Weiner L, Brissette J L, Ramani N, Model P
Laboratory of Genetics, Rockefeller University, New York, NY 10021, USA.
Nucleic Acids Res. 1995 Jun 11;23(11):2030-6. doi: 10.1093/nar/23.11.2030.
The phage shock protein operon (pspABCE) of Escherichia coli is strongly induced by adverse environmental conditions. Expression is controlled principally at the transcriptional level, and transcription is directed by the sigma factor sigma 54. PspB and PspC are required for high-level psp expression during osmotic shock, ethanol treatment and f1 infection, but heat-induced expression is independent of these proteins. We report here that the promoter region contains an upstream activation sequence (UAS) that is required for psp induction and has the enhancer-like ability to activate at a distance. A DNA-binding activity is detected in crude protein extracts that is dependent on the UAS and induced by heat shock. We further show that integration host factor (IHF) binds in vitro to a site between the UAS and sigma 54 recognition sequence. In bacteria lacking IHF, psp expression is substantially reduced in response to high temperature and ethanol. During osmotic shock in contrast, psp expression is only weakly stimulated by IHF, and IHF mutants can strongly induce the operon. The dependence of psp expression on IHF varies with the inducing condition, but does not correlate with dependence on PspB and PspC, indicating distinct, agent-specific activation mechanisms.
大肠杆菌的噬菌体休克蛋白操纵子（pspABCE）在不利环境条件下会被强烈诱导。其表达主要在转录水平受到控制，转录由σ因子σ54指导。在渗透休克、乙醇处理和f1感染期间，高水平的psp表达需要PspB和PspC，但热诱导表达不依赖于这些蛋白质。我们在此报告，启动子区域包含一个上游激活序列（UAS），它是psp诱导所必需的，并且具有远距离激活的增强子样能力。在粗蛋白提取物中检测到一种依赖于UAS且受热休克诱导的DNA结合活性。我们进一步表明，整合宿主因子（IHF）在体外与UAS和σ54识别序列之间的一个位点结合。在缺乏IHF的细菌中，高温和乙醇刺激下psp的表达会大幅降低。相比之下，在渗透休克期间，IHF对psp表达的刺激较弱，并且IHF突变体可以强烈诱导该操纵子。psp表达对IHF的依赖性随诱导条件而变化，但与对PspB和PspC的依赖性无关，这表明存在不同的、特定因子的激活机制。
