Instituto de Parasitología y Biomedicina López-Neyra IPBLN-CSIC, CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento s/n, 18100 Armilla, Granada, Spain.
Cell Mol Life Sci. 2012 Jan;69(1):103-13. doi: 10.1007/s00018-011-0729-z. Epub 2011 May 20.
Hepatitis C virus (HCV) translation is mediated by an internal ribosome entry site (IRES) located at the 5' end of the genomic RNA. The 3' untranslatable region (3'UTR) stimulates translation by the recruitment of protein factors that simultaneously bind to the 5' end of the viral genome. This leads to the formation of a macromolecular complex with a closed loop conformation, similar to that described for the cap-translated mRNAs. We previously demonstrated the existence of a long-range RNA-RNA interaction involving subdomain IIId of the IRES region and the stem-loop 5BSL3.2 of the CRE element at the 3' end of the viral genome. The present study provides evidence that the enhancement of HCV IRES-dependent translation mediated by the 3'UTR is negatively controlled by the CRE region in the human hepatoma cell lines Huh-7 and Hep-G2 in a time-dependent manner. Domain 5BSL3.2 is the major partner in this process. Mutations in this motif lead to an increase in IRES activity by up to eightfold. These data support the existence of a functional high order structure in the HCV genome that involves two evolutionarily conserved RNA elements, domain IIId in the IRES and stem-loop 5BSL3.2 in the CRE region. This interaction could have a role in the circularisation of the viral genome.
丙型肝炎病毒 (HCV) 的翻译是由位于基因组 RNA 5'端的内部核糖体进入位点 (IRES) 介导的。3'非翻译区 (3'UTR) 通过募集同时结合病毒基因组 5'端的蛋白因子来刺激翻译。这导致形成具有闭合环构象的大分子复合物，类似于描述的帽翻译的 mRNA。我们之前证明了涉及 IRES 区域的亚结构域 IIId 和病毒基因组 3'端 CRE 元件的茎环 5BSL3.2 的长距离 RNA-RNA 相互作用的存在。本研究提供的证据表明，在人肝癌细胞系 Huh-7 和 Hep-G2 中，3'UTR 对 HCV IRES 依赖性翻译的增强是受 CRE 区域以时间依赖方式负调控的。5BSL3.2 结构域是该过程的主要伙伴。该基序中的突变导致 IRES 活性增加高达 8 倍。这些数据支持 HCV 基因组中存在涉及两个进化上保守的 RNA 元件（IRES 中的 IIId 结构域和 CRE 区域中的茎环 5BSL3.2）的功能性高级结构的存在。这种相互作用可能在病毒基因组的环化中起作用。
