Wu Zhiqun, Earle John, Saito Shin'ichi, Anderson Carl W, Appella Ettore, Xu Yang
Section of Molecular Biology, Division of Biology, University of California, San Diego, La Jolla, California 92093-0322, USA.
Mol Cell Biol. 2002 Apr;22(8):2441-9. doi: 10.1128/MCB.22.8.2441-2449.2002.
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.
最近的研究表明，人类p53在Ser20位点的磷酸化对于通过破坏MDM2与p53之间的相互作用来稳定p53以应对DNA损伤很重要。为了在更生理的环境中研究这种DNA损伤诱导的磷酸化事件的必要性，我们在小鼠胚胎干细胞（ES细胞）的内源性p53基因中引入了一个错义突变，该突变将人类丝氨酸20的小鼠等效物丝氨酸23（S23）替换为丙氨酸（A）。携带p53（S23A）突变的小鼠胚胎成纤维细胞在DNA损伤后将p53以及p21和Mdm2蛋白积累至正常水平。此外，携带p53（S23A）突变的ES细胞和胸腺细胞在DNA损伤后也将p53蛋白积累至野生型水平，并与野生型细胞类似地经历p53依赖性凋亡。因此，小鼠p53在Ser23位点的磷酸化对于p53对紫外线和电离辐射治疗诱导的DNA损伤的反应不是必需的。
