MULTIPLE RNA-POLYMERASE CONFORMATIONS AND GREA - CONTROL OF THE FIDELITY OF TRANSCRIPTION
MULTIPLE RNA-POLYMERASE CONFORMATIONS AND GREA - CONTROL OF THE FIDELITY OF TRANSCRIPTION
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DOI：
10.1126/science.8235608
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发表时间：
1993-11-05
期刊：
影响因子：
56.9
通讯作者：
VONHIPPEL, PH
中科院分区：
文献类型：
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作者：
ERIE, DA;HAJISEYEDJAVADI, O;VONHIPPEL, PH
采用稳态前错误掺入动力学方法研究了大肠杆菌RNA聚合酶在转录延伸过程中向新生RNA中添加单核苷酸的情况。结果与分支动力学机制相吻合，该机制允许在每个模板位置处在活化的和未活化的酶复合物之间进行构象切换，这两者都可以从溶液中结合核苷酸三磷酸（NTPs）。该复合物通常以长寿命的激活状态存在，只有当转录减慢时才变得不激活。该模型允许转录中的多个水平的核苷酸区分，因为在不存在正确的NTP或如果3'末端残基不正确匹配的情况下，复合物可以在未活化状态下被“动力学捕获”。转录切割因子GreA（或GreA增强的活性）通过优先切割含有在延伸复合物的未活化状态下错误掺入的残基的转录物来增加转录的保真度。GreA的这种切割机制可以防止体内形成“死端”转录复合物。
Pre-steady state kinetics of misincorporation were used to investigate the addition of single nucleotides to nascent RNA by Escherichia coli RNA polymerase during transcription elongation. The results were fit with a branched kinetic mechanism that permits conformational switching, at each template position, between an activated and an unactivated enzyme complex, both of which can bind nucleotide triphosphates (NTPs) from solution. The complex exists most often in the long-lived activated state, and only becomes unactivated when transcription is slowed. This model permits multiple levels of nucleotide discrimination in transcription, since the complex can be ''kinetically trapped'' in the unactivated state in the absence of the correct NTP or if the 3' terminal residue is incorrectly matched. The transcription cleavage factor GreA (or an activity enhanced by GreA) increased the fidelity of transcription by preferential cleavage of transcripts containing misincorporated residues in the unactivated state of the elongation complex. This cleavage mechanism by GreA may prevent the formation of ''dead-end'' transcription complexes in vivo.