Page J E, Pilcher A S, Yagi H, Sayer J M, Jerina D M, Dipple A
Chemistry of Carcinogenesis Laboratory, ABL-Basic Research Program, NCI-FCRDC, Frederick, Maryland 21702, USA.
Chem Res Toxicol. 1999 Mar;12(3):258-63. doi: 10.1021/tx980244l.
The four adducts that arise by cis ring opening of the four optically active benzo[a]pyrene diol epoxides by the exocyclic N6-amino group of deoxyadenosine were incorporated synthetically into each of two different oligonucleotide 16-mers, 5'-TTTXGAGTCTGCTCCC-3' [context I(A)] and 5'-CAGXTTTAGAGTCTGC-3' [context II(A)], at the X position. The eight resultant oligonucleotides were separately ligated into bacteriophage M13mp7L2 and replicated in Escherichia coli that had been SOS-induced, and the progeny were analyzed to evaluate the consequences of replication past these adducts. The presence of these adducts reduced plaque yields substantially. However, the progeny obtained exhibited high frequencies of base substitution mutation ranging from 9 to 68%, depending upon the individual adduct and the sequence context in which it was placed. For most of the adducts, A --> T transversion was the mutation found most frequently in either sequence context, and mutation frequencies in context I(A) were always substantially greater than those in context II(A). In context I(A), adducts with an R configuration at the site of nucleoside attachment were more mutagenic than those with an S configuration. In both sequence contexts that were studied, the cis adduct arising from the (7S,8R)-diol (9S,10R)-epoxide was the most mutagenic adduct. These findings clearly show that individual mutation frequencies are determined by the combined effects of both adduct structure and sequence context.
通过脱氧腺苷的环外N6-氨基对四种旋光性苯并[a]芘二醇环氧化物进行顺式开环产生的四种加合物，被合成引入到两条不同的16聚体寡核苷酸5'-TTTXGAGTCTGCTCCC-3' [上下文I(A)]和5'-CAGXTTTAGAGTCTGC-3' [上下文II(A)]的X位置。将得到的八条寡核苷酸分别连接到噬菌体M13mp7L2中，并在经SOS诱导的大肠杆菌中复制，对后代进行分析以评估越过这些加合物进行复制的后果。这些加合物的存在显著降低了噬菌斑产量。然而，获得的后代表现出9%至68%的高碱基替代突变频率，这取决于单个加合物及其所处的序列上下文。对于大多数加合物，A→T颠换是在任何一种序列上下文中最常发现的突变，并且上下文I(A)中的突变频率总是大大高于上下文II(A)中的突变频率。在上下文I(A)中，核苷连接位点具有R构型的加合物比具有S构型的加合物更具诱变性。在所研究的两种序列上下文中，由(7S,8R)-二醇(9S,10R)-环氧化物产生的顺式加合物是最具诱变性的加合物。这些发现清楚地表明，个体突变频率是由加合物结构和序列上下文的综合作用决定的。
