Figueroa N, Bossi L
Sclavo Research Center, Siena, Italy.
Proc Natl Acad Sci U S A. 1988 Dec;85(24):9416-20. doi: 10.1073/pnas.85.24.9416.
We show that transcription modulation of a plasmid sequence in exponentially growing Escherichia coli cells leads to a rapid change in the linking number of plasmid DNA. Activation of transcription is accompanied by an increase in the plasmid's level of negative supercoiling. The added superhelical turns, whose number is proportional to the strength of the promoter and to the length of the transcript, are promptly removed when transcription is turned off. The transcription-induced increase of template supercoiling can still be detected in the presence of an inhibitor of ATP-dependent DNA gyrase [DNA topoisomerase (ATP-hydrolyzing), EC 5.99.1.3]. Altogether, our results indicate that, in addition to being under a general control, DNA superhelicity can be modulated locally in response to the topological perturbations associated with DNA tracking processes. We discuss a model in which supercoiling changes are produced by differential swiveling activities on the opposite sides of a transcriptional flow during transcriptional modulation.
我们表明，在指数生长的大肠杆菌细胞中，质粒序列的转录调控会导致质粒DNA连接数的快速变化。转录激活伴随着质粒负超螺旋水平的增加。当转录关闭时，额外的超螺旋圈（其数量与启动子强度和转录本长度成正比）会迅速消除。在存在ATP依赖性DNA促旋酶[DNA拓扑异构酶（ATP水解），EC 5.99.1.3]抑制剂的情况下，仍可检测到转录诱导的模板超螺旋增加。总之，我们的结果表明，除了受到一般控制外，DNA超螺旋度还可以响应与DNA追踪过程相关的拓扑扰动而进行局部调节。我们讨论了一个模型，其中超螺旋变化是由转录调控期间转录流两侧的差异旋转活性产生的。
