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：

---

由 NarL 在大肠杆菌 ogt 启动子处激活。


大肠杆菌 NarX/NarL 双组分响应调节系统可响应硝酸根离子调节基因表达，NarL 蛋白是一种全局转录因子，可激活许多目标启动子处的转录起始。其中一个靶标是大肠杆菌ogt启动子，它控制O6-烷基鸟嘌呤-DNA-烷基转移酶的表达，它依赖于NarL与位于转录起始上游-44.5和-77.5位置的两个DNA靶标的结合。在这里，我们描述了ogt启动子衍生物，其可以仅通过在位置-44.5或位置-77.5处的NarL结合来激活。我们发现当位于-67.5位时，NarL也可以激活ogt启动子。我们提供的数据表明，ogt 启动子处转录起始的 NarL 依赖性激活是由于 NarL 与 RNA 聚合酶 α 亚基 C 端结构域中的决定簇之间的直接相互作用所致。足迹实验表明，在 -44.5 启动子处，NarL 和 RNA 聚合酶 α 亚基的 C 端结构域结合到启动子 DNA 的相对面，这表明转录激活的不寻常机制。我们的工作提出了启动子处激活剂依赖性转录的新组织以及生物技术的未来应用。