Combinatorial effects of NusA and NusG on transcription elongation and Rho-dependent termination in Escherichia coli
Combinatorial effects of NusA and NusG on transcription elongation and Rho-dependent termination in Escherichia coli
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DOI：
10.1006/jmbi.1998.1691
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发表时间：
1998-05-01
影响因子：
5.6
通讯作者：
Richardson, JP
中科院分区：
文献类型：
--
作者：
Burns, CM;Richardson, LV;Richardson, JP
来自大肠杆菌的转录因子 NusA 和 NusG 是 RNA 聚合酶延伸反应和 Rho 依赖性转录终止的调节剂。 NusA 降低伸长率和终止效率，而 NusG 则增加这两种活性。两种 Nus 因子都能够与 Rho 和 RNA 聚合酶发生物理相互作用。旨在确定这些因素是否独立或竞争作用的纯化组分实验表明，伸长率的变化是其各自效应的综合，对终止的综合效应取决于反应条件，并且这两个因素不会竞争其作用位点以实现任一效应。还发现这两个因素不会显着增强体外转录过程中 200 μM 鸟苷 3',5'-二磷酸 (ppGpp) 引起的轻微 (20%) 伸长抑制。结果还表明，NusA和NusG对RNA聚合酶延伸和Rho功能的影响与延伸和终止之间的反比关系相反，而预期Rho作用与RNA聚合酶延伸的动力学耦合。这一特性表明，除了已知的对 RNA 聚合酶影响暂停长度的作用外，这些因素还对 Rho 依赖性终止过程的其他一些限速步骤起作用。 (C) 1998 学术出版社有限公司。
The transcription factors NusA and NusG from Escherichia coli are modulators of the RNA polymerase elongation reaction and Rho-dependent transcription termination. NusA decreases the elongation rate and termination efficiency while NusG increases both activities. Both Nus factors are able to physically interact with Rho and with RNA polymerase. Experiments with purified components designed to determine whether these factors act independently or competitively showed that the change in elongation rate was a composite of their individual effects, that the combined effect on termination was dependent on the reaction conditions and that the two factors do not compete for their sites of action for either effect. The two factors were also found not to enhance significantly the slight (20%) inhibition of elongation caused by 200 mu M guanosine 3',5'-bisdiphosphate (ppGpp) during transcription in vitro. The results also show that the effects of NusA and NusG on RNA polymerase elongation and Rho function are contrary to the inverse relationship between elongation and termination that is expected for a kinetic coupling of Rho action to RNA polymerase elongation. This property suggests that in addition to their known actions on RNA polymerase that influence the length of pausing, these factors act on some other rate-limiting step of the Rho-dependent termination process. (C) 1998 Academic Press Limited.