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首页> 外文期刊>Journal of Molecular Biology >REGULATION OF ESCHERICHIA COLI TOPA GENE TRANSCRIPTION - INVOLVEMENT OF A SIGMA(S)-DEPENDENT PROMOTER
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REGULATION OF ESCHERICHIA COLI TOPA GENE TRANSCRIPTION - INVOLVEMENT OF A SIGMA(S)-DEPENDENT PROMOTER

机译：大肠埃希氏菌大肠杆菌TOP基因转录的调控-依赖SIGMA的启动子的参与

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摘要

To investigate the regulation of Escherichia coli topA gene transcription, primer extension was employed to determine the transcription initiation sites from the chromosomal topA gene. When cells were grown in LB medium to log phase, four transcription initiation sites could be identified. Three of these sites corresponded to promoters P1, P2 and P4 previously characterized using topA-galK fusion plasmids. The P3 promoter that is active on the plasmid was not utilized at the chromosomal topA gene under the conditions employed. There was a new transcription initiation site corresponding to a new promoter Px1. When cells started to enter stationary phase, promoter Px1 gradually became the major transcription initiation site for topA, while transcription from promoters P2 and P4 decreased. In an E. coli mutant lacking sigma(s) (the rpoS gene product), the stationary phase specific sigma factor, the induction of transcription from promoter Px1 was abolished. In another mutant lacking H-NS activity, resulting in increased sigma(s) level in log-phase, the transcription from promoter Px1 during log phase was increased. Thus Px1 appeared to be regulated by sigma(s). Thee activity of promoter P1 on the chromosome increased during heat shock, consistent with the previous result obtained using the topA-galK fusion plasmid showing that P1 is a sigma(32)-dependent heat shock promoter. Promoters P2 and P4 were most likely to be recognized by sigma(70). The total level of topoisomerase I protein in the rpoS mutant was not reduced significantly in stationary phase due to increased transcription initiation from the other topA promoters. The utilization of multiple sigma factors for transcription initiation of topA could be important for adaptation of E. coli to change in growth conditions. (C) 1997 Academic Press Limited. [References: 42]
机译：为了研究大肠杆菌topA基因转录的调控，引物延伸用于确定染色体topA基因的转录起始位点。当细胞在LB培养基中生长至对数期时，可以鉴定出四个转录起始位点。这些位点中的三个对应于先前使用topA-galK融合质粒表征的启动子P1，P2和P4。在所用条件下，在质粒topA基因上未利用对质粒有活性的P3启动子。有一个对应于新启动子Px1的新转录起始位点。当细胞开始进入稳定期时，启动子Px1逐渐成为topA的主要转录起始位点，而启动子P2和P4的转录减少。在缺少sigma（rpoS基因产物），固定相特异性sigma因子的大肠杆菌突变体中，取消了启动子Px1转录的诱导。在另一个缺乏H-NS活性的突变体中，导致对数期的sigma水平增加，对数期启动子Px1的转录增加。因此，Px1似乎受sigma（s）的调节。在热激过程中，启动子P1在染色体上的活性增加，这与使用topA-galK融合质粒获得的先前结果一致，后者显示P1是Sigma（32）依赖性热激启动子。启动子P2和P4最有可能被sigma（70）识别。由于来自其他topA启动子的转录起始增加，rpoS突变体中拓扑异构酶I蛋白的总水平在固定相中并未显着降低。利用多个sigma因子进行topA转录起始可能对大肠杆菌适应生长条件的变化很重要。 （C）1997 Academic Press Limited。 [参考：42]

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