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Mutation of mouse p53 Ser23 and the response to DNA damage
Zhiqun Wu1, John Earle, Shin'ichi Saito
1Section of Molecular Biology, Division of Biology, University of California, San Diego, La Jolla, California 92093-0322, USA.
Abstract:
Recent studies have suggested that phosphorylation of human p53 at Ser20 is important for stabilizing p53 in response to DNA damage through disruption of the interaction between MDM2 and p53. To examine the requirement for this DNA damage-induced phosphorylation event in a more physiological setting, we introduced a missense mutation into the endogenous p53 gene of mouse embryonic stem (ES) cells that changes serine 23 (S23), the murine equivalent of human serine 20, to alanine (A). Murine embryonic fibroblasts harboring the p53(S23A) mutation accumulate p53 as well as p21 and Mdm2 proteins to normal levels after DNA damage. Furthermore, ES cells and thymocytes harboring the p53(S23A) mutation also accumulate p53 protein to wild-type levels and undergo p53-dependent apoptosis similarly to wild-type cells after DNA damage. Therefore, phosphorylation of murine p53 at Ser23 is not required for p53 responses to DNA damage induced by UV and ionizing radiation treatment.
Insights
Phosphorylation of mouse p53 at Ser23 is not essential for stabilizing p53 protein or inducing apoptosis after DNA damage. This finding suggests other mechanisms regulate p53 stability and function in response to cellular stress.
Area of Science:
- Molecular Biology
- Cellular Biology
- Genetics
Background:
- Recent studies suggest human p53 phosphorylation at Ser20 stabilizes p53 after DNA damage by disrupting MDM2 interaction.
- The precise role of this phosphorylation in a physiological context remains to be fully elucidated.
Purpose of the Study:
- To investigate the necessity of DNA damage-induced p53 phosphorylation at Ser23 in mice for p53 stabilization and apoptosis.
- To determine if Ser23 phosphorylation is required for p53 responses to UV and ionizing radiation.
Main Methods:
- Generated mouse embryonic stem (ES) cells with a p53(S23A) missense mutation, replacing serine 23 with alanine.
- Analyzed p53, p21, and Mdm2 protein accumulation in response to DNA damage in mutant and wild-type cells.
- Assessed p53-dependent apoptosis in ES cells and thymocytes harboring the p53(S23A) mutation.
Main Results:
- Mouse embryonic fibroblasts with the p53(S23A) mutation exhibited normal accumulation of p53, p21, and Mdm2 proteins post-DNA damage.
- ES cells and thymocytes with the p53(S23A) mutation showed wild-type levels of p53 protein accumulation.
- Mutant cells underwent p53-dependent apoptosis similarly to wild-type cells following DNA damage.
Conclusions:
- Phosphorylation of murine p53 at Ser23 is not required for p53 protein stabilization after DNA damage.
- The p53(S23A) mutation does not impair p53-dependent apoptosis in response to UV and ionizing radiation.
- Murine p53 responses to DNA damage are independent of Ser23 phosphorylation.