Blakqori Gjon, van Knippenberg Ingeborg, Elliott Richard M
Centre for Biomolecular Sciences, School of Biology, University of St. Andrews, North Haugh, St. Andrews KY16 9ST, Scotland, United Kingdom.
J Virol. 2009 Apr;83(8):3637-46. doi: 10.1128/JVI.02201-08. Epub 2009 Feb 4.
The mRNAs of Bunyamwera virus (BUNV), the prototype of the Bunyaviridae family, possess a 5' cap structure but lack a 3' poly(A) tail, a common feature of eukaryotic mRNAs that greatly enhances translation efficiency. Viral mRNAs also contain untranslated regions (UTRs) that flank the coding sequence. Using model virus-like mRNAs that harbor the Renilla luciferase reporter gene, we found that the 3' UTR of the BUNV small-segment mRNA mediated efficient translation in the absence of a poly(A) tail. Viral UTRs did not increase RNA stability, and polyadenylation did not significantly enhance reporter activity. Translation of virus-like mRNAs in transfected cells was unaffected by knockdown of poly(A)-binding protein (PABP) but was markedly reduced by depletion of eukaryotic initiation factor 4G, suggesting a PABP-independent process for translation initiation. In BUNV-infected cells, translation of polyadenylated but not virus-like mRNAs was inhibited. Furthermore, we demonstrate that the viral nucleocapsid protein binds to, and colocalizes with, PABP in the cytoplasm early in infection, followed by nuclear retention of PABP. Our results suggest that BUNV corrupts PABP function in order to inhibit translation of polyadenylated cellular mRNAs while its own mRNAs are translated in a PABP-independent process.
布尼亚病毒科的原型——布尼亚维拉病毒(BUNV)的信使核糖核酸(mRNA)具有5'帽结构,但缺乏3'多聚腺苷酸尾,这是真核生物mRNA的一个共同特征,可极大提高翻译效率。病毒mRNA还包含位于编码序列两侧的非翻译区(UTR)。利用携带海肾荧光素酶报告基因的模型病毒样mRNA,我们发现BUNV小片段mRNA的3'UTR在没有多聚腺苷酸尾的情况下介导了高效翻译。病毒UTR并未增加RNA稳定性,多聚腺苷酸化也未显著增强报告基因活性。转染细胞中病毒样mRNA的翻译不受多聚腺苷酸结合蛋白(PABP)敲低的影响,但真核起始因子4G的缺失会使其显著降低,这表明翻译起始过程不依赖PABP。在BUNV感染的细胞中,多聚腺苷酸化的mRNA而非病毒样mRNA的翻译受到抑制。此外,我们证明病毒核衣壳蛋白在感染早期与PABP在细胞质中结合并共定位,随后PABP被滞留于细胞核中。我们的结果表明,BUNV破坏PABP功能以抑制多聚腺苷酸化的细胞mRNA的翻译,而其自身的mRNA以不依赖PABP的过程进行翻译。