Mechanism of site-selective DNA nicking by the hydrodioxyl (perhydroxyl) radical.
Mechanism of site-selective DNA nicking by the hydrodioxyl (perhydroxyl) radical.
复制标题
氢二氧基（过羟基）自由基对 DNA 进行位点选择性切口的机制。
DOI：
10.1021/bi952010w
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Webb,TL
中科院分区：
文献类型：
--
作者：
Dix,TA;Hess,KM;Medina,MA;Sullivan,RW;Tilly,SL;Webb,TL
在以前的研究中，证明了在仿生条件下，过氧化氢（过羟基）自由基[HOO·，超氧化物（O2·-）的共轭酸]“切口”DNA的能力，并观察到序列选择性。还观察到背景水平的非特异性切口。这篇论文支持了O2·-/HOO·在序列选择性切口中从脱氧核糖环上夺取5 '-氢原子作为起始事件。两个实验支持所提出的机制。首先，使用确定的序列5 '-32 P标记的限制性片段作为DNA底物，在切口位点仅产生游离的（未烷基化的）3'-磷酸。其次，使用聚（dA）·聚（T）作为底物，在反应中由脱氧核糖环断裂形成糠醛。这两个结果都与用于引发位点选择性切口的5 '-氢原子提取一致。在脱氧核糖环的其他位点的氢原子提取和/或碱基氧化和损失，随后是链断裂可能是造成非特异性切口的原因。5 '-提取机制与其他O2衍生和金属相关氧化剂引起的机制形成对比，这可能为HOO·在体内的反应性提供生物标志物。
In previous studies, the ability of the hydrodioxyl (perhydroxyl) radical [HOO•, the conjugate acid of superoxide (O2•-)] to “nick” DNA under biomimetic conditions was demonstrated, and a sequence selectivity was observed. A background level of nonspecific nicking also was noted. This paper provides support for 5‘-hydrogen atom abstraction from the deoxyribose ring as the initial event in the sequence-selective nicking by O2•-/HOO•. Two experiments support the proposed mechanism. First, using a defined sequence 5‘-32P-labeled restriction fragment as the DNA substrate, only free (unalkylated) 3‘-phosphate is produced at the site of nicking. Second, using poly (dA)·poly (T) as the substrate, furfural is formed in the reaction from deoxyribose ring breakdown. Both results are consistent with 5‘-hydrogen atom abstraction for initiation of the site-selective nicking. Hydrogen atom abstraction at other sites of the deoxyribose ring and/or base oxidation and loss followed by strand scission likely are responsible for the nonspecific nicking. The 5‘-abstraction mechanism contrasts to those elicited by other O2-derived and metal-associated oxidants, which may provide a biomarker for the reactivity of HOO•in vivo.