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外文期刊>The biochemical journal
>Competition between NarL-dependent activation and Fis-dependent repression controls expression from the Escherichia coli yeaR and ogt promoters
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Competition between NarL-dependent activation and Fis-dependent repression controls expression from the Escherichia coli yeaR and ogt promoters
pThe iEscherichia coli/i NarL protein is a global gene regulatory factor that activates transcription at many target promoters in response to nitrate and nitrite ions. Although most NarL-dependent promoters are also co-dependent on a second transcription factor, FNR protein, two targets, the iyeaR/i and iogt/i promoters, are activated by NarL alone with no involvement of FNR. Biochemical and genetic studies presented here show that activation of the iyeaR/i promoter is dependent on the binding of NarL to a single target centred at position ?43.5, whereas activation at the iogt/i promoter requires NarL binding to tandem DNA targets centred at position ?45.5 and ?78.5. NarL-dependent activation at both the iyeaR/i and iogt/i promoters is decreased in rich medium and this depends on Fis, a nucleoid-associated protein. DNase I footprinting studies identified Fis-binding sites that overlap the iyeaR/i promoter NarL site at position ?43.5, and the iogt/i promoter NarL site at position ?78.5, and suggest that Fis represses both promoters by displacing NarL. The iogt/i gene encodes an Osup6/sup-alkylguanine DNA alkyltransferase and, hence, this is the first report of expression of a DNA repair function being controlled by nitrate ions./p
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机译：>大肠埃希氏菌NarL蛋白是一种全球性的基因调节因子，可响应许多硝酸盐和亚硝酸盐离子而激活许多靶标启动子的转录。尽管大多数NarL依赖性启动子也共同依赖于第二转录因子FNR蛋白，但两个靶标 yeaR 和 ogt 启动子却被NarL单独激活，而没有FNR的参与。这里介绍的生化和遗传研究表明， yeaR 启动子的激活取决于NarL与以43.5位为中心的单个靶标的结合，而在 ogt 启动子上的激活要求NarL与以位置45.5和78.5为中心的串联DNA靶结合。在丰富培养基中，在 yeaR 和 ogt 启动子上的NarL依赖性激活都降低了，这取决于Fis（一种与核苷相关的蛋白）。 DNase I足迹研究确定了Fis结合位点，该位点与 yeaR 启动子NarL位点重叠在第43.5位，而 ogt 启动子NarL位点重叠在第78.5位，提示Fis通过取代NarL抑制两个启动子。 ogt 基因编码一个O 6 -烷基鸟嘌呤DNA烷基转移酶，因此，这是第一个报道DNA修复功能受硝酸根离子控制的报道。
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