IFIT1 Differentially Interferes with Translation and Replication of Alphavirus Genomes and Promotes Induction of Type I Interferon.
IFIT1 Differentially Interferes with Translation and Replication of Alphavirus Genomes and Promotes Induction of Type I Interferon.
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DOI：
10.1371/journal.ppat.1004863
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发表时间：
2015-04
期刊：
影响因子：
6.7
通讯作者：
Frolov I
中科院分区：
文献类型：
--
作者：
Reynaud JM;Kim DY;Atasheva S;Rasalouskaya A;White JP;Diamond MS;Weaver SC;Frolova EI;Frolov I
甲病毒是一组广泛分布于人类和动物的病原体。已经确定它们的复制对I型IFN治疗敏感，但IFN抑制功能的机制尚不清楚。利用一个新的实验系统，我们证明了在IFN-β存在下，干扰素刺激基因（ISGs）的激活不会干扰甲病毒病毒粒子附着在细胞上，也不会干扰它们的进入和核衣壳的分解。然而，它强烈影响病毒粒子传递的病毒特异性rna的翻译。ISG的产物之一IFIT1蛋白在这个翻译块中起主要作用，尽管也涉及一个独立于IFIT1的机制。研究发现，在IFIT1浓度增加的情况下，甲病毒基因组的5 ' utr在驱动翻译的能力上存在显著差异。先前的研究表明，自然循环的甲病毒对组织培养中复制的适应导致5‘UTR突变的积累，这增加了位于基因组5 ’端启动子的效率。在这里，我们发现这些突变也降低了病毒RNA对ifit1诱导的翻译抑制的抗性。在IFIT1水平较高的情况下，具有wt 5 ' utr的甲型病毒成为I型IFN的有效诱导剂，提示了I型IFN诱导的新机制。我们利用IFIT1与甲病毒相互作用的这一知识，开发了委内瑞拉马脑炎和基孔肯雅病毒的新减毒变体，这些病毒对IFIT1的抗病毒作用更敏感，因此可以作为新的候选疫苗。甲病毒是一类非常重要的人类病原体，通过蚊子媒介在脊椎动物宿主之间传播。甲病毒在脊椎动物中的复制取决于它们在细胞和机体水平上干扰宿主抗病毒反应的能力。鉴定影响病毒复制的细胞因子及其功能特征可能对设计新的有效候选疫苗至关重要。我们已经证明干扰素刺激基因之一IFIT1的蛋白产物是一种有效的α病毒基因组翻译抑制剂，并最终抑制病毒复制。甲病毒基因组5 ‘非翻译区（5’UTRs）的二级结构在甲病毒抵抗这种抑制作用中发挥了关键作用。此外，在表达IFIT1的细胞中，发现对IFIT1低敏感性的wt α病毒也能诱导高水平的I型IFN。总之，我们的数据表明，甲病毒5 ' utr是进化选择的，既满足作为正链和负链RNA合成启动子的功能，又支持抵抗IFIT1的抑制作用。我们进一步利用这一新知识来开发突变的甲型病毒，其对IFIT1表现出更高的敏感性和更弱的表型。
Alphaviruses are a group of widely distributed human and animal pathogens. It is well established that their replication is sensitive to type I IFN treatment, but the mechanism of IFN inhibitory function remains poorly understood. Using a new experimental system, we demonstrate that in the presence of IFN-β, activation of interferon-stimulated genes (ISGs) does not interfere with either attachment of alphavirus virions to the cells, or their entry and nucleocapsid disassembly. However, it strongly affects translation of the virion-delivered virus-specific RNAs. One of the ISG products, IFIT1 protein, plays a major role in this translation block, although an IFIT1-independent mechanism is also involved. The 5’UTRs of the alphavirus genomes were found to differ significantly in their ability to drive translation in the presence of increased concentration of IFIT1. Prior studies have shown that adaptation of naturally circulating alphaviruses to replication in tissue culture results in accumulation of mutations in the 5’UTR, which increase the efficiency of the promoter located in the 5’end of the genome. Here, we show that these mutations also decrease resistance of viral RNA to IFIT1-induced translation inhibition. In the presence of higher levels of IFIT1, alphaviruses with wt 5’UTRs became potent inducers of type I IFN, suggesting a new mechanism of type I IFN induction. We applied this knowledge of IFIT1 interaction with alphaviruses to develop new attenuated variants of Venezuelan equine encephalitis and chikungunya viruses that are more sensitive to the antiviral effects of IFIT1, and thus could serve as novel vaccine candidates. Alphaviruses represent a group of highly important human pathogens, which are transmitted by mosquito vectors between vertebrate hosts. Alphavirus replication in vertebrates depends on their ability to interfere with host antiviral responses on both cellular and organismal levels. The identification of cellular factors, which affect virus replication, and characterization of their functions may prove crucial for the design of new effective vaccine candidates. We have demonstrated that the protein product of one of the interferon-stimulated genes, IFIT1, is a potent inhibitor of translation of the incoming alphavirus genomes and ultimately, virus replication. The secondary structure of the 5’untranslated regions (5’UTRs) of alphavirus genomes was shown to play a critical role in alphavirus resistance to this inhibitory effect. Moreover, in IFIT1-expressing cells, wt alphaviruses exhibiting low sensitivity to IFIT1 also were found to induce high levels of type I IFN. Altogether, our data show that alphavirus 5’UTRs were evolutionarily selected to meet the requirements of both functioning as promoters for positive- and negative-strand RNA synthesis and supporting the resistance to inhibitory effects of IFIT1. We further exploited this new knowledge to develop mutated alphaviruses, which displayed higher sensitivity to IFIT1 and more attenuated phenotypes.
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