The Escherichia coli NarX/NarL two-component response-regulator system regulates gene expression in response to nitrate ions and the NarL protein is a global transcription factor, which activates transcript initiation at many target promoters. One such target, the E. coli ogt promoter, which controls the expression of an O6-alkylguanine-DNA-alkyltransferase, is dependent on NarL binding to two DNA targets centred at positions -44.5 and -77.5 upstream from the transcript start. Here, we describe ogt promoter derivatives that can be activated solely by NarL binding either at position -44.5 or position -77.5. We show that NarL can also activate the ogt promoter when located at position -67.5. We present data to argue that NarL-dependent activation of transcript initiation at the ogt promoter results from a direct interaction between NarL and a determinant in the C-terminal domain of the RNA polymerase α subunit. Footprinting experiments show that, at the -44.5 promoter, NarL and the C-terminal domain of the RNA polymerase α subunit bind to opposite faces of promoter DNA, suggesting an unusual mechanism of transcription activation. Our work suggests new organisations for activator-dependent transcription at promoters and future applications for biotechnology.

中文翻译：

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由NarL在大肠杆菌ogt启动子处激活。

大肠杆菌NarX / NarL两组分响应调节系统可调节基因表达，以响应硝酸根离子，而NarL蛋白是一种全局转录因子，可激活许多靶标启动子处的转录起始。一种这样的靶标，即控制O6-烷基鸟嘌呤-DNA-烷基转移酶表达的大肠杆菌Ogt启动子，取决于NarL与两个DNA靶标的结合，所述两个DNA靶标位于转录物起始上游的-44.5和-77.5位置。在这里，我们描述了ogt启动子衍生物，其可以通过在-44.5或-77.5位置处的NarL结合单独激活。我们显示，当位于-67.5位置时，NarL也可以激活ogt启动子。我们提出的数据认为，在ogt启动子上转录起始的NarL依赖性激活是由NarL与RNA聚合酶α亚基C末端结构域中的决定簇之间的直接相互作用引起的。足迹实验表明，在-44.5启动子处，NarL和RNA聚合酶α亚基的C末端结构域与启动子DNA的相对表面结合，提示转录激活的异常机制。我们的工作建议在启动子和未来生物技术应用中建立依赖于激活子的转录的新组织。提示转录激活的异常机制。我们的工作建议在启动子和生物技术的未来应用中建立依赖于激活子的转录的新组织。提示转录激活的异常机制。我们的工作建议在启动子和生物技术的未来应用中建立依赖于激活子的转录的新组织。