The differentially expressed genes induced by EV71 infection. Homo sapiens

Virus infection may shut off host protein synthesis in order to achieve the replicative advantage over host cells. It is well known that human pathogenic viruses, particularly the picornaviruses, can block host protein synthesis by cleavage or inhibition of eukaryotic initiation factors (eIFs). In this study we found a novel mechanism that microRNA (miRNA) is involved in viral pathogenesis. Infection of enteroviruses can disturb the expression of host miRNAs, in which miR-141 is up-regulated and inhibits host protein synthesis by post-transcriptional repression of the target gene eIF4E, a key element for cap-dependent translation of host proteins. Knockdown of miR-141 by a specific siRNA, antagomiR-141, could restore host eIF4E expression, delay the occurrence of cytopathic effect (CPE), and impair virus propagation. We demonstrated that EV71 infection could increase early growth response 1 (EGR1) expression which induced miR-141 causing the eIF4E suppression; while silencing of EGR1 attenuated virus production. Our results suggest that enterovirus infection causes the EGR1-mediated upregulation of host miR-141, further lead to the translational switch from cap-dependent to cap-independent protein synthesis in the host cells, an environmental beneficial for viral propagation. This novel mechanism may highlight a new approach for future development of antiviral therapy. Overall design: Enteroviruses in the Picornaviridae family are important human pathogens which can cause fatal diseases, including cardiopulmonary failure, aseptic meningitis, paralysis, myocarditis, and encephalomyelitis. Virus infection may induce shutoff of host protein synthesis, particularly in picornavirus, whose protein translation is cap-independent. It is known that poliovirus 2A protease cleaves eIF4G, a scaffold component of mammalian cell translational complex, leading to the shut down of host protein synthesis. Nevertheless, the cleavage of eIF4G may not be sufficient for the complete shutoff of host protein synthesis. Previous studies showed that cleavage of polyA-binding protein (PABP) by viral protease 3C and dephosphorylation of the translational repressor, eIF4E binding protein 1 (4E-BP1), also contribute to this process. The cap-binding protein, eIF4E, is the most crucial factor in determining whether cap-dependent or -independent translation takes place. The mechanism by which viral infection modulates host cell protein synthesis through interfering eIF4E expression is not yet known. miRNAs are a newly discovered class of small non-protein-coding RNAs that may act via endogenous RNA interference. Our understanding of its role in the dynamic interplay between virus and host components is quite limited. Since both virus infection and miRNAs could hinder cellular protein synthesis, whether miRNAs are involved during virus infection in shutting off host protein synthesis is still unknown. To address this issue, we analyze the altered gene and microRNA expression after EV71 infection. ***This submission represents the mRNA expression component of the study only***

病毒感染可通过阻断宿主蛋白质合成，以获得相较于宿主细胞的复制优势。众所周知，人致病性病毒，尤其是小核糖核酸病毒（picornaviruses），可通过切割或抑制真核起始因子（eukaryotic initiation factors, eIFs）来阻断宿主蛋白质合成。本研究发现了一种参与病毒致病过程的全新机制：微小RNA（microRNA, miRNA）参与病毒致病。肠道病毒感染可干扰宿主微小RNA的表达，其中miR-141表达上调，并通过转录后抑制靶基因eIF4E的表达来阻断宿主蛋白质合成——eIF4E是宿主蛋白帽依赖型翻译的关键因子。通过特异性小干扰RNA（small interfering RNA, siRNA）antagomiR-141敲低miR-141，可恢复宿主eIF4E的表达，延缓细胞病变效应（cytopathic effect, CPE）的发生，并削弱病毒增殖能力。本研究证实，肠道病毒71型（EV71）感染可上调早期生长应答因子1（early growth response 1, EGR1）的表达，而EGR1可诱导miR-141的表达，进而抑制eIF4E的功能；而沉默EGR1则可减弱病毒的产生。本研究结果表明，肠道病毒感染通过EGR1介导宿主miR-141的上调，进而促使宿主细胞内蛋白质合成从帽依赖型转向帽非依赖型，这一过程可为病毒增殖提供有利的细胞环境。这一全新机制可为未来抗病毒治疗策略的开发提供新的思路。
整体实验设计：
小核糖核酸病毒科（Picornaviridae）肠道病毒是重要的人致病性病毒，可引发致命性疾病，包括心肺衰竭、无菌性脑膜炎、瘫痪、心肌炎以及脑脊髓炎。病毒感染可诱导宿主蛋白质合成的阻断，在小核糖核酸病毒中尤为明显，这类病毒的蛋白质翻译本身为帽非依赖型。已知脊髓灰质炎病毒的2A蛋白酶可切割真核翻译复合物的支架组分eIF4G，从而导致宿主蛋白质合成的关闭。然而，仅eIF4G的切割并不足以完全阻断宿主蛋白质合成。既往研究显示，病毒蛋白酶3C对聚腺苷酸结合蛋白（polyA-binding protein, PABP）的切割，以及翻译抑制因子eIF4E结合蛋白1（4E-BP1）的去磷酸化，同样参与这一过程。帽结合蛋白eIF4E是决定蛋白质合成采用帽依赖型还是帽非依赖型翻译的最关键因子。而病毒感染通过调控eIF4E的表达来调节宿主细胞蛋白质合成的具体机制，目前仍未明确。微小RNA是一类新近发现的小型非编码RNA，可通过内源性RNA干扰发挥作用。目前学界对其在病毒与宿主成分动态互作中所发挥的作用的认知仍十分有限。既然病毒感染与微小RNA均可阻碍细胞蛋白质合成，那么微小RNA是否参与病毒感染过程中宿主蛋白质合成的阻断，目前仍不明确。为解答这一问题，本研究分析了EV71感染后宿主基因与微小RNA的表达变化。
***本次提交仅包含本研究的mRNA表达组学部分***