Thermoregulation of Shigella and Escherichia coli EIEC pathogenicity.: A temperature-dependent structural transition of DNA modulates accessibility of virF promoter to transcriptional repressor H-NS
Thermoregulation of Shigella and Escherichia coli EIEC pathogenicity.: A temperature-dependent structural transition of DNA modulates accessibility of virF promoter to transcriptional repressor H-NS
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DOI：
10.1093/emboj/17.23.7033
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发表时间：
1998-12-01
期刊：
影响因子：
11.4
通讯作者：
Gualerzi, CO
中科院分区：
文献类型：
--
作者：
Falconi, M;Colonna, B;Gualerzi, CO
志贺氏菌质粒携带的virF编码AraC家族的转录调节因子的表达是启动级联事件所必需的，该级联事件导致编码入侵功能的几个操纵子的激活。H-NS是主要的核相关蛋白之一，通过在低于临界温度时抑制virF的体内转录来控制毒力基因的温度依赖性表达（类似于32摄氏度），这种温度依赖性的转录调节已经在体外重现，并且在virF启动子上的H-NS的靶点被鉴定为以-250和-250为中心的两个位点。1由固有的DNA曲率分开。H-NS在32 ℃以下协同结合这两个位点，但在37 ℃下不结合。virF启动子区域内的DNA超螺旋不影响H-NS结合，但H-NS介导的转录抑制是必要的。4 - 60 ℃之间的电泳分析表明，包含两个H-NS位点的virF启动子片段在类似于32 ℃的温度下经历特异性和温度依赖性构象转变。我们的研究结果表明，这种修改的DNA目标可能会调节H-NS分子之间的合作相互作用的virF启动子区域中的两个遥远的网站绑定，因此代表的物理基础H-NS依赖的热调节毒力基因的表达。
The expression of plasmid-borne virF of Shigella encoding a transcriptional regulator of the AraC family, is required to initiate a cascade of events resulting in activation of several operons encoding invasion functions. H-NS, one of the main nucleoid-associated proteins, controls the temperature-dependent expression of the virulence genes by repressing the in vivo transcription of virF only below a critical temperature (similar to 32 degrees C), This temperature-dependent transcriptional regulation has been reproduced in vitro and the targets of H-NS on the virF promoter were identified as two sites centred around -250 and -1 separated by an intrinsic DNA curvature. H-NS bound cooperatively to these two sites below 32 degrees C, but not at 37 degrees C. DNA supercoiling within the virF promoter region did not influence H-NS binding but was necessary for the H-NS-mediated transcriptional repression. Electrophoretic analysis between 4 and 60 degrees C showed that the virF promoter fragment, comprising the two H-NS sites, undergoes a specific and temperature-dependent conformational transition at similar to 32 degrees C. Our results suggest that this modification of the DNA target may modulate a cooperative interaction between H-NS molecules bound at two distant sites in the virF promoter region and thus represents the physical basis for the H-NS-dependent thermoregulation of virulence gene expression.