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摘要 : 2015年10月26日,Nature 出版集团旗下子刊《Nature》在线发表了加州大学洛杉矶分校的周正洪教授的一篇用冷冻电镜技术揭开呼肠孤病毒三维结构的研究文章

 2015年10月26日,Nature 出版集团旗下子刊《Nature》在线发表了加州大学洛杉矶分校的周正洪教授的一篇用冷冻电镜技术揭开呼肠孤病毒三维结构的研究文章,展示了这种双链RNA病毒的基因组和TEC结构。华南农业大学动科院孙京臣教授参与该研究。

呼肠孤病毒的蛋白衣壳包装着分节段的双链RNA基因组,并且通过TEC(transcriptional enzyme complex)进行内源性mRNA合成。研究人员通过冷冻电镜和不对称重建,解析了休眠状态CPV(q-CPV)的基因组结构。他们还在q-CPV和t-CPV(有转录活性)中明确了TEC的原位结构。

研究显示,CPV的10个dsRNA片段以一种特异性的不对称方式与10个TEC结合,每个dsRNA片段直接结合一个TEC。TEC含有两个广泛互作的亚基,一个RNA依赖的RNA聚合酶(RdRP)和一个NTPase VP4。当q-CPV转变为t-CPV的时候,RdRP的bracelet结构域会出现显著的构象改变,形成通道允许RNA模板进入并接触聚合酶活性位点。此外,CSP(capsid shell protein)的两个亚基与VP4和RdRP存在互作。这一发现将感知环境线索的外部蛋白与病毒内的RNA转录关联起来。


In situ structures of the segmented genome and RNA polymerase complex inside a dsRNA virus


Viruses in the Reoviridae, like the triple-shelled human rotavirus and the single-shelled insect cytoplasmic polyhedrosis virus (CPV), all package a genome of segmented double-stranded RNAs (dsRNAs) inside the viral capsid and carry out endogenous messenger RNA synthesis through a transcriptional enzyme complex (TEC)1. By direct electron-counting cryoelectron microscopy and asymmetric reconstruction, we have determined the organization of the dsRNA genome inside quiescent CPV (q-CPV) and the in situ atomic structures of TEC within CPV in both quiescent and transcribing (t-CPV) states. We show that the ten segmented dsRNAs in CPV are organized with ten TECs in a specific, non-symmetric manner, with each dsRNA segment attached directly to a TEC. The TEC consists of two extensively interacting subunits: an RNA-dependent RNA polymerase (RdRP) and an NTPase VP4. We find that the bracelet domain of RdRP undergoes marked conformational change when q-CPV is converted to t-CPV, leading to formation of the RNA template entry channel and access to the polymerase active site. An amino-terminal helix from each of two subunits of the capsid shell protein (CSP) interacts with VP4 and RdRP. These findings establish the link between sensing of environmental cues by the external proteins and activation of endogenous RNA transcription by the TEC inside the virus.

来源: Nature 浏览次数:0


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