Havelda Z, Burgyán J
Agricultural Biotechnology Center, Plant Science Institute, Gödöllô, Hungary.
Virology. 1995 Dec 1;214(1):269-72. doi: 10.1006/viro.1995.9929.
Defective interfering (DI) RNA of cymbidium ringspot tombusvirus (CymRSV) was used to identify the cis-acting nature of the last 77-nt sequence of the viral genome which is required for DI RNA accumulation. The 3'-terminal cis-essential domain of both genomic and DI RNAs can be folded into a stable stem-loop structure composed of three hairpins and two short non-base-paired regions. None of the three conserved stem-loops can be deleted without abolishing the infectivity of DI RNA. Similarly, those mutants in which base-paired stem regions were disrupted by single-, double-, or triple-base substitutions were unable to replicate. However, when the original structures were reconstructed by compensatory mutations the viability of the molecules was also restored. Limited mutation (1 or 2 nt) in the non-base-paired region did not show any significant effect on viral replication. Our results strongly suggest that the proposed structure for the 3' terminus of the viral genome is very important for viral RNA replication. It is very likely that the function of this structure is to promote the minus-strand synthesis of CymRSV DI RNA. Evidence is provided that the proposed 3'-terminal structure is relevant not only for CymRSV DI but for genomic RNA as well.
大花蕙兰环斑番茄斑萎病毒（CymRSV）的缺陷干扰（DI）RNA被用于鉴定病毒基因组最后77个核苷酸序列的顺式作用性质，该序列是DI RNA积累所必需的。基因组RNA和DI RNA的3'末端顺式必需结构域均可折叠成由三个发夹和两个短的非碱基配对区域组成的稳定茎环结构。三个保守茎环中的任何一个都不能删除，否则会消除DI RNA的感染性。同样，那些碱基配对茎区域被单碱基、双碱基或三碱基取代破坏的突变体也无法复制。然而，当通过补偿性突变重建原始结构时，分子的活力也得以恢复。非碱基配对区域的有限突变（1或2个核苷酸）对病毒复制没有任何显著影响。我们的结果强烈表明，病毒基因组3'末端的提议结构对病毒RNA复制非常重要。很可能该结构的功能是促进CymRSV DI RNA的负链合成。有证据表明，提议的3'末端结构不仅与CymRSV DI相关，也与基因组RNA相关。
