Argonaute quenching and global changes in Dicer homeostasis caused by a pathogen-encoded GW repeat protein
Argonaute quenching and global changes in Dicer homeostasis caused by a pathogen-encoded GW repeat protein
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DOI：
10.1101/gad.1908710
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发表时间：
2010-05-01
影响因子：
10.5
通讯作者：
Voinnet, Olivier
中科院分区：
文献类型：
--
作者：
Azevedo, Jacinthe;Garcia, Damien;Voinnet, Olivier
在植物和无脊椎动物中，由RNaseIII Dicer引导Argonaute （AGO）蛋白加工的病毒衍生sirna是抗病毒rna诱导沉默复合物（RISC）的一部分。作为一种防御手段，病毒产生抑制蛋白（VSRs）来抑制宿主的沉默机制，但其作用机制和细胞靶点在很大程度上仍然未知。在这里，我们展示了萝卜皱缩病毒（TCV）衣壳，P38蛋白，作为一个同源二聚体，或其多个，模拟宿主编码的甘氨酸/色氨酸(GW)-含蛋白质通常需要在不同生物体的RISC组装/功能。P38 GW残基直接特异性结合拟南芥AGO1，除了在内源性microrna介导的沉默中发挥作用外，还被鉴定为tcv衍生sirna的主要效应体。P38 GW残基的点突变足以消除TCV毒力，在拟南芥ago1亚胚突变体中恢复TCV毒力，揭示了这两种蛋白之间的物理和遗传相互作用。我们进一步揭示了P38对AGO1的猝灭如何深刻影响四种拟南芥Dicers的细胞可用性，揭示了一个AGO1依赖的、将这些因子功能连接在一起的稳态网络。在植物和后生动物的先天免疫和适应性免疫的背景下，讨论了GW蛋白模仿对宿主沉默途径的可能广泛发生和预期后果。
In plants and invertebrates, viral-derived siRNAs processed by the RNaseIII Dicer guide Argonaute (AGO) proteins as part of antiviral RNA-induced silencing complexes (RISC). As a counterdefense, viruses produce suppressor proteins (VSRs) that inhibit the host silencing machinery, but their mechanisms of action and cellular targets remain largely unknown. Here, we show that the Turnip crinckle virus (TCV) capsid, the P38 protein, acts as a homodimer, or multiples thereof, to mimic host-encoded glycine/tryptophane (GW)-containing proteins normally required for RISC assembly/function in diverse organisms. The P38 GW residues bind directly and specifically to Arabidopsis AGO1, which, in addition to its role in endogenous microRNA-mediated silencing, is identified as a major effector of TCV-derived siRNAs. Point mutations in the P38 GW residues are sufficient to abolish TCV virulence, which is restored in Arabidopsis ago1 hypomorphic mutants, uncovering both physical and genetic interactions between the two proteins. We further show how AGO1 quenching by P38 profoundly impacts the cellular availability of the four Arabidopsis Dicers, uncovering an AGO1-dependent, homeostatic network that functionally connects these factors together. The likely widespread occurrence and expected consequences of GW protein mimicry on host silencing pathways are discussed in the context of innate and adaptive immunity in plants and metazoans.