The Nodaviridae are a family of isometric RNA viruses that infect insects and fish. Their genomes, which are among the smallest known for animal viruses, consist of two co-encapsidated positive-sense RNA segments: RNA1 encodes the viral contribution to the RNA-dependent RNA polymerase (RdRp) which replicates the viral genome, whereas RNA2 encodes the capsid protein precursor. In this study, the RNA1 sequences of two insect nodaviruses - Nodamura virus (the prototype of the genus) and Boolarra virus - are reported as well as detailed comparisons of their encoded RdRps with those of three other nodaviruses of insects and one of fish. Although the 5' and 3' untranslated regions did not reveal common features of RNA sequence or secondary structure, these divergent viruses showed similar genome organizations and encoded RdRps that had from 26 to 99% amino acid sequence identity. All six RdRp amino acid sequences contained canonical RNA polymerase motifs in their C-terminal halves and conserved elements of predicted secondary structure throughout. A search for structural homologues in the protein structure database identified the poliovirus RdRp, 3D(pol), as the best template for homology modelling of the RNA polymerase domain of Pariacoto virus and allowed the construction of a congruent three-dimensional model. These results extend our understanding of the relationships among the RNA1 segments of nodaviruses and the predicted structures of their encoded RdRps.

译文

:Nodaviridae是感染昆虫和鱼类的等距RNA病毒家族。它们的基因组是动物病毒中已知最小的基因组,由两个共衣壳化的正义RNA片段组成:RNA1编码病毒对复制病毒基因组的RNA依赖性RNA聚合酶(RdRp)的贡献,而RNA2编码衣壳蛋白前体。在这项研究中,报道了两种昆虫诺达病毒RNA的序列-Nodamura病毒(属原型)和Boolarra病毒-以及它们编码的RdRps与其他三种昆虫和一种鱼类诺达病毒的RNA序列的详细比较。尽管5'和3'非翻译区未揭示RNA序列或二级结构的共同特征,但这些趋异病毒显示相似的基因组组织并编码具有26%至99%氨基酸序列同一性的RdRps。所有六个RdRp氨基酸序列在其C末端一半均包含规范的RNA聚合酶基序,并且在整个预测过程中均包含保守的二级结构元素。在蛋白质结构数据库中搜索结构同源物,发现脊髓灰质炎病毒RdRp,3D(pol)是对帕里亚科托病毒RNA聚合酶结构域进行同源建模的最佳模板,并可以构建全等的三维模型。这些结果扩展了我们对诺达病毒RNA1片段之间的关系及其编码的RdRps的预测结构的理解。

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