Wadsworth Center, New York State Department of Health, Albany, New York, USA.
J Virol. 2013 May;87(9):5182-92. doi: 10.1128/JVI.00100-13. Epub 2013 Feb 28.
Coronaviruses selectively package genomic RNA into assembled virions, despite the great molar excess of subgenomic RNA species that is present in infected cells. The genomic packaging signal (PS) for the coronavirus mouse hepatitis virus (MHV) was originally identified as an element that conferred packaging capability to defective interfering RNAs. The MHV PS is an RNA structure that maps to the region of the replicase gene encoding the nonstructural protein 15 subunit of the viral replicase-transcriptase complex. To begin to understand the role and mechanism of action of the MHV PS in its native genomic locus, we constructed viral mutants in which this cis-acting element was altered, deleted, or transposed. Our results demonstrated that the PS is pivotal in the selection of viral genomic RNA for incorporation into virions. Mutants in which PS RNA secondary structure was disrupted or entirely ablated packaged large quantities of subgenomic RNAs, in addition to genomic RNA. Moreover, the PS retained its function when displaced to an ectopic site in the genome. Surprisingly, the PS was not essential for MHV viability, nor did its elimination have a severe effect on viral growth. However, the PS was found to provide a distinct selective advantage to MHV. Viruses containing the PS readily outcompeted their otherwise isogenic counterparts lacking the PS.
冠状病毒选择性地将基因组 RNA 包装到组装的病毒粒子中，尽管感染细胞中存在大量亚基因组 RNA 物种。冠状病毒鼠肝炎病毒 (MHV) 的基因组包装信号 (PS) 最初被确定为赋予缺陷干扰 RNA 包装能力的元件。MHV PS 是一种 RNA 结构，映射到编码病毒复制酶-转录酶复合物中非结构蛋白 15 亚基的复制酶基因的区域。为了开始了解 MHV PS 在其天然基因组位置中的作用和作用机制，我们构建了改变、缺失或易位该顺式作用元件的病毒突变体。我们的结果表明，PS 在选择病毒基因组 RNA 用于包装到病毒粒子中起着关键作用。破坏 PS RNA 二级结构或完全消除 PS 的突变体除了基因组 RNA 外，还包装了大量的亚基因组 RNA。此外，当 PS 移位到基因组中的异位位点时，它保留了其功能。令人惊讶的是，PS 对 MHV 的生存能力并非必不可少，其消除也不会对病毒生长产生严重影响。然而，发现 PS 为 MHV 提供了明显的选择优势。含有 PS 的病毒很容易胜过其他没有 PS 的同系物。
