Tahara S, Bergmann C, Nelson G, Anthony R, Dietlin T, Kyuwa S, Stohlman S
Department of Microbiology, University of Southern California School of Medicine, Los Angeles.
Adv Exp Med Biol. 1993;342:111-6. doi: 10.1007/978-1-4615-2996-5_18.
A time dependent decrease in cell surface expression of major histocompatibility complex (MHC) class 1 proteins was found during JHMV infection of the mouse macrophage J774.1 cells line by radioimmunoassay. MHC class I, actin and CSF-1 receptor mRNA levels were also found to decrease during infection. Surprisingly, not all host cell mRNA were similarly affected, suggesting that the apparent MHV-induced translational shut off of host cell protein synthesis during infection was specific for only some host cell mRNAs. Interestingly, two mRNAs found to be refractory to JHMV infection encode monokines, suggesting a role in pathogenesis. To understand the mechanism(s) of this preferential mRNA stability and the apparent shut off of host cell mRNA, translation lysates were prepared from infected and uninfected cells. Translation of host mRNAs in these extracts showed no apparent loss of translational ability in the infected cells vs. the uninfected cells; however, viral mRNAs were preferentially translated in the lysates from the infected cells. Chimeric mRNAs containing the MHV leader upstream of a globin reporter gene showed that preferential translation was a property of the MHV leader RNA. Deletional analysis showed that the sequences responsible for this cis translational augmentation are in a 12 nucleotide (nt) tract at the 3' end of the leader. The previously reported interaction of the nucleocapsid protein with these nts suggest that it may play a role in translational augmentation of MHV mRNAs.
通过放射免疫测定法发现，在小鼠巨噬细胞J774.1细胞系感染JHMV期间，主要组织相容性复合体（MHC）I类蛋白的细胞表面表达随时间下降。还发现感染期间MHC I类、肌动蛋白和CSF-1受体mRNA水平也下降。令人惊讶的是，并非所有宿主细胞mRNA都受到类似影响，这表明感染期间明显由MHV诱导的宿主细胞蛋白质合成的翻译关闭仅对某些宿主细胞mRNA具有特异性。有趣的是，发现两种对JHMV感染具有抗性的mRNA编码单核因子，提示其在发病机制中起作用。为了解这种优先mRNA稳定性和宿主细胞mRNA明显关闭的机制，从感染和未感染的细胞中制备了翻译裂解物。这些提取物中宿主mRNA的翻译在感染细胞与未感染细胞中未显示出明显的翻译能力丧失；然而，病毒mRNA在感染细胞的裂解物中被优先翻译。含有球蛋白报告基因上游MHV前导序列的嵌合mRNA表明，优先翻译是MHV前导RNA的特性。缺失分析表明，负责这种顺式翻译增强的序列位于前导序列3'端的一个12个核苷酸（nt）的片段中。先前报道的核衣壳蛋白与这些核苷酸的相互作用表明，它可能在MHV mRNA的翻译增强中起作用。
