Shives Katherine D, Massey Aaron R, May Nicholas A, Morrison Thomas E, Beckham J David
Department of Immunology and Microbiology, University of Colorado Graduate School, Aurora, CO 80045, USA.
Department of Medicine, Division of Infectious Diseases, University of Colorado School of Medicine, Aurora, CO 80045, USA.
Viruses. 2016 Oct 18;8(10):287. doi: 10.3390/v8100287.
West Nile virus (WNV) is a (+) sense, single-stranded RNA virus in the genus. WNV RNA possesses an GpppN 5' cap with 2'--methylation that mimics host mRNAs preventing innate immune detection and allowing the virus to translate its RNA genome through the utilization of cap-dependent translation initiation effectors in a wide variety of host species. Our prior work established the requirement of the host mammalian target of rapamycin complex 1 (mTORC1) for optimal WNV growth and protein expression; yet, the roles of the downstream effectors of mTORC1 in WNV translation are unknown. In this study, we utilize gene deletion mutants in the ribosomal protein kinase called S6 kinase (S6K) and eukaryotic translation initiation factor 4E-binding protein (4EBP) pathways downstream of mTORC1 to define the role of mTOR-dependent translation initiation signals in WNV gene expression and growth. We now show that WNV growth and protein expression are dependent on mTORC1 mediated-regulation of the eukaryotic translation initiation factor 4E-binding protein/eukaryotic translation initiation factor 4E-binding protein (4EBP/eIF4E) interaction and eukaryotic initiation factor 4F (eIF4F) complex formation to support viral growth and viral protein expression. We also show that the canonical signals of mTORC1 activation including ribosomal protein s6 (rpS6) and S6K phosphorylation are not required for WNV growth in these same conditions. Our data suggest that the mTORC1/4EBP/eIF4E signaling axis is activated to support the translation of the WNV genome.
西尼罗河病毒（WNV）是该属中的一种正链单链RNA病毒。WNV RNA具有一个带有2'-甲基化的GpppN 5'帽，该帽模拟宿主mRNA，可防止先天免疫检测，并使病毒能够通过利用多种宿主物种中的帽依赖性翻译起始效应因子来翻译其RNA基因组。我们之前的工作确定了宿主哺乳动物雷帕霉素复合物1（mTORC1）靶点对于WNV最佳生长和蛋白质表达的必要性；然而，mTORC1下游效应因子在WNV翻译中的作用尚不清楚。在本研究中，我们利用核糖体蛋白激酶中的基因缺失突变体，即mTORC1下游的S6激酶（S6K）和真核翻译起始因子4E结合蛋白（4EBP）途径，来确定mTOR依赖性翻译起始信号在WNV基因表达和生长中的作用。我们现在表明，WNV的生长和蛋白质表达依赖于mTORC1介导的对真核翻译起始因子4E结合蛋白/真核翻译起始因子4E结合蛋白（4EBP/eIF4E）相互作用以及真核起始因子4F（eIF4F）复合物形成的调节，以支持病毒生长和病毒蛋白表达。我们还表明，在相同条件下，WNV生长不需要mTORC1激活的典型信号，包括核糖体蛋白s6（rpS6）和S6K磷酸化。我们的数据表明，mTORC1/4EBP/eIF4E信号轴被激活以支持WNV基因组的翻译。
