Welnowska Ewelina, Castelló Alfredo, Moral Pablo, Carrasco Luis
Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma de Madrid, Madrid, Spain.
J Mol Biol. 2009 Dec 4;394(3):506-21. doi: 10.1016/j.jmb.2009.09.036. Epub 2009 Sep 19.
Cytolytic viruses abrogate host protein synthesis to maximize the translation of their own mRNAs. In this study, we analyzed the eukaryotic initiation factor (eIF) 4G requirement for translation of vesicular stomatitis virus (VSV) and vaccinia virus (VV) mRNAs in HeLa cells using two different strategies: eIF4G depletion by small interfering RNAs or cleavage of eIF4G by expression of poliovirus 2A protease. Depletion of eIF4GI or eIF4GII moderately inhibits cellular protein synthesis, whereas silencing of both factors has only a slightly higher effect. Under these conditions, the extent of VSV protein synthesis is similar to that of nondepleted control cells, whereas VV expression is substantially reduced. Similar results were obtained when eIF4E was depleted. On the other hand, eIF4G cleavage by poliovirus 2A protease strongly inhibits translation of VV protein expression, whereas translation directed by VSV mRNAs is not abrogated, even though VSV mRNAs are capped. Therefore, the requirement for eIF4F activity is different for VV and VSV, suggesting that the molecular mechanism by which their mRNAs initiate their translation is also different. Consistent with these findings, eIF4GI does not colocalize with ribosomes in VSV-infected cells, while eIF2alpha locates at perinuclear sites coincident with ribosomes.
溶细胞性病毒消除宿主蛋白合成，以最大化自身mRNA的翻译。在本研究中，我们使用两种不同策略分析了真核起始因子（eIF）4G对水泡性口炎病毒（VSV）和痘苗病毒（VV）mRNA在HeLa细胞中翻译的需求：通过小干扰RNA耗尽eIF4G或通过表达脊髓灰质炎病毒2A蛋白酶切割eIF4G。耗尽eIF4GI或eIF4GII适度抑制细胞蛋白合成，而同时沉默这两个因子的效果仅略高一点。在这些条件下，VSV蛋白合成的程度与未耗尽的对照细胞相似，而VV的表达则大幅降低。当eIF4E被耗尽时也获得了类似结果。另一方面，脊髓灰质炎病毒2A蛋白酶切割eIF4G强烈抑制VV蛋白表达的翻译，而由VSV mRNA指导的翻译并未被消除，即使VSV mRNA有帽结构。因此，VV和VSV对eIF4F活性的需求不同，这表明它们的mRNA起始翻译的分子机制也不同。与这些发现一致，在VSV感染的细胞中，eIF4GI不与核糖体共定位，而eIF2α位于与核糖体重合的核周部位。
