Jubin R, Vantuno N E, Kieft J S, Murray M G, Doudna J A, Lau J Y, Baroudy B M
Department of Antiviral Therapy, Schering-Plough Research Institute, Kenilworth, New Jersey 07033, USA.
J Virol. 2000 Nov;74(22):10430-7. doi: 10.1128/jvi.74.22.10430-10437.2000.
The hepatitis C virus (HCV) internal ribosome entry site (IRES) is a highly structured RNA element that directs cap-independent translation of the viral polyprotein. Morpholino antisense oligonucleotides directed towards stem loop IIId drastically reduced HCV IRES activity. Mutagenesis studies of this region showed that the GGG triplet (nucleotides 266 through 268) of the hexanucleotide apical loop of stem loop IIId is essential for IRES activity both in vitro and in vivo. Sequence comparison showed that apical loop nucleotides (UUGGGU) were absolutely conserved across HCV genotypes and the GGG triplet was strongly conserved among related Flavivirus and Pestivirus nontranslated regions. Chimeric IRES elements with IIId derived from GB virus B (GBV-B) in the context of the HCV IRES possess translational activity. Mutations within the IIId stem loop that abolish IRES activity also affect the RNA structure in RNase T(1)-probing studies, demonstrating the importance of correct RNA folding to IRES function.
丙型肝炎病毒（HCV）内部核糖体进入位点（IRES）是一种高度结构化的RNA元件，可指导病毒多聚蛋白的不依赖帽子结构的翻译。针对茎环IIId的吗啉代反义寡核苷酸显著降低了HCV IRES活性。该区域的诱变研究表明，茎环IIId六核苷酸顶端环的GGG三联体（核苷酸266至268）在体外和体内对IRES活性均至关重要。序列比较显示，顶端环核苷酸（UUGGGU）在HCV各基因型中绝对保守，并且GGG三联体在相关黄病毒属和瘟病毒属的非翻译区中高度保守。在HCV IRES背景下，含有源自GB病毒B（GBV-B）的IIId的嵌合IRES元件具有翻译活性。在IIId茎环内消除IRES活性的突变在核糖核酸酶T1探测研究中也影响RNA结构，这证明了正确的RNA折叠对IRES功能的重要性。
