University of Chicago, Department of Molecular Genetics and Cell Biology, 929 E. 57th Street W522A, Chicago, IL 60637, USA.
University of Illinois Chicago, College of Pharmacy, Department of Pharmaceutical Sciences, Rockford, IL 61107, USA.
Cell Chem Biol. 2021 Jun 17;28(6):776-787.e8. doi: 10.1016/j.chembiol.2020.11.011. Epub 2020 Dec 21.
Topoisomerase 1 (Top1) reversibly nicks chromosomal DNA to relax strain accumulated during transcription, replication, chromatin assembly, and chromosome condensation. The Top1 poison camptothecin targets cancer cells by trapping the enzyme in the covalent complex Top1, tethered to cleaved DNA by a tyrosine-3'-phosphate bond. In vitro mechanistic studies point to interfacial inhibition, where camptothecin binding to the Top1-DNA interface stabilizes Top1. Here we present a complementary covalent mechanism that is critical in vivo. We observed that camptothecins induce oxidative stress, leading to lipid peroxidation, lipid-derived electrophile accumulation, and Top1 poisoning via covalent modification. The electrophile 4-hydroxy-2-nonenal can induce Top1 on its own and forms a Michael adduct to a cysteine thiol in the Top1 active site, potentially blocking tyrosine dephosphorylation and 3' DNA phosphate release. Thereby, camptothecins may leverage a physiological cysteine-based redox switch in Top1 to mediate their selective toxicity to rapidly proliferating cancer cells.
拓扑异构酶 1（Top1）可逆地切开染色体 DNA，以松弛转录、复制、染色质组装和染色体浓缩过程中积累的张力。拓扑异构酶 1 抑制剂喜树碱通过将酶捕获在共价复合物 Top1 中，从而靶向癌细胞，由酪氨酸 3'-磷酸酯键将酶与断裂的 DNA 连接。体外机制研究指出，喜树碱与 Top1-DNA 界面的结合稳定了 Top1，从而产生界面抑制。在这里，我们提出了一种在体内至关重要的互补共价机制。我们观察到喜树碱会诱导氧化应激，导致脂质过氧化、脂质衍生的亲电物积累以及通过共价修饰导致 Top1 中毒。亲电物 4-羟基-2-壬烯醛本身可以诱导 Top1，并与 Top1 活性位点中的半胱氨酸巯基形成迈克尔加成物，可能阻止酪氨酸去磷酸化和 3' DNA 磷酸酯的释放。因此，喜树碱可能利用 Top1 中基于生理半胱氨酸的氧化还原开关来介导其对快速增殖的癌细胞的选择性毒性。
