Abstract

8-Oxoguanine (8-oxoG) is the most common DNA base modification in the mammalian genome, associated with oxidative stress. Here we analysed the alterations in the distribution of 8-oxoG across the entire murine genome, before and after an elevation of oxidative stress by the use of ferric nitrilotriacetate (Fe-NTA) as an oxidative stress inducer in the renal proximal tubules. We isolated DNA fragments containing 8-oxoGs with immunoprecipitation from the murine genome, and amplified them by PCR for a distribution analysis with microarray-based comparative genomic hybridisation. The distribution profiles revealed that frequencies of 8-oxoG fluctuated with a cycle of 1–10 Mb along the chromosomes and the amplitude of the fluctuation was reduced after Fe-NTA administration. The distributions of 8-oxoG along the entire genome in the control and oxidatively stressed conditions were negatively correlated with that of gene density but positively correlated with that of Lamin B1 interaction, which corresponds to lamina-associated domains. These results on the murine genome were consistent with those on the rat genome we previously reported. We further discovered a negative correlation between the distributions of 8-oxoG and transcriptional activity along the genome. Finally, a comparison of the distributions before and after Fe-NTA administration suggested that 8-oxoGs are generated in response to the augmented oxidative stress preferentially in the transcriptionally active genomic regions, where 8-oxoGs have been less accumulated in the control condition.

摘要

8-氧鸟嘌呤 (8-oxoG) 是哺乳动物基因组中最常见的 DNA 碱基修饰，与氧化应激有关。在这里，我们通过使用次氮基三乙酸铁 (Fe-NTA) 作为肾近端小管中的氧化应激诱导剂，在氧化应激升高之前和之后分析了 8-oxoG 在整个小鼠基因组中分布的变化。我们从小鼠基因组中通过免疫沉淀分离了含有 8-oxoGs 的 DNA 片段，并通过 PCR 扩增它们，以使用基于微阵列的比较基因组杂交进行分布分析。分布图显示，8-oxoG 的频率沿染色体以 1-10 Mb 的周期波动，并且在 Fe-NTA 给药后波动幅度减小。在对照和氧化应激条件下，8-oxoG 沿整个基因组的分布与基因密度呈负相关，但与对应于叶片相关域的 Lamin B1 相互作用呈正相关。小鼠基因组上的这些结果与我们之前报道的大鼠基因组上的结果一致。我们进一步发现 8-oxoG 的分布与基因组转录活性之间存在负相关。最后，Fe-NTA 给药前后分布的比较表明，8-oxoGs 是在转录活性基因组区域优先响应增强的氧化应激而产生的，其中 8-oxoGs 在对照条件下积累较少。