Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis.
Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis.
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DOI：
10.1186/1743-422x-9-178
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发表时间：
2012-08-29
期刊：
影响因子：
4.8
通讯作者：
Roy P
中科院分区：
文献类型：
--
作者：
Boyce M;Celma CC;Roy P
蓝舌病毒(Bluetongue Virus，BTV)是呼肠孤病毒科的一种双链RNA(DsRNA)病毒，编码10个线性dsRNA片段。BTV mRNAs是由病毒RNA依赖的RNA聚合酶(RdRp)合成的，作为基因组片段的精确和正义拷贝。BTV感染哺乳动物细胞后，迅速将细胞蛋白质合成替换为病毒蛋白质合成，但在环状病毒属中病毒基因表达的调节尚未被研究。利用基于BTV基因组片段10与GFP融合的mRNA报告系统，我们鉴定了该属的蛋白质特征--非结构蛋白1(NS1)，它足以上调翻译。利用嵌合mRNAs中可定量的Renilla荧光素酶ORF两侧的BTV基因组片段的非翻译区(UTRs)，证明了这一现象在病毒基因中的广泛适用性。病毒mRNAs的UTRs被证明是蛋白质合成数量的决定因素，NS1的预表达增加了每种情况下的蛋白质合成数量。在病毒感染的细胞中，通过利用反向遗传学产生表达报告基因与基因组片段10融合的复制病毒，证实了NS1预表达引起的表达增加。此外，NS1介导的表达上调仅限于缺少细胞3‘聚(A)序列的mRNAs，该序列识别3’端是在细胞mRNA存在的情况下特异性增加病毒mRNA翻译的必要决定因素。NS1被认为是病毒蛋白质合成的正调控因子。我们提出了一个翻译调控模型，其中NS1上调病毒蛋白质的合成，包括其自身，并创建一个NS1表达的正反馈环，从而迅速增加所有病毒蛋白的表达。病毒报告mRNAs在细胞mRNAs之间的有效翻译可以解释在感染过程中观察到的细胞蛋白质合成被病毒蛋白质合成取代的原因。
Bluetongue virus (BTV) is a double-stranded RNA (dsRNA) virus of the Reoviridae family, which encodes its genes in ten linear dsRNA segments. BTV mRNAs are synthesised by the viral RNA-dependent RNA polymerase (RdRp) as exact plus sense copies of the genome segments. Infection of mammalian cells with BTV rapidly replaces cellular protein synthesis with viral protein synthesis, but the regulation of viral gene expression in the Orbivirus genus has not been investigated. Using an mRNA reporter system based on genome segment 10 of BTV fused with GFP we identify the protein characteristic of this genus, non-structural protein 1 (NS1) as sufficient to upregulate translation. The wider applicability of this phenomenon among the viral genes is demonstrated using the untranslated regions (UTRs) of BTV genome segments flanking the quantifiable Renilla luciferase ORF in chimeric mRNAs. The UTRs of viral mRNAs are shown to be determinants of the amount of protein synthesised, with the pre-expression of NS1 increasing the quantity in each case. The increased expression induced by pre-expression of NS1 is confirmed in virus infected cells by generating a replicating virus which expresses the reporter fused with genome segment 10, using reverse genetics. Moreover, NS1-mediated upregulation of expression is restricted to mRNAs which lack the cellular 3′ poly(A) sequence identifying the 3′ end as a necessary determinant in specifically increasing the translation of viral mRNA in the presence of cellular mRNA. NS1 is identified as a positive regulator of viral protein synthesis. We propose a model of translational regulation where NS1 upregulates the synthesis of viral proteins, including itself, and creates a positive feedback loop of NS1 expression, which rapidly increases the expression of all the viral proteins. The efficient translation of viral reporter mRNAs among cellular mRNAs can account for the observed replacement of cellular protein synthesis with viral protein synthesis during infection.