Department of Microbiology and Molecular Genetics, University of California, Davis, CA, 95616, USA.
Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, 80523, USA.
Virology. 2022 Jan;566:1-8. doi: 10.1016/j.virol.2021.11.002. Epub 2021 Nov 17.
Subviral agents are nucleic acids which lack the features for classification as a virus. Tombusvirus-like associated RNAs (tlaRNAs) are subviral positive-sense, single-stranded RNAs that replicate autonomously, yet depend on a coinfecting virus for encapsidation and transmission. TlaRNAs produce abundant subgenomic RNA (sgRNA) upon infection. Here, we investigate how the well-studied tlaRNA, ST9, produces sgRNA and its function. We found ST9 is a noncoding RNA, due to its lack of protein coding capacity. We used resistance assays with eukaryotic Exoribonuclease-1 (XRN1) to investigate sgRNA production via incomplete degradation of genomic RNA. The ST9 3' untranslated region stalled XRN1 very near the 5' sgRNA end. Thus, the XRN family of enzymes drives sgRNA accumulation in ST9-infected tissue by incomplete degradation of ST9 RNA. This work suggests tlaRNAs are not just parasites of viruses with compatible capsids, but also mutually beneficial partners that influence host cell RNA biology.
亚病毒因子是缺乏病毒分类特征的核酸。类似 T4 噬菌体的伴随 RNA（tlaRNA）是亚病毒正链单链 RNA，能自主复制，但依赖于共感染的病毒进行包装和传播。tlaRNA 在感染时会产生大量的亚基因组 RNA（sgRNA）。在这里，我们研究了研究得很好的 tlaRNA ST9 如何产生 sgRNA 及其功能。我们发现 ST9 是一种非编码 RNA，因为它缺乏蛋白编码能力。我们使用真核 Exoribonuclease-1（XRN1）的抗性测定来研究通过不完全降解基因组 RNA 产生 sgRNA 的情况。ST9 的 3'非翻译区使 XRN1 在非常接近 5' sgRNA 末端的位置停滞。因此，XRN 家族的酶通过不完全降解 ST9 RNA 驱动 ST9 感染组织中 sgRNA 的积累。这项工作表明，tlaRNA 不仅是具有兼容衣壳的病毒的寄生虫，还是影响宿主细胞 RNA 生物学的互惠互利的伙伴。
