BENZO(A)PYRENE MUTAGENIC MECHANISMS

苯并[a]芘是一种强有力的诱变剂/致癌物，它通过 ITS(+)-抗-7，8-二醇-9，10-环氧化物((+)-抗-B{a}PDE)给DNA 加合物，主要位于N_2-Gua和N_6-Ade。它的作用机制 研究了(+)-抗B{a}PDE的诱变作用 和随机诱变的方法。(10)大肠杆菌质粒为 构建的含有5‘-TGC-3’序列中的(+)-抗B{a}P-n2-gua的 并用于确定G-&GT；T突变实际上是 完全诱导。(2)用(+)-抗B{a}PDE进行随机诱变。 在我们开发的系统中进行了研究，其中一个质粒a supF目标基因 体外加合并转化到大肠杆菌中。G-&GT；T突变 主要存在于5‘-Tg-3“序列上下文中，与 位点特异性研究表明，(+)-抗B{a}P-N-Gua是 负责任。相反，5‘-GG-3’、5‘-CG-3’和5‘-AG-3’序列 上下文显示GC-&gt；AT和GC-&gt；CG突变的比例很大。 G115是主要的碱基配对热点。一些突变的复杂性 建议：(1)存在两种可能的构象 在G115处加成，具有不同的突变结果；或(2)存在 G115上的一个不稳定的加合物，它被转化为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。更有可能的是 N_2-GUA加合物可以采用多种构象，其中一种是 稳定，而另一个是不稳定的。这可能与以下证据有关 在G115的诱变研究中获得了多种构象。这个 下面的统一假设将得到检验。单一加合物可以采用 多种构象，每一种构象都可能导致不同类型的 突变(S)。此外，dna还可以影响加合物的构象。 序列上下文，以及环境因素，如供暖。

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.