Exoribonuclease-resistant RNAs (xrRNAs) are discrete elements that block the progression of 5' to 3' exoribonucleases using specifically folded RNA structures. A recently discovered class of xrRNA is widespread in several genera of plant-infecting viruses, within both noncoding and protein-coding subgenomic RNAs. The structure of one such xrRNA from a dianthovirus revealed three-dimensional details of the resistant fold but did not answer all questions regarding the conservation and diversity of this xrRNA class. Here, we present the crystal structure of a representative polerovirus xrRNA that contains sequence elements that diverge from the previously solved structure. This new structure rationalizes previously unexplained sequence conservation patterns and shows interactions not present in the first structure. Together, the structures of these xrRNAs from dianthovirus and polerovirus genera support the idea that these plant virus xrRNAs fold through a defined pathway that includes a programmed intermediate conformation. This work deepens our knowledge of the structure-function relationship of xrRNAs and shows how evolution can craft similar RNA folds from divergent sequences.

中文翻译：

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Polerovirus 外切核糖核酸酶抗性 RNA 的晶体结构显示了不同的序列如何整合到一个保守的折叠中

外切核糖核酸酶抗性 rna (xrRNA) 是离散元件，可使用特定折叠的 RNA 结构阻止 5' 到 3' 外切糖核酸酶的进展。最近发现的一类 xrRNA 在几个植物感染病毒属中广泛存在，包括非编码和蛋白质编码的亚基因组 RNA。一种来自双核病毒的此类 xrRNA 的结构揭示了抗性折叠的三维细节，但并未回答有关该 xrRNA 类别的保守性和多样性的所有问题。在这里，我们展示了具有代表性的杆状病毒 xrRNA 的晶体结构，其中包含与先前解决的结构不同的序列元素。这种新结构使以前无法解释的序列保守模式合理化，并显示出第一个结构中不存在的相互作用。一起，来自石竹病毒属和杆状病毒属的这些 xrRNA 的结构支持这样的观点，即这些植物病毒 xrRNA 通过包括程序化中间构象的确定途径折叠。这项工作加深了我们对 xrRNA 结构-功能关系的了解，并展示了进化如何从不同的序列中制作出相似的 RNA 折叠。