Koh Y S, Chung W H, Lee J H, Roe J H
Department of Microbiology, Cheju National University Medical School, Korea.
Mol Gen Genet. 1999 Mar;261(2):374-80. doi: 10.1007/s004380050978.
The ribA gene, encoding GTP cyclohydrolase II in Escherichia coli, is a member of the soxRS regulon, which is induced by superoxide-generating agents. By evaluating lacZ expression driven by the ribA promoter carrying different lengths of upstream region in a monolysogen, we found that the superoxide-responsive element resides between 56 and 94 nucleotides upstream of the transcriptional start site. Purified SoxS protein bound to this region and protected nucleotides between positions -80 and -58 from degradation by DNase I. This region contains a putative SoxS-binding sequence (soxbox) in reverse orientation. The SoxS protein interacted specifically with four guanine residues within the soxbox sequence, as demonstrated by methylation interference analysis. These results clearly indicate that SoxS binds to the reversed soxbox sequence in the ribA gene, while in other known genes of the soxRS regulon it binds to the normally oriented soxbox. Possible modes of interaction between SoxS and RNA polymerase are discussed.
在大肠杆菌中编码GTP环水解酶II的ribA基因是soxRS调节子的成员，该调节子由产生超氧化物的试剂诱导。通过评估在单溶原菌中由携带不同长度上游区域的ribA启动子驱动的lacZ表达，我们发现超氧化物反应元件位于转录起始位点上游56至94个核苷酸之间。纯化的SoxS蛋白结合到该区域，并保护-80至-58位之间的核苷酸不被DNase I降解。该区域包含一个反向的假定SoxS结合序列（soxbox）。甲基化干扰分析表明，SoxS蛋白与soxbox序列内的四个鸟嘌呤残基特异性相互作用。这些结果清楚地表明，SoxS与ribA基因中的反向soxbox序列结合，而在soxRS调节子的其他已知基因中，它与正常方向的soxbox结合。文中还讨论了SoxS与RNA聚合酶之间可能的相互作用模式。
