WWP2 promotes degradation of transcription factor OCT4 in human embryonic stem cells
WWP2 promotes degradation of transcription factor OCT4 in human embryonic stem cells
复制标题
WWP2促进人胚胎干细胞中转录因子OCT4的降解
DOI：
10.1038/cr.2009.31
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发表时间：
2009-05-01
期刊：
影响因子：
44.1
通讯作者：
Jin, Ying
中科院分区：
文献类型：
--
作者：
Xu, Huiming;Wang, Weicheng;Jin, Ying
POU转录因子OCT 4不仅在维持胚胎干细胞的多能性和自我更新状态中起重要作用，而且通过基因剂量效应作为细胞命运决定因子。然而，控制细胞内OCT 4蛋白水平的分子机制仍然难以捉摸。在这里，我们报告，人WWP 2，E3泛素（Ub）蛋白连接酶，通过其WW结构域与OCT 4特异性相互作用，并在体外和体内增强OCT 4的Ub修饰。我们首先证明了人ES细胞中的内源性OCT 4可以被Ub后修饰。此外，我们发现WWP 2通过26 S蛋白酶体以剂量依赖性方式促进OCT 4的降解，并且WWP 2的活性位点半胱氨酸残基是其酶活性和对OCT 4的蛋白水解作用所必需的。值得注意的是，我们的数据显示，当WWP 2表达被特异性RNA干扰（RNAi）下调时，内源性OCT 4蛋白水平显著升高，这表明WWP 2是在人ES细胞中维持适当OCT 4蛋白水平的重要调节剂。此外，北方印迹分析表明，WWP 2转录本广泛存在于各种人体组织/器官中，并在未分化的人ES细胞中高度表达。然而，其表达水平在人ES细胞分化后迅速下降，表明WWP 2的表达可能受到发育调控。我们的研究结果表明，WWP 2是人ES细胞中OCT 4蛋白水平的重要调节因子。
POU transcription factor OCT4 not only plays an essential role in maintaining the pluripotent and self-renewing state of embryonic stem (ES) cells but also acts as a cell fate determinant through a gene dosage effect. However, the molecular mechanisms that control the intracellular OCT4 protein level remain elusive. Here, we report that human WWP2, an E3 ubiquitin (Ub)-protein ligase, interacts with OCT4 specifically through its WW domain and enhances Ub modification of OCT4 both in vitro and in vivo. We first demonstrated that endogenous OCT4 in human ES cells can be post-translationally modified by Ub. Furthermore, we found that WWP2 promoted degradation of OCT4 through the 26S proteasome in a dosage-dependent manner, and the active site cysteine residue of WWP2 was required for both its enzymatic activity and proteolytic effect on OCT4. Remarkably, our data show that the endogenous OCT4 protein level was significantly elevated when WWP2 expression was downregulated by specific RNA interference (RNAi), suggesting that WWP2 is an important regulator for maintaining a proper OCT4 protein level in human ES cells. Moreover, northern blot analysis showed that the WWP2 transcript was widely present in diverse human tissues/organs and highly expressed in undifferentiated human ES cells. However, its expression level was quickly decreased after human ES cells differentiated, indicating that WWP2 expression might be developmentally regulated. Our findings demonstrate that WWP2 is an important regulator of the OCT4 protein level in human ES cells.