Bokal A J, Ross W, Gourse R L
Department of Bacteriology, University of Wisconsin-Madison 53706.
J Mol Biol. 1995 Jan 20;245(3):197-207. doi: 10.1006/jmbi.1994.0016.
The E. coli rrnB P1 promoter owes its strength, in part, to the transcriptional activator protein FIS. FIS binds to three sites upstream of the RNA polymerase (RNAP) binding site and increases transcription in vivo four to ten-fold. In this report, hydroxyl radical and DMS footprinting analyses show that FIS binds to its three sites along one side of the DNA helix, and that FIS bound at the promoter-proximal site (site I) and RNAP bound at the promoter are in close proximity. The binding of FIS at site I and RNAP at the promoter are mutually cooperative. These observations support a model for direct interaction between the FIS protein bound at site I and RNAP in transcription activation at rrnB P1. We also find that FIS does not bind cooperatively to its three sites upstream of rrnB P1, and that the relatively small activation associated with FIS bound at sites II and III does not result indirectly by facilitation of binding of FIS to site I.
大肠杆菌rrnB P1启动子的强度部分归因于转录激活蛋白FIS。FIS与RNA聚合酶（RNAP）结合位点上游的三个位点结合，并在体内将转录提高4至10倍。在本报告中，羟基自由基和二甲基亚砜足迹分析表明，FIS沿着DNA螺旋的一侧与其三个位点结合，并且结合在启动子近端位点（位点I）的FIS与结合在启动子上的RNAP紧密相邻。FIS在位点I的结合与RNAP在启动子上的结合相互协同。这些观察结果支持了一种模型，即结合在位点I的FIS蛋白与rrnB P1转录激活中的RNAP之间存在直接相互作用。我们还发现，FIS不会与其在rrnB P1上游的三个位点协同结合，并且与结合在位点II和III的FIS相关的相对较小的激活作用并非通过促进FIS与位点I的结合而间接产生。
