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Acetylation of p53 inhibits its ubiquitination by Mdm2
Muyang Li1, Jianyuan Luo, Christopher L Brooks
1Institute for Cancer Genetics, and Department of Pathology, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA.
Abstract:
In response to DNA damage, the activity of the p53 tumor suppressor is modulated by protein stabilization and post-translational modifications including acetylation. Interestingly, both acetylation and ubiquitination can modify the same lysine residues at the C terminus of p53, implicating a role of acetylation in the regulation of p53 stability. However, the direct effect of acetylation on Mdm2-mediated ubiquitination of p53 is still lacking because of technical difficulties. Here, we have developed a method to obtain pure acetylated p53 proteins from cells, and by using an in vitro purified system, we provide the direct evidence that acetylation of the C-terminal domain is sufficient to abrogate its ubiquitination by Mdm2. Importantly, even in the absence of DNA damage, acetylation of the p53 protein is capable of reducing the ubiquitination levels and extending its half-life in vivo. Moreover, we also show that acetylation of p53 can affect its ubiquitination through other mechanisms in addition to the site competition. This study has significant implications regarding a general mechanism by which protein acetylation modulates ubiquitination-dependent proteasome proteolysis.
Insights
Acetylation of the p53 tumor suppressor prevents its ubiquitination and degradation by Mdm2. This post-translational modification stabilizes p53, impacting its role in DNA damage response and cancer progression.
Area of Science:
- Molecular Biology
- Cellular Biology
- Biochemistry
Background:
- The p53 tumor suppressor's activity is regulated by post-translational modifications like acetylation and ubiquitination.
- Acetylation and ubiquitination can target the same lysine residues on p53, suggesting a link between these modifications and protein stability.
- Previous studies faced technical challenges in directly assessing the impact of acetylation on Mdm2-mediated p53 ubiquitination.
Purpose of the Study:
- To investigate the direct effect of p53 acetylation on its ubiquitination by Mdm2.
- To elucidate the role of acetylation in regulating p53 stability and degradation.
- To explore the broader implications of acetylation in modulating ubiquitination-dependent proteolysis.
Main Methods:
- Development of a novel method to isolate pure acetylated p53 proteins from cellular sources.
- Utilizing an in vitro purified system to directly assess the interaction between acetylated p53 and Mdm2.
- In vivo experiments to evaluate the impact of p53 acetylation on ubiquitination levels and protein half-life.
Main Results:
- Acetylation of p53's C-terminal domain is sufficient to inhibit Mdm2-mediated ubiquitination.
- Acetylation of p53 reduces ubiquitination and extends its half-life in vivo, even without DNA damage.
- Evidence suggests acetylation influences p53 ubiquitination through mechanisms beyond direct site competition.
Conclusions:
- Protein acetylation can directly abrogate Mdm2-mediated ubiquitination of p53.
- Acetylation serves as a key regulator of p53 stability, independent of DNA damage.
- This study reveals a general mechanism where acetylation modulates ubiquitination-dependent protein degradation, with implications for cancer therapy.