFR inhibition.
Main Results:
- CUL4A E3 ligase polyubiquitylates PCNA at Lys-164 in the absence of Tyr-211 phosphorylation, leading to degradation.
- Mutation of Lys-164 prevents PCNA ubiquitylation and degradation.
- EGFR activation inhibits PCNA-CUL4A interaction; EGFR inhibition enhances it, promoting PCNA degradation.
- Substituting wild-type PCNA with Y211F mutant PCNA increases sensitivity to EGFR inhibition.
Conclusions:
- CUL4A is the ubiquitin ligase mediating PCNA degradation.
- This pathway links cell surface receptor tyrosine kinase signaling to DNA replication machinery.
- CUL4A-mediated PCNA degradation is a potential therapeutic target in cancer treatment.
Related Concept Videos
02:38Mitogens and the Cell Cycle
01:23Negative Regulator Molecules
01:15Receptor Downregulation in MVBs
The EGFR can initiate signaling pathways that lead to cell proliferation, migration, and differentiation. Overexpression of EGFR stimulates cells to proliferate. Excessive EGFR activation may...
02:23Abnormal Proliferation
02:36DNA Damage can Stall the Cell Cycle
02:36DNA Damage Can Stall the Cell Cycle