A putative ATPase mediates RNA transcription and capping in a dsRNA virus.
A putative ATPase mediates RNA transcription and capping in a dsRNA virus.
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假定的 ATP 酶介导 dsRNA 病毒中的 RNA 转录和加帽
DOI：
10.7554/elife.07901
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发表时间：
2015-08-04
期刊：
影响因子：
7.7
通讯作者：
Zhou ZH
中科院分区：
文献类型：
--
作者：
Yu X;Jiang J;Sun J;Zhou ZH
dsRNA病毒中的mRNA转录是一个高度调节的过程，但这种调节的机制尚不清楚。在这里，通过核苷三磷酸酶（NTH）测定和比较6个高分辨率（2.9-3.1 μ m）冷冻电镜结构的细胞质型多角体病毒与结合配体，我们表明，大亚结构域的鸟苷酰转移酶（GT酶）结构域的转塔蛋白（TP）也有一个ATP结合位点，很可能是一个ATP酶。S-腺苷-L-甲硫氨酸（SAM）作为信号分子，与TP的甲基化酶2结构域结合，诱导病毒衣壳的构象变化，进而激活推定的ATP酶。ATP结合/水解导致用于有效mRNA合成的扩大的衣壳、用于His 217介导的鸟苷酰转移的开放的GTase结构域和用于SAM结合和甲基转移的开放的甲基化酶-1结构域。两者合计，我们的数据支持的作用，推定的ATP酶介导的激活的mRNA转录和封端内的病毒。DOI：http://dx.doi.org/10.7554/eLife.07901.001病毒只能通过入侵其他生物体的细胞来复制，如植物和动物。每种病毒都携带DNA或核糖核酸（RNA）分子形式的遗传物质，这些分子被包装在由蛋白质制成的外壳中。胞质型多角体病毒的基因组由一种称为双链RNA的RNA组成。一旦进入宿主细胞，病毒基因组的一部分被复制，在一个称为转录的过程中制造“信使RNA”分子。被称为鸟苷酰和甲基的小化学基团被添加到信使RNA中，然后它们被用作模板来制造病毒蛋白质。一种称为S-腺苷-L-甲硫氨酸（SAM）的小分子可以通过与病毒外壳中称为turner的蛋白质结合来激活病毒基因组的转录。转塔蛋白参与将鸟苷酰和甲基基团添加到信使RNA分子中，但尚不清楚该蛋白质如何激活转录。在这里，Yu等人使用一种称为冷冻电子显微镜的技术来研究病毒如何结合SAM以激活转录。实验表明，SAM与转塔蛋白的一个区域或“结构域”的结合导致病毒外壳的变化。这使得转塔蛋白的另一个结构域能够结合一种称为ATP的小分子并将其分解。分解ATP释放的能量导致病毒外壳的进一步变化，从而激活转录，并将鸟苷酰和甲基基团添加到新产生的信使RNA中。在未来，直接观察每种病毒内部RNA的实验将为细胞质多角体病毒和其他类似病毒的基因组如何转录提供新的见解。DOI：http://dx.doi.org/10.7554/eLife.07901.002网站
mRNA transcription in dsRNA viruses is a highly regulated process but the mechanism of this regulation is not known. Here, by nucleoside triphosphatase (NTPase) assay and comparisons of six high-resolution (2.9–3.1 Å) cryo-electron microscopy structures of cytoplasmic polyhedrosis virus with bound ligands, we show that the large sub-domain of the guanylyltransferase (GTase) domain of the turret protein (TP) also has an ATP-binding site and is likely an ATPase. S-adenosyl-L-methionine (SAM) acts as a signal and binds the methylase-2 domain of TP to induce conformational change of the viral capsid, which in turn activates the putative ATPase. ATP binding/hydrolysis leads to an enlarged capsid for efficient mRNA synthesis, an open GTase domain for His217-mediated guanylyl transfer, and an open methylase-1 domain for SAM binding and methyl transfer. Taken together, our data support a role of the putative ATPase in mediating the activation of mRNA transcription and capping within the confines of the virus. DOI: http://dx.doi.org/10.7554/eLife.07901.001 Viruses can only replicate by invading the cells of other organisms, such as plants and animals. Each virus carries genetic material in the form of molecules of DNA or ribonucleic acid (RNA), which are packaged in a shell made of proteins. The cytoplasmic polyhedrosis virus has a genome made of a type of RNA called double-stranded RNA. Once inside a host cell, sections of the virus genome are copied to make molecules of ‘messenger RNA’ in a process called transcription. Small chemical groups called guanylyl and methyl groups are added to the messenger RNAs before they are used as templates to make the virus proteins. A small molecule called S-adenosyl-L-methionine (SAM) can activate transcription of the virus genome by binding to a protein called turret in the shell of the virus. The turret protein is involved in adding the guanylyl and methyl groups to the messenger RNA molecules, but it is not clear how the protein activates transcription. Here, Yu et al. used a technique called cryo electron microscopy to study how the virus binds SAM to activate transcription. The experiments show that the binding of SAM to one region or ‘domain’ of the turret protein leads to changes in the virus shell. This enables another domain of the turret protein to bind a small molecule called ATP and break it down. The energy released from breaking down ATP causes further changes of the shell of the virus to activate transcription and the addition of guanylyl and methyl groups to the newly made messenger RNAs. In the future, experiments that directly observe the RNA inside each virus shall offer fresh insights as to how the genomes of cytoplasmic polyhedrosis virus and other similar viruses are transcribed. DOI: http://dx.doi.org/10.7554/eLife.07901.002