Rochman Mark, Aviv Michal, Glaser Gad, Muskhelishvili Georgi
Max Planck Institute for terrestrial Microbiology, Karl-von-Frisch-Strasse, D-35043 Marburg, Germany.
EMBO Rep. 2002 Apr;3(4):355-60. doi: 10.1093/embo-reports/kvf067. Epub 2002 Mar 15.
Binding of the Escherichia coli global transcription factor FIS to the upstream activating sequence (UAS) of stable RNA promoters activates transcription on the outgrowth of cells from stationary phase. Paradoxically, while these promoters require negative supercoiling of DNA for optimal activity, FIS counteracts the increase of negative superhelical density by DNA gyrase. We demonstrate that binding of FIS at the UAS protects the rrnA P1 promoter from inactivation at suboptimal superhelical densities. This effect is correlated with FIS-dependent constraint of writhe and facilitated untwisting of promoter DNA. We infer that FIS maintains stable RNA transcription by stabilizing local writhe in the UAS. These results suggest a novel mechanism of transcriptional regulation by a transcription factor acting as a local topological homeostat.
大肠杆菌全局转录因子FIS与稳定RNA启动子的上游激活序列(UAS)结合,可在细胞从稳定期生长时激活转录。矛盾的是,虽然这些启动子需要DNA的负超螺旋以实现最佳活性,但FIS会抵消DNA促旋酶引起的负超螺旋密度增加。我们证明,FIS在UAS处的结合可保护rrnA P1启动子在次优超螺旋密度下不被失活。这种效应与FIS依赖的扭曲约束以及启动子DNA解旋的促进相关。我们推断,FIS通过稳定UAS中的局部扭曲来维持稳定RNA转录。这些结果提示了一种由转录因子作为局部拓扑稳态调节器进行转录调控的新机制。