Schmid S E, Daune M P, Fuchs R P
Proc Natl Acad Sci U S A. 1982 Jul;79(13):4133-7. doi: 10.1073/pnas.79.13.4133.
Plasmid DNA was modified in vitro to various extents with N-acetoxy-N-2-acetylaminofluorene or UV irradiation. The modified plasmid DNAs were then used to transform Escherichia coli strains having different repair capabilities. Both survival and mutagenesis frequencies of the plasmid were measured as a function of the number of lesions per plasmid molecule. The majority of N-2-acetylaminofluorene (AAF) adducts, like thymine dimers, were repaired by the excision (uvrA+-dependent) pathway. In rec+ strains, dose-dependent mutagenesis occurred in either AAF- or UV-modified plasmid DNA. This is in contrast with results obtained in recA- strains, in which only AAF adducts gave rise to a lower, but dose-dependent, mutagenesis frequency. In these recA- strains there was no UV mutagenesis. Unlike what is observed with phages, induction of the "SOS" functions by UV irradiation of the bacteria prior to transformation did not increase the survival or the mutagenesis of the plasmid.
用N-乙酰氧基-N-2-乙酰氨基芴或紫外线照射对质粒DNA进行不同程度的体外修饰。然后用修饰后的质粒DNA转化具有不同修复能力的大肠杆菌菌株。测定质粒的存活率和诱变频率与每个质粒分子损伤数的函数关系。大多数N-2-乙酰氨基芴(AAF)加合物,如胸腺嘧啶二聚体,通过切除(依赖uvrA+)途径进行修复。在rec+菌株中,AAF或紫外线修饰的质粒DNA中均发生剂量依赖性诱变。这与recA-菌株中获得的结果相反,在recA-菌株中,只有AAF加合物产生较低但剂量依赖性的诱变频率。在这些recA-菌株中没有紫外线诱变。与噬菌体不同,在转化前对细菌进行紫外线照射诱导“SOS”功能并不会增加质粒的存活率或诱变率。