Tsung K, Brissette R E, Inouye M
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey at Rutgers, Piscataway 08854.
Proc Natl Acad Sci U S A. 1990 Aug;87(15):5940-4. doi: 10.1073/pnas.87.15.5940.
The OmpR binding sequence (OBS) in the upstream region of the ompF promoter of Escherichia coli was fused to 27 synthetic promoters. Transcription from a number of weak promoters, regardless of their sequences, was dramatically activated in the presence of OmpR, a transcriptional activator. In vivo DNA footprinting revealed that OmpR enhanced the binding of RNA polymerase to the promoters. This enhancement was essential for transcription of weak promoters, while OmpR binding to the OBS fused to a strong promoter was inhibitory for transcription. These results indicate that OmpR stabilizes the formation of an RNA polymerase-promoter complex, possibly a closed promoter complex, and that a transcription activator can serve not only as a positive but also as a negative regulator for gene expression.
将大肠杆菌ompF启动子上游区域的OmpR结合序列（OBS）与27个合成启动子融合。无论其序列如何，许多弱启动子的转录在转录激活因子OmpR存在的情况下都会显著激活。体内DNA足迹分析表明，OmpR增强了RNA聚合酶与启动子的结合。这种增强对于弱启动子的转录至关重要，而OmpR与融合到强启动子上的OBS结合则抑制转录。这些结果表明，OmpR稳定了RNA聚合酶-启动子复合物（可能是封闭启动子复合物）的形成，并且转录激活因子不仅可以作为基因表达的正调控因子，还可以作为负调控因子。
