SARS coronavirus nsp1 protein induces template-dependent endonucleolytic cleavage of mRNAs: viral mRNAs are resistant to nsp1-induced RNA cleavage.
SARS coronavirus nsp1 protein induces template-dependent endonucleolytic cleavage of mRNAs: viral mRNAs are resistant to nsp1-induced RNA cleavage.
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DOI：
10.1371/journal.ppat.1002433
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发表时间：
2011-12
期刊：
影响因子：
6.7
通讯作者：
Makino S
中科院分区：
文献类型：
--
作者：
Huang C;Lokugamage KG;Rozovics JM;Narayanan K;Semler BL;Makino S
SARS冠状病毒非结构蛋白1（nonstructural protein，nsp 1）是一种有效的宿主基因表达抑制剂，其作用方式独特：与40 S核糖体结合，抑制核糖体翻译功能，诱导宿主mRNA降解。我们以前的研究表明，nsp 1诱导RNA修饰报告mRNA的5′端附近有一个短的5′非翻译区和RNA切割在脑心肌炎病毒内部核糖体进入位点（IRES）区域的双顺反子RNA模板，但不是在这些IRES元件从丙型肝炎病毒或蟋蟀麻痹病毒。通过使用主要的无细胞体外翻译系统，本研究揭示了nsp 1主要在加帽mRNA模板的5′非翻译区附近诱导核酸内切RNA切割。使用携带不同IRES的双顺反子mRNA的实验表明，nsp 1诱导I型和II型小核糖核酸病毒IRES元件的核糖体加载区域内的核酸内切酶RNA切割，但不诱导经典猪瘟病毒IRES的核酸内切酶RNA切割，其特征在于是丙型肝炎病毒样IRES。nsp 1诱导的模板mRNA的RNA切割没有表现出明显的偏好，在RNA切割位点的特定核苷酸序列。值得注意的是，SCoV mRNAs具有5′帽结构和3′聚腺苷酸尾，与典型的宿主mRNAs相似，对nsp 1介导的RNA切割不敏感，重要的是，5′端前导序列的存在保护了SCoV mRNAs免受nsp 1诱导的核酸内切酶RNA切割。病毒mRNAs从nsp 1诱导的RNA切割中逃逸可能是病毒规避nsp 1作用的重要策略，从而导致病毒mRNAs和病毒蛋白在感染过程中的有效积累。严重急性呼吸综合征（SARS）冠状病毒（SCoV）是SARS的病原体。SCoV的nsp 1蛋白阻断宿主蛋白质合成，包括感染细胞中病毒复制的一般抑制剂I型干扰素。这一发现表明，SCoV nsp 1蛋白在SARS感染的严重症状中起着关键作用。Nsp 1与40 S核糖体亚基结合，这是蛋白质合成的必要组分，并使核糖体的翻译活性失活。此外，与40 S核糖体结合的nsp 1诱导宿主mRNA的修饰，导致这些RNA在SCoV感染的细胞中加速衰变。我们发现，nsp 1诱导的RNA修饰的性质是RNA切割，nsp 1不识别宿主mRNA中的特定核苷酸来诱导这种切割。有趣的是，nsp 1不诱导SCoV mRNA中的RNA切割。这些数据表明，nsp 1诱导宿主mRNA的RNA切割，以抑制宿主基因的表达，包括那些具有抗病毒功能的基因;然而，病毒mRNA免于这种切割事件，这最有可能促进感染细胞中有效的SCoV蛋白合成和病毒复制。
SARS coronavirus (SCoV) nonstructural protein (nsp) 1, a potent inhibitor of host gene expression, possesses a unique mode of action: it binds to 40S ribosomes to inactivate their translation functions and induces host mRNA degradation. Our previous study demonstrated that nsp1 induces RNA modification near the 5′-end of a reporter mRNA having a short 5′ untranslated region and RNA cleavage in the encephalomyocarditis virus internal ribosome entry site (IRES) region of a dicistronic RNA template, but not in those IRES elements from hepatitis C or cricket paralysis viruses. By using primarily cell-free, in vitro translation systems, the present study revealed that the nsp1 induced endonucleolytic RNA cleavage mainly near the 5′ untranslated region of capped mRNA templates. Experiments using dicistronic mRNAs carrying different IRESes showed that nsp1 induced endonucleolytic RNA cleavage within the ribosome loading region of type I and type II picornavirus IRES elements, but not that of classical swine fever virus IRES, which is characterized as a hepatitis C virus-like IRES. The nsp1-induced RNA cleavage of template mRNAs exhibited no apparent preference for a specific nucleotide sequence at the RNA cleavage sites. Remarkably, SCoV mRNAs, which have a 5′ cap structure and 3′ poly A tail like those of typical host mRNAs, were not susceptible to nsp1-mediated RNA cleavage and importantly, the presence of the 5′-end leader sequence protected the SCoV mRNAs from nsp1-induced endonucleolytic RNA cleavage. The escape of viral mRNAs from nsp1-induced RNA cleavage may be an important strategy by which the virus circumvents the action of nsp1 leading to the efficient accumulation of viral mRNAs and viral proteins during infection. Severe acute respiratory syndrome (SARS) coronavirus (SCoV) is the causative agent of SARS. The nsp1 protein of SCoV blocks host protein synthesis, including type I interferon, a general inhibitor of virus replication, in infected cells. This finding suggests that SCoV nsp1 protein plays a key role in the severe symptoms that accompany SARS infection. Nsp1 binds to the 40S ribosome subunit, which is an essential component for protein synthesis, and inactivates the translation activity of the ribosome. Furthermore, nsp1 binding to the 40S ribosome induces the modification of host mRNAs, leading to the accelerated decay of these RNAs in SCoV-infected cells. We found that the nature of nsp1-induced RNA modification was RNA cleavage and that nsp1 did not recognize specific nucleotides in host mRNAs to induce this cleavage. Interestingly, nsp1 did not induce RNA cleavage in SCoV mRNAs. These data indicate that nsp1 induces RNA cleavage of host mRNAs to suppress the expression of host genes, including those having antiviral functions; yet viral mRNAs are spared from such cleavage events, which, most likely, facilitate efficient SCoV protein synthesis and virus replication in infected cells.
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影响因子：
3.7
作者：
Cheng A;Zhang W;Xie Y;Jiang W;Arnold E;Sarafianos SG;Ding J
通讯作者：
Ding J
DOI：
10.1074/jbc.m310875200
发表时间：
2004-01-16
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Fan K;Wei P;Feng Q;Chen S;Huang C;Ma L;Lai B;Pei J;Liu Y;Chen J;Lai L
通讯作者：
Lai L
影响因子：
5.4
作者：
Harcourt, BH;Jukneliene, D;Baker, SC
通讯作者：
Baker, SC
影响因子：
29.4
作者：
Honda, M;Kaneko, S;Lemon, SM
通讯作者：
Lemon, SM
影响因子：
56.9
作者：
Anand, K;Ziebuhr, J;Hilgenfeld, R
通讯作者：
Hilgenfeld, R