Jin Yetao, Zeng Shelya X, Dai Mu-Shui, Yang Xiang-Jiao, Lu Hua
Department of Biochemistry and Molecular Biology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97201, USA.
J Biol Chem. 2002 Aug 23;277(34):30838-43. doi: 10.1074/jbc.M204078200. Epub 2002 Jun 14.
Our previous study shows that MDM2, a negative feedback regulator of the tumor suppressor p53, inhibits p300-mediated p53 acetylation. Because PCAF (p300/CREB-binding protein-associated factor) also acetylates and activates p53 after DNA damage, in this study we have examined the effect of MDM2 on PCAF-mediated p53 acetylation. We have found that MDM2 inhibited p53 acetylation by PCAF in vitro. In addition, when overexpressed, MDM2 inhibited PCAF-mediated p53 acetylation in cells. MDM2 interacted with PCAF both in vitro and in cells, as assessed using GST fusion protein interaction and immunoprecipitation assays, respectively. Consistent with the above results, MDM2 significantly repressed the activation of p53 transcriptional activity by PCAF without apparently affecting the level of p53. In addition, MDM2 co-resided with p53 at the p53-responsive mdm2 and p21(waf1/cip1) promoters, inhibiting expression of the endogenous p21(waf1/cip1). These results demonstrate that MDM2 can inhibit PCAF-mediated p53 acetylation and activation.
我们之前的研究表明，MDM2作为肿瘤抑制因子p53的负反馈调节因子，可抑制p300介导的p53乙酰化。由于PCAF（p300/CREB结合蛋白相关因子）在DNA损伤后也能使p53乙酰化并激活p53，因此在本研究中，我们检测了MDM2对PCAF介导的p53乙酰化的影响。我们发现，MDM2在体外可抑制PCAF介导的p53乙酰化。此外，当MDM2过表达时，它在细胞中可抑制PCAF介导的p53乙酰化。分别使用GST融合蛋白相互作用和免疫沉淀试验评估发现，MDM2在体外和细胞中均与PCAF相互作用。与上述结果一致，MDM2可显著抑制PCAF对p53转录活性的激活，且对p53水平无明显影响。此外，MDM2与p53共同存在于p53反应性的mdm2和p21（waf1/cip1）启动子处，抑制内源性p21（waf1/cip1）的表达。这些结果表明，MDM2可抑制PCAF介导的p53乙酰化和激活。
