DAMAGE TO THE DNA BASES IN MAMMALIAN CHROMATIN BY HYDROGEN-PEROXIDE IN THE PRESENCE OF FERRIC AND CUPRIC IONS
DAMAGE TO THE DNA BASES IN MAMMALIAN CHROMATIN BY HYDROGEN-PEROXIDE IN THE PRESENCE OF FERRIC AND CUPRIC IONS
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DOI：
10.1016/0003-9861(91)90366-q
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发表时间：
1991-03-01
影响因子：
3.9
通讯作者：
GAJEWSKI, E
中科院分区：
文献类型：
--
作者：
DIZDAROGLU, M;RAO, G;GAJEWSKI, E
本文研究了在铁、铜离子存在下用过氧化氢处理哺乳动物染色质时DNA碱基的修饰。哺乳动物染色质中的10种DNA碱基产物在染色质水解和水解产物的三甲基硅烷化后，通过使用气相色谱-质谱法与选择离子监测进行了鉴定和定量。该技术允许分析染色质中修饰的DNA碱基，而不需要首先从染色质中分离DNA。修饰的碱基是典型的羟基自由基诱导的DNA产物，表明羟基自由基参与了它们的形成。这也证实了由典型的羟基自由基清除剂的产物形成的抑制。产物形成的抑制是更突出的螯合离子比unchelated离子的存在下，表明一个可能的位点特异性形成的羟基自由基时，金属离子结合到染色质。过氧化氢在铜离子的存在下比在铁离子的存在下引起更多的DNA损伤。螯合铜离子引起显着抑制产物的形成。相比之下，DNA更广泛地破坏螯合铁离子的存在下，比在存在的非螯合铁离子。抗坏血酸的存在下，一般增加了产品的产率，表明增加生产的羟基自由基的金属离子的抗坏血酸还原。超氧化物歧化酶只在螯合铁离子的情况下才能部分抑制产物的形成。染色质中修饰碱基的产率低于在相同条件下用小牛胸腺DNA观察到的产率。
Modification of DNA bases in mammalian chromatin upon treatment with hydrogen peroxide in the presence of ferric and cupric ions was studied. Ten DNA base products in mammalian chromatin were identified and quantitated by the use of gas chromatography-mass spectrometry with selected-ion monitoring after hydrolysis of chromatin and trimethylsilylation of hydrolysates. This technique permitted the analysis of modified DNA bases in chromatin without the necessity of isolation of DNA from chromatin first. Modified bases identified were typical hydroxyl radical-induced products of DNA, indicating the involvement of hydroxyl radical in their formation. This was also confirmed by inhibition of product formation by typical scavengers of hydroxyl radical. The inhibition of product formation was much more prominent in the presence of chelated ions than unchelated ions, indicating a possible site-specific formation of hydroxyl radical when metal ions are bound to chromatin. Hydrogen peroxide in the presence of cupric ions caused more DNA damage than in the presence of ferric ions. Chelation of cupric ions caused a marked inhibition in product formation. By contrast, DNA was damaged more extensively in the presence of chelated ferric ions than in the presence of unchelated ferric ions. The presence of ascorbic acid generally increased the yields of the products, indicating increased production of hydroxyl radical by reduction of metal ions by ascorbic acid. Superoxide dismutase afforded partial inhibition of product formation only in the case of chelated iron ions. The yields of the modified bases in chromatin were lower than those observed with calf thymus DNA under the same conditions.