CpG methylation reduces genomic instability.
CpG methylation reduces genomic instability.
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发表时间：
1999-12
影响因子：
4
通讯作者：
R. Rizwana;P. Hahn
中科院分区：
文献类型：
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作者：
R. Rizwana;P. Hahn
肿瘤细胞中DNA的低甲基化与基因组的不稳定性有关，并被认为是由于有丝分裂重组的激活。我们已经研究了两个650 kb的双分钟染色体中存在的两个小鼠肿瘤细胞系，耐甲氨蝶呤的甲基化模式。两种细胞系中均存在扩增二氢叶酸还原酶基因的双微小染色体的多个拷贝。在其中一个细胞系（Mut F）中，双微小染色体中的两个未甲基化的CpG岛很容易被甲基化敏感的稀有切割限制性内切酶切割。在另一个细胞系（Mut C）中，双微小染色体中的切割位点部分甲基化，对切割具有抗性。具有两个未甲基化的CpG岛的双微小染色体经历快速二聚化，而具有部分甲基化的CpG岛的双微小染色体在连续培养中超过一年在大小上不变。部分甲基化的CpG岛可以通过氮杂胞苷处理或通过在培养物中延长时间自然地去甲基化，并且变得对用稀切限制性内切核酸酶切割敏感。Mut C双微小染色体，与新的去甲基化的CpG岛，但不是双微小染色体与部分甲基化的CpG岛，经历缺失和二聚化。这些结果表明CpG岛甲基化控制大DNA分子之间和内部的有丝分裂重组的作用。
Hypomethylation of DNA in tumor cells is associated with genomic instability and has been suggested to be due to activation of mitotic recombination. We have studied the methylation patterns in two 650 kb double minute chromosomes present in two mouse tumor cell lines, resistant to methotrexate. Multiple copies of the double minute chromosomes amplifying the dihydrofolate reductase gene are present in both the cell lines. In one of the cell lines (Mut F), two unmethylated CpG islands in the double minute chromosomes are readily cleaved by methylation-sensitive rare-cutting restriction endonucleases. In the other cell line (Mut C), the cleavage sites in the double minute chromosomes are partially methylated and resistant to cleavage. The double minute chromosomes with the two unmethylated CpG islands undergo rapid dimerization, whereas the double minute chromosomes with the partially methylated CpG islands are unchanged in size for over a year in continuous culture. The partially methylated CpG islands can be demethylated by azacytidine treatment or naturally by extended time in culture, and become sensitive to cleavage with the rare-cutting restriction endonucleases. The Mut C double minute chromosomes, with the newly demethylated CpG islands, but not the double minute chromosomes with the partially methylated CpG islands, undergo deletions and dimerizations. These results suggest a role for CpG island methylation controlling mitotic recombination between and within large DNA molecules.