Certain positive-sense single-stranded RNA viruses contain elements at their 3′ termini that structurally mimic tRNAs. These tRNA-like structures (TLSs) are classified based on which amino acid is covalently added to the 3′ end by host aminoacyl-tRNA synthetase. Recently, a cryoEM reconstruction of a representative tyrosine-accepting tRNA-like structure (TLS^Tyr) from brome mosaic virus (BMV) revealed a unique mode of recognition of the viral anticodon-mimicking domain by tyrosyl-tRNA synthetase. Some viruses in the hordeivirus genus of Virgaviridae are also selectively aminoacylated with tyrosine, yet these TLS RNAs have a different architecture in the 5′ domain that comprises the atypical anticodon loop mimic. Herein, we present bioinformatic and biochemical data supporting a distinct secondary structure for the 5′ domain of the hordeivirus TLS^Tyr compared to those in Bromoviridae. Despite forming a different secondary structure, the 5′ domain is necessary to achieve robust in vitro aminoacylation. Furthermore, a chimeric RNA containing the 5′ domain from the BMV TLS^Tyr and the 3′ domain from a hordeivirus TLS^Tyr are aminoacylated, illustrating modularity in these structured RNA elements. We propose that the structurally distinct 5′ domain of the hordeivirus TLS^Tyrs performs the same role in mimicking the anticodon loop as its counterpart in the BMV TLS^Tyr. Finally, these structurally and phylogenetically divergent types of TLS^Tyr provide insight into the evolutionary connections between all classes of viral tRNA-like structures.

中文翻译：

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酪氨酸接受 tRNA 样结构的多样性和模块化

某些正义单链 RNA 病毒的 3' 末端含有在结构上模仿 tRNA 的元件。这些 tRNA 样结构 (TLS) 根据宿主氨酰基-tRNA 合成酶将哪些氨基酸共价添加到 3' 末端进行分类。最近，对来自雀麦花叶病毒（BMV）的代表性酪氨酸接受 tRNA 样结构（TLS ^Tyr）进行冷冻电镜重建，揭示了酪氨酰-tRNA 合成酶识别病毒反密码子模拟结构域的独特模式。Virgaviridae大麦病毒属中的一些病毒也被酪氨酸选择性氨酰化，但这些 TLS RNA 在 5' 结构域具有不同的结构，包含非典型反密码子环模拟物。在此，我们提供的生物信息学和生化数据支持大麦病毒TLS ^Tyr的 5' 结构域与雀麦病毒科中的相比具有独特的二级结构。尽管形成了不同的二级结构，5' 结构域对于实现稳健的体外氨酰化是必需的。此外，含有 BMV TLS ^{Tyr的 5' 结构域和}大麦病毒TLS ^Tyr的 3' 结构域的嵌合 RNA被氨酰化，说明了这些结构化 RNA 元件的模块化。我们提出，大麦病毒TLS ^Tyr s 结构上不同的 5' 结构域在模仿反密码子环方面发挥着与 BMV TLS ^Tyr中的对应物相同的作用。最后，这些结构和系统发育上不同类型的 TLS ^Tyr提供了对所有类别病毒 tRNA 样结构之间进化联系的深入了解。