草鱼呼肠孤病毒（GCRV）是我国分离鉴定的第一株鱼类病毒，拥有自主知识产权，也是国际上研究得最为系统的水生动物呼肠孤病毒。近日，中国科学院武汉病毒研究所方勤研究员与湖南师范大学刘红荣教授及清华大学生命科学学院程凌鹏副研究员等人合作，在国际上首次解析了双层二十面体衣壳草鱼呼肠孤病毒内部聚合酶复合物和核酸的三维结构，为进一步阐明双链RNA病毒内部结构及病毒复制和转录机制提供了丰富的结构信息。相关研究于2018年6月25日在线发表于美国科学院院刊PNAS（Proceedings of the NationalAcademy of Sciences, USA）上，题为 “Structureof RNA polymerase complex and genome within a dsRNA virus provides insightsinto the mechanisms of transcription and assembly”。
Fig. 1. Structures of the aquareovirus genome and RdRp complex within the capsid (filtered to 8- resolution).
Fig. 2. Structures of VP2, VP4, and VP3A. 研究表明呼肠孤病毒科病毒的RNA聚合酶和基因组排列为一个不完整的二重三次对称，其双链RNA分层状排列，相邻的RNA平行排列。本研究进一步否定了近二十年来占据双链RNA病毒研究领域的“病毒衣壳内的RNA基因组和聚合酶呈线轴状排列”这一主流观点，为阐明双链RNA病毒的复制和转录的分子机制提供了结构基础。
Most double-stranded RNA (dsRNA) viruses transcribe RNA plus strands within a common innermost capsid shell. This process requires coordinated efforts by RNA-dependent RNA polymerase (RdRp) together with other capsid proteins and genomic RNA. Here we report the near-atomic resolution structure of the RdRp protein VP2 in complex with its cofactor protein VP4 and genomic RNA within an aquareovirus capsid using 200-kV cryoelectron microscopy and symmetry-mismatch reconstruction. The structure of these capsid proteins enabled us to observe the elaborate nonicosahedral structure within the double-layered icosahedralcapsid. Our structure shows that the RdRp complex is anchored at the inner surface of the capsid shell and interacts with genomic dsRNA and four of thefive asymmetrically arranged N termini of the capsid shell proteins under the fivefold axis, implying roles for these N termini in virus assembly. The binding site of the RNA end at VP2 is different from the RNA cap binding site identified in the crystal structure of orthoreovirus RdRp λ3, although the structures of VP2 and λ3 are almost identical. A loop, which was thought to separate the RNA template and transcript, interacts with an apical domain of the capsid shell protein, suggesting a mechanism for regulating RdR preplication and transcription. A conserved nucleoside triphosphate binding site was localized in our RdRp cofactor protein VP4 structure, and interactions between the VP4 and the genomic RNA were identified.
参考文献：
1. Xurong Wang, FuxianZhang, Rui Su, Xiaowu Li, Wenyuan Chen, Qingxiu Chen, Tao Yang, Jiawei Wang,Hongrong Liu, Qin Fang, and Lingpeng Cheng. Structure of RNA polymerase complexand genome within a dsRNA virus provides insights into the mechanisms oftranscription and assembly.PNAS June 25, 2018. 20180388.
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