乙型肝炎病毒X蛋白促进SMC5/6降解以增强乙肝病毒复制。
Hepatitis B Virus X Protein Promotes Degradation of SMC5/6 to Enhance HBV Replication.
作者信息
Murphy Christopher M, Xu Yanping, Li Feng, Nio Kouki, Reszka-Blanco Natalia, Li Xiaodong, Wu Yaxu, Yu Yanbao, Xiong Yue, Su Lishan
机构信息
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
出版信息
Cell Rep. 2016 Sep 13;16(11):2846-2854. doi: 10.1016/j.celrep.2016.08.026.
The hepatitis B virus (HBV) regulatory protein X (HBx) activates gene expression from the HBV covalently closed circular DNA (cccDNA) genome. Interaction of HBx with the DDB1-CUL4-ROC1 (CRL4) E3 ligase is critical for this function. Using substrate-trapping proteomics, we identified the structural maintenance of chromosomes (SMC) complex proteins SMC5 and SMC6 as CRL4(HBx) substrates. HBx expression and HBV infection degraded the SMC5/6 complex in human hepatocytes in vitro and in humanized mice in vivo. HBx targets SMC5/6 for ubiquitylation by the CRL4(HBx) E3 ligase and subsequent degradation by the proteasome. Using a minicircle HBV (mcHBV) reporter system with HBx-dependent activity, we demonstrate that SMC5/6 knockdown, or inhibition with a dominant-negative SMC6, enhance HBx null mcHBV-Gluc gene expression. Furthermore, SMC5/6 knockdown rescued HBx-deficient HBV replication in human hepatocytes. These results indicate that a primary function of HBx is to degrade SMC5/6, which restricts HBV replication by inhibiting HBV gene expression.
乙型肝炎病毒（HBV）调节蛋白X（HBx）可激活HBV共价闭合环状DNA（cccDNA）基因组的基因表达。HBx与DDB1-CUL4-ROC1（CRL4）E3连接酶的相互作用对该功能至关重要。利用底物捕获蛋白质组学技术，我们鉴定出染色体结构维持（SMC）复合体蛋白SMC5和SMC6为CRL4（HBx）的底物。在体外人肝细胞和体内人源化小鼠中，HBx的表达及HBV感染均会导致SMC5/6复合体降解。HBx将SMC5/6作为CRL4（HBx）E3连接酶进行泛素化修饰的靶点，随后通过蛋白酶体进行降解。利用具有HBx依赖性活性的微环HBV（mcHBV）报告系统，我们证明敲低SMC5/6或用显性负性SMC6进行抑制可增强HBx缺失的mcHBV-Gluc基因表达。此外，敲低SMC5/6可挽救人肝细胞中HBx缺陷型HBV的复制。这些结果表明，HBx的主要功能是降解SMC5/6，而SMC5/6通过抑制HBV基因表达来限制HBV复制。
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