Department of Cell Biology and Molecular Genetics, University of Maryland College Park, College Park, MD 20742, USA.
Virology. 2010 Jul 5;402(2):271-80. doi: 10.1016/j.virol.2010.03.036. Epub 2010 Apr 18.
Plus-strand RNA viruses serve as templates for translation and then transcription by newly synthesized RdRp. A ribosome-binding tRNA-shaped structure (TSS) and upstream hairpin H4 in the 3' UTR of Turnip crinkle virus (TCV) play key roles in translation and transcription. Second-site mutations generated to compensate for altering the critical asymmetric internal loop of H4 included a three- to two-base alteration in the terminal loop of a 3' proximal hairpin (Pr) located downstream of the TSS. Unlike the non-deleterious three-base alteration, single mutations in Pr loop were detrimental for RdRp transcription while enhancing translation and RdRp binding. One deleterious mutation in the Pr loop altered the structures of both the TSS and H4. These complex interactions in the 3' UTR support a compact structural arrangement likely permitting RdRp access to a number of residues within a 195-base region including the 3' end that are necessary for efficient transcription initiation.
正链 RNA 病毒可作为新合成 RdRp 的翻译和转录模板。芜菁皱缩病毒（TCV）3'UTR 中的核糖体结合 tRNA 样结构（TSS）和上游发夹 H4 在翻译和转录中发挥关键作用。为了弥补改变 H4 关键非对称内环而产生的第二位置突变包括 TSS 下游 3'近端发夹（Pr）末端环中的三到两个碱基改变。与非有害的三碱基改变不同，Pr 环中的单个突变对 RdRp 转录有害，同时增强翻译和 RdRp 结合。Pr 环中的一个有害突变改变了 TSS 和 H4 的结构。UTR 中的这些复杂相互作用支持紧凑的结构排列，可能允许 RdRp 进入包括 3'末端在内的 195 个碱基区域的多个残基，这些残基对于有效转录起始是必需的。
