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首页> 外文期刊>Molecular and Cellular Biology >Translation Initiation Factor 2γ Mutant Alters Start Codon Selection Independent of Met-tRNA Binding
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Translation Initiation Factor 2γ Mutant Alters Start Codon Selection Independent of Met-tRNA Binding

机译：翻译起始因子2γ突变体改变起始密码子选择，独立于Met-tRNA结合。

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Selection of the AUG start codon for translation in eukaryotes is governed by codon-anticodon interactions between the initiator Met-tRNAiMet and the mRNA. Translation initiation factor 2 (eIF2) binds Met-tRNAiMet to the 40S ribosomal subunit, and previous studies identified Sui? mutations in eIF2 that enhanced initiation from a noncanonical UUG codon, presumably by impairing Met-tRNAiMet binding. Consistently, an eIF2γ-N135D GTP-binding domain mutation impairs Met-tRNAiMet binding and causes a Sui? phenotype. Intragenic A208V and A382V suppressor mutations restore Met-tRNAiMet binding affinity and cell growth; however, only A208V suppresses the Sui? phenotype associated with the eIF2γ-N135D mutation. An eIF2γ-A219T mutation impairs Met-tRNAiMet binding but unexpectedly enhances the fidelity of initiation, suppressing the Sui? phenotype associated with the eIF2γ-N135D,A382V mutant. Overexpression of eIF1, which is thought to monitor codon-anticodon interactions during translation initiation, likewise suppresses the Sui? phenotype of the eIF2γ mutants. We propose that structural alterations in eIF2γ subtly alter the conformation of Met-tRNAiMet on the 40S subunit and thereby affect the fidelity of start codon recognition independent of Met-tRNAiMet binding affinity.
机译：在真核生物中用于翻译的AUG起始密码子的选择受启动子Met-tRNA i Met 和mRNA之间的密码子-反密码子相互作用控制。翻译起始因子2（eIF2）将Met-tRNA i Met 结合到40S核糖体亚基上，先前的研究在eIF2中发现Sui ？突变可能是通过削弱Met-tRNA i Met 结合而增强了非规范UUG密码子的启动。一致地，eIF2γ-N135DGTP结合域突变损害Met-tRNA i Met 结合并导致Sui ？表型。内源性A208V和A382V抑制子突变可恢复Met-tRNA i Met 的结合亲和力和细胞生长;然而，只有A208V抑制与eIF2γ-N135D突变相关的Sui ？表型。 eIF2γ-A219T突变削弱Met-tRNA i Met 的结合，但出乎意料地增强了起始保真度，从而抑制了与eIF2γ相关的Sui ？表型-N135D，A382V突变体。 eIF1的过表达被认为可以监测翻译起始过程中的密码子-反密码子相互作用，同样会抑制eIF2γ突变体的Sui ？表型。我们认为，eIF2γ中的结构改变会巧妙地改变40S亚基上Met-tRNA i Met 的构象，从而影响起始密码子识别的保真度，独立于Met-tRNA < sub> i Met 绑定亲和力。

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