Structural changes enable start codon recognition by the eukaryotic translation initiation complex.
Structural changes enable start codon recognition by the eukaryotic translation initiation complex.
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DOI：
10.1016/j.cell.2014.10.001
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发表时间：
2014-10-23
期刊：
影响因子：
64.5
通讯作者：
Ramakrishnan V
中科院分区：
文献类型：
--
作者：
Hussain T;Llácer JL;Fernández IS;Munoz A;Martin-Marcos P;Savva CG;Lorsch JR;Hinnebusch AG;Ramakrishnan V
在真核细胞翻译起始过程中，启动子tRNA不能完全插入到40S核糖体亚基上的P编码区。这种构象(Pout)与扫描Aug起始密码子的mRNA相兼容。碱基与Aug配对被认为促进异构化为更稳定的构象(PIN)，从而阻止扫描并促进eIF1从40S亚基解离。在这里，我们提出了一个酵母预引发复合体的冷冻EM重建，分辨率为4.0，在eIF1释放之前，启动子tRNA处于PIN状态。该结构揭示了eIF1A的N端尾部对密码子-反密码子双链的稳定，eIF1结构的变化可能在其随后的释放中起作用，以及eIF2构象的变化。该基因遍历整个基因裂解区，并与eIF2α、eIF1a和核糖体元件的调节域相连，这些元件允许识别AUG密码子周围的上下文核苷酸。酵母48S翻译起始复合体的结构在分辨率为4.0时，扭曲的启动子α被困在识别起始密码子的过程中，密码子-反密码子双链由eIF1AeIF2的N端尾部稳定，eIF2与−2和−3位的关键核苷酸接触。这张从扫描到密码子识别转变的快照为许多遗传和生化发现提供了一个框架，这些发现是当前真核细胞翻译启动模型的基础。
During eukaryotic translation initiation, initiator tRNA does not insert fully into the P decoding site on the 40S ribosomal subunit. This conformation (POUT) is compatible with scanning mRNA for the AUG start codon. Base pairing with AUG is thought to promote isomerization to a more stable conformation (PIN) that arrests scanning and promotes dissociation of eIF1 from the 40S subunit. Here, we present a cryoEM reconstruction of a yeast preinitiation complex at 4.0 Å resolution with initiator tRNA in the PIN state, prior to eIF1 release. The structure reveals stabilization of the codon-anticodon duplex by the N-terminal tail of eIF1A, changes in the structure of eIF1 likely instrumental in its subsequent release, and changes in the conformation of eIF2. The mRNA traverses the entire mRNA cleft and makes connections to the regulatory domain of eIF2α, eIF1A, and ribosomal elements that allow recognition of context nucleotides surrounding the AUG codon. Structure of a partial yeast 48S translation initiation complex at 4.0 Å resolution A distorted initiator tRNA is trapped in the act of recognizing the start codon The codon-anticodon duplex is stabilized by the N-terminal tail of eIF1A eIF2α makes contacts with key nucleotides at the −2 and −3 positions of the mRNA The cryoEM structure of a partial yeast 48S preinitiation complex at 4.0 Å resolution shows initiator tRNAi in the act of recognizing the start codon prior to eIF1 release. This snapshot of the transition from scanning to codon recognition provides a framework for numerous genetic and biochemical findings underlying the current model for eukaryotic translation initiation.
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