PHYSICAL AND CHEMICAL INTERACTIONS OF BPDE AND DNA

由化学致癌物引发的肿瘤被认为是由 与DNA的结合导致关键原生生物的激活/去激活- 癌基因和抑癌基因。我们一直在研究环境问题 前致癌物苯并(A)芘(BaP)，作为理解的模型 分子致癌。BaP被转化为一种有效的化学物质 通过细胞代谢产生致癌物质，这种中间体是7R，8S- 二羟基-9S，10R-环氧基-7，8，9，10-四氢BP((+)-抗BPDE)。A(-)- 也制造了抗BPDE对映体，但这种代谢物的含量减少了50倍 生物活性。这两种立体异构体都与DNA结合形成 主要和次要的加合物和构象研究一直受到 只有微克量的异相修饰的可用性 用于研究的DNA。由于致癌物质的生物学特性和 非致癌立体异构体可能是由于 构象，本研究的目标之一是合成足够的 主要和次要的BPDE加合物的量来实现这些 学习。另一个目标是描述重要的次要加成物，如 作为通过顺式打开BPDE加合物而形成的那些 学习。另一个目标是描述重要的次要加成物，如 由于BPDE环氧化物的顺式开环和dCyd烷基化而形成的 产品，因为它们可能对 致癌物质。我们的具体目标是(I)合成BPDE修饰的 脱氧核苷酸和BPDE修饰的寡核苷酸(ODN)，(Ii) 对改性单体和低聚物进行构象研究， (3)研究顺式加合物的形成机理；(4)分析顺式加合物的形成机理 结构和表征dCyd加合物在DNA中的存在。这个 方法是合成BPDE-脱氧核苷并将它们结合在一起 转化为位点特异的致癌物修饰的ODN。ODN将由以下人员组成 使用顺式和反式脱氧核苷的BPDE修饰的dGuo和dado 来自(+)-和(-)-反立体异构体的加合物。合成的 将开发制造BPDE-dCyd加合物的方法，这 致癌物质修饰的脱氧核苷也将用于构建ODN 只有一个特定部位的损伤。构象将是 通过UV、CD、荧光和核磁共振光谱和X射线进行评估 结晶学。我们将研究它的作用机制和性质。 卤素催化的顺式DNA加合物的形成。我们还将 完成dCyd加合物在DNA中的表征和存在 以评估它们对BaP生物效应的重要性。这个 这项工作的长期目标是确定相对生物学的 形成的每个BPDE-DNA加合物的活性，以便 评估哪个人(S)可能是肿瘤的始作俑者 这种重要且普遍存在的环境污染物的性质。

Tumor initiation by chemical carcinogens is thought to result from binding to DNA that leads to activation/deactivation of critical proto- oncogenes and suppressor genes. We have been studying the environmental pro-carcinogen benzo(a)pyrene (BaP), as a model for understanding molecular carcinogenesis. BaP is converted into a potent chemical carcinogen by cellular metabolism and this intermediate is 7R,8S- dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydroBP ((+)-anti-BPDE). A (-)- anti-BPDE enantiomer is also made but this metabolite has 50-fold less biological activity. Both of these stereoisomers bind to DNA to form major and minor adducts and conformational studies have been hampered by the availability of only microgram quantities of heterogeneously modified DNAs for study. Since the biological properties of the carcinogenic and non-carcinogenic stereoisomers may result from differences in conformation, one goal of this research is to synthesize sufficient quantities of both the major and minor BPDE adducts to carry out these studies. Another goal is to characterize important minor adducts, such as those formed by cis opening of the BPDE adducts to carry out these studies. Another goal is to characterize important minor adducts, such as those formed by cis opening of the BPDE epoxide and dCyd alkylation products, since they may be responsible for the mutagenic properties of the carcinogen. Our specific aims are to (i) synthesize BPDE-modified deoxynucleotides and BPDE-modified oligodeoxynucleotides (ODNs), (ii) carry out conformational studies on the modified monomers and oligomers, (iii) study the mechanism of cis adduct formation, and (iv) analyze the structure and characterize the occurrence of dCyd adducts in DNA. The approach will be to synthesize BPDE-deoxynucleosides and incorporate them into site-specific, carcinogen-modified ODNs. The ODNs will be made with BPDE-modified dGuo and dAdo employing cis and trans deoxynucleoside adducts derived from both the (+)- and (-)-anti-stereoisomers. Synthetic methods for making BPDE-dCyd adducts will be developed, and this carcinogen-modified deoxynucleoside will also be used to construct ODNs containing a single, site-specific lesion. Conformations will be evaluated by UV, CD, fluorescence, and NMR spectroscopies and by X-ray crystallography. We will study the mechanism and properties of the halogen-catalyzed formation of cis adducts with DNA. We will also complete the characterization and occurrence of dCyd adducts in DNA, in order to assess their importance to the biological effects of BaP. The long term goal of this work is to determine the relative biological activity of each of the BPDE-DNA adducts that are formed, in order to assess which one(s) may be responsible for the tumor initiating properties of this important and ubiquitous environmental contaminant.