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Updated: Jun 23, 2025

Purification of Ubiquitinated p53 Proteins from Mammalian Cells
Published on: March 21, 2022
The phosphorylation-deubiquitination positive feedback loop of the CHK2-USP7 axis stabilizes p53 under oxidative
Jingwei Liu1, Liangzi Cao2, Yubang Wang2
1The College of Basic Medical Science, Health Sciences Institute, China Medical University, Shenyang, Liaoning Province 110122, China; Key Laboratory of Cell Biology of the Ministry of Public Health, Key Laboratory of Medical Cell Biology of the Ministry of Education, Key Laboratory of Precision Diagnosis and Treatment of Gastrointestinal Tumors of the Ministry of Education, Liaoning Province Collaborative Innovation Center of Aging-Related Disease Diagnosis and Treatment and Prevention, China Medical University, Shenyang, Liaoning Province 110122, China; Department of Anus and Intestine Surgery, First Affiliated Hospital of China Medical University, Shenyang, Liaoning Province 110001, China.
Abstract:
p53 regulates multiple signaling pathways and maintains cell homeostasis under conditions of DNA damage and oxidative stress. Although USP7 has been shown to promote p53 stability via deubiquitination, the USP7-p53 activation mechanism has remained unclear. Here, we propose that DNA damage induces reactive oxygen species (ROS) production and activates ATM-CHK2, and CHK2 then phosphorylates USP7 at S168 and T231. USP7 phosphorylation is essential for its deubiquitination activity toward p53. USP7 also deubiquitinates CHK2 at K119 and K131, increasing CHK2 stability and creating a positive feedback loop between CHK2 and USP7. Compared to peri-tumor tissues, thyroid cancer and colon cancer tissues show higher CHK2 and phosphorylated USP7 (S168, T231) levels, and these levels are positively correlated. Collectively, our results uncover a phosphorylation-deubiquitination positive feedback loop involving the CHK2-USP7 axis that supports the stabilization of p53 and the maintenance of cell homeostasis.
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