Effect of isopropyl-beta-D-thiogalactopyranosid induction of the lac operon on the specificity of spontaneous and doxorubicin-induced mutations in Escherichia coli.
Effect of isopropyl-beta-D-thiogalactopyranosid induction of the lac operon on the specificity of spontaneous and doxorubicin-induced mutations in Escherichia coli.
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异丙基-β-D-硫代吡喃半乳糖诱导乳糖操纵子对大肠杆菌自发突变和阿霉素诱导突变的特异性的影响。
DOI：
10.1002/em.2850260104
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发表时间：
1995
影响因子：
2.8
通讯作者：
Sedwick,WD
中科院分区：
文献类型：
--
作者：
Veigl,ML;Donover,SP;Anderson,RD;Akst,L;Sedwick,CE;Sedwick,WD
以前以F lacl/lacO为内源性基因靶点的阿霉素诱导突变研究主要集中在靶基因lacO区3′端大缺失的性质。本研究认为，这些缺失的分布上的Lac阻遏物结合的影响。报告了在异丙基-β-D-硫代半乳糖苷（IPTG;一种阻止阻遏物结合tolacO的诱导剂）解除Lac阻遏的条件下分离的突变体的大肠杆菌uvrB-中自发和多柔比星诱导的dandlacO突变的DNA序列水平分析结果。在存在和不存在IPTG的情况下，从多柔比星处理的培养物中分离的缺失的位置表明，多柔比星优先将缺失端点集中在邻近其结合位点的lacO中，并且这些缺失端点的分布不受Lac阻遏物结合的调节。相反，自发缺失端点优先聚集在环中远离回文序列的条件下的镇压。然而，当Lac阻遏物/lacO结合复合物被IPTG解离时，自发的3′-缺失端点按比例分布在lac Opalindrome的假定茎和环之间，IPTG诱导Lac操纵子的唯一最显著的效果是消除了+6 inlacO处T：A→C：G转换的“热点”。这种碱基取代“热点”占受抑制细菌培养物中总阿霉素诱导突变体的17.6%和自发突变体的16.4%，占在IPTG存在下进行的类似实验中总突变的约1%。在+6位的大量突变仅在不存在IPTG的情况下由多柔比星诱导，然而，这表明在该转变“热点”处的多柔比星诱导的和自发的突变均由Lac阻遏物结合tolacO介导。© 1995 Wiley利斯公司
Previous studies of doxorubicin‐induced mutations employingF lacl/lacOas an endogenous gene target have focused on properties of large deletions with 3′ endpoints residing in thelacOregion of the target gene. This study considers the influence of Lac represser binding on the distribution of these deletions. Results of the DNA sequence level analysis of spontaneous and doxorubicin‐inducedi−dandlacOmutations inEscherichia coli uvrB−are reported for mutants isolated under conditions where Lac repression is relieved by isopropyl‐β‐D‐thioga‐lactopyranosid (IPTG; an inducer that prevents represser binding tolacO). The location of deletions isolated from doxorubicin‐treated cultures in the presence and absence of IPTG suggests that doxoru‐bicin preferentially focuses deletion endpoints adjacent to its binding sites inlacOand that the distribution of these deletion endpoints is not modulated by Lac represser binding. In contrast, spontaneous deletion endpoints are preferentially clustered in the loop away from the palindromic sequences under conditions of repression. However, when the Lac repressor/lacObinding complex is dissociated by IPTG, the spontaneous 3′‐deletion endpoints distribute proportionally between the putative stem and loop of thelacOpalindrome.The single most striking effect of IPTG induction of the Lac operon was elimination of a “hot spot” for T:A→C:G transitions at position +6 inlacO. This base substitution “hot spot,” which accounted for 17.6% of total doxorubicin‐induced mutants and 16.4% of spontaneous mutants in repressed bacterial cultures, accounted for approximately 1% of total mutations in similar experiments carried out in the presence of IPTG. A large number of mutations at the +6 position are induced only by doxorubicin in the absence of IPTG, however, suggesting that both doxorubicin‐induced and spontaneous mutation at this transition “hot spot” are mediated by Lac represser binding tolacO. © 1995 Wiley‐Liss, Inc.