DNA glycosylases from the Fpg/Nei structural superfamily are base excision repair enzymes involved in the removal of a wide variety of mutagen and potentially lethal oxidized purines and pyrimidines. Although involved in genome stability, the recent discovery of synthetic lethal relationships between DNA glycosylases and other pathways highlights the potential of DNA glycosylase inhibitors for future medicinal chemistry development in cancer therapy. By combining biochemical and structural approaches, the physical target of 2-thioxanthine (2TX), an uncompetitive inhibitor of Fpg, was identified. 2TX interacts with the zinc finger (ZnF) DNA binding domain of the enzyme. This explains why the zincless hNEIL1 enzyme is resistant to 2TX. Crystal structures of the enzyme bound to DNA in the presence of 2TX demonstrate that the inhibitor chemically reacts with cysteine thiolates of ZnF and induces the loss of zinc. The molecular mechanism by which 2TX inhibits Fpg may be generalized to all prokaryote and eukaryote ZnF-containing Fpg/Nei-DNA glycosylases. Cell experiments show that 2TX can operate in cellulo on the human Fpg/Nei DNA glycosylases. The atomic elucidation of the determinants for the interaction of 2TX to Fpg provides the foundation for the future design and synthesis of new inhibitors with high efficiency and selectivity.

中文翻译：

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2-硫黄嘌呤对 Fpg/Nei DNA 糖基化酶的锌指氧化：生化和 X 射线结构表征

来自 Fpg/Nei 结构超家族的 DNA 糖基化酶是碱基切除修复酶，参与去除多种诱变剂和可能致命的氧化嘌呤和嘧啶。尽管涉及基因组稳定性，但最近发现 DNA 糖基化酶与其他途径之间的合成致死关系突出了 DNA 糖基化酶抑制剂在未来癌症治疗药物化学开发中的潜力。通过结合生化和结构方法，确定了 Fpg 的一种非竞争性抑制剂2-噻黄嘌呤(2TX) 的物理靶标。2TX 与酶的锌指 (ZnF) DNA 结合域相互作用。这解释了为什么无锌HNEIL1 酶对 2TX 具有抗性。在 2TX 存在下与 DNA 结合的酶的晶体结构表明，抑制剂与 ZnF 的半胱氨酸硫醇盐发生化学反应并诱导锌的损失。2TX 抑制 Fpg 的分子机制可以推广到所有含 ZnF 的原核生物和真核生物 Fpg/Nei-DNA 糖基化酶。细胞实验表明，2TX 可以在纤维素中对人 Fpg/Nei DNA 糖基化酶起作用。2TX 与 Fpg 相互作用的决定因素的原子阐明为未来设计和合成具有高效率和选择性的新型抑制剂提供了基础。