Barnard Anne M L, Green Jeffrey, Busby Stephen J W
School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
J Bacteriol. 2003 Oct;185(20):5993-6004. doi: 10.1128/JB.185.20.5993-6004.2003.
FNR is an Escherichia coli transcription factor that regulates the transcription of many genes in response to anaerobiosis. We have constructed a series of artificial FNR-dependent promoters, based on the melR promoter, in which a consensus FNR binding site was centered at position -41.5 relative to the transcription start site. A second consensus FNR binding site was introduced at different upstream locations, and promoter activity was assayed in vivo. FNR can activate transcription from these promoters when the upstream FNR binding site is located at many different positions. However, sharp repression is observed when the upstream-bound FNR is located near positions -85 or -95. This repression is relieved by the FNR G74C substitution mutant, previously identified as being defective in transcription repression at the yfiD promoter. A parallel series of artificial FNR-dependent promoters, carrying a consensus FNR binding site at position -61.5 and a second upstream DNA site for FNR, was also constructed. Again, promoter activity was repressed by FNR when the upstream-bound FNR was located at particular positions.
FNR是一种大肠杆菌转录因子，可响应无氧状态调节许多基因的转录。我们基于melR启动子构建了一系列人工FNR依赖性启动子，其中一个共有FNR结合位点位于相对于转录起始位点的-41.5位置处。在不同的上游位置引入了第二个共有FNR结合位点，并在体内测定了启动子活性。当上游FNR结合位点位于许多不同位置时，FNR可激活这些启动子的转录。然而，当上游结合的FNR位于-85或-95位置附近时，会观察到明显的抑制作用。这种抑制作用可被FNR G74C替代突变体解除，该突变体先前被鉴定为在yfiD启动子的转录抑制方面存在缺陷。还构建了一系列平行的人工FNR依赖性启动子，在-61.5位置带有一个共有FNR结合位点以及一个用于FNR的第二个上游DNA位点。同样，当上游结合的FNR位于特定位置时，启动子活性会被FNR抑制。
