Mulder J, Robertson M E, Seamons R A, Belsham G J
BBSRC Institute for Animal Health, Pirbright, Woking, Surrey GU24 ONF, United Kingdom.
J Virol. 1998 Nov;72(11):8813-9. doi: 10.1128/JVI.72.11.8813-8819.1998.
The role of the cap-binding complex, eIF4F, in the translation of vaccinia virus mRNAs has been analyzed within infected cells. Plasmid DNAs, which express dicistronic mRNAs containing a picornavirus internal ribosome entry site, produced within vaccinia virus-infected cells both beta-glucuronidase and a cell surface-targeted single-chain antibody (sFv). Cells expressing sFv were selected from nonexpressing cells, enabling analysis of protein synthesis specifically within the transfected cells. Coexpression of poliovirus 2A or foot-and-mouth disease virus Lb proteases, which cleaved translation initiation factor eIF4G, greatly inhibited cap-dependent protein (beta-glucuronidase) synthesis. Under these conditions, internal ribosome entry site-directed expression of sFv continued and cell selection was maintained. Furthermore, vaccinia virus protein synthesis persisted in the selected cells containing cleaved eIF4G. Thus, late vaccinia virus protein synthesis has a low requirement for the intact cap-binding complex eIF4F. This may be attributed to the short unstructured 5' noncoding regions of the vaccinia virus mRNAs, possibly aided by the presence of poly(A) at both 5' and 3' termini.
帽结合复合物eIF4F在痘苗病毒mRNA翻译中的作用已在受感染细胞内进行了分析。在痘苗病毒感染的细胞中产生了表达含有微小核糖核酸病毒内部核糖体进入位点的双顺反子mRNA的质粒DNA，同时产生了β-葡萄糖醛酸酶和一种靶向细胞表面的单链抗体（sFv）。从非表达细胞中筛选出表达sFv的细胞，从而能够特异性分析转染细胞内的蛋白质合成。脊髓灰质炎病毒2A或口蹄疫病毒Lb蛋白酶（它们可切割翻译起始因子eIF4G）的共表达极大地抑制了帽依赖性蛋白（β-葡萄糖醛酸酶）的合成。在这些条件下，sFv的内部核糖体进入位点导向的表达持续进行，细胞筛选得以维持。此外，痘苗病毒蛋白合成在含有切割后的eIF4G的选定细胞中持续存在。因此，痘苗病毒晚期蛋白合成对完整的帽结合复合物eIF4F的需求较低。这可能归因于痘苗病毒mRNA的短无结构5'非编码区，5'和3'末端都存在多聚（A）可能也起到了辅助作用。
