Moriya M, Zhang W, Johnson F, Grollman A P
Department of Pharmacological Sciences, State University of New York, Stony Brook 11794-8651.
Proc Natl Acad Sci U S A. 1994 Dec 6;91(25):11899-903. doi: 10.1073/pnas.91.25.11899.
A single-stranded shuttle vector containing a single 3,N4-etheno-2'-deoxycytidine (epsilon dC) or 1,N2-(1,3-propano)-2'- deoxyguanosine (PdG) DNA adduct was used to investigate translesional DNA synthesis in Escherichia coli and simian kidney (COS) cells. The presence of either exocyclic adduct was associated with reduced numbers of transformants. In E. coli, this inhibitory effect could be overcome partially by irradiating cells with UV light before transformation. Translesional synthesis past both exocyclic lesions was accompanied by targeted mutations. For PdG, the primary mutagenic events observed in both hosts were PdG-->T transversions; in preirradiated E. coli, PdG-->A transitions were also observed. The targeted mutation frequency for single-stranded DNA that contained PdG was 100% in nonirradiated E. coli, 68% in preirradiated cells, and 8% in COS cells. In contrast, the targeted mutation frequency for single-stranded DNA that contained epsilon dC was 2% in nonirradiated E. coli, 32% in preirradiated cells, and 81% in COS cells. The primary mutations generated by epsilon dC in both E. coli and COS cells were epsilon dC-->A and epsilon dC-->T base substitutions. These observations appear to reflect the variable specificity of DNA replication complexes in incorporating bases opposite certain adducts. We conclude that DNA synthesis past the same DNA adduct can have strikingly different consequences in bacteria and mammalian cells, underscoring the importance of establishing the intrinsic mutagenic potential of DNA adducts in mammalian cells.
使用一种含有单个3,N4-乙撑-2'-脱氧胞苷（εdC）或1,N2-(1,3-丙二烯)-2'-脱氧鸟苷（PdG）DNA加合物的单链穿梭载体，来研究大肠杆菌和猴肾（COS）细胞中的跨损伤DNA合成。任何一种外环加合物的存在都与转化子数量减少有关。在大肠杆菌中，这种抑制作用可通过在转化前用紫外线照射细胞而部分克服。跨越这两种外环损伤的跨损伤合成伴随着靶向突变。对于PdG，在两种宿主中观察到的主要诱变事件是PdG→T颠换；在预先照射的大肠杆菌中，还观察到PdG→A转换。在未照射的大肠杆菌中，含有PdG的单链DNA的靶向突变频率为100%，在预先照射的细胞中为68%，在COS细胞中为8%。相比之下，含有εdC的单链DNA的靶向突变频率在未照射的大肠杆菌中为2%，在预先照射的细胞中为32%，在COS细胞中为81%。εdC在大肠杆菌和COS细胞中产生的主要突变是εdC→A和εdC→T碱基替换。这些观察结果似乎反映了DNA复制复合物在掺入与某些加合物相对的碱基时的可变特异性。我们得出结论，跨越相同DNA加合物的DNA合成在细菌和哺乳动物细胞中可能产生截然不同的后果，这突出了确定DNA加合物在哺乳动物细胞中的内在诱变潜力的重要性。
