ABSTRACT

Subgenomic RNAs are produced by several RNA viruses through incomplete degradation of their genomic RNA by the exoribonuclease Xrn1, and have been shown to be essential for viral growth and pathogenicity. Within the flavivirus genus of the Flaviviridae family, two distinct classes of Xrn1-resistant RNA motifs have been proposed; one for mosquito-borne and insect-specific flaviviruses, and one for tick-borne flaviviruses and no-known-vector flaviviruses. We investigated tick-borne and no-known-vector flavivirus Xrn1-resistant RNA motifs through systematic in vitro mutational analysis and showed that both classes actually possess very similar structural configurations, including a double pseudoknot and a base-triple at identical, conserved locations. For the no-known-vector flavivirus Modoc virus, we show that in vivo generation of subgenomic flaviviral RNA was affected by mutations targeted at nucleotides involved in the structural features of flaviviral Xrn1-resistant RNA motifs that were defined in this work. Our results suggest that throughout the genus flavivirus Xrn1-resistant RNA motifs adopt the same topologically conserved structure.

摘要

亚基因组 RNA 是由几种 RNA 病毒通过核糖核酸外切酶 Xrn1 不完全降解其基因组 RNA 产生的，已被证明对病毒生长和致病性至关重要。在黄病毒科的黄病毒属中，已经提出了两类不同的 Xrn1 抗性 RNA 基序：一种用于蚊媒和昆虫特异性黄病毒，一种用于蜱传黄病毒和未知载体黄病毒。我们通过系统的体外突变分析研究了蜱传病毒和未知载体黄病毒 Xrn1 抗性 RNA 基序，结果表明这两类病毒实际上具有非常相似的结构构型，包括在相同保守位置的双假结和碱基三重结构。对于未知载体黄病毒莫多克病毒，我们发现亚基因组黄病毒RNA的体内生成受到针对本工作中定义的黄病毒Xrn1抗性RNA基序结构特征所涉及的核苷酸的突变的影响。我们的结果表明，整个黄病毒属 Xrn1 抗性 RNA 基序采用相同的拓扑保守结构。