Department of Medical Laboratory and Radiation Sciences, University of Vermont, Burlington, Vermont 05405, USA.
DNA Cell Biol. 2012 Jun;31(6):908-16. doi: 10.1089/dna.2011.1509. Epub 2011 Dec 20.
An understanding of cellular processes that determine the response to ionizing radiation (IR) exposure is essential to improve radiotherapy and to assess risks to human health after accidental radiation exposure. Exposure to IR induces a multitude of biological effects. Recent studies have indicated the involvement of epigenetic events in regulating the responses of irradiated cells. DNA methylation, where the cytosine bases in CpG dimers are converted to 5-methyl cytosine, is an epigenetic event that has been shown to regulate a variety of biological processes. We investigated the DNA methylation changes in irradiated TK6 and WTK1 human cells that differ in sensitivity to IR. The global DNA methylation alterations as measured by an enzyme-linked immunosorbent assay-based assay showed hypomethylation in both type of cells. Using an arbitrarily primed polymerase chain reaction (AP-PCR) approach, we observed time-dependent dynamic changes in the regional genomic DNA methylation patterns in both cell lines. The AP-PCR DNA methylation profiles were different between TK6 and WTK1 cells, indicating the involvement of differential genomic DNA responses to radiation treatment. The analysis of the components of the DNA methylation machinery showed the modulation of maintenance and de novo methyltransferases in irradiated cells. DNMT1 mRNA levels were increased in TK6 cells after irradiation but were repressed in WTK1 cells. DNMT3A and DNMT3B were induced in both cells after radiation treatment. TET1, involved in the conversion of 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC), was induced in both cells. This study demonstrates that irradiated cells acquire epigenetic changes in the DNA methylation patterns, and the associated cellular machinery are involved in the response to radiation exposure. This study also shows that DNA methylation patterns change at different genomic regions and are dependent on time after irradiation and the genetic background of the cell.
理解决定细胞对电离辐射（IR）暴露反应的细胞过程对于改善放疗和评估意外辐射暴露后对人类健康的风险至关重要。暴露于 IR 会引起多种生物学效应。最近的研究表明，表观遗传事件参与调节辐照细胞的反应。DNA 甲基化是一种表观遗传事件，其中 CpG 二聚体中的胞嘧啶碱基被转化为 5-甲基胞嘧啶，已被证明可调节多种生物学过程。我们研究了对 IR 敏感性不同的辐照 TK6 和 WTK1 人细胞中的 DNA 甲基化变化。通过基于酶联免疫吸附测定的测定法测量的全局 DNA 甲基化改变显示两种类型的细胞均呈低甲基化。使用任意引物聚合酶链反应（AP-PCR）方法，我们观察到两种细胞系中区域基因组 DNA 甲基化模式的时间依赖性动态变化。AP-PCR DNA 甲基化图谱在 TK6 和 WTK1 细胞之间存在差异，表明对辐射处理的差异基因组 DNA 反应的参与。对 DNA 甲基化机制组件的分析表明，维持和从头甲基转移酶在辐照细胞中受到调节。DNMT1 mRNA 水平在照射后在 TK6 细胞中增加，但在 WTK1 细胞中受到抑制。DNMT3A 和 DNMT3B 在两种细胞经辐射处理后均被诱导。参与将 5-甲基胞嘧啶（5-mC）转化为 5-羟甲基胞嘧啶（5-hmC）的 TET1 在两种细胞中均被诱导。本研究表明，辐照细胞获得了 DNA 甲基化模式中的表观遗传变化，并且相关的细胞机制参与了对辐射暴露的反应。本研究还表明，DNA 甲基化模式在不同的基因组区域发生变化，并且取决于照射后时间和细胞的遗传背景。
