Gordia S, Gutierrez C
Laboratoire de Microbiologie et Genetique Moleculaire, Toulouse, France.
Mol Microbiol. 1996 Feb;19(4):729-36. doi: 10.1046/j.1365-2958.1996.418945.x.
The transcription of the osmotically inducible gene osmC of Escherichia coli is initiated by two overlapping promoters, osmCp1 and osmCp2. The existence of these two promoters was confirmed by site-directed mutagenesis. osmC transcription is regulated by the growth phase. In a medium of low osmotic pressure, expression of osmC is induced at the onset of decelerating phase and continues during the beginning of stationary phase. At elevated osmotic pressure, the induction occurs somewhat earlier during growth. Both promoters are repressed during early exponential phase. osmCp2 is induced during entry into stationary phase. Transcription from osmCp1, which is approximately 10-fold lower than that of osmCp2 in rich medium, starts during the mid-log phase and stops in early stationary phase. In the absence of sigmaS, the stationary-phase sigma factor encoded by rpoS, osmCp2 expression is much reduced while expression of osmCp1 is unaffected. As a consequence, the regulation of osmC as a function of growth is at least partially independent of sigmaS.
大肠杆菌渗透诱导基因osmC的转录由两个重叠的启动子osmCp1和osmCp2起始。通过定点诱变证实了这两个启动子的存在。osmC转录受生长阶段调控。在低渗透压培养基中，osmC的表达在减速期开始时被诱导，并在稳定期开始阶段持续。在渗透压升高时，诱导在生长过程中稍早发生。两个启动子在指数早期阶段均被抑制。osmCp2在进入稳定期时被诱导。osmCp1的转录在对数中期开始，在稳定早期停止，在丰富培养基中其转录水平比osmCp2低约10倍。在没有由rpoS编码的稳定期σ因子sigmaS的情况下，osmCp2的表达大幅降低，而osmCp1的表达不受影响。因此，osmC作为生长函数的调控至少部分独立于sigmaS。
