MOLECULAR MODELING IN CARCINOGENESIS

致癌作用的分子模型

• 批准号: 6012087
• 负责人: EDWARD L LOECHLER
• 金额: $ 21.8万
• 依托单位: BOSTON UNIVERSITY (CHARLES RIVER CAMPUS)
• 依托单位国家: 美国
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-12-01 至 2002-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6012087
• 关键词: adduct; benzopyrenes; chemical carcinogenesis; chemical models; chemical structure; chemical substitution; computer simulation; conformation; methyl group; molecular dynamics; mutagens; nucleic acid sequence; nucleic acid structure; point mutation; site directed mutagenesis; stereoisomer; structural biology

Benzo{a}pyrene is a potent mutagen/carcinogen that is metabolically activated inside cells, including to its (+)-anti-7,8-diol-9,10- epoxide [(+)-anti-B[a]PDE, which gives DNA adducts, principally a N2-dG. We showed that (+)-anti-B[a]PDE able to induce such a diverse array of mutations? Base substitution mutations predominate, and principally occur at G:C base pairs, where GC->TA, GC->AT and GC->CG are all significant (57%, 23%, 20%, respectively). We have done molecular biological/mutagenesis work to show that (+)-trans-antiB[a]P-n2-Gus is capable of inducing a preponderance of G->T mutations (> approximately 95 percent) in 5'-TGC sequences, or a preponderance of G->A mutations (->approximately 95 percent) in a 5'-AGA sequence. This raises the question: how can a single entity [i.e., (+)-trans-anti-B[a]P-N2-Gua] induce a different pattern of mutations depending on sequence context? Our working hypothesis has been that adduct mutational complexity is due to adduct conformational complexity, and that adduct conformation and, thereby, mutation is controlled by various factors, notably, DNA sequence context. To study adduct conformation, we did molecular modeling, and found that, based on first principles, (=)-trans-anti-B[a]P-N2-Gua can adopt at least 16 conformations. This is a large number, and probably all are not relevant to base substitutions mutagenesis, we have used a combination of common sense and the results of our molecular mechanical calculations to conclude that three conformations are most likely to be relevant to mutagenesis. Furthermore, we noticed a correlation. In a sequence where G->T mutations predominated (5'-TGC) a base displaced conformation of (+)-trans-anti-B[a]P-N2-Gua with the dG moiety in the major groove (Gma5) was calculated to be lower in energy. In two sequences where we observed G->A mutations were found more equally (5'-CGG, 5'-GGG) Gma5 and Gmi3 were calculated to be more similar in energy. This correlation suggests the hypothesis that Gma5 is the conformation responsible for G->T mutations and Gmi3 is responsible for G->A mutations. We are pursuing this hypothesis in molecular biological/mutagenesis studies (funded separately). Herein we propose three specific aims to pursue this hypothesis using molecular modeling and computational chemical techniques.

苯并{a}芘是一种有效的诱变剂/致癌物，在细胞内被代谢激活，包括其(+)-抗7,8-二醇-9,10-环氧化物[(+)-抗b [a]PDE，其产生DNA加合物，主要是N2-dG。我们发现(+)-anti-B[a]PDE能够诱导如此多样化的突变？碱基取代突变占主导地位，主要发生在G:C碱基对，其中GC->TA、GC-> at和GC->CG均显著（分别为57%、23%和20%）。我们已经完成了分子生物学/诱变工作，表明(+)-trans- antib [a]P-n2-Gus能够在5'- tgc序列中诱导显性G->T突变（约95%），或在5'- aga序列中诱导显性G-> a突变（约95%）。这就提出了一个问题：单个实体[即(+)-反式-抗- b [a]P-N2-Gua]如何根据序列上下文诱导不同的突变模式？我们的工作假设是加合物突变的复杂性是由于加合物构象的复杂性，而加合物构象和突变是由各种因素控制的，特别是DNA序列背景。为了研究加合物的构象，我们进行了分子建模，发现基于第一性原理，(=)-trans-anti-B[a]P-N2-Gua至少有16种构象。这是一个很大的数字，可能都与碱基取代突变无关，我们已经使用常识和我们的分子力学计算的结果相结合，得出结论，三种构象最有可能与诱变有关。此外，我们注意到一种相关性。在G->T突变占主导地位的序列（5'- tgc）中，计算出(+)-反式-抗- b [a]P-N2-Gua的碱基移位构象（dG部分位于主槽（Gma5））的能量较低。在我们观察到G->A突变更为均匀的两个序列（5'- cgg, 5'- ggg）中，Gma5和Gmi3在能量上更为相似。这种相关性表明Gma5是导致G->T突变的构象，Gmi3是导致G->A突变的构象。我们正在分子生物学/诱变研究中追求这一假设（单独资助）。在这里，我们提出了三个具体的目标，以追求这一假设使用分子模型和计算化学技术。