Borman A M, Le Mercier P, Girard M, Kean K M
Unité de Virologie Moléculaire (CNRS URA 1966) and 1 Laboratoire des Lyssavirus, Institut Pasteur, 25, rue du Dr Roux, 75724 Paris cedex 15, France.
Nucleic Acids Res. 1997 Mar 1;25(5):925-32. doi: 10.1093/nar/25.5.925.
We recently compared the efficiency of six picornaviral internal ribosome entry segments (IRESes) and the hepatitis C virus (HCV) IRES for their ability to drive internal initiation of translationin vitro. Here we present the results of a similar comparison performed in six different cultured cell lines infected with a recombinant vaccinia virus expressing the T7 polymerase and transfected with dicistronic plasmids. The IRESes could be divided into three groups: (i) the cardiovirus and aphthovirus IRESes (and the HCV element) direct internal initiation efficiently in all cell lines tested; (ii) the enterovirus and rhinovirus IRESes are at least equally efficient in several cell lines, but are extremely inefficient in certain cell types; and (iii) the hepatitis A virus IRES is incapable of directing efficient internal initiation in any of the cell lines used (including human hepatocytes). These are the same three groups found when IRESes were classified according to their activitiesin vitro, or according to sequence homologies. In a mouse neuronal cell line, the poliovirus and other type I IRESes were not functional in an artificial bicistronic context. However, infectious poliovirions were produced efficiently after transfection of these cells with a genomic length RNA. Furthermore, activity of the type I IRESes was dramatically increased upon co-expression of the poliovirus 2A proteinase, demonstrating that while IRES efficiency may vary considerably from one cell type to another, at least in some cases viral proteins are capable of overcoming cell-specific translational defects.
我们最近比较了六种微小核糖核酸病毒内部核糖体进入片段（IRESes）和丙型肝炎病毒（HCV）IRES在体外驱动翻译内部起始的能力。在此，我们展示了在六种不同的培养细胞系中进行的类似比较结果，这些细胞系感染了表达T7聚合酶的重组痘苗病毒，并转染了双顺反子质粒。IRESes可分为三组：（i）心病毒和口疮病毒IRESes（以及HCV元件）在所有测试的细胞系中均能有效地直接启动内部起始；（ii）肠道病毒和鼻病毒IRESes在几种细胞系中至少同样有效，但在某些细胞类型中效率极低；（iii）甲型肝炎病毒IRES在所用的任何细胞系（包括人肝细胞）中都无法有效地指导内部起始。当根据IRESes在体外的活性或序列同源性进行分类时，也会发现这相同的三组。在小鼠神经元细胞系中，脊髓灰质炎病毒和其他I型IRESes在人工双顺反子环境中无功能。然而，用基因组长度的RNA转染这些细胞后，能高效产生有感染性的脊髓灰质炎病毒颗粒。此外，在共表达脊髓灰质炎病毒2A蛋白酶后，I型IRESes的活性显著增加，这表明虽然IRES效率在不同细胞类型之间可能有很大差异，但至少在某些情况下，病毒蛋白能够克服细胞特异性的翻译缺陷。
