Timmer R T, Benkowski L A, Schodin D, Lax S R, Metz A M, Ravel J M, Browning K S
Department of Chemistry and Biochemistry, University of Texas, Austin 78712.
J Biol Chem. 1993 May 5;268(13):9504-10.
Satellite tobacco necrosis virus RNA (STNV RNA) is a naturally uncapped viral RNA that contains 1239 nucleotides: 29 in the 5' untranslated region (UTR), 591 in the coding region and 619 in the 3' UTR. Mutations were made in the 5' and 3' UTRs, and the effects of these mutations on translational efficiency and cap independence were measured in an in vitro translation system from wheat germ. Removal of the first 12 nucleotides or 10 changes in the nucleotide sequence of the 5' UTR reduced translational efficiency approximately 3-fold; capping of these 5' mutant mRNAs restored their translational efficiencies. Truncation of the 3' UTR to nucleotide 627 or 700, or deletion of nucleotides 627-737, reduced translational efficiency more than 20-fold; capping of these 3' mutant mRNAs restored their translational efficiencies. These modifications in the 3' UTR increased the concentration of initiation factor 4F required for translation. Chimeric mRNAs were constructed which contained the coding region of rabbit alpha-globin mRNA and either the 5' UTR, 3' UTR, or both the 5' and 3' UTRs of STNV RNA. Both the 5' and 3' UTRs of STNV RNA were necessary to obtain cap-independent translation. These findings indicate that interaction between 5' UTR and the region between nucleotides 627 and 737 in the 3' UTR are required for cap-independent translation.
卫星烟草坏死病毒RNA（STNV RNA）是一种天然无帽的病毒RNA，含有1239个核苷酸：5'非翻译区（UTR）有29个核苷酸，编码区有591个核苷酸，3'UTR有619个核苷酸。对5'和3'UTR进行了突变，并在小麦胚芽的体外翻译系统中测量了这些突变对翻译效率和不依赖帽结构的影响。去除5'UTR的前12个核苷酸或5'UTR核苷酸序列中的10个变化使翻译效率降低了约3倍；对这些5'突变mRNA进行加帽处理可恢复其翻译效率。将3'UTR截短至核苷酸627或700，或缺失核苷酸627 - 737，使翻译效率降低了20倍以上；对这些3'突变mRNA进行加帽处理可恢复其翻译效率。3'UTR中的这些修饰增加了翻译所需的起始因子4F的浓度。构建了嵌合mRNA，其包含兔α-珠蛋白mRNA的编码区以及STNV RNA的5'UTR、3'UTR或5'和3'UTR。STNV RNA的5'和3'UTR对于获得不依赖帽结构的翻译都是必需的。这些发现表明，不依赖帽结构的翻译需要5'UTR与3'UTR中核苷酸627和737之间的区域相互作用。
