DNA ALKYLATION BY THE ANTITUMOR ANTIBIOTIC LEINAMYCIN

雷诺霉素是一种破坏DNA的天然产物，具有强大的抗癌活性。这种抗生素在结构上是独特的，代表了一种新的破坏DNA的抗生素。由于其强大的抗癌活性和雷诺霉素损伤DNA的新的化学机制，对这种抗生素的研究具有实际意义和基础意义。雷诺霉素的DNA损伤是由抗生素与硫醇的反应引发的，最近的研究表明，这种化合物既会引起氧化DNA损伤，也会引起烷基化DNA损伤。DNA烷基化化学是这一提议的焦点，它是通过令人惊讶的硫醇介导的雷诺霉素重排发生的，该重排产生了亲电的表硫离子，该离子使鸟嘌呤残基的N7位双链DNA烷基化。虽然我们对雷诺霉素损伤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远不完整。这项提案中描述的工作研究了雷诺霉素-DNA相互作用的几个新方面，并将提供对这种不同寻常的抗生素如何有效地使DNA烷化的更深层次的理解。本工作的具体目标如下：(1)表征雷诺霉素-DNA加合物。这包括研究雷诺霉素与DNA烷基化的序列特异性，分析雷诺霉素-鸟苷加合物的稳定性，寻找新的雷诺霉素-DNA加合物(不包括N7-鸟苷)。(2)研究雷诺霉素的“交替”(非硫醇激活)激活方式。到目前为止，雷诺霉素一直被描述为一种硫醇依赖的DNA损伤剂。我们计划研究在我们最近的工作过程中发现的几种可供选择的、非硫醇激活的模式，用于雷诺霉素激活DNA烷基化。(3)用来那霉素检测非共价DNA结合。我们已经获得了雷诺霉素与DNA非共价结合的初步证据。我们将研究抗生素的结构特征，这些结构特征对于DNA结合、DNA结合方式以及雷诺霉素与双链DNA的亲和力都是重要的。

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.