Shi B, Ding S, Symons R H
Department of Plant Science, Waite Institute, University of Adelaide, Glen Osmond, Australia.
J Gen Virol. 1997 Mar;78 ( Pt 3):505-10. doi: 10.1099/0022-1317-78-3-505.
Two abundant subgenomic RNAs, designated RNA 3B and RNA 5, were found to be associated with the V strain of tomato aspermy cucumovirus (V-TAV). Sequence determination showed that the 3'-terminal 323 nucleotides (nt) of RNA 3B was identical to RNA 5, whereas its 5'-terminal 163 nt was a direct repeat (one nt difference) of the 5'-half of RNA 5, and that both RNAs are completely homologous to the 3'-terminal untranslated region of TAV RNA 3. TAV RNAs 3B and 5 were also detected in the infection of a pseudorecombinant virus consisting of TAV RNA 3 and RNAs 1 and 2 from cucumber mosaic virus. Furthermore, only RNA 5, not RNA 3B, was detected in a TAV mutant in which one of the repeats was deleted from RNA 3. These genetic studies clearly show that both RNA species are derived from TAV RNA 3. However, in contrast to TAV RNAs 4 and 4A, which encode coat protein and 2b protein, respectively, RNAs 3B and 5 represent a novel class of subgenomic RNAs from TAV that do not function as mRNAs. Possible functional roles for such a class of viral subgenomic RNAs are discussed.
发现两种丰富的亚基因组RNA，分别命名为RNA 3B和RNA 5，与番茄不孕黄瓜花叶病毒（V-TAV）的V株系相关。序列测定表明，RNA 3B的3'末端323个核苷酸（nt）与RNA 5相同，而其5'末端163 nt是RNA 5 5'端一半的直接重复序列（相差1个nt），并且这两种RNA与TAV RNA 3的3'末端非翻译区完全同源。在由TAV RNA 3以及黄瓜花叶病毒的RNA 1和RNA 2组成的假重组病毒感染过程中也检测到了TAV的RNA 3B和5。此外，在一个TAV突变体中，RNA 3中的一个重复序列被删除，在该突变体中仅检测到RNA 5，未检测到RNA 3B。这些遗传学研究清楚地表明，这两种RNA均源自TAV RNA 3。然而，与分别编码外壳蛋白和2b蛋白的TAV RNA 4和4A不同，RNA 3B和5代表了TAV的一类新型亚基因组RNA，它们不作为mRNA发挥功能。本文讨论了这类病毒亚基因组RNA可能的功能作用。
