Naturally occurring H-DNA-forming sequences are mutagenic in mammalian cells.
Naturally occurring H-DNA-forming sequences are mutagenic in mammalian cells.
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DOI：
10.1073/pnas.0405116101
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发表时间：
2004-09
影响因子：
11.1
通讯作者：
Guliang Wang;K. Vasquez
中科院分区：
文献类型：
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作者：
Guliang Wang;K. Vasquez
自然产生的DNA序列可以形成非规范结构，如H-DNA，这些结构丰富，并调节几个与疾病相关的基因的表达。在这里，我们证明了H-DNA形成序列在哺乳动物细胞中具有内在的突变性。这一发现表明，DNA是诱变的一个因素，而不仅仅是最终产物。通过使用在人c-myc启动子中发现的内源性H-DNA形成序列，在COS-7细胞中报告基因的突变频率比背景增加了大约20倍。在H-DNA基因座附近检测到H-DNA诱导的双链断裂。突变体的结构在断裂点显示出微同源性，与DSB的非同源末端连接修复一致。这些结果表明，在Burkitt淋巴瘤和t(12；15)BALB/c浆细胞瘤等疾病中，H-DNA诱导的c-myc基因易位中存在DSB，这些疾病的大多数断裂点都在H-DNA形成部位附近。因此，我们的发现表明，H-DNA是DSB引起的遗传不稳定性的来源之一，并表明自然发生的DNA序列在哺乳动物中是诱变的，可能有助于遗传进化和疾病。
Naturally occurring DNA sequences can form noncanonical structures such as H-DNA, which are abundant and regulate the expression of several disease-linked genes. Here, we show that H-DNA-forming sequences are intrinsically mutagenic in mammalian cells. This finding suggests that DNA is a causative factor in mutagenesis and not just the end product. By using the endogenous H-DNA-forming sequence found in the human c-myc promoter, mutation frequencies in a reporter gene were increased approximately 20-fold over background in COS-7 cells. H-DNA-induced double-strand breaks (DSBs) were detected near the H-DNA locus. The structures of the mutants revealed microhomologies at the breakpoints, consistent with a nonhomologous end-joining repair of the DSBs. These results implicate H-DNA-induced DSBs in c-myc gene translocations in diseases such as Burkitt's lymphoma and t(12;15) BALB/c plasmacytomas, where most breakpoints are found near the H-DNA-forming site. Thus, our findings suggest that H-DNA is a source of genetic instability resulting from DSBs and demonstrate that naturally occurring DNA sequences are mutagenic in mammals, perhaps contributing to genetic evolution and disease.