Transcription factor Oct4 plays critical roles in maintaining pluripotency and controlling lineage commitment of embryonic stem cells （ESCs）. Our previous study indicates that Wwp2, a mouse HECT-type E3 ubiquitin li...Transcription factor Oct4 plays critical roles in maintaining pluripotency and controlling lineage commitment of embryonic stem cells （ESCs）. Our previous study indicates that Wwp2, a mouse HECT-type E3 ubiquitin ligase, ubiquitinates Oct4 and promotes its degradation in a heterologous system. However, roles of Wwp2 in regulating en- dogenous Oct4 protein levels as well as molecular characteristics of the function of Wwp2 have not been determined. Here, we report that Wwp2 plays an important role in Oct4 ubiquitination and degradation during differentiation of embryonal carcinoma cells （ECCs）, although it does not appear to affect Oct4 protein levels in the undifferentiated ECCs and ESCs. Importantly, inhibition of Wwp2 expression by specific RNA interference elevates the Oct4 protein level, leading to attenuation in retinoid acid-induced activation of differentiation-related marker genes. Mechanisti- cally, Wwp2 catalyzes Oct4 poly-ubiquitination via the lysine 63 linkage in a dosage-dependent manner. Interest- ingly, Wwp2 also regulates its own ligase activity in a similar manner. Moreover, auto-ubiquitination of Wwp2 occurs through an intra-molecular mechanism. Taken together, these results demonstrate a crucial role of Wwp2 in con- trolling endogenous Oct4 protein levels during differentiation processes of ECCs and suggest an interesting dosage- dependent mechanism for regulating the catalytic activity of the E3 ubiquitin ligase, Wwp2.展开更多
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 effec...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 hu- man 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 en- dogenous 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.展开更多
目的探讨WWP的E3泛素连接酶2(ww domain-containing protein 2,WWP2)沉默对肝癌细胞系黏附、侵袭和迁移的影响作用。方法通过RNA沉默技术降低肝癌细胞系的WWP2水平,用Transwell法检测细胞迁移和侵袭,CCK-8法检测细胞的增殖情况,Western ...目的探讨WWP的E3泛素连接酶2(ww domain-containing protein 2,WWP2)沉默对肝癌细胞系黏附、侵袭和迁移的影响作用。方法通过RNA沉默技术降低肝癌细胞系的WWP2水平,用Transwell法检测细胞迁移和侵袭,CCK-8法检测细胞的增殖情况,Western blot法检测caspase7、caspase8、Bcl-2、Bax、PTEN、p-Akt及Akt的蛋白水平。结果沉默WWP2后,肝癌细胞BEL-7404和Huh7的WWP2mRNA和蛋白的表达水平明显下降(P<0.001),BEL-7404细胞和Huh7细胞的凋亡相关标志物caspase7、caspase8及Bax的蛋白水平表达都显著升高(P<0.01)、PTEN的蛋白水平升高(P<0.01),Bcl-2、p-Akt的蛋白水平显著下降(P<0.01),肝癌细胞BEL-7404和Huh7的细胞活力、黏附能力、侵袭能力和迁移能力都明显减弱(P<0.001)。结论沉默WWP2可抑制肝癌BEL-7404细胞和Huh7细胞增殖、黏附、侵袭和迁移,并促进细胞凋亡,其作用机制可能与PTEN/Akt信号通路相关。展开更多
Protein ubiquitination is an important means of posttranslational modification which plays an essential role in the regulation of various aspects of leukocyte development and function. The specificity of ubiquitin tag...Protein ubiquitination is an important means of posttranslational modification which plays an essential role in the regulation of various aspects of leukocyte development and function. The specificity of ubiquitin tagging to a protein substrate is determined by E3 ubiquitin ligases via defined E3-substrate interactions. In this review, we will focus on two E3 ligases, VHL and Itch, to discuss the latest progress in understanding their roles in the differentiation and function of CD4+ T helper cell subsets, the stability of regulatory T cells, effector function of CD8+ T cells, as well as the development and maturation of innate lymphoid cells. The biological implications of these E3 ubiquitin ligases will be highlighted in the context of normal and dysregulated immune responses including the control of homeostasis, inflammation, auto-immune responses and anti-tumor immunity. Further elucidation of the ubiquitin system in immune cells will help in the design of new therapeutic interventions for human immunological diseases and cancer.展开更多
基金We thank Dr Richard Baer （Pathology, Columbia University, New York, USA） for generously providing various Ub mutant plasmids. This study was supported by Grants from the National Natural Science Foundation of China （30871257, 30730051） and the National High Technology Research, Development Program of China （2006CB943901 and 2007CB947904）, the Shanghai Sci- ence and Technology Developmental Foundation （08JC1413100） and the Shanghai Leading Academic Discipline Project （$30201）.
文摘Transcription factor Oct4 plays critical roles in maintaining pluripotency and controlling lineage commitment of embryonic stem cells （ESCs）. Our previous study indicates that Wwp2, a mouse HECT-type E3 ubiquitin ligase, ubiquitinates Oct4 and promotes its degradation in a heterologous system. However, roles of Wwp2 in regulating en- dogenous Oct4 protein levels as well as molecular characteristics of the function of Wwp2 have not been determined. Here, we report that Wwp2 plays an important role in Oct4 ubiquitination and degradation during differentiation of embryonal carcinoma cells （ECCs）, although it does not appear to affect Oct4 protein levels in the undifferentiated ECCs and ESCs. Importantly, inhibition of Wwp2 expression by specific RNA interference elevates the Oct4 protein level, leading to attenuation in retinoid acid-induced activation of differentiation-related marker genes. Mechanisti- cally, Wwp2 catalyzes Oct4 poly-ubiquitination via the lysine 63 linkage in a dosage-dependent manner. Interest- ingly, Wwp2 also regulates its own ligase activity in a similar manner. Moreover, auto-ubiquitination of Wwp2 occurs through an intra-molecular mechanism. Taken together, these results demonstrate a crucial role of Wwp2 in con- trolling endogenous Oct4 protein levels during differentiation processes of ECCs and suggest an interesting dosage- dependent mechanism for regulating the catalytic activity of the E3 ubiquitin ligase, Wwp2.
基金Acknowledgments We are grateful to Dr DA Melton （Harvard University） for shar- ing his human ES cells with us. The study was supported by grants from the National High Technology Research and Development Program of China （2006CB943900）, the National Natural Science Foundation of China （General Program, 30500088）, the Shang- hai Jiao Tong University School of Medicine, and the Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. The study was also supported by the Shanghai Leading Academic Deciline Project （S30201）.
文摘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 hu- man 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 en- dogenous 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.
文摘目的构建E3泛素连接酶WWP2基因的真核表达载体,并鉴定其表达。方法利用PCR扩增技术扩增人WWP2基因的编码序列,把WWP2基因插入酶切后的pc DNA3.1-Flag空载体,用PCR法、酶切法及基因测序的方法检测重组质粒的正确性,然后将所构建质粒pc DNA3.1-Flag-WWP2转染入人胚肾细胞HEK293T中,并利用免疫印记法检测其表达情况。结果 pc DNA3.1-Flag-WWP2真核表达载体构建成功,且能实现在HEK293T细胞中的表达。结论文章成功构建了带Flag标签的人WWP2真核表达载体,为后续的WWP2基因功能以及作为肺癌治疗新靶点的可行性研究奠定了基础。
文摘目的探讨WWP的E3泛素连接酶2(ww domain-containing protein 2,WWP2)沉默对肝癌细胞系黏附、侵袭和迁移的影响作用。方法通过RNA沉默技术降低肝癌细胞系的WWP2水平,用Transwell法检测细胞迁移和侵袭,CCK-8法检测细胞的增殖情况,Western blot法检测caspase7、caspase8、Bcl-2、Bax、PTEN、p-Akt及Akt的蛋白水平。结果沉默WWP2后,肝癌细胞BEL-7404和Huh7的WWP2mRNA和蛋白的表达水平明显下降(P<0.001),BEL-7404细胞和Huh7细胞的凋亡相关标志物caspase7、caspase8及Bax的蛋白水平表达都显著升高(P<0.01)、PTEN的蛋白水平升高(P<0.01),Bcl-2、p-Akt的蛋白水平显著下降(P<0.01),肝癌细胞BEL-7404和Huh7的细胞活力、黏附能力、侵袭能力和迁移能力都明显减弱(P<0.001)。结论沉默WWP2可抑制肝癌BEL-7404细胞和Huh7细胞增殖、黏附、侵袭和迁移,并促进细胞凋亡,其作用机制可能与PTEN/Akt信号通路相关。
文摘Protein ubiquitination is an important means of posttranslational modification which plays an essential role in the regulation of various aspects of leukocyte development and function. The specificity of ubiquitin tagging to a protein substrate is determined by E3 ubiquitin ligases via defined E3-substrate interactions. In this review, we will focus on two E3 ligases, VHL and Itch, to discuss the latest progress in understanding their roles in the differentiation and function of CD4+ T helper cell subsets, the stability of regulatory T cells, effector function of CD8+ T cells, as well as the development and maturation of innate lymphoid cells. The biological implications of these E3 ubiquitin ligases will be highlighted in the context of normal and dysregulated immune responses including the control of homeostasis, inflammation, auto-immune responses and anti-tumor immunity. Further elucidation of the ubiquitin system in immune cells will help in the design of new therapeutic interventions for human immunological diseases and cancer.
