The p122 subunit of Tobacco mosaic virus replicase is a potent silencing suppressor and compromises both small interfering RNA- and MicroRNA-mediated pathways
The p122 subunit of Tobacco mosaic virus replicase is a potent silencing suppressor and compromises both small interfering RNA- and MicroRNA-mediated pathways
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DOI：
10.1128/jvi.01230-07
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发表时间：
2007-11-01
影响因子：
5.4
通讯作者：
Burgyan, Jozsef
中科院分区：
文献类型：
--
作者：
Csorba, Tibor;Bovi, Aurelie;Burgyan, Jozsef
RNA沉默在植物中的功能之一是防御分子寄生物，如病毒、反转录转座子和转基因。植物病毒是基于RNA沉默的抗病毒防御的诱导物和靶标。复制中间体或折叠的病毒RNA激活RNA沉默，产生小干扰RNA（siRNA），这是抗病毒反应的关键参与者。病毒能够通过表达沉默抑制蛋白来抵消RNA沉默。已经表明，许多鉴定的沉默抑制蛋白结合长双链RNA或siRNA，从而阻止沉默效应复合物的组装。在这项研究中，我们表明，122 kDa的复制酶亚基（p122）的十字花科感染烟草花叶病毒（cr-TMV）是一个有效的沉默抑制蛋白。我们发现p122蛋白优先结合双链21-核苷酸（nt）siRNA和microRNA（miRNA）中间体，其中2-nt 3'突出端抑制siRNA和miRNA掺入沉默相关复合物（例如，RNA诱导的沉默复合物[RISC]），但不能干扰先前编程的RISC。此外，我们的研究结果还表明，病毒感染和/或p122对ARNA和miRNA分子的隔离增强了miRNA的积累，尽管阻止了其甲基化。然而，p122沉默抑制子不能阻止hst-15突变体中某些miRNAs的甲基化，其中miRNAs的核输出受到损害。
One of the functions of RNA silencing in plants is to defend against molecular parasites, such as viruses, retrotransposons, and transgenes. Plant viruses are inducers, as well as targets, of RNA silencing-based antiviral defense. Replication intermediates or folded viral RNAs activate RNA silencing, generating small interfering RNAs (siRNAs), which are the key players in the antiviral response. Viruses are able to counteract RNA silencing by expressing silencing-suppressor proteins. It has been shown that many of the identified silencing-suppressor proteins bind long double-stranded RNA or siRNAs and thereby prevent assembly of the silencing effector complexes. In this study, we show that the 122-kDa replicase subunit (p122) of crucifer-infecting Tobacco mosaic virus (cr-TMV) is a potent silencing- suppressor protein. We found that the p122 protein preferentially binds to double-stranded 21-nucleotide (nt) siRNA and microRNA (miRNA) intermediates with 2-nt 3' overhangs inhibiting the incorporation of siRNA and miRNA into silencing-related complexes (e.g., RNA-induced silencing complex [RISC]) both in vitro and in planta but cannot interfere with previously programmed RISCs. In addition, our results also suggest that the virus infection and/or sequestration of the ARNA and miRNA molecules by p122 enhances miRNA accumulation despite preventing its methylation. However, the p122 silencing suppressor does not prevent the methylation of certain miRNAs in hst-15 mutants, in which the nuclear export of miRNAs is compromised.