Sequence distribution of acetaldehyde-derived N2-Ethyl-dG adducts along duplex DNA
Sequence distribution of acetaldehyde-derived N2-Ethyl-dG adducts along duplex DNA
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DOI：
10.1021/tx7001146
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发表时间：
2007-10-01
影响因子：
4.1
通讯作者：
Tretyakova, Natalia
中科院分区：
文献类型：
--
作者：
Matter, Brock;Guza, Rebecca;Tretyakova, Natalia
乙醛（AA）是乙醇的主要代谢物，可能与饮用酒精饮料相关的胃肠道癌症风险增加有关。此外，AA是烟草烟雾中含量最多的致癌物之一，在实验动物中诱发呼吸道肿瘤。AA与DNA的结合在dG的外环氨基上诱导出n -2-乙基-dG的希夫碱加合物，这在核苷水平上是可逆的，但可以通过还原成n -2-乙基-dG来稳定。对HPRT报告基因和p53肿瘤抑制基因的诱变研究表明，AA能够诱导G -> A转位和A -> T转位，以及移码和剪接突变。aa诱导的点突变在5‘- agg -3’三核苷酸上最为突出，可能是序列特异性加合物形成、错配和/或修复的结果。然而，DNA序列对乙醛加合物形成的偏好以前没有被研究过。在本研究中，我们采用了实验室开发的稳定同位素标记- hplc - esi +-MS/MS方法，分析了乙醛衍生的n -2-乙基- dg加合物沿双链寡核苷酸的分布，这些寡核苷酸代表了两个突出的肺癌突变“热点”及其周围的DNA序列。将1,7，NH2-N-15-2-C-13-dG放置在K-ras原癌基因和p53抑癌基因衍生的DNA双链中的特定位置，然后进行AA处理和NaBH3CN还原，将n -2-乙基- dg转化为n -2-乙基- dg。采用毛细管高效液相色谱- esi +-质谱/质谱法定量了来自同位素标记和未标记的鸟嘌呤核碱基的n -2-乙基- dg加合物，并绘制了沿DNA双链形成的加合物图谱。我们发现n -2-乙基- dg加合物的形成仅受局部序列背景的微弱影响，而在CG二核苷酸中存在5-甲基leytoine时则略有增加。这些结果与其他烟草致癌物质- dna加合物沿K-ras和p53衍生双链的序列选择性形成以及苯并[a]芘二醇环氧化物和丙烯醛对内源性甲基化CG二核苷酸的优先修饰形成对比。
Acetaldehyde (AA) is the major metabolite of ethanol and may be responsible for an increased gastrointestinal cancer risk associated with alcohol beverage consumption. Furthermore, AA is one of the most abundant carcinogens in tobacco smoke and induces tumors of the respiratory tract in laboratory animals. AA binding to DNA induces Schiff base adducts at the exocyclic amino group of dG, N-2-ethylidene-dG, which are reversible on the nucleoside level but can be stabilized by reduction to N-2-ethyl-dG. Mutagenesis studies in the HPRT reporter gene and in the p53 tumor suppressor gene have revealed the ability of AA to induce G -> A transitions and A -> T transversions, as well as frameshift and splice mutations. AA-induced point mutations are most prominent at 5'-AGG-3'trinucleotides, possibly a result of sequence specific adduct formation, mispairing, and/or repair. However, DNA sequence preferences for the formation of acetaldehyde adducts have not been previously examined. In the present work, we employed a stable isotope labeling-HPLC-ESI+-MS/MS approach developed in our laboratory to analyze the distribution of acetaldehyde-derived N-2-ethyl-dG adducts along double-stranded oligode oxynucleotides representing two prominent lung cancer mutational "hotspots" and their surrounding DNA sequences. 1,7,NH2-N-15-2-C-13-dG was placed at defined positions within DNA duplexes derived from the K-ras protooncogene and the p53 tumor suppressor gene, followed by AA treatment and NaBH3CN reduction to convert N-2-ethylidene-dG to N-2-ethyl-dG. Capillary HPLC-ESI+-MS/MS was used to quantify N-2-ethyl-dG adducts originating from the isotopically labeled and unlabeled guanine nucleobases and to map adduct formation along DNA duplexes. We found that the formation of N-2-ethyl-dG adducts was only weakly affected by the local sequence context and was slightly increased in the presence of 5-methyleytosine within CG dinucleotides. These results a re in contrast with sequence-selective formation of other tobacco carcinogen-DNA adducts along K-ras- and p53-derived duplexes and the preferential modification of endogenously methylated CG dinucleotides by benzo[a]pyrene diol epoxide and acrolein.