Verbeek H, Nilsson L, Bosch L
Department of Biochemistry, Leiden University, Gorlaeus Laboratories, The Netherlands.
Biochimie. 1991 Jun;73(6):713-8. doi: 10.1016/0300-9084(91)90051-2.
The upstream activator sequence (UAS) of the thrU(tufB) operon, which is the target of the trans-activating protein FIS, has a bent structure. Here we show that the center of bending lies around position -95, between the two FIS-binding regions. Studies with fis+ and fis- cells show that FIS-induced bending of the UAS plays a major role in the trans-activation of the thrU(tufB) operon. This has been concluded from the finding that insertions of small DNA segments, comprising less than one or two complete helix turns, in the junction of the UAS and the RNA polymerase-binding site reduce transcription significantly. Partial restoration of transcriptional activity occurs when one or more full helix turns are inserted. These data are in line with but do not prove that a direct interaction between FIS and RNA polymerase is involved in trans-activation. A role of bending per se resulting from FIS/DNA interaction cannot be excluded.
苏氨酸操纵子（thrU[tufB]）的上游激活序列（UAS）是反式激活蛋白FIS的作用靶点，具有弯曲结构。我们在此表明，弯曲中心位于两个FIS结合区域之间的约-95位附近。对fis+和fis-细胞的研究表明，FIS诱导的UAS弯曲在thrU[tufB]操纵子的反式激活中起主要作用。这一结论是基于以下发现：在UAS与RNA聚合酶结合位点的连接处插入小于一或两个完整螺旋圈的小DNA片段会显著降低转录。当插入一个或多个完整螺旋圈时，转录活性会部分恢复。这些数据与FIS和RNA聚合酶之间的直接相互作用参与反式激活一致，但并未证明这一点。不能排除FIS/DNA相互作用导致的弯曲本身所起的作用。
