Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, BIO5 Institute, Room 102, 1657 E. Helen Street, Tucson, AZ 85721, USA.
Bioorg Med Chem. 2012 Jul 15;20(14):4413-21. doi: 10.1016/j.bmc.2012.05.033. Epub 2012 May 23.
The natural product leinamycin has been found to produce abasic sites in duplex DNA through the hydrolysis of the glycosidic bond of guanine residues modified by this drug. In the present study, using a synthetic oligonucleotide duplex, we demonstrate spontaneous DNA strand cleavage at leinamycin-induced abasic sites through a β-elimination reaction. However, methoxyamine modification of leinamycin-induced abasic sites was found to be refractory to the spontaneous β-elimination reaction. Furthermore, this complex was even resistant to the δ-elimination reaction with hot piperidine treatment. Bleomycin and methyl methanesulfonate also induced strand cleavage in a synthetic oligonucleotide duplex even without thermal treatment. However, methoxyamine has a negligible effect on DNA strand cleavage induced by both drugs, suggesting that the mechanism of DNA cleavage induced by leinamycin might be different from those induced by bleomycin or methyl methanesulfonate. In this study, we also assessed the cytotoxicity of leinamycin against a collection of mammalian cell lines defective in various repair pathways. The mammalian cell line defective in the nucleotide excision repair (NER) or base excision repair (BER) pathways was about 3 to 5 times more sensitive to leinamycin as compared to the parental cell line. In contrast, the radiosensitive mutant xrs-5 cell line deficient in V(D)J recombination showed similar sensitivity towards leinamycin compared to the parental cell line. Collectively, our findings suggest that both NER and BER pathways play an important role in the repair of DNA damage caused by leinamycin.
天然产物莱菔素通过水解该药物修饰的鸟嘌呤残基的糖苷键，被发现能在双链 DNA 中产生无碱基位点。在本研究中，我们使用合成的寡核苷酸双链证明了莱菔素诱导的无碱基位点通过β-消除反应自发发生 DNA 链断裂。然而，发现莱菔素诱导的无碱基位点的甲氧胺修饰对自发β-消除反应具有抗性。此外，该复合物甚至对用热哌啶处理的δ-消除反应具有抗性。博来霉素和甲基甲烷磺酸盐即使不经热处理也能在合成的寡核苷酸双链中诱导链断裂。然而，甲氧胺对两种药物诱导的 DNA 链断裂几乎没有影响，表明莱菔素诱导的 DNA 断裂的机制可能与博来霉素或甲基甲烷磺酸盐诱导的机制不同。在这项研究中，我们还评估了莱菔素对一系列具有不同修复途径缺陷的哺乳动物细胞系的细胞毒性。核苷酸切除修复（NER）或碱基切除修复（BER）途径有缺陷的哺乳动物细胞系对莱菔素的敏感性比亲本细胞系高约 3 到 5 倍。相比之下，缺乏 V(D)J 重组的放射敏感突变 xrs-5 细胞系对莱菔素的敏感性与亲本细胞系相似。总的来说，我们的发现表明 NER 和 BER 途径在修复莱菔素引起的 DNA 损伤中都起着重要作用。
