Ambrose Rebecca L, Lander Gabriel C, Maaty Walid S, Bothner Brian, Johnson John E, Johnson Karyn N
School of Biological Sciences, The University of Queensland, Brisbane, Australia.
J Gen Virol. 2009 Sep;90(Pt 9):2191-200. doi: 10.1099/vir.0.012104-0. Epub 2009 May 27.
The vinegar fly, Drosophila melanogaster, is a popular model for the study of invertebrate antiviral immune responses. Several picorna-like viruses are commonly found in both wild and laboratory populations of D. melanogaster. The best-studied and most pathogenic of these is the dicistrovirus Drosophila C virus. Among the uncharacterized small RNA viruses of D. melanogaster, Drosophila A virus (DAV) is the least pathogenic. Historically, DAV has been labelled as a picorna-like virus based on its particle size and the content of its RNA genome. Here, we describe the characterization of both the genome and the virion structure of DAV. Unexpectedly, the DAV genome was shown to encode a circular permutation in the palm-domain motifs of the RNA-dependent RNA polymerase. This arrangement has only been described previously for a subset of viruses from the double-stranded RNA virus family Birnaviridae and the T=4 single-stranded RNA virus family Tetraviridae. The 8 A (0.8 nm) DAV virion structure computed from cryo-electron microscopy and image reconstruction indicates that the virus structural protein forms two discrete domains within the capsid. The inner domain is formed from a clear T=3 lattice with similarity to the beta-sandwich domain of tomato bushy stunt virus, whilst the outer domain is not ordered icosahedrally, but forms a cage-like structure that surrounds the core domain. Taken together, this indicates that DAV is highly divergent from previously described viruses.
果蝇，即黑腹果蝇，是研究无脊椎动物抗病毒免疫反应的常用模型。在黑腹果蝇的野生种群和实验室种群中，通常都能发现几种类微小核糖核酸病毒。其中研究最充分且致病性最强的是双顺反子病毒果蝇C病毒。在黑腹果蝇未被表征的小RNA病毒中，果蝇A病毒（DAV）致病性最弱。从历史上看，基于其颗粒大小和RNA基因组的内容，DAV一直被归类为类微小核糖核酸病毒。在此，我们描述了DAV的基因组和病毒粒子结构的特征。出乎意料的是，DAV基因组被证明在RNA依赖的RNA聚合酶的掌状结构域基序中编码了一种环状排列。这种排列此前仅在双链RNA病毒科双RNA病毒属的一部分病毒以及T = 4单链RNA病毒科四病毒属中被描述过。通过冷冻电子显微镜和图像重建计算出的8 Å（0.8纳米）DAV病毒粒子结构表明，病毒结构蛋白在衣壳内形成了两个离散的结构域。内部结构域由一个清晰的T = 3晶格构成，与番茄丛矮病毒的β-三明治结构域相似，而外部结构域并非二十面体有序排列，而是形成了一个围绕核心结构域的笼状结构。综上所述，这表明DAV与先前描述的病毒有很大差异。
