Cooperativity between DNA methyltransferases in the maintenance methylation of repetitive elements
Cooperativity between DNA methyltransferases in the maintenance methylation of repetitive elements
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DOI：
10.1128/mcb.22.2.480-491.2002
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发表时间：
2002-01-01
影响因子：
5.3
通讯作者：
Jones, PA
中科院分区：
文献类型：
--
作者：
Liang, GG;Chan, MF;Jones, PA
我们使用系统基因敲除DNA甲基转移酶的小鼠胚胎干（ES）细胞来描述DNA甲基转移酶1 （Dnmt1）和Dumt3a和-3b在维持小鼠基因组甲基化模式中的作用。Dnmt1单独能够维持分析的大多数CpG-poor区域的甲基化。相比之下，Dnmt1、Dnmt3a和/或Dumt3b对于包括丰富的小鼠LINE-1启动子的精选序列的甲基化都是必需的。我们使用了一种新的半甲基化分析方法，表明即使在野生型细胞中，这些序列也含有高水平的半甲基化DNA，这表明甲基化的维持性较差。我们发现Dnmt3a和/或-3b可以在细胞短暂暴露于5-aza-CdR后将这些序列的甲基化恢复到预处理水平，而Dnmt1本身不能。我们得出结论，Dnmt3a和/或Dnmt3b正在进行的从头甲基化补偿了Dnmt1对这些内源性重复序列的低效维持甲基化。我们的研究结果揭示了胚胎干细胞中哺乳动物DNA甲基转移酶之间以前未被认识到的合作程度。
We used mouse embryonic stem (ES) cells with systematic gene knockouts for DNA methyltransferases to delineate the roles of DNA methyltransferase 1 (Dnmt1) and Dumt3a and -3b in maintaining methylation patterns in the mouse genome. Dnmt1 alone was able to maintain methylation of most CpG-poor regions analyzed. In contrast, both Dnmt1 and Dnmt3a and/or Dumt3b were required for methylation of a select class of sequences which included abundant murine LINE-1 promoters. We used a novel hemimethylation assay to show that even in wild-type cells these sequences contain high levels of hemimethylated DNA, suggestive of poor maintenance methylation. We showed that Dnmt3a and/or -3b could restore methylation of these sequences to pretreatment levels following transient exposure of cells to 5-aza-CdR, whereas Dnmt1 by itself could not. We conclude that ongoing de novo methylation by Dnmt3a and/or Dnmt3b compensates for inefficient maintenance methylation by Dnmt1 of these endogenous repetitive sequences. Our results reveal a previously unrecognized degree of cooperativity among mammalian DNA methyltransferases in ES cells.