Global shape mimicry of tRNA within a viral internal ribosome entry site mediates translational reading frame selection
Global shape mimicry of tRNA within a viral internal ribosome entry site mediates translational reading frame selection
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DOI：
10.1073/pnas.1512088112
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发表时间：
2015-11-24
影响因子：
11.1
通讯作者：
Jan, Eric
中科院分区：
文献类型：
--
作者：
Au, Hilda H.;Cornilescu, Gabriel;Jan, Eric
DicistroVirus基因间区内部核糖体进入位点(IRES)采用三重伪节RNA结构，占据核心核糖体的E、P和A位点，直接募集核糖体并在非AUG密码子启动翻译。DicistroVirus IRESS的一个子集指导0和+1框架的翻译，分别产生病毒结构蛋白和称为ORFx的+1重叠开放阅读框架。在这里，我们证明了位于蜜蜂DicistroVirus以色列急性麻痹病毒(IAPV)IRES PKI结构域三螺旋连接核心的两个不成对的腺苷的特定突变可以解偶联0和+1帧翻译，表明该结构采用了有助于0或+1帧翻译的不同构象。利用重组的翻译系统，我们发现在突变的IRESS上组装的直接排他性0或+1帧翻译的核糖体缺乏阅读框架保真度。最后，核磁共振/小角X射线散射混合方法揭示了IAPV IRES的PKI结构域采用了类似于完整tRNA的RNA结构。TRNA形状模拟使病毒IRES能够进入核糖体tRNA结合部位，并与核糖体形成分子间接触，这是启动IRES在特定阅读框架中翻译所必需的。
The dicistrovirus intergenic region internal ribosome entry site (IRES) adopts a triple-pseudoknotted RNA structure and occupies the core ribosomal E, P, and A sites to directly recruit the ribosome and initiate translation at a non-AUG codon. A subset of dicistrovirus IRESs directs translation in the 0 and +1 frames to produce the viral structural proteins and a +1 overlapping open reading frame called ORFx, respectively. Here we show that specific mutations of two unpaired adenosines located at the core of the three-helical junction of the honey bee dicistrovirus Israeli acute paralysis virus (IAPV) IRES PKI domain can uncouple 0 and +1 frame translation, suggesting that the structure adopts distinct conformations that contribute to 0 or +1 frame translation. Using a reconstituted translation system, we show that ribosomes assembled on mutant IRESs that direct exclusive 0 or +1 frame translation lack reading frame fidelity. Finally, a nuclear magnetic resonance/small-angle X-ray scattering hybrid approach reveals that the PKI domain of the IAPV IRES adopts an RNA structure that resembles a complete tRNA. The tRNA shape-mimicry enables the viral IRES to gain access to the ribosome tRNA-binding sites and form intermolecular contacts with the ribosome that are necessary for initiating IRES translation in a specific reading frame.