DNA ALKYLATION BY THE ANTITUMOR ANTIBIOTIC LEINAMYCIN

Leinamycin 是一种破坏 DNA 的天然产物，具有有效的抗癌活性。 这种抗生素结构独特，代表了一类新型 DNA 损伤抗生素。 由于其强大的抗癌活性以及莱纳霉素损伤 DNA 的新颖化学机制，对这种抗生素的研究具有实际意义和根本意义。 莱纳霉素对 DNA 的损伤是由抗生素与硫醇的反应引发的，最近的研究表明，该化合物会引起氧化和烷基化 DNA 损伤。 作为本提案重点的 DNA 烷基化化学是通过令人惊讶的硫醇介导的莱那霉素重排发生的，产生亲电子的表锍离子，该离子在鸟嘌呤残基的 N7 处烷基化双链 DNA。尽管我们对来那霉素损伤 DNA 的机制有了初步的了解，但我们对这种抗生素与 DNA 相互作用所涉及的化学反应和分子识别过程的了解还远未完成。该提案中描述的工作研究了莱那霉素-DNA 相互作用的几个新方面，并将更深入地了解这种不寻常的抗生素如何有效地烷基化 DNA。 该工作的具体目标如下： (1) 表征 Leinamycin-DNA 加合物。 其中包括研究来那霉素 DNA 烷基化的序列特异性、分析来那霉素-鸟苷加合物的稳定性以及寻找新的来那霉素-DNA 加合物（N7-鸟苷除外）。 (2) 研究莱纳霉素激活的“替代”（非硫醇激活）模式。 迄今为止，Leinamycin 已被定性为硫醇依赖性 DNA 损伤剂。 我们计划研究我们在最近的工作过程中发现的几种替代的、非硫醇激活的模式，用于通过莱纳霉素激活 DNA 烷基化。 (3) 检查 Leinamycin 的非共价 DNA 缔合。 我们已获得初步证据表明莱那霉素与 DNA 非共价结合。 将检查对 DNA 结合很重要的抗生素结构特征、DNA 缔合模式以及来那霉素对双链 DNA 的亲和力。

Leinamycin is a DNA-damaging natural product with potent anticancer activity. This antibiotic is structurally unique and represents a new class of DNA-damaging antibiotics. Because of its potent anticancer activity and the novel chemical mechanisms by which leinamycin damages DNA, studies of this antibiotic are of both practical and fundamental interest. DNA damage by leinamycin is triggered by reaction of the antibiotic with thiols and recent work has shown that the compound causes both oxidative and alkylative DNA damage. The DNA-alkylation chemistry that is the focus of this proposal occurs via a surprising thiol-mediated rearrangement of leinamycin that yields an electrophilic episulfonium ion which alkylates double-stranded DNA at N7 of guanine residues. Although we have a preliminary grasp on the mechanisms by which leinamycin damages DNA, our understanding of the chemical reactions and molecular-recognition processes involved in the interaction of this antibiotic with DNA is far from complete. The work described in this proposal investigates several novel aspects of leinamycin-DNA interactions and will provide a deeper understanding of how this unusual antibiotic efficiently alkylates DNA. The Specific Aims of the proposed work are as follows: (1) Characterize Leinamycin-DNA adducts. The includes investigation of the sequence-specificity of DNA alkylation by leinamycin, analysis of the stability of leinamycin-guanosine adducts, and searches for new leinamycin-DNA adducts (other than N7-guanosine). (2) Investigate "Alternate" (Non Thiol-Activated) Modes of Leinamycin Activation. Leinamycin has thus far been characterized as a thiol-dependent DNA damaging agent. We plan to investigate several alternate, non thiol-activated modes for the activation of DNA alkylation by leinamycin that we have discovered during the course of our recent work. (3) Examine Non-Covalent DNA Association by Leinamycin. We have obtained preliminary evidence that leinamycin non-covalently associates with DNA. The structural features of the antibiotic that are important for DNA binding, the mode of DNA association and the affinity of leinamycin for duplex DNA will be examined.