Child Stephanie J, Jarrahian Sohail, Harper Victoria M, Geballe Adam P
Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA.
J Virol. 2002 May;76(10):4912-8. doi: 10.1128/jvi.76.10.4912-4918.2002.
The cellular response to viral infection often includes activation of pathways that shut off protein synthesis and thereby inhibit viral replication. In order to enable efficient replication, many viruses carry genes such as the E3L gene of vaccinia virus that counteract these host antiviral pathways. Vaccinia virus from which the E3L gene has been deleted (VVDeltaE3L) is highly sensitive to interferon and exhibits a restricted host range, replicating very inefficiently in many cell types, including human fibroblast and U373MG cells. To determine whether human cytomegalovirus (CMV) has a mechanism for preventing translational shutoff, we evaluated the ability of CMV to complement the deficiencies in replication and protein synthesis associated with VVDeltaE3L. CMV, but not UV-inactivated CMV, rescued VVDeltaE3L late gene expression and replication. Thus, complementation of the VVDeltaE3L defect appears to depend on de novo CMV gene expression and is not likely a result of CMV binding to the cell receptor or of a virion structural protein. CMV rescued VVDeltaE3L late gene expression even in the presence of ganciclovir, indicating that CMV late gene expression is not required for complementation of VVDeltaE3L. The striking decrease in overall translation after infection with VVDeltaE3L was prevented by prior infection with CMV. Finally, CMV blocked both the induction of eukaryotic initiation factor 2alpha (eIF2alpha) phosphorylation and activation of RNase L by VVDeltaE3L. These results suggest that CMV has one or more immediate-early or early genes that ensure maintenance of a high protein synthetic capacity during infection by preventing activation of the PKR/eIF2alpha phosphorylation and 2-5A oligoadenylate synthetase/RNase L pathways.
细胞对病毒感染的反应通常包括激活一些途径，这些途径会关闭蛋白质合成从而抑制病毒复制。为了实现高效复制，许多病毒携带诸如痘苗病毒E3L基因之类的基因来对抗这些宿主抗病毒途径。缺失E3L基因的痘苗病毒（VVDeltaE3L）对干扰素高度敏感，并且表现出受限的宿主范围，在包括人成纤维细胞和U373MG细胞在内的许多细胞类型中复制效率非常低。为了确定人巨细胞病毒（CMV）是否具有防止翻译关闭的机制，我们评估了CMV补充与VVDeltaE3L相关的复制和蛋白质合成缺陷的能力。CMV（而非紫外线灭活的CMV）挽救了VVDeltaE3L晚期基因的表达和复制。因此，VVDeltaE3L缺陷的互补似乎依赖于CMV的从头基因表达，不太可能是CMV与细胞受体结合或病毒粒子结构蛋白的结果。即使在存在更昔洛韦的情况下，CMV也挽救了VVDeltaE3L晚期基因的表达，这表明CMV晚期基因表达对于VVDeltaE3L的互补不是必需的。预先感染CMV可防止感染VVDeltaE3L后总体翻译的显著下降。最后，CMV阻断了VVDeltaE3L诱导的真核起始因子2α（eIF2α）磷酸化和RNase L的激活。这些结果表明，CMV具有一个或多个立即早期或早期基因，通过防止PKR/eIF2α磷酸化和2-5A寡腺苷酸合成酶/RNase L途径的激活来确保在感染期间维持高蛋白质合成能力。
