BENZO(A)PYRENE MUTAGENIC MECHANISMS

苯并[a]芘是一种强效诱变剂/致癌物，通过以下方式与DNA反应： 其（+）-抗-7，8-二醇-9，10-环氧化物（（+）-抗-B {a}PDE），得到DNA 加合物，主要在N2 -Gua和N6 -Ade。 的机制 使用两种位点特异性PCR方法研究了（+）-抗-B {a}PDE的诱变。 和随机诱变方法。 (10大肠coli质粒， 构建了在5 '-TGC-3'序列中含有（+）-抗-B {a}P-N2-Gua 上下文，并用于确定G->T突变几乎是 完全诱导。(2)用（+）-抗-B {a}PDE进行随机诱变， 在我们开发的一个系统中进行了研究，其中将supF靶基因的质粒 体外转化E.杆菌 G->T突变 在5 '-TG-3”序列背景中占主导地位，这与 位点特异性研究表明，（+）-抗B {a}P-N2-Gua是 责任 相反，5 '-GG-3'、5 '-CG-3'和5 '-AG-3'序列 背景显示了显著比例的GC->AT和GC->CG突变。 G115是主要的碱基配对热点。 一些突变的复杂性 建议：（1）有两种可能的构象为一个 G115加合物具有不同的突变结果;或（2）存在 在G115处的不稳定加合物，其转化为AP位点。 初步 数据显示，前者的可能性更大。 （+）-抗B {a}PDE生成 不稳定的加合物，可能不是N7-Gua加合物。 可能性较大 N2-Gua加合物可以采用多种构象，其中一种是 一个稳定，另一个不稳定。 这可能与以下证据有关： 在G115的诱变研究中获得的多种构象。 的 将检验以下统一假设。 单个加合物可以采用 多种构象，每种构象都可能导致不同类型的 突变。 此外，加合物构象可以受到DNA的影响 序列背景，以及环境因素，如加热。

Benzo [a] pyrene is a potent mutagen/carcinogen and reacts with DNA via its (+)-anti-7, 8-diol-9, 10-epoxide ( (+)-anti-B{a}PDE) to give DNA adducts, principally at N2 -Gua and N6 -Ade. The mechanisms of mutagenesis by (+)-anti-B{a}PDE was investigated using both site-specific and random mutagenesis approaches. (10 An E. coli plasmid was constructed that contained (+)-anti-B{a}P-N2-Gua in a 5'-TGC-3' sequence context and was used to determine the G->T mutations were virtually exclusively induced. (2) random mutagenesis by (+)-anti-B{a}PDE was studied in a system we developed, where a plasmid a supF target gene was adducted in vitro and transformed into E. coli. G->T mutations predominated in 5'-TG-3" sequence contexts, which correlated with the site-specific studies and suggested that (+)-anti-B{a}P-N2-Gua was responsible. In contrast, 5'-GG-3', 5'-CG-3' and 5'-AG-3' sequence contexts showed a significant fraction of GC->AT and GC->CG mutations. G115 was the major base pairing hot-spot. Some mutational complexity suggested either: (1) that there are two possible conformations for an adduct at G115 with different mutational outcomes; or (2) that there is a labile adduct at G115, which is converted to an AP-site. Preliminary data suggests that the former is more likely. (+)-anti-B{a}PDE generates labile adducts, which are probably not N7-Gua adducts. It is more likely that N2-Gua adducts can adopt multiple conformations, where one is stable, while the other is labile. This may relate to the evidence for multiple conformations obtained in mutagenesis studies at G115. The following unifying hypothesis will be tested. A single adduct can adopt multiple conformations, each of which can cause a different kind of mutation (s). Furthermore, adduct conformation can be influenced by DNA sequence context, as well as environmental factors, such as heating.