Viruses are obligate, intracellular pathogens that must manipulate and exploit host molecular mechanisms to prosper in the hostile cellular environment. Here we review the strategies used by viruses to evade the immunity controlled by 21- to 26-nt small RNAs. Viral suppressors of RNA silencing (VSRs) are encoded by genetically diverse viruses infecting plants, invertebrates, and vertebrates. VSRs target key steps in the small RNA pathways by inhibiting small RNA production, sequestering small RNAs, or preventing short- and long-distance spread of RNA silencing. However, although VSRs are required for infection, explicit data demonstrating a role of silencing suppression in virus infection are available only for a few VSRs. A subset of VSRs bind double-stranded RNA, but a distinct protein fold is revealed for each of the four VSRs examined. We propose that VSR families are evolved independently as a viral adaptation to immunity. Unresolved issues on the role of RNA silencing in virus-host interactions are highlighted.

中文翻译：

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病毒防御：逃避RNA沉默免疫的多种策略。

病毒是专性的细胞内病原体，必须操纵和利用宿主分子机制才能在恶劣的细胞环境中繁荣发展。在这里，我们回顾了病毒用于逃避21到26 nt小RNA控制的免疫力的策略。RNA沉默（VSR）的病毒抑制因子由感染植物，无脊椎动物和脊椎动物的遗传多样性病毒编码。VSR通过抑制小RNA的产生，隔离小RNA或防止RNA沉默的短距离和长距离传播，来靶向小RNA途径中的关键步骤。但是，尽管感染需要使用VSR，但仅在少数VSR中提供了显示沉默抑制在病毒感染中作用的显式数据。VSR的一个子集与双链RNA结合，但是对于所检查的四个VSR中的每一个，其蛋白质折叠都不同。我们提出，VSR家族是作为对免疫的病毒适应性独立进化的。强调了RNA沉默在病毒-宿主相互作用中的作用尚未解决的问题。