Institut für Genetik, Universität zu Köln, Zülpicher Str. 47a, 50674 Köln, Germany.
Mol Microbiol. 2012 Mar;83(6):1109-23. doi: 10.1111/j.1365-2958.2012.07993.x. Epub 2012 Feb 14.
The LysR-type transcription factor LeuO is involved in regulation of pathogenicity determinants and stress responses in Enterobacteriaceae, and acts as antagonist of the global repressor H-NS. Expression of the leuO gene is repressed by H-NS, and it is upregulated in stationary phase and under amino acid starvation conditions. Here, we show that the heterodimer of the FixJ/NarL-type transcription regulators RcsB and BglJ strongly activates expression of leuO and that RcsB-BglJ regulates additional loci. Activation of leuO by RcsB-BglJ is independent of the Rcs phosphorelay system. RcsB-BglJ binds to the leuO promoter region and activates one of two leuO promoters mapped in vivo. Moreover, LeuO antagonizes activation of leuO by RcsB-BglJ and acts as negative autoregulator in vivo and in vitro. Further, the H-NS paralogue StpA causes repression of leuO in addition to H-NS. Together, our data suggest a complex arrangement of regulatory elements and they indicate a feedback control mechanism of leuO expression.
LysR 型转录因子 LeuO 参与肠杆菌科中致病性决定因素和应激反应的调节，并且作为全局抑制剂 H-NS 的拮抗剂。LeuO 基因的表达受 H-NS 抑制，在静止期和氨基酸饥饿条件下上调。在这里，我们表明 FixJ/NarL 型转录调节因子 RcsB 和 BglJ 的异二聚体强烈激活 LeuO 的表达，并且 RcsB-BglJ 调节其他基因座。RcsB-BglJ 对 LeuO 的激活不依赖于 Rcs 磷酸传递系统。RcsB-BglJ 结合到 LeuO 启动子区域并激活体内定位的两个 LeuO 启动子之一。此外，LeuO 在体内和体外拮抗 RcsB-BglJ 对 LeuO 的激活，并作为负自调节因子。此外，H-NS 同源物 StpA 除了 H-NS 之外还会抑制 LeuO 的表达。总之，我们的数据表明存在一个复杂的调节元件排列，并表明 LeuO 表达的反馈控制机制。
