Said B, Shank R C
Department of Community and Environmental Medicine, University of California, Irvine 92717.
Nucleic Acids Res. 1991 Mar 25;19(6):1311-6. doi: 10.1093/nar/19.6.1311.
A synthetic DNA fragment was constructed to determine the effect of 5' and 3' neighbors of guanine runs on the binding of chemical carcinogens. Determinations were made on the relative intensity of reactivity between aflatoxin B1 or benzo(a)pyrene and methylnitrosourea or 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea with various guanine positions in an endlabeled DNA fragment of known sequence. After reaction, the fragments were depurinated to produce strand breaks to allow Maxam and Gilbert sequencing for guanine positions. Relative reaction intensities were compared densitometrically. 3' neighbors exerted greater influence on carcinogen binding than did 5' neighbors, the influence extended only to the adjacent guanine and depended upon the chemical nature of the carcinogen. In addition, the presence of one carcinogen adduct in the guanine run influenced the formation of a subsequent adduct when the DNA was exposed to a second carcinogen, and this effect also depended on the nature of the second carcinogen. The results suggest that DNA adduct formation in the presence of multiple carcinogens is more complicated than an additive mechanism would suggest.
构建了一个合成DNA片段，以确定鸟嘌呤链的5'和3'相邻碱基对化学致癌物结合的影响。对黄曲霉毒素B1或苯并(a)芘与甲基亚硝基脲或1-(2-氯乙基)-3-环己基-1-亚硝基脲之间的反应相对强度进行了测定，这些致癌物与已知序列的末端标记DNA片段中的不同鸟嘌呤位置发生反应。反应后，将片段脱嘌呤以产生链断裂，以便对鸟嘌呤位置进行Maxam和Gilbert测序。通过光密度法比较相对反应强度。3'相邻碱基对致癌物结合的影响比5'相邻碱基对更大，这种影响仅扩展到相邻的鸟嘌呤，并且取决于致癌物的化学性质。此外，当DNA暴露于第二种致癌物时，鸟嘌呤链中一种致癌物加合物的存在会影响随后加合物的形成，这种影响也取决于第二种致癌物的性质。结果表明，在多种致癌物存在的情况下，DNA加合物的形成比加成机制所表明的更为复杂。
