KSHV inhibits stress granule formation by viral ORF57 blocking PKR activation.
KSHV inhibits stress granule formation by viral ORF57 blocking PKR activation.
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DOI：
10.1371/journal.ppat.1006677
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发表时间：
2017-10
期刊：
影响因子：
6.7
通讯作者：
Zheng ZM
中科院分区：
文献类型：
--
作者：
Sharma NR;Majerciak V;Kruhlak MJ;Zheng ZM
TIA-1阳性应激颗粒(SG)代表停滞的mRNAs的存储位置，通常与细胞的抗病毒反应有关。在这份报告中，我们提供了卡波西肉瘤相关疱疹病毒(KSHV)通过病毒裂解蛋白ORF57抑制SG形成而克服宿主抗病毒反应的证据。通过免疫荧光分析，我们发现KSHV裂解感染的B淋巴细胞对SG的诱导是无效的。KSHV ORF57是病毒基因表达和新病毒后代产生的重要转录后调节因子，它抑制实验中亚砷酸盐和PolyI：C诱导的SG形成，但不抑制热应激诱导的SG形成。具有内切核酸酶活性的KSHV ORF37(VSOX)也能抑制亚砷酸盐诱导的SG的形成，而KSHV RTA、vIRF-2、ORF45、ORF59和LANA则无此作用。ORF57通过其RNA结合基序与PKR激活蛋白(PACT)和蛋白激酶R(PKR)结合，阻止PKR途径中的PACT-PKR相互作用，从而抑制KSHV的产生。一直以来，下调PKR的表达显著促进KSHV病毒粒子的产生。ORF57与PKR相互作用，抑制PKR结合的双链RNA及其自身磷酸化，从而抑制eIF2α的磷酸化和SG的形成。与KSHV ORF57相似的同源蛋白HSV-1ICP27，而不是EBVEB2，在阻断PKR/eIF2ICP27/SG途径方面与KSHVORF57相似。此外，KSHV ORF57还抑制Poly I：C诱导的TLR3磷酸化。总之，我们的数据首次证明KSHVORF57在调节PKR/eIF2α/SG轴中起作用，并在病毒裂解感染过程中促进病毒的产生。哺乳动物RNA颗粒，包括应激颗粒，是宿主细胞抗病毒反应的重要组成部分，它们的组装广泛地被RNA病毒所抵消。在Kaposi肉瘤相关疱疹病毒(KSHV)裂解感染的B细胞中，我们发现KSHV感染通过表达病毒裂解蛋白ORF57和ORF37(VSOX)来抑制SG的组装。KSHV ORF57通过结合并阻止PACT激活PKR来阻断亚砷酸盐诱导的SG的形成。ORF57还与PKR的两个双链结合基序相互作用，阻止其与Poly I：C和自磷酸化的结合，从而抑制eIF2α的磷酸化和SG的形成。一直以来，PKR的敲除增加了KSHV病毒粒子的产生。KSHV ORF57的这一功能在同源HSV-1 ICP27中是保守的，但在EBV EB2中不是。我们的结论是，KSHV ORF57拮抗宿主对病毒裂解感染和产生的抗病毒防御。
TIA-1 positive stress granules (SG) represent the storage sites of stalled mRNAs and are often associated with the cellular antiviral response. In this report, we provide evidence that Kaposi’s sarcoma-associated herpesvirus (KSHV) overcomes the host antiviral response by inhibition of SG formation via a viral lytic protein ORF57. By immunofluorescence analysis, we found that B lymphocytes with KSHV lytic infection are refractory to SG induction. KSHV ORF57, an essential post-transcriptional regulator of viral gene expression and the production of new viral progeny, inhibits SG formation induced experimentally by arsenite and poly I:C, but not by heat stress. KSHV ORF37 (vSOX) bearing intrinsic endoribonuclease activity also inhibits arsenite-induced SG formation, but KSHV RTA, vIRF-2, ORF45, ORF59 and LANA exert no such function. ORF57 binds both PKR-activating protein (PACT) and protein kinase R (PKR) through their RNA-binding motifs and prevents PACT-PKR interaction in the PKR pathway which inhibits KSHV production. Consistently, knocking down PKR expression significantly promotes KSHV virion production. ORF57 interacts with PKR to inhibit PKR binding dsRNA and its autophosphorylation, leading to inhibition of eIF2α phosphorylation and SG formation. Homologous protein HSV-1 ICP27, but not EBV EB2, resembles KSHV ORF57 in the ability to block the PKR/eIF2α/SG pathway. In addition, KSHV ORF57 inhibits poly I:C-induced TLR3 phosphorylation. Altogether, our data provide the first evidence that KSHV ORF57 plays a role in modulating PKR/eIF2α/SG axis and enhances virus production during virus lytic infection. Mammalian RNA granules, including stress granules (SG), are important components of the host cell antiviral responses and their assembly is widely counteracted by RNA viruses. In Kaposi’s sarcoma-associated herpesvirus (KSHV) lytically infected B cells, we found that KSHV infection inhibits the assembly of SG by expression of viral lytic protein ORF57 and ORF37 (vSOX). KSHV ORF57 blocks arsenite-induced SG formation by binding to and preventing PACT from activating PKR. ORF57 also interacts with two double-stranded RNA binding motifs of PKR and prevents its binding with poly I:C and autophosphorylation, subsequent inhibition of eIF2α phosphorylation and SG formation. Consistently, knockdown of PKR increases production of KSHV virions. This function of KSHV ORF57 is conserved in homolog HSV-1 ICP27, but not in EBV EB2. We conclude that KSHV ORF57 antagonizes host antiviral defenses for virus lytic infection and production.
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影响因子：
64.8
作者：
Alexopoulou, L;Holt, AC;Flavell, RA
通讯作者：
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DOI：
10.1073/pnas.0703348104
发表时间：
2007-05-22
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作者：
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影响因子：
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作者：
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