Ramos L A, Lipman R, Tomasz M, Basu A K
Department of Chemistry, University of Connecticut, Storrs 06269, USA.
Chem Res Toxicol. 1998 Jan;11(1):64-9. doi: 10.1021/tx970163+.
To determine the mutagenic and genotoxic properties of the major guanine N2-adduct formed by the antitumor drug mitomycin C, we have synthesized a decanucleotide, d(TTACG[MC]TATCT), containing the adduct, which was inserted into a gapped bacteriophage M13 genome. Analysis of the constructed genome indicated that 41% ligation of the adducted 10-mer occurred on both sides of the gap, whereas the control 10-mer ligated with 34% efficiency. After transfection of the adducted single-stranded M13 DNA into Escherichia coli, the adduct was found to be highly genotoxic. Viability of the adducted genome in a repair-competent strain was only 7%, which increased to 12% and 15% upon induction of SOS by irradiating the cells with 254-nm light at 20 and 50 J/m2, respectively. Even lower viability of 2%, 4.6%, and 0.2% was observed in uvrA, uvrB, and uvrC strains, respectively, which increased up to 10-fold with SOS. An examination of the surviving phage populations revealed that the adduct was not detectably mutagenic. No mutants from the repair-proficient strain were detected after analysis of more than 2500 progeny phage. Only 0.2% of the survivors were mutants in the uvrA strain. It is uncertain, however, if they were induced by the adduct, since all the mutants showed untargeted mutations. We conclude that the major guanine N2-adduct formed by mitomycin C is cytotoxic but not appreciably mutagenic in E. coli.
为了确定抗肿瘤药物丝裂霉素C形成的主要鸟嘌呤N2加合物的诱变和基因毒性特性，我们合成了一种含有该加合物的十聚体d(TTACG[MC]TATCT)，并将其插入有缺口的噬菌体M13基因组中。对构建的基因组分析表明，加合的十聚体在缺口两侧的连接率为41%，而对照十聚体的连接效率为34%。将加合的单链M13 DNA转染到大肠杆菌后，发现该加合物具有高度基因毒性。在具有修复能力的菌株中，加合基因组的存活率仅为7%，分别用20 J/m2和50 J/m2的254 nm光照射细胞诱导SOS后，存活率分别提高到12%和15%。在uvrA、uvrB和uvrC菌株中观察到的存活率甚至更低，分别为2%、4.6%和0.2%，在诱导SOS后增加了10倍。对存活噬菌体群体的检查表明，该加合物没有可检测到的诱变作用。在分析了超过2500个后代噬菌体后，未检测到来自修复 proficient 菌株的突变体。在uvrA菌株中，只有0.2%的幸存者是突变体。然而，尚不确定它们是否由加合物诱导，因为所有突变体都显示出非靶向突变。我们得出结论，丝裂霉素C形成的主要鸟嘌呤N2加合物在大肠杆菌中具有细胞毒性，但没有明显的诱变作用。
