Simić D, Vuković-Gacić B, Knezević-Vukcević J
Laboratory for Microbiology, Faculty of Biology, University of Belgrade, Studentski trg 3, 11000 Belgrade, Yugoslavia.
Mutat Res. 1998 Jun 18;402(1-2):51-7. doi: 10.1016/s0027-5107(97)00281-9.
Escherichia coli K12 assay-system is designed in order to detect bioantimutagens, agents preventing mutagenesis by modulation of DNA repair and replication. The assay is composed of four tests aimed at the detection of inhibition of spontaneous and induced mutations (Tests A and B) and at the estimation whether the anti-mutagenic agent acts by increasing the fidelity of DNA replication (Test B), by inhibition of SOS error prone repair (Test C), or by favoring error-free recombinational repair (Test D). In Test A, repair proficient strain and its uvrA counterpart are used for detection of spontaneous and UV-induced mutations, while in Test B mismatch repair deficient strains (mutH, mutS, mutL and uvrD) are used for amplified detection of spontaneous mutations caused by replication errors. In Test C, repair proficient strain carrying sfiA::lacZ fusion is used for measuring the level of SOS induction by monitoring the level of beta-galactosidase. In Test D, the strains carrying different recA alleles (recA+, recA730 and DeltarecA) are used for measuring intrachromosomal recombination between nonoverlapping deletions in duplicated lac operon, by monitoring Lac+ recombinants. The assay-system is validated with model bioantimutagens and used for detection of anti-mutagenic potential of different terpenoid fractions from sage (Salvia officinalis L.). Extract E1/3 of cultivated sage, distinguished from others by its high content of monoterpenoid camphor, reduces UV-induced mutagenesis in Test A, while it has no effect in Tests B and C. In Test D, it enhances intrachromosomal recombination in untreated and UV-irradiated recA+ and recA730 strains. The results suggest that the protective effect is due to stimulation of recombinational repair, similarly to coumarin. We speculate that monoterpenoids from sage enhance genetic recombination by intervening in a formation of RecA-DNA complex and channeling it into recombination reaction.
设计大肠杆菌K12检测系统是为了检测生物抗诱变剂，即通过调节DNA修复和复制来预防诱变的物质。该检测由四个试验组成，旨在检测自发突变和诱导突变的抑制情况（试验A和B），并评估抗诱变剂是否通过提高DNA复制的保真度（试验B）、抑制SOS易错修复（试验C）或促进无差错重组修复（试验D）来发挥作用。在试验A中，修复能力正常的菌株及其uvrA对应菌株用于检测自发突变和紫外线诱导的突变，而在试验B中，错配修复缺陷菌株（mutH、mutS、mutL和uvrD）用于放大检测由复制错误引起的自发突变。在试验C中，携带sfiA::lacZ融合基因的修复能力正常的菌株用于通过监测β-半乳糖苷酶的水平来测量SOS诱导水平。在试验D中，携带不同recA等位基因（recA+、recA730和DeltarecA）的菌株用于通过监测Lac+重组体来测量重复的乳糖操纵子中不重叠缺失之间的染色体内重组。该检测系统已用模型生物抗诱变剂进行了验证，并用于检测鼠尾草（Salvia officinalis L.）不同萜类组分的抗诱变潜力。栽培鼠尾草的提取物E1/3，以其高含量的单萜樟脑与其他提取物区分开来，在试验A中可降低紫外线诱导的诱变作用，而在试验B和C中无作用。在试验D中，它可增强未处理和紫外线照射的recA+和recA730菌株中的染色体内重组。结果表明，其保护作用是由于重组修复的刺激，类似于香豆素。我们推测，鼠尾草中的单萜类化合物通过干预RecA-DNA复合物的形成并将其引导至重组反应中来增强基因重组。
