A study of endonuclease III-sensitive sites in irradiated DNA:: detection of α-particle-induced oxidative damage
A study of endonuclease III-sensitive sites in irradiated DNA:: detection of α-particle-induced oxidative damage
复制标题
DOI：
10.1093/carcin/20.5.905
复制
发表时间：
1999-05-01
期刊：
影响因子：
4.7
通讯作者：
Michael, BD
中科院分区：
文献类型：
--
作者：
Prise, KM;Pullar, CHL;Michael, BD
诱导DNA氧化损伤的化学试剂与电离辐射之间的一个重要区别是，辐射引起的损伤是局部聚集在DNA上的。模型和实验研究都预测了电离辐射引起的损伤聚集的重要性及其对辐射质量的依赖。随着线性能量转移的增加，预计在DNA的1-20 bp区域内将形成复杂的损伤，以及链断裂，这些位点可能包含多个受损的碱基。我们比较了单链断裂（ssb）和双链断裂（dsb）的产量，以及用核酸内切酶III处理辐照DNA所产生的产量，该酶识别DNA中的许多氧化嘧啶并将其转化为链断裂。质粒DNA在两种不同的清除条件下辐照，以测试OH自由基与Co-60 γ射线或来自Pu-238源的α粒子的参与。在低清除率条件下（10 mM Tris）， γ辐照诱导7.1 × 10(-7) ssb Gy/bp，在endo III处理下增加3.7倍，达到2.6 × 10(-6) ssb Gy/bp。相比之下，dsb的产量增加了4.2倍，从1.5 × 10（-8）到6.3 × 10(-8) dsb Gy/bp，这相当于在酶处理下，额外2.5%的endo iii敏感位点被转化为dsb。对于α粒子，这一比例增加到9%。考虑到endo III敏感位点可能仅占DNA中诱导的碱基损伤的40%，这表明在X-和α粒子辐照DNA中测量的ssb中，高达6%和22%的ssb可能具有与它们相关的损伤碱基，从而导致损伤的复杂性。
An important difference between chemical agents that induce oxidative damage in DNA and ionizing radiation is that radiation-induced damage is clustered locally on the DNA, Both modelling and experimental studies have predicted the importance of clustering of lesions induced by ionizing radiation and its dependence on radiation quality. With increasing linear energy transfer, it is predicted that complex lesions will be formed within 1-20 bp regions of the DNA, As well as strand breaks, these sites may contain multiple damaged bases, We have compared the yields of single strand breaks (ssb) and double strand breaks (dsb) along with those produced by treatment of irradiated DNA with the enzyme endonuclease III, which recognizes a number of oxidized pyrimidines in DNA and converts them to strand breaks. Plasmid DNA was irradiated under two different scavenging conditions to test the involvement of OH radicals with either Co-60 gamma-rays or alpha-particles from a Pu-238 source. Under low scavenging conditions (10 mM Tris) gamma-irradiation induced 7.1x10(-7) ssb Gy/bp, which increased 3.7-fold to 2.6 x 10(-6) ssb Gy/bp with endo III treatment. In contrast the yields of dsb increased by 4.2-fold from 1.5 x 10(-8) to 6.3 x 10(-8) dsb Gy/bp, This equates to an additional 2.5% of the endo III-sensitive sites being converted to dsb on enzyme treatment. For alpha-particles this increased to 9%. Given that endo III sensitive sites may only constitute similar to 40% of the base lesions induced in DNA, this suggests that up to 6% of the ssb measured in X- and 22% in alpha-particle-irradiated DNA could have damaged bases associated with them contributing to lesion complexity.