Hypernegative supercoiling of the DNA template during transcription elongation in vitro.
Hypernegative supercoiling of the DNA template during transcription elongation in vitro.
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DOI：
10.1016/s0021-9258(17)42136-3
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发表时间：
1994-01
期刊：
影响因子：
--
通讯作者：
M. Drolet;M. Drolet;X. Bi;Leroy F. Liu
中科院分区：
文献类型：
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作者：
M. Drolet;M. Drolet;X. Bi;Leroy F. Liu
从大肠杆菌topA突变体中分离出具有比正常高几倍的负超螺旋性的超螺旋质粒DNA。这些超负超螺旋质粒DNA的形成显然是由转录诱导的。我们发现从topA突变体中分离的超负超螺旋质粒DNA含有R环。为了研究超负超螺旋质粒DNA的形成机制，我们已经能够在体外用纯化的RNA聚合酶和DNA旋转酶复制超负超螺旋DNA。超负超螺旋质粒DNA模板在体外的形成需要转录延伸，并与R环的形成紧密相连。我们提出拓扑异构酶I的作用之一是抑制转录延伸过程中R环的形成。
Supercoiled plasmid DNAs with negative superhelicity several times higher than normal have been isolated from Escherichia coli topA mutants. The formation of these hypernegatively supercoiled plasmid DNAs is apparently induced by transcription. We show that hypernegatively supercoiled plasmid DNAs isolated from topA mutants contain R-loop(s). To study the mechanism of formation of hypernegatively supercoiled plasmid DNA, we have been able to reproduce hypernegatively supercoiled DNA in vitro using purified RNA polymerase and DNA gyrase. The formation of hypernegatively supercoiled plasmid DNA template in vitro is shown to require transcription elongation and is tightly linked to R-loop formation. We propose that one of the roles of topoisomerase I is to suppress R-loop formation during transcription elongation.