Kenesi Erzsébet, Carbonell Alberto, Lózsa Rita, Vértessy Beáta, Lakatos Lóránt
Department of Dermatology and Allergology, University of Szeged, Szeged H-6720, Hungary.
Instituto de Biología Molecular y Celular de Plantas (Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia), Valencia 46022, Spain.
Nucleic Acids Res. 2017 Jul 27;45(13):7736-7750. doi: 10.1093/nar/gkx379.
In most eukaryotes, RNA silencing is an adaptive immune system regulating key biological processes including antiviral defense. To evade this response, viruses of plants, worms and insects have evolved viral suppressors of RNA silencing proteins (VSRs). Various VSRs, such as P1 from Sweet potato mild mottle virus (SPMMV), inhibit the activity of RNA-induced silencing complexes (RISCs) including an ARGONAUTE (AGO) protein loaded with a small RNA. However, the specific mechanisms explaining this class of inhibition are unknown. Here, we show that SPMMV P1 interacts with AGO1 and AGO2 from Arabidopsis thaliana, but solely interferes with AGO1 function. Moreover, a mutational analysis of a newly identified zinc finger domain in P1 revealed that this domain could represent an effector domain as it is required for P1 suppressor activity but not for AGO1 binding. Finally, a comparative analysis of the target RNA binding capacity of AGO1 in the presence of wild-type or suppressor-defective P1 forms revealed that P1 blocks target RNA binding to AGO1. Our results describe the negative regulation of RISC, the small RNA containing molecular machine.
在大多数真核生物中，RNA沉默是一种适应性免疫系统，可调节包括抗病毒防御在内的关键生物学过程。为了逃避这种反应，植物、蠕虫和昆虫的病毒进化出了RNA沉默蛋白的病毒抑制因子（VSRs）。各种VSRs，如甘薯轻斑驳病毒（SPMMV）的P1，可抑制RNA诱导沉默复合体（RISCs）的活性，包括装载有小RNA的AGO蛋白。然而，解释这类抑制作用的具体机制尚不清楚。在这里，我们表明SPMMV P1与拟南芥的AGO1和AGO2相互作用，但仅干扰AGO1的功能。此外，对P1中新鉴定的锌指结构域的突变分析表明，该结构域可能代表一个效应结构域，因为它是P1抑制活性所必需的，但不是AGO1结合所必需的。最后，对野生型或抑制缺陷型P1形式存在下AGO1的靶RNA结合能力的比较分析表明，P1阻断了靶RNA与AGO1的结合。我们的结果描述了含小RNA的分子机器RISC的负调控。
