FIS modulates growth phase-dependent topological transitions of DNA in Escherichia coli
FIS modulates growth phase-dependent topological transitions of DNA in Escherichia coli
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DOI：
10.1046/j.1365-2958.1997.5951971.x
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发表时间：
1997-11-01
影响因子：
3.6
通讯作者：
Muskhelishvili, G
中科院分区：
文献类型：
--
作者：
Schneider, R;Travers, A;Muskhelishvili, G
大肠杆菌 DNA 结合蛋白 FIS 在两个不相关的酶反应（DNA 的位点特异性倒转和稳定 RNA 启动子的转录激活）中充当 DNA 结构因子。在这两个过程中，FIS 促进了两个结构不同的核蛋白复合物的组装和动态转变。我们之前提出，在这些系统中，FIS 通过在 DNA 中的多个螺旋定相位点结合来稳定扭曲的 DNA 微环。然而，FIS 也在许多非特异性位点结合并弯曲 DNA，并且在指数早期达到最大水平时，FIS 可能会占据大肠杆菌染色体的相当一部分。在这里，我们证明 fis 影响 DNA 超冷却水平的生长阶段特异性改变。 fis 的表达加速了稳定期中度超结肠质粒的积累，这些质粒在营养转变后通过 FIS 得以稳定。根据这种功能，FIS 在体外调节拓扑异构酶的松弛和超冷却活性，使 RNA 保持在适度的超冷却状态。我们的结果表明 FIS 的主要作用是调节细菌生长过程中的染色体动力学。
The Escherichia coli DNA-binding protein FIS serves as a DNA architectural factor in two unrelated enzymatic reactions, the site-specific inversion of DNA and transcriptional activation of stable RNA promoters. In both these processes, FIS facilitates the assembly and dynamic transitions of two structurally distinct nucleoprotein complexes. We have proposed previously that, in these systems, FIS stabilizes writhed DNA microloops by binding at multiple helically phased sites in DNA. However, FIS also binds and bends DNA at many non-specific sites and, at its maximum levels in the early exponential phase, FIS could potentially occupy a considerable part of the E. coli chromosome. Here, we show that fis affects growth phase-specific alterations in the supercoliing level of DNA. Expression of fis accelerates the accumulation of moderately supercolied plasmids in stationary phase, which are stabilized by FIS after nutritional shift-up. In accordance with such a function, FIS modulates the relaxing and supercoliing activities of topoisomerases in vitro in a way that keeps RNA in a moderately supercolied state. Our results suggest that the primary role of FIS is to modulate chromosomal dynamics during bacterial growth.