Nuclear-cytoplasmic compartmentalization of the herpes simplex virus 1 infected cell transcriptome is co-ordinated by the viral endoribonuclease vhs and cofactors to facilitate the translation of late proteins.
Nuclear-cytoplasmic compartmentalization of the herpes simplex virus 1 infected cell transcriptome is co-ordinated by the viral endoribonuclease vhs and cofactors to facilitate the translation of late proteins.
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DOI：
10.1371/journal.ppat.1007331
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发表时间：
2018-11
期刊：
影响因子：
6.7
通讯作者：
Elliott G
中科院分区：
文献类型：
--
作者：
Pheasant K;Möller-Levet CS;Jones J;Depledge D;Breuer J;Elliott G
HSV 1编码一种称为病毒体宿主关闭（vhs）的核糖核酸内切酶，其在感染后期产生并包装成病毒体。特别的是，vhs不仅对宿主而且对病毒转录物都有活性，并且参与宿主关闭和病毒转录组的时间表达。另外两种病毒蛋白-VP 22和VP 16-被提出来调节vhs以防止不受控制的和致命的mRNA降解，但它们的作用机制尚不清楚。我们对人成纤维细胞进行了双转录组分析和单细胞mRNA FISH，这种细胞类型在没有VP 22的情况下，HSV 1感染导致极端的翻译关闭。在野生型感染，宿主的mRNA表现出广泛的易感性，从耐药的VHS范围减少1000倍，一个变化，是独立的相对丰度或转录速率。然而，未发现vhs内切核糖核酸酶活性对Δ22感染的细胞中的任何细胞转录组过度活性，而是延迟，而其对病毒转录组和特别是晚期mRNA的活性最低限度地增强。有趣的是，立即早期和早期成绩单表现出VHS依赖的核滞留后，在野生型感染，但后期成绩单细胞质。然而，在没有VP 22的情况下，不仅早期，而且后期成绩单保留在细胞核中的VHS依赖的机制，一个特征，扩展到细胞成绩单，没有有效地降解的VHS。此外，VP 22结合VP 16的能力增强，但不是根本的救援vhs诱导的核保留的晚期转录本。因此，HSV 1感染中的翻译关闭主要是vhs诱导的核滞留而不是感染细胞mRNA降解的结果。因此，我们揭示了一种新的机制，其中vhs和它的辅因子，包括VP 22引起的感染细胞转录组的时间和空间的调节，从而协调有效的后期蛋白质的生产。疱疹病毒是在细胞核中复制并通过利用宿主细胞mRNA生物发生机制（包括转录、核输出、翻译和周转）表达其基因的大型DNA病毒。因此，这些病毒表达多种因子，这些因子使得能够利用细胞途径进行最佳病毒生产，并且协同工作以关闭宿主基因表达并以充分描述的级联方式过表达病毒基因，该级联以立即早期、早期和晚期蛋白质的时间模式发生。我们已经分析了宿主和病毒转录组的整体和单细胞变化，以揭示病毒核糖核酸内切酶（称为vhs）关闭早期病毒基因表达的新机制。这是通过在晚期基因表达开始时vhs诱导整个感染细胞转录组的核保留来实现的。为了能够从早期蛋白质生产切换到晚期蛋白质生产，病毒需要第二个因子VP 22来特异性抑制晚期转录物的核保留，从而允许它们在细胞质中翻译。以这种方式，HSV 1激发了受感染细胞转录组的时间和空间调节，以协调有效的晚期蛋白质产生，这一过程可能与一般疱疹病毒相关。
HSV1 encodes an endoribonuclease termed virion host shutoff (vhs) that is produced late in infection and packaged into virions. Paradoxically, vhs is active against not only host but also virus transcripts, and is involved in host shutoff and the temporal expression of the virus transcriptome. Two other virus proteins—VP22 and VP16 –are proposed to regulate vhs to prevent uncontrolled and lethal mRNA degradation but their mechanism of action is unknown. We have performed dual transcriptomic analysis and single-cell mRNA FISH of human fibroblasts, a cell type where in the absence of VP22, HSV1 infection results in extreme translational shutoff. In Wt infection, host mRNAs exhibited a wide range of susceptibility to vhs ranging from resistance to 1000-fold reduction, a variation that was independent of their relative abundance or transcription rate. However, vhs endoribonuclease activity was not found to be overactive against any of the cell transcriptome in Δ22-infected cells but rather was delayed, while its activity against the virus transcriptome and in particular late mRNA was minimally enhanced. Intriguingly, immediate-early and early transcripts exhibited vhs-dependent nuclear retention later in Wt infection but late transcripts were cytoplasmic. However, in the absence of VP22, not only early but also late transcripts were retained in the nucleus by a vhs-dependent mechanism, a characteristic that extended to cellular transcripts that were not efficiently degraded by vhs. Moreover, the ability of VP22 to bind VP16 enhanced but was not fundamental to the rescue of vhs-induced nuclear retention of late transcripts. Hence, translational shutoff in HSV1 infection is primarily a result of vhs-induced nuclear retention and not degradation of infected cell mRNA. We have therefore revealed a new mechanism whereby vhs and its co-factors including VP22 elicit a temporal and spatial regulation of the infected cell transcriptome, thus co-ordinating efficient late protein production. Herpesviruses are large DNA viruses that replicate in the nucleus and express their genes by exploiting host cell mRNA biogenesis mechanisms including transcription, nuclear export, translation and turnover. As such, these viruses express multiple factors that enable the appropriation of cellular pathways for optimal virus production, and work in concert to shut off host gene expression and to overexpress virus genes in a well-described cascade that occurs in a temporal pattern of immediate-early, early and late proteins. We have analysed global and single cell changes in the host and virus transcriptome to uncover a novel mechanism by which the viral endoribonuclease, termed vhs, turns off early virus gene expression. This is achieved through the vhs-induced nuclear retention of the entire infected cell transcriptome at the onset of late gene expression. To enable the switch from early to late protein production the virus then requires a second factor called VP22 to specifically inhibit the nuclear retention of late transcripts allowing their translation in the cytoplasm. In this way, HSV1 elicits a temporal and spatial regulation of the infected cell transcriptome to co-ordinate efficient late protein production, a process that may be relevant to herpesviruses in general.
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