突变型起始因子3对起始密码子和起始tRNA的识别改变
Altered discrimination of start codons and initiator tRNAs by mutant initiation factor 3.
作者信息
O'Connor M, Gregory S T, Rajbhandary U L, Dahlberg A E
机构信息
Department of Molecular and Cellular Biology and Biochemistry, Brown University, Providence, Rhode Island 02912, USA. Michael_O'
出版信息
RNA. 2001 Jul;7(7):969-78. doi: 10.1017/s1355838201010184.
IF3 is essential for ensuring the fidelity of the initiation step of translation in bacterial cells. Mutations at residues R99 and R131 in the C-terminal domain of the factor have previously been shown to increase initiation from the non-canonical GUA codon. Here we show that these mutant forms of IF3 fail to discriminate against initiation from many different non-AUG codons. They also enhance the activity of mutant tRNAs carrying changes in the three consecutive G-C pairs that are conserved in the anticodon stem of initiator tRNAs. In addition, the IF3 mutants stimulate initiations from leaderless mRNAs and from internal initiation codons, in the absence of any SD-anti-SD interaction. These results indicate that IF3 ensures the accuracy of initiation by inspecting both the codon-anticodon pairing and unique features of the initiator tRNA as well as suppressing initiation from other potential start sites within the mRNA.
IF3对于确保细菌细胞中翻译起始步骤的准确性至关重要。此前已表明，该因子C端结构域中R99和R131残基处的突变会增加从非规范GUA密码子起始的频率。在此我们表明，这些IF3突变形式无法区分许多不同的非AUG密码子起始。它们还增强了携带起始tRNA反密码子茎中保守的三个连续G-C对发生变化的突变tRNA的活性。此外，在没有任何SD-反SD相互作用的情况下，IF3突变体刺激无领导mRNA和内部起始密码子的起始。这些结果表明，IF3通过检查密码子-反密码子配对以及起始tRNA的独特特征来确保起始的准确性，并抑制mRNA内其他潜在起始位点的起始。
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