Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA.
Virology. 2011 Jan 20;409(2):338-47. doi: 10.1016/j.virol.2010.10.015. Epub 2010 Nov 10.
Small plus-stranded RNA viruses do not code for RNA helicases that would facilitate the proper folding of viral RNAs during replication. Instead, these viruses might use RNA chaperones as shown here for the essential p33 replication protein of Tomato bushy stunt virus (TBSV). In vitro experiments demonstrate that the purified recombinant p33 promotes strand separation of a DNA/RNA duplex. In addition, p33 renders dsRNA templates sensitive to single-strand specific S1 nuclease, suggesting that p33 can destabilize highly structured RNAs. We also demonstrate that the RNA chaperone activity of p33 facilitates self-cleavage by a ribozyme in vitro. In addition, purified p33 facilitates in vitro RNA synthesis on double-stranded (ds)RNA templates up to 5-fold by a viral RNA-dependent RNA polymerase. We propose that the RNA chaperone activity of p33 facilitates the initiation of plus-strand synthesis as well as affects RNA recombination. Altogether, the TBSV RNA chaperone might perform similar biological functions to the helicases of other RNA viruses with much larger coding capacity.
小型正链 RNA 病毒不编码 RNA 解旋酶，而 RNA 解旋酶在复制过程中有助于病毒 RNA 的正确折叠。相反，这些病毒可能会使用 RNA 伴侣，如图中所示，番茄丛矮病毒（TBSV）的必需 p33 复制蛋白。体外实验表明，纯化的重组 p33 可促进 DNA/RNA 双链的链分离。此外，p33 使 dsRNA 模板对单链特异性 S1 核酸酶敏感，表明 p33 可以使高度结构化的 RNA 不稳定。我们还证明，p33 的 RNA 伴侣活性有助于体外核酶的自我切割。此外，纯化的 p33 通过病毒 RNA 依赖性 RNA 聚合酶将双链 (ds)RNA 模板上的体外 RNA 合成提高 5 倍。我们提出，p33 的 RNA 伴侣活性有助于起始正链合成，并影响 RNA 重组。总的来说，TBSV RNA 伴侣可能执行与其他 RNA 病毒的解旋酶相似的生物学功能，而其他 RNA 病毒的编码能力要大得多。
