MUTATIONS IN THE GENE CODING FOR ESCHERICHIA-COLI DNA TOPOISOMERASE-I AFFECT TRANSCRIPTION AND TRANSPOSITION
MUTATIONS IN THE GENE CODING FOR ESCHERICHIA-COLI DNA TOPOISOMERASE-I AFFECT TRANSCRIPTION AND TRANSPOSITION
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DOI：
10.1073/pnas.78.5.2747
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发表时间：
1981-01-01
期刊：
影响因子：
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通讯作者：
WANG, JC
中科院分区：
文献类型：
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作者：
STERNGLANZ, R;DINARDO, S;WANG, JC
突变的顶部，结构基因的E。coliDNA拓扑异构酶I，并定位于染色体上cysB附近28分钟。携带顶端基因缺失的菌株是存活的。顶部突变对转录和转座产生多效性效应。缺乏DNA拓扑异构酶I的突变体具有更快的诱导速率和更高水平的分解产物敏感性酶，包括β-葡聚糖酶和β-葡聚糖酶。半乳糖苷酶。这种通过顶部突变的转录的一般激活可以归因于当拓扑异构酶活性被消除时体内DNA的负超螺旋性的增加。转座的频率Tn 5，转座子携带卡那霉素抗性，减少了40或更多的因素在顶部的突变体。直接或间接的作用的拓扑异构酶在转位进行了讨论。Tn 3的转座频率不依赖于顶部。基于E. coli top突变体，似乎最初在鼠伤寒沙门氏菌中研究的supX基因（Dubnau和Margolin，（1972））可能是DNA拓扑异构酶I的结构基因。
Mutations in top, the structural gene for E. coli DNA topoisomerase I, were identified and mapped at 28 min on the chromosome, near cysB. Strains carrying deletions of the top gene are viable. The top mutations exert pleiotropic effects on transcription and transposition. Mutants lacking DNA topoisomerase I have a more rapid rate of induction and a higher level of catabolite-sensitive enzymes including tryptophanase and .beta.-galactosidase. This general activation of transcription by top mutations can be attributed to an increase in the negative superhelicity of the DNA in vivo when the topoisomerase activity is abolished. The frequency of transposition of Tn5, a transposon carrying kanamycin resistance, is decreased by a factor of 40 or more in top mutants. A direct or indirect role of the topoisomerase in transposition is discussed. The transposition frequency of Tn3 is not dependent on top. Based on the studies of the E. coli top mutants, it appears that the supX gene, which was originally studied in Salmonella typhimurium (Dubnau and Margolin, (1972)) is likely to be the structural gene for DNA topoisomerase I.