Kellner Stefanie, DeMott Michael S, Cheng Ching Pin, Russell Brandon S, Cao Bo, You Delin, Dedon Peter C
Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
Nat Chem Biol. 2017 Aug;13(8):888-894. doi: 10.1038/nchembio.2407. Epub 2017 Jun 12.
Genomic modification by sulfur in the form of phosphorothioate (PT) is widespread among prokaryotes, including human pathogens. Apart from its physiological functions, PT sulfur has redox and nucleophilic properties that suggest effects on bacterial fitness in stressful environments. Here we show that PTs are dynamic and labile DNA modifications that cause genomic instability during oxidative stress. In experiments involving isotopic labeling coupled with mass spectrometry, we observed sulfur replacement in PTs at a rate of ∼2% h in unstressed Escherichia coli and Salmonella enterica. Whereas PT levels were unaffected by exposure to hydrogen peroxide (HO) or hypochlorous acid (HOCl), PT turnover increased to 3.8-10% h after HOCl treatment and was unchanged by HO, consistent with the repair of HOCl-induced sulfur damage. PT-dependent sensitivity to HOCl extended to cytotoxicity and DNA strand breaks, which occurred at HOCl doses that were orders of magnitude lower than the corresponding doses of HO. The genotoxicity of HOCl in PT-containing bacteria suggests reduced fitness in competition with HOCl-producing organisms and during infections in humans.
硫以硫代磷酸酯（PT）的形式对基因组进行修饰在原核生物中广泛存在，包括人类病原体。除了其生理功能外，PT硫具有氧化还原和亲核特性，这表明其在应激环境中对细菌适应性有影响。在此我们表明，PT是动态且不稳定的DNA修饰，在氧化应激期间会导致基因组不稳定。在涉及同位素标记与质谱联用的实验中，我们观察到在未受应激的大肠杆菌和肠炎沙门氏菌中，PT中的硫以约2%/小时的速率被替换。虽然PT水平不受过氧化氢（H₂O₂）或次氯酸（HOCl）暴露的影响，但HOCl处理后PT周转增加到3.8 - 10%/小时，而H₂O₂处理则无变化，这与HOCl诱导的硫损伤修复一致。PT依赖的对HOCl的敏感性扩展到细胞毒性和DNA链断裂，其发生时HOCl的剂量比相应的H₂O₂剂量低几个数量级。HOCl在含PT细菌中的遗传毒性表明，在与产生HOCl的生物体竞争以及人类感染期间，其适应性降低。
