Expression of accumulated capacity for initiation of chromosome and minichromosome replication in dnaA mutants of Escherichia coli.
Expression of accumulated capacity for initiation of chromosome and minichromosome replication in dnaA mutants of Escherichia coli.
复制标题
大肠杆菌 dnaA 突变体中染色体和微染色体复制起始积累能力的表达。
DOI：
10.1128/jb.154.3.1371-1380.1983
复制
发表时间：
1983
影响因子：
3.2
通讯作者：
Helmstetter,CE
中科院分区：
文献类型：
--
作者：
LaDuca,RJ;Helmstetter,CE
研究了温度敏感型大肠杆菌dna突变体在允许和非允许温度下的染色体和小染色体复制。[14C]胸苷摄取的周期性被检测到，在中等温度下培养接近生长的指数晚期-早期稳定期。将培养物暴露于营养上移引起染色体复制的刺激，并与新一轮复制的快速启动有关，这与暴露于氯霉素后观察到的情况非常相似。添加利福平也会引起刺激，但程度要小得多。染色体复制的诱导起始分两波进行，就像把培养物简单地转移到允许的温度一样。在中等温度下，添加氯霉素也刺激了小染色体的复制，进一步证明了对氯霉素处理有反应的染色体区域位于oriC附近。这些发现与Orr等人提出的结论一致，即氯霉素诱导的起始是dna基因产物参与起始转录步骤的结果。结果还表明，dnaA基因产物的活性通常不参与控制染色体复制起始频率。
Chromosome and minichromosome replication were examined in temperature-sensitive dnaA mutants of Escherichia coli growing at temperatures between permissive and nonpermissive. Periodicities in [14C]thymidine uptake were detected as cultures incubated at intermediate temperatures approached late exponential-early stationary phase of growth. Exposure of the cultures to a nutritional shift-up caused a stimulation of chromosome replication associated with a rapid initiation of new rounds of replication, very similar to that observed after exposure to chloramphenicol. Addition of rifampin also caused a stimulation, but to a much lesser extent. The induced initiations of chromosome replication took place in two waves, as was the case when the cultures were simply shifted to permissive temperature. Minichromosomes were also stimulated to replicate by the addition of chloramphenicol at intermediate temperatures, providing further evidence that the chromosomal region which responded to the chloramphenicol treatment was in the vicinity of oriC. The findings are consistent with the conclusion that the initiations induced by chloramphenicol are consequences of the involvement of the dnaA gene product in a transcriptional step at initiation, as suggested by Orr et al. The results also suggest that the activity of the dnaA gene product is not normally involved in controlling the frequency of initiation of chromosome replication.