Genetic evidence of pre-recruitment as the mechanism of transcription activation by SoxS of Escherichia coli:: The dominance of DNA binding mutations of SoxS
Genetic evidence of pre-recruitment as the mechanism of transcription activation by SoxS of Escherichia coli:: The dominance of DNA binding mutations of SoxS
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DOI：
10.1016/j.jmb.2004.09.007
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发表时间：
2004-11-12
影响因子：
5.6
通讯作者：
Wolf, RE
中科院分区：
文献类型：
--
作者：
Griffith, KL;Wolf, RE
SoxS，大肠杆菌超氧化物（SoxRS）调节子的直接转录激活因子，显示出几个不寻常的特征，这表明它是不太可能激活转录的ususal招聘机制。因此，内源性产生超氧化物并由此引发防御反应的试剂引发SoxS的从头合成，并且由于SoxS结合位点是高度简并的，每个细胞的SoxS结合位点的数量远远超过每个细胞的SoxS分子的数量。为了解释SoxRS系统的这些独特特征，我们提出了“预募集”作为SoxS激活调节子基因转录的机制。在预募集中，新合成的SoxS分子与溶液中的RNA聚合酶形成二元复合物。这些复合物提供信息内容，以允许每个细胞2500个SoxS分子扫描每个细胞65，000个SoxS结合位点，以获得每个细胞200个SoxS依赖性启动子内的结合位点。作为SoxS是否通过募集或预募集激活转录的测试，我们确定了赋予缺陷DNA结合的SoxS突变的显性关系。我们发现soxS DNA结合突变对野生型等位基因是显性的，这一结果与招募前假设一致，但与通过招募发挥功能的激活剂的预期相反。此外，虽然通过募集发挥功能的激活剂的阳性对照突变通常是显性的，但soxS阳性对照突变不是。最后，以SoxRS系统为例，我们讨论了通过预募集功能的转录激活因子的严格调控的生理要求。(C)2004爱思唯尔有限公司保留所有权利。
SoxS, the direct transcriptional activator of the Escherichia coli superoxide (SoxRS) regulon, displays several unusual characteristics which suggest that it is unlikely to activate transcription by the ususal recruitment mechanism. Thus, agents that generate superoxide endogenously and thereby provoke the defense response elicit the de novo synthesis of SoxS, and with the SoxS binding site being highly degenerate, the number of SoxS binding sites per cell far exceeds the number of SoxS molecules per cell. To account for these distinctive features of the SoxRS system, we proposed "pre-recruitment" as the mechanism by which SoxS activates transcription of the regulon's genes. In pre-recruitment, newly synthesized SoxS molecules form binary complexes with RNA polymerase in solution. These complexes provide the information content to allow the 2500 molecules of SoxS per cell to scan the 65,000 SoxS binding sites per cell for the 200 binding sites per cell that reside within SoxS-dependent promoters. As a test of whether SoxS activates transcription by recruitment or pre-recruitment, we determined the dominance relationships of SoxS mutations conferring defective DNA binding. We found that soxS DNA binding mutations are dominant to the wild-type allele, a result consistent with the pre-recruitment hypothesis, but opposite to that expected for an activator that functions by recruitment. Moreover, whereas positive control mutations of activators functioning by recruitment are usually dominant, a soxS positive control mutation was not. Lastly, with the SoxRS system as an example, we discuss the physiological requirement for stringent regulation of transcriptional activators that function by pre-recruitment. (C) 2004 Elsevier Ltd. All rights reserved.