SOS-dependent A → G transitions induced by hydroxyl radical generating system hypoxanthine xanthine oxidase/Fe3+/EDTA are accompanied by the increase of Fapy-adenine content in M13 mp18 phage DNA
SOS-dependent A → G transitions induced by hydroxyl radical generating system hypoxanthine xanthine oxidase/Fe3+/EDTA are accompanied by the increase of Fapy-adenine content in M13 mp18 phage DNA
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DOI：
10.1016/s0921-8777(99)00012-9
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发表时间：
1999-05-14
期刊：
影响因子：
--
通讯作者：
Tudek, B
中科院分区：
文献类型：
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作者：
Graziewicz, MA;Zastawny, TH;Tudek, B
采用气相色谱/同位素稀释-质谱选择离子监测法（GC/IDMS-SIM）测定次黄嘌呤/黄嘌呤氧化酶/Fe ~（3+）/EDTA修饰的ss M13 mp 18噬菌体DNA中的氧化碱基。观察到DNA中氧化碱基含量的剂量依赖性增加，其中FapyGua、胸腺嘧啶乙二醇和FapyAde的增加最大。8-OH-Gua的量在非氧化和氧化DNA中均相对较高，并且增加到与FapyAde和ThyGly相同的程度。转染大肠杆菌后，DNA氧化导致噬菌体存活率急剧下降。生存率提高2.8倍后，诱导的SOS系统的紫外线照射的细菌和突变频率的lacZ基因在SOS条件下增加7倍，在未照射的细菌。突变谱与以前报道的不同，突变在M13 lacZ序列中随机分布，这与以前的发现相反，在非螯合金属离子的情况下，在几个簇中发现了其他类型的突变。因此，DNA氧化条件和金属离子对DNA碱基的可及性可能是产生不同DNA损伤和突变的重要因素。在SOS诱导的和未诱导的大肠杆菌中均发现但在SOS诱导的细胞中具有更高突变频率的主要碱基取代是C -> A（类似于SOS条件下增加20倍）、G -> A（增加9倍）和G -> C（增加4.5倍）。只有极少数的G → T转换被发现，特别是大量的A → G转换只出现在SOS诱导的细菌中，并伴随着噬菌体DNA中FapyAde含量的增加，而2-OH-Ade检测不到。因此，在SOS诱导的细菌中，咪唑开环腺嘌呤可能在DNA复制过程中模仿鸟嘌呤，并与胞嘧啶配对产生A -> G转换。(C)1999 Elsevier Science B. V.保留所有权利。
Gas chromatography/isotope dilution-mass spectrometry with selected ion monitoring (GC/IDMS-SIM) was used to measure oxidised bases in hypoxanthine/xanthine oxidase/Fe3+/EDTA modified ss M13 mp18 phage DNA. A dose-dependent increase of oxidised bases content in DNA was observed with the biggest augmentation of FapyGua, thymine glycol and FapyAde, The amount of 8-OH-Gua was relatively high both in non-oxidised and oxidised DNA, and increased to the same extent as FapyAde and ThyGly. DNA oxidation caused a dramatic decrease in phage survival after transfection to E, coli. Survival was improved 2.8-fold after induction of the SOS system by UV irradiation of bacteria and mutation frequency of the lacZ gene in SOS conditions increased 7-fold over that in non-irradiated bacteria. Spectrum of mutations was different from those reported previously and mutations were distributed rather randomly within M13 lacZ sequence, which was in contrast to previous findings, where with non-chelated metal ions other types of mutations were found in several clusters. Thus, conditions of DNA oxidation and accessibility of metal ions for DNA bases might be important factors for generating different DNA damages and mutations. Major base substitutions found both in SOS-induced and non-induced E, coli but with higher mutation frequency in SOS-induced cells were C --> A (similar to 20-fold increase in SOS-conditions), G --> A (9-fold increase) and G --> C (4.5-fold increase). Very few G --> T transitions were found. A particularly large group of A --> G transitions appeared only in SOS-induced bacteria and was accompanied by augmentation of FapyAde content in the phage DNA with undetectable 2-OH-Ade. It is then possible that imidazole ring-opened adenine mimics guanine during DNA replication and pairs with cytosine yielding A --> G transitions in SOS-induced bacteria. (C) 1999 Elsevier Science B.V. All rights reserved.