State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, 54 Xianlie Road, Guangzhou, China.
Curr Mol Med. 2013 Jul;13(6):968-78. doi: 10.2174/15665240113139990052.
It is well established that the tumor suppressor p53 plays major roles in regulating apoptosis and cell cycle progression. In addition, recent studies have demonstrated that p53 is actively involved in regulating cell differentiation in muscle, the circulatory system and various carcinoma tissues. We have recently shown that p53 also controls lens differentiation. Regarding the mechanism, we reveal that p53 directly regulates c-Maf and Prox1, two important transcription factors to control cell differentiation in the ocular lens. In the present study, we present further evidence to show that p53 can regulate lens differentiation by controlling expression of the differentiation genes coding for the lens crystallins. First, the αA and βA3/A1 gene promoters or introns all contain putative p53 binding sites. Second, gel mobility shifting assays revealed that the p53 protein in nuclear extracts from lens epithelial cells directly binds to the p53 binding sites found in these crystallin gene promoters or introns. Third, exogenous wild type p53 induces dose-dependent expression of the luciferase reporter gene driven by different crystallin gene promoters and the exogenous dominant negative mutant p53 causes dose-dependent inhibition of the same crystallin genes. Fourth, ChIP assays revealed that p53 binds to crystallin gene promoters in vivo. Finally, in the p53 knockout mouse lenses, expression levels of various crystallins were found down-regulated in comparison with those from the wild type mouse lenses. Together, our results reveal that p53 directly regulates expression of different sets of genes to control lens differentiation.
众所周知，肿瘤抑制因子 p53 在调节细胞凋亡和细胞周期进程中起着重要作用。此外，最近的研究表明，p53 还积极参与调节肌肉、循环系统和各种癌组织中的细胞分化。我们最近表明，p53 还控制着晶状体的分化。关于其机制，我们揭示了 p53 可以通过直接调节 c-Maf 和 Prox1 这两个重要的转录因子来控制眼部晶状体中的细胞分化。在本研究中，我们进一步提供了证据表明，p53 可以通过控制编码晶状体晶体蛋白的分化基因的表达来调节晶状体分化。首先，αA 和 βA3/A1 基因启动子或内含子都含有潜在的 p53 结合位点。其次，凝胶迁移率变动分析显示，来自晶状体上皮细胞的核提取物中的 p53 蛋白可直接与这些晶体蛋白基因启动子或内含子中发现的 p53 结合位点结合。第三，外源性野生型 p53 诱导不同晶体蛋白基因启动子驱动的荧光素酶报告基因的剂量依赖性表达，而外源性显性失活突变型 p53 导致相同晶体蛋白基因的剂量依赖性抑制。第四，ChIP 分析显示，p53 在体内与晶体蛋白基因启动子结合。最后，在 p53 敲除小鼠晶状体中，与野生型小鼠晶状体相比，各种晶体蛋白的表达水平发现下调。总之，我们的结果表明，p53 直接调节不同基因的表达来控制晶状体分化。
