Regulation by Nucleoid-Associated Proteins at the Escherichia coli nir Operon Promoter
Regulation by Nucleoid-Associated Proteins at the Escherichia coli nir Operon Promoter
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DOI：
10.1128/jb.01015-08
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发表时间：
2008-11-01
影响因子：
3.2
通讯作者：
Busby, Stephen J. W.
中科院分区：
文献类型：
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作者：
Browning, Douglas F.;Cole, Jeffrey A.;Busby, Stephen J. W.
大肠杆菌 K-12 nir 操纵子启动子可以通过富马酸和硝酸盐还原调节剂 (FNR) 与转录起始上游 -41.5 位置中心的位点结合来完全激活，并且这种激活通过整合宿主因子 (IHF) 和 Fis（反转刺激因子）蛋白的上游结合来调节。因此，转录起始通过 IHF 和 Fis 与位置 -88 (IHF I) 和位置 -142 (Fis I) 中心位点的结合而受到抑制，并通过 IHF 与位置 -115 (IHF II) 处的位点结合而激活。在这里，我们利用突变分析和生物化学来研究 IHF 和 Fis 在这些位点的作用。我们表明，IHF 和 Fis 的作用是位置依赖性的，并且 IHF II 的功能独立于 IHF I 和 Fis I。通过体外测定，我们报告 IHF 和 Fis 通过干扰 RNA 聚合酶结合来抑制转录起始。相关肠道细菌中 nir 启动子上游 IHF 和 Fis 结合位点的差异固定了厌氧生长条件下 nir 操纵子的表达水平。
The Escherichia coli K-12 nir operon promoter can be fully activated by binding of the regulator of fumarate and nitrate reduction (FNR) to a site centered at position -41.5 upstream of the transcript start, and this activation is modulated by upstream binding of the integration host factor (IHF) and Fis ( factor for inversion stimulation) proteins. Thus, transcription initiation is repressed by the binding of IHF and Fis to sites centered at position -88 (IHF I) and position -142 (Fis I) and activated by IHF binding to a site at position -115 (IHF II). Here, we have exploited mutational analysis and biochemistry to investigate the actions of IHF and Fis at these sites. We show that the effects of IHF and Fis are position dependent and that IHF II functions independently of IHF I and Fis I. Using in vitro assays, we report that IHF and Fis repress transcription initiation by interfering with RNA polymerase binding. Differences in the upstream IHF and Fis binding sites at the nir promoter in related enteric bacteria fix the level of nir operon expression under anaerobic growth conditions.