Venezuelan Equine Encephalitis Virus nsP2 Protein Regulates Packaging of the Viral Genome into Infectious Virions
Venezuelan Equine Encephalitis Virus nsP2 Protein Regulates Packaging of the Viral Genome into Infectious Virions
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DOI：
10.1128/jvi.03142-12
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发表时间：
2013-04-01
影响因子：
5.4
通讯作者：
Frolov, Ilya
中科院分区：
文献类型：
--
作者：
Kim, Dal Young;Atasheva, Svetlana;Frolov, Ilya
甲病毒是地理上分布最广、但往往被忽视的人类和动物病原体之一。它们能够在脊椎动物和昆虫来源的多种细胞中复制，并广泛用于体内和体外异种遗传信息的表达。尽管它们在一系列研究应用中被使用，并被认为是一种公共卫生威胁，但人们对甲病毒的生物学还不够了解。在这项研究中，我们研究了一种甲病毒委内瑞拉马脑炎病毒（VEEV）的进化过程，以了解其在衣壳蛋白引入一系列突变时对病毒基因组低效包装的适应机制。来自这项研究的新数据表明，衣壳蛋白包装病毒基因组的能力的强烈改变导致适应性突变的积累，不仅在衣壳特异性螺旋I中，而且在非结构蛋白nsP2中。在蛋白酶结构域和蛋白质的氨基端检测到nsp2特异性突变，该蛋白先前被认为是蛋白酶辅助因子。这些突变增加了传染性病毒的滴度，对病毒RNA复制产生了强烈的积极影响，介导了细胞病变表型的发展，并使病毒能够发展为扩散性感染。结果表明，甲病毒基因组的包装不仅取决于RNA中的包装信号和衣壳蛋白中带正电的氨基酸的存在，而且nsP2直接或间接地参与了RNA的封装过程。
Alphaviruses are one of the most geographically widespread and yet often neglected group of human and animal pathogens. They are capable of replicating in a wide variety of cells of both vertebrate and insect origin and are widely used for the expression of heterologous genetic information both in vivo and in vitro. In spite of their use in a range of research applications and their recognition as a public health threat, the biology of alphaviruses is insufficiently understood. In this study, we examined the evolution process of one of the alphaviruses, Venezuelan equine encephalitis virus (VEEV), to understand its adaptation mechanism to the inefficient packaging of the viral genome in response to serial mutations introduced into the capsid protein. The new data derived from this study suggest that strong alterations in the ability of capsid protein to package the viral genome leads to accumulation of adaptive mutations, not only in the capsid-specific helix I but also in the nonstructural protein nsP2. The nsP2-specific mutations were detected in the protease domain and in the amino terminus of the protein, which was previously proposed to function as a protease cofactor. These mutations increased infectious virus titers, demonstrated a strong positive impact on viral RNA replication, mediated the development of a more cytopathic phenotype, and made viruses capable of developing a spreading infection. The results suggest not only that packaging of the alphavirus genome is determined by the presence of packaging signals in the RNA and positively charged amino acids in the capsid protein but also that nsP2 is either directly or indirectly involved in the RNA encapsidation process.