Robb Nicole C, Smith Matt, Vreede Frank T, Fodor Ervin
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK.
J Gen Virol. 2009 Jun;90(Pt 6):1398-1407. doi: 10.1099/vir.0.009639-0. Epub 2009 Mar 4.
The influenza virus RNA polymerase transcribes the negative-sense viral RNA segments (vRNA) into mRNA and replicates them via complementary RNA (cRNA) intermediates into more copies of vRNA. It is not clear how the relative amounts of the three RNA products, mRNA, cRNA and vRNA, are regulated during the viral life cycle. We found that in viral ribonucleoprotein (vRNP) reconstitution assays involving only the minimal components required for viral transcription and replication (the RNA polymerase, the nucleoprotein and a vRNA template), the relative levels of accumulation of RNA products differed from those observed in infected cells, suggesting a regulatory role for additional viral proteins. Expression of the viral NS2/NEP protein in RNP reconstitution assays affected viral RNA levels by reducing the accumulation of transcription products and increasing the accumulation of replication products to more closely resemble those found during viral infection. This effect was functionally conserved in influenza A and B viruses and was influenza-virus-type-specific, demonstrating that the NS2/NEP protein changes RNA levels by specific alteration of the viral transcription and replication machinery, rather than through an indirect effect on the host cell. Although NS2/NEP has been shown previously to play a role in the nucleocytoplasmic export of viral RNPs, deletion of the nuclear export sequence region that is required for its transport function did not affect the ability of the protein to regulate RNA levels. A role for the NS2/NEP protein in the regulation of influenza virus transcription and replication that is independent of its viral RNP export function is proposed.
流感病毒RNA聚合酶将负义病毒RNA片段（vRNA）转录为mRNA，并通过互补RNA（cRNA）中间体将它们复制成更多的vRNA拷贝。目前尚不清楚在病毒生命周期中，三种RNA产物（mRNA、cRNA和vRNA）的相对量是如何被调控的。我们发现在仅涉及病毒转录和复制所需最小成分（RNA聚合酶、核蛋白和vRNA模板）的病毒核糖核蛋白（vRNP）重组试验中，RNA产物的相对积累水平与在感染细胞中观察到的不同，这表明其他病毒蛋白具有调控作用。在RNP重组试验中表达病毒NS2/NEP蛋白，通过减少转录产物的积累和增加复制产物的积累来影响病毒RNA水平，使其更接近病毒感染期间的水平。这种效应在甲型和乙型流感病毒中功能保守，且具有流感病毒类型特异性，表明NS2/NEP蛋白通过特异性改变病毒转录和复制机制来改变RNA水平，而不是通过对宿主细胞的间接作用。尽管先前已证明NS2/NEP在病毒RNP的核质输出中起作用，但缺失其运输功能所需的核输出序列区域并不影响该蛋白调节RNA水平的能力。我们提出了NS2/NEP蛋白在流感病毒转录和复制调控中的作用，该作用独立于其病毒RNP输出功能。
