DNA SUPERCOILING AND THE ANAEROBIC AND GROWTH-PHASE REGULATION OF TONB GENE-EXPRESSION
DNA SUPERCOILING AND THE ANAEROBIC AND GROWTH-PHASE REGULATION OF TONB GENE-EXPRESSION
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DOI：
10.1128/jb.170.6.2816-2826.1988
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发表时间：
1988-06-01
影响因子：
3.2
通讯作者：
HIGGINS, CF
中科院分区：
文献类型：
--
作者：
DORMAN, CJ;BARR, GC;HIGGINS, CF
我们发现，几个相互作用的环境因素影响细胞内DNA的拓扑结构。体内DNA的负超螺旋通过厌氧生长而增加，并且也受到生长阶段的影响。发现大肠杆菌和鼠伤寒沙门氏菌的tonB启动子对DNA超螺旋的变化高度敏感。表达增加新生霉素，DNA促旋酶的抑制剂，并减少了增加DNA超螺旋的因素。质粒编码的tonB基因的表达被γ增强。δ的以距离和取向独立的方式顺式插入。γ的res位点和TnpR蛋白两者。δ，其已知作为I型拓扑异构酶起作用，是这种激活所必需的，tonB表达在生长周期中增加，并通过厌氧而减少。在广泛的条件下，来自质粒的tonB表达与该质粒的超螺旋水平之间存在极好的相关性。染色体tonB基因以与质粒编码基因相同的方式调节。因此，tonB表达的生理调节响应于厌氧和生长阶段似乎是介导的环境诱导的DNA超螺旋性的变化。
We show that several interacting environmental factors influence the topology of intracellular DNA. Negative supercoiling of DNA in vivo is increased by anaerobic growth and is also influenced by growth phase. The tonB promoter of Escherichia coli and Salmonella typhimurium was found to be highly sensitive to changes in DNA supercoiling. Expression was increased by novobiocin, an inhibitor of DNA gyrase, and was decreased by factors which increase DNA superhelicity. Expression of the plasmid-encoded tonB gene was enhanced by .gamma..delta. insertions in cis in a distance- and orientation-independent fashion. Both the res site and the TnpR protein of .gamma..delta., which is known to function as a type I topoisomerase, were required for this activation, tonB expression increased during the growth cycle and was reduced by anaerobiosis. There was excellent correlation between tonB expression from a plasmid and the level of supercoiling of that plasmid under a wide range of conditions. The chromosomal tonB gene was regulated in a manner identical to that of the plasmid-encoded gene. Thus, the physiological regulation of tonB expression in response to anaerobiosis and growth phase appears to be mediated by environmentally induced changes in DNA superhelicity.