Wwp2, an E3 ubiquitin ligase that targets transcription factor Oct-4 for ubiquitination
Wwp2, an E3 ubiquitin ligase that targets transcription factor Oct-4 for ubiquitination
复制标题
Wwp2，一种 E3 泛素连接酶，靶向转录因子 Oct-4 进行泛素化
DOI：
10.1074/jbc.m400516200
复制
发表时间：
2004-05-28
影响因子：
4.8
通讯作者：
Ying, J
中科院分区：
文献类型：
--
作者：
Xu, HM;Liao, B;Ying, J
POU转录因子Oct-4是影响多能胚胎干细胞命运的主要调节因子。然而，调控Oct-4激活和表达的确切机制仍有待阐明。在这里，我们描述了一种新的小鼠泛素连接酶WWP2，它与Oct-4特异地相互作用，并在体内和体外促进其泛素化。值得注意的是，WWP2的催化失活点突变体的表达取消了Oct-4泛素化。此外，WWP2在泛素过度表达的情况下促进Oct-4的降解。用蛋白酶体抑制剂处理可以阻止这种降解。在异源OCT-4驱动的报告系统中，将单个泛素与OCT-4融合可使其转录活性失活。此外，WWP2在胚胎干细胞中的过表达显著降低了Oct-4的转录活性。总的来说，我们第一次证明了Oct-4可以被泛素化翻译后修饰，并且这种修饰显著抑制了它的转录活性。这些结果揭示了Oct-4的功能状态，除了它的表达水平之外，还决定了它的转录活性，这一结果为理解Oct-4如何定义胚胎干细胞的命运开辟了一条新的途径。
The POU transcription factor Oct-4 is a master regulator affecting the fate of pluripotent embryonic stem cells. However, the precise mechanisms by which the activation and expression of Oct-4 are regulated still remain to be elucidated. We describe here a novel murine ubiquitin ligase, Wwp2, that specifically interacts with Oct-4 and promotes its ubiquitination both in vivo and in vitro. Remarkably, the expression of a catalytically inactive point mutant of Wwp2 abolishes Oct-4 ubiquitination. Moreover, Wwp2 promotes Oct-4 degradation in the presence of overexpressed ubiquitin. The degradation is blocked by treatment with proteasome inhibitor. Fusion of a single ubiquitin to Oct-4 inactivates its transcriptional activity in a heterologous Oct-4 driven reporter system. Furthermore, overexpression of Wwp2 in embryonic stem cells significantly reduces the Oct-4-transcriptional activities. Collectively, we demonstrate for the first time that Oct-4 can be posttranslationally modified by ubiquitination and that this modification dramatically suppresses its transcriptional activity. These results reveal that the functional status of Oct-4, in addition to its expression level, dictates its transcriptional activity, and the results open up a new avenue to understand how Oct-4 defines the fate of embryonic stem cells.