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首页> 外文期刊>RNA >Ribosomal binding to the internal ribosomal entry site of classical swine fever virus.
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Ribosomal binding to the internal ribosomal entry site of classical swine fever virus.

机译：核糖体与经典猪瘟病毒内部核糖体进入位点的结合。

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摘要

Most eukaryotic mRNAs require the cap-binding complex elF4F for efficient initiation of translation, which occurs as a result of ribosomal scanning from the capped 5' end of the mRNA to the initiation codon. A few cellular and viral mRNAs are translated by a cap and end-independent mechanism known as internal ribosomal entry. The internal ribosome entry site (IRES) of classical swine fever virus (CSFV) is approximately 330 nt long, highly structured, and mediates internal initiation of translation with no requirement for elF4F by recruiting a ribosomal 43S preinitiation complex directly to the initiation codon. The key interaction in this process is the direct binding of ribosomal 40S subunits to the IRES to form a stable binary complex in which the initiation codon is positioned precisely in the ribosomal P site. Here, we report the results of analyses done using enzymatic footprinting and mutagenesis of the IRES to identify structural components in it responsible for precise binding of the ribosome. Residues flanking the initiation codon and extending from nt 363-391, a distance equivalent to the length of the 40S subunit mRNA-binding cleft, were strongly protected from RNase cleavage, as were nucleotides in the adjacent pseudoknot and in the more distal subdomain IIId1. Ribosomal binding and IRES-mediated initiation were abrogated by disruption of helix 1b of the pseudoknot and very severely reduced by mutation of the protected residues in IIId1 and by disruption of domain IIIa. These observations are consistent with a model for IRES function in which binding of the region flanking the initiation codon to the decoding region of the ribosome is determined by multiple additional interactions between the 40S subunit and the IRES.
机译：大多数真核mRNA需要帽结合复合物eIF4F才能有效起始翻译，这是由于从mRNA的5'端至起始密码子的核糖体扫描而产生的。一些细胞和病毒的mRNA通过称为内部核糖体进入的上限和末端独立机制进行翻译。经典猪瘟病毒（CSFV）的内部核糖体进入位点（IRES）长约330 nt，结构高度高，可通过直接向起始密码子募集核糖体43S预起始复合物来介导内部翻译起始，而无需elF4F。此过程中的关键相互作用是核糖体40S亚基与IRES的直接结合，形成稳定的二元复合物，其中起始密码子正好位于核糖体P位点。在这里，我们报告使用酶促足迹和IRES诱变来确定其中负责核糖体精确结合的结构成分的分析结果。残基位于起始密码子旁并从nt 363-391延伸，该距离等于40S亚基mRNA结合裂隙的长度，与相邻的假结和更远端的亚结构域IIId1中的核苷酸一样，它们被强烈保护免受RNase切割。核糖体结合和IRES介导的启动被假结螺旋1b的破坏所废除，并且由于IIId1中受保护残基的突变和结构域IIIa的破坏而大大降低。这些观察结果与IRES功能模型一致，在IRES功能模型中，起始密码子两侧的区域与核糖体的解码区域的结合是通过40S亚基和IRES之间的多次附加相互作用来确定的。

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