Antiviral RISC mainly targets viral mRNA but not genomic RNA of tospovirus.
Antiviral RISC mainly targets viral mRNA but not genomic RNA of tospovirus.
复制标题
抗病毒 RISC 主要针对病毒 mRNA，但不针对 tospovirus 的基因组 RNA
DOI：
10.1371/journal.ppat.1009757
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发表时间：
2021-07
期刊：
影响因子：
6.7
通讯作者：
Tao X
中科院分区：
文献类型：
--
作者：
Hong H;Wang C;Huang Y;Xu M;Yan J;Feng M;Li J;Shi Y;Zhu M;Shen D;Wu P;Kormelink R;Tao X
负链(-)RNA植物病毒(NSVs)的抗病毒RNA沉默/干扰(RNAi)研究较单链正链(+)RNA植物病毒少。从后者，基因组和亚基因组的mRNA分子是RNAi的靶点。然而，植物NSV的基因组RNA链通常紧密包裹在病毒核衣壳(N)蛋白中，形成核糖核蛋白(RNPs)，核糖核蛋白是病毒复制、转录和运动的核心单位。本研究在体外和体内研究了抗病毒RNA诱导沉默复合体(RISC)对新城疫病毒基因组RNA和mRNA分子的靶向作用。从感染TospoVirus的N.benthamiana植物中分离的RISC组分在体外特异性地切割裸露的、纯化的TospoVirus基因组RNA，但不能切割与病毒N蛋白复合的基因组RNAs。在植物RISC复合体中，由携带TospoVirus Nss或Gn基因片段的烟草骚乱病毒(TRV)激活，主要针对相应的病毒mRNAs，很少有基因组(病毒和病毒互补链)RNA组装成RNPs。相反，对于(+)单链RNA黄瓜花叶病毒(CMV)，RISC复合体被携带CMV 2a或2b基因片段的TRV激活，靶向CMV基因组RNA。总之，结果表明，抗病毒RNAi主要针对病毒mRNAs，而它们的基因组RNA在RNPs中受到很好的保护，免受RISC介导的切割。考虑到RNPs在所有NSV的复制周期中的重要作用，本研究的发现可能适用于属于这一组的所有病毒。
Antiviral RNA silencing/interference (RNAi) of negative-strand (-) RNA plant viruses (NSVs) has been studied less than for single-stranded, positive-sense (+)RNA plant viruses. From the latter, genomic and subgenomic mRNA molecules are targeted by RNAi. However, genomic RNA strands from plant NSVs are generally wrapped tightly within viral nucleocapsid (N) protein to form ribonucleoproteins (RNPs), the core unit for viral replication, transcription and movement. In this study, the targeting of the NSV tospoviral genomic RNA and mRNA molecules by antiviral RNA-induced silencing complexes (RISC) was investigated, in vitro and in planta. RISC fractions isolated from tospovirus-infected N. benthamiana plants specifically cleaved naked, purified tospoviral genomic RNAs in vitro, but not genomic RNAs complexed with viral N protein. In planta RISC complexes, activated by a tobacco rattle virus (TRV) carrying tospovirus NSs or Gn gene fragments, mainly targeted the corresponding viral mRNAs and hardly genomic (viral and viral-complementary strands) RNA assembled into RNPs. In contrast, for the (+)ssRNA cucumber mosaic virus (CMV), RISC complexes, activated by TRV carrying CMV 2a or 2b gene fragments, targeted CMV genomic RNA. Altogether, the results indicated that antiviral RNAi primarily targets tospoviral mRNAs whilst their genomic RNA is well protected in RNPs against RISC-mediated cleavage. Considering the important role of RNPs in the replication cycle of all NSVs, the findings made in this study are likely applicable to all viruses belonging to this group.
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