Gomada M, Inouye S, Imaishi H, Nakazawa A, Nakazawa T
Department of Biochemistry, Yamaguchi University School of Medicine, Japan.
Mol Gen Genet. 1992 Jun;233(3):419-26. doi: 10.1007/BF00265439.
Transcription from the promoter of a positive regulatory gene, xylS, on the TOL plasmid of Pseudomonas putida is activated by another positive regulator, XylR, in the presence of m-xylene and is dependent on RNA polymerase containing the NtrA protein (sigma 54). Deletion analysis of the upstream region of the xylS gene revealed an upstream regulatory sequence (URS), located between 145 and 188 bp upstream from the transcription start site. The URS is active in either orientation and can be placed 3.9 kb further upstream without loss of activity. Dependence of activation on helical periodicity was observed in the region between the URS and the promoter of the xylS gene, suggesting DNA loop formation between these two sites, which are located about 100 bp apart. The expression of xylR was autogenously repressed by XylR protein. This autogenous repression is decreased in an NtrA- background, irrespective of the presence of the xylS promoter in cis, indicating that NtrA protein, or NtrA-containing RNA polymerase that is not bound to the xylS promoter, is involved in the binding of XylR protein to the URS.
恶臭假单胞菌TOL质粒上正向调节基因xylS的启动子转录，在间二甲苯存在的情况下，被另一个正向调节因子XylR激活，并且依赖于含有NtrA蛋白（σ54）的RNA聚合酶。对xylS基因上游区域的缺失分析揭示了一个上游调节序列（URS），位于转录起始位点上游145至188 bp之间。URS在任一方向上均有活性，并且可以放置在上游3.9 kb处而不丧失活性。在URS和xylS基因启动子之间的区域观察到激活对螺旋周期性的依赖性，这表明这两个位点之间形成了DNA环，它们相距约100 bp。xylR的表达被XylR蛋白自身抑制。在NtrA-背景中，这种自身抑制作用减弱，无论顺式中是否存在xylS启动子，这表明NtrA蛋白或未与xylS启动子结合的含NtrA的RNA聚合酶参与了XylR蛋白与URS的结合。
