Gao Kun, Wang Chenji, Jin Xiaofeng, Xiao Jiantao, Zhang Enceng, Yang Xianmei, Wang Dejie, Huang Haojie, Yu Long, Zhang Pingzhao
State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for Genetics and Development, School of Life Sciences, Fudan University, 2005 Songhu Road, Shanghai 200433, China.
Department of Urology, Shanghai First People's Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai 200080, China.
Cancer Lett. 2016 May 28;375(1):133-141. doi: 10.1016/j.canlet.2016.02.013. Epub 2016 Feb 27.
The oncoprotein MDM2 is an E3 ubiquitin ligase that targets tumor suppressor p53 for ubiquitination and proteasomal degradation, restraining the potent activity of p53 and enabling cell survival and proliferation. Dysregulation of MDM2-p53 axis was frequently observed in human cancers. Originally, it is proposed that MDM2 degradation was mainly achieved by destructive self-ubiquitination. However, recent study suggests that MDM2 may be targeted for degradation by an external E3 ubiquitin ligase(s) under physiological levels. Here, we identified E3 ubiquitin ligase RNF12 as an MDM2-interacting protein through yeast two hybrid methods. We demonstrated that RNF12 targets MDM2 for ubiquitination and proteasomal-dependent degradation, which is independent of MDM2's self-ubiquitination activity. Accordingly, RNF12 elevates p53 protein level by abrogating MDM2-mediated p53 degradation and ubiquitination. Finally, we showed that RNF12 regulates cell growth suppression and DNA damage-induced apoptosis in a p53-dependent manner. Taken together, we establish RNF12 as a novel positive regulator of p53 pathway and an external E3 ubiquitin ligase for MDM2 destruction. These data shed light on the potential roles of RNF12 in MDM2-p53 axis and tumor suppression.
癌蛋白MDM2是一种E3泛素连接酶，它靶向肿瘤抑制因子p53进行泛素化和蛋白酶体降解，抑制p53的强大活性，从而使细胞得以存活和增殖。MDM2-p53轴的失调在人类癌症中经常被观察到。最初，人们认为MDM2的降解主要是通过破坏性的自身泛素化来实现的。然而，最近的研究表明，在生理水平下，MDM2可能被一种外部E3泛素连接酶靶向降解。在这里，我们通过酵母双杂交方法鉴定出E3泛素连接酶RNF12是一种与MDM2相互作用的蛋白。我们证明，RNF12靶向MDM2进行泛素化和蛋白酶体依赖性降解，这与MDM2的自身泛素化活性无关。因此，RNF12通过消除MDM2介导的p53降解和泛素化来提高p53蛋白水平。最后，我们表明RNF12以p53依赖的方式调节细胞生长抑制和DNA损伤诱导的凋亡。综上所述，我们确立了RNF12是p53通路的一种新型正向调节因子，也是一种用于破坏MDM2的外部E3泛素连接酶。这些数据揭示了RNF12在MDM2-p53轴和肿瘤抑制中的潜在作用。
