The Host Factor AUF1 p45 Supports Flavivirus Propagation by Triggering the RNA Switch Required for Viral Genome Cyclization
The Host Factor AUF1 p45 Supports Flavivirus Propagation by Triggering the RNA Switch Required for Viral Genome Cyclization
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DOI：
10.1128/jvi.01647-17
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发表时间：
2018-03-01
影响因子：
5.4
通讯作者：
Behrens, Sven-Erik
中科院分区：
文献类型：
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作者：
Friedrich, Susann;Engelmann, Susanne;Behrens, Sven-Erik
在以前的研究中，我们发现细胞RNA结合蛋白AUF 1支持黄病毒西尼罗病毒的复制过程。在这里，我们证明了该蛋白质也能够有效增殖登革病毒和寨卡病毒，表明AUF 1是一种通用的黄病毒宿主因子。进一步的研究表明，AUF 1亚型p45显著刺激病毒RNA复制的起始，并且蛋白质的RNA伴侣活性增强病毒5 'UAR和3' UAR基因组环化序列的相互作用。最有趣的是，我们观察到AUF 1 p45不仅使病毒基因组的3 '末端茎环（3' SL）不稳定，而且使病毒基因组的5 '末端茎环B（SL B）不稳定。RNA结构分析显示，AUF 1 p45增加了3 'SL和SLB内确定的核苷酸的可及性，并且以这种方式暴露了两个UAR环化元件。相反，AUF 1 p45不调节直接基因组5'端的茎环A（SLA）的折叠，其被认为是病毒RNA依赖性RNA聚合酶（RdRp）的启动子。这些发现表明，AUF 1 p45通过使黄病毒基因组的5'和3'末端内的特定茎环结构不稳定，协助基因组环化，并同时使RdRp能够启动RNA合成。因此，我们的研究突出了细胞RNA结合蛋白诱导黄病毒RNA开关的作用，这对病毒复制至关重要。重要性黄病毒科黄病毒属包括重要的人类病原体，如登革热，西尼罗河病毒和寨卡病毒。黄病毒RNA基因组复制的起始需要从线性形式转化为环化形式。这涉及在基因组5'和3'末端的几个RNA基序的相当大的结构重组。具体地，它需要茎结构的解链以暴露互补的5'和3'环化元件，以使它们能够在环化期间退火。在这里，我们表明，细胞RNA分子伴侣，AUF 1 p45，它支持所有上述三种黄病毒的复制，特异性地重排病毒基因组两端的茎结构，并以这种方式允许环化元件的5 '-3'相互作用。因此，AUF 1 p45触发黄病毒基因组中的RNA开关，这对病毒复制至关重要。这些发现代表了细胞（宿主）因素如何促进RNA病毒繁殖的重要例子。
In previous studies, we showed that the cellular RNA-binding protein AUF1 supports the replication process of the flavivirus West Nile virus. Here we demonstrate that the protein also enables effective proliferation of dengue virus and Zika virus, indicating that AUF1 is a general flavivirus host factor. Further studies demonstrated that the AUF1 isoform p45 significantly stimulates the initiation of viral RNA replication and that the protein's RNA chaperone activity enhances the interactions of the viral 5'UAR and 3'UAR genome cyclization sequences. Most interestingly, we observed that AUF1 p45 destabilizes not only the 3'-terminal stem-loop (3'SL) but also 5'-terminal stem-loop B (SLB) of the viral genome. RNA structure analyses revealed that AUF1 p45 increases the accessibility of defined nucleotides within the 3'SL and SLB and, in this way, exposes both UAR cyclization elements. Conversely, AUF1 p45 does not modulate the fold of stem-loop A (SLA) at the immediate genomic 5' end, which is proposed to function as a promoter of the viral RNA-dependent RNA polymerase (RdRp). These findings suggest that AUF1 p45, by destabilizing specific stem-loop structures within the 5' and 3' ends of the flaviviral genome, assists genome cyclization and concurrently enables the RdRp to initiate RNA synthesis. Our study thus highlights the role of a cellular RNA-binding protein inducing a flaviviral RNA switch that is crucial for viral replication.IMPORTANCE The genus Flavivirus within the Flaviviridae family includes important human pathogens, such as dengue, West Nile, and Zika viruses. The initiation of replication of the flaviviral RNA genome requires a transformation from a linear to a cyclized form. This involves considerable structural reorganization of several RNA motifs at the genomic 5' and 3' ends. Specifically, it needs a melting of stem structures to expose complementary 5' and 3' cyclization elements to enable their annealing during cyclization. Here we show that a cellular RNA chaperone, AUF1 p45, which supports the replication of all three aforementioned flaviviruses, specifically rearranges stem structures at both ends of the viral genome and in this way permits 5'-3' interactions of cyclization elements. Thus, AUF1 p45 triggers the RNA switch in the flaviviral genome that is crucial for viral replication. These findings represent an important example of how cellular (host) factors promote the propagation of RNA viruses.