Virus-like vesicles of Kaposi’s Sarcoma-Associated Herpesvirus activate lytic replication through triggering differentiation signaling (microRNA)

Virus-like vesicles (VLVs) are membrane derived cellular vesicles that resemble native envelope viruses in organization and conformation, but lack viral capsid and/or genome. During productive virus infection, both infectious virions and non-infectious VLVs are produced and released into the extracellular space. VLVs have been shown to play a role in intercellular communication and in facilitating virus infection. The study of VLVs in the context of gammaherpesvirus infection has been largely restricted due to the technical difficulty of separating VLVs and virions. Here we report a strategy for using a KSHV mutant deficient in capsid assembly to isolate VLVs during infection. Using Mass Spectrometry analysis, we identified that VLVs contain viral glycoproteins required for cellular entry, and tegument proteins involved in regulating lytic replication. Functional analysis showed that VLVs could activate the RTA promoter, the lytic switch for KSHV, and further induce KSHV lytic gene expression from latency. We used RNA sequencing to do a genome-wide analysis of cellular responses triggered by VLVs, and revealed that PRDM1, a master regulator in cell differentiation, was up-regulated. Our data shows that VLVs play an important role in promoting KSHV lytic replication by inducing PRDM1 expression which activates the RTA promoter. Our study significantly extends our current understanding of VLVs. Analyze microRNA in KSHV VLVs

病毒样囊泡（Virus-like vesicles, VLVs）是一类膜来源的细胞囊泡，其结构与构象与天然包膜病毒高度相似，但缺乏病毒衣壳和/或基因组。在产毒性病毒感染过程中，感染性病毒粒子与非感染性VLVs均会产生并释放至细胞外间隙。已有研究表明，VLVs可参与细胞间通讯并促进病毒感染。由于分离VLVs与病毒粒子存在技术瓶颈，目前针对γ疱疹病毒感染背景下VLVs的研究在很大程度上受到限制。本研究报道了一种策略：利用衣壳组装缺陷型KSHV突变株在感染过程中分离VLVs。通过质谱（Mass Spectrometry）分析，我们发现VLVs含有细胞入侵所需的病毒糖蛋白，以及参与调控病毒裂解复制的被膜蛋白。功能分析结果显示，VLVs可激活KSHV的裂解激活开关——RTA启动子，并进一步诱导潜伏状态下的KSHV裂解基因表达。我们通过RNA测序（RNA sequencing）对VLVs触发的细胞应答进行了全基因组分析，发现细胞分化的核心调控因子PRDM1发生了表达上调。本研究数据表明，VLVs可通过诱导PRDM1表达以激活RTA启动子，从而在促进KSHV裂解复制的过程中发挥重要作用。本研究显著拓展了学界对VLVs的现有认知。分析KSHV VLVs中的微小RNA（microRNA）