GreA and GreB proteins revive backtracked RNA polymerase in vivo by promoting transcript trimming
GreA and GreB proteins revive backtracked RNA polymerase in vivo by promoting transcript trimming
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DOI：
10.1093/emboj/19.24.6853
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发表时间：
2000-12-15
期刊：
影响因子：
11.4
通讯作者：
Rahmouni, AR
中科院分区：
文献类型：
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作者：
Toulmé, F;Mosrin-Hauman, C;Rahmouni, AR
大肠杆菌的GreA和GreB蛋白在体外对转录延伸有多种影响，但其生理功能尚不清楚。在这里，我们研究了这些因素是否以及如何影响RNA聚合酶（RNAP）在体内的横向振荡，在一个蛋白质读块上观察到。当RNAP在一个（ATC/TAG）序列中停滞时，它似乎在模板的上游和下游位置之间振荡，间隔3bp，同时修剪转录本3'端及其重新合成。使用一组突变的大肠杆菌菌株，我们发现细胞中存在GreA或GreB对于诱导这种修剪是必不可少的。我们进一步表明，与稳定在下游位置的三元配合物相反，振荡配合物在很大程度上依赖于GreA/ greb诱导的“裂解-重启”过程，以获得催化能力。显然，通过促进转录物的缩短和催化序列的重新排列，Gre因子在体内的功能是拯救RNAP，使其不被阻止在模板位置，从而损害三元配合物的横向稳定性。
The GreA and GreB proteins of Escherichia coli show a multitude of effects on transcription elongation in vitro, yet their physiological functions are poorly understood. Here, we investigated whether and how these factors influence lateral oscillations of RNA polymerase (RNAP) in vivo, observed at a protein readblock, When RNAP is stalled within an (ATC/TAG), sequence, it appears to oscillate between an upstream and a downstream position on the template, 3 bp apart, with concomitant trimming of the transcript 3' terminus and its re-synthesis. Using a set of mutant E.coli strains, we show that the presence of GreA or GreB in the cell is essential to induce this trimming. We show further that in contrast to a ternary complex that is stabilized at the downstream position, the oscillating complex relies heavily on the GreA/GreB-induced 'cleavage-and-restart' process to become catalytically competent. Clearly, by promoting transcript shortening and re-alignment of the catalytic register, the Gre factors function in vivo to rescue RNAP from being arrested at template positions where the lateral stability of the ternary complex is impaired.