The role of MET1 in RNA-directed de novo and maintenance methylation of CG dinucleotides
The role of MET1 in RNA-directed de novo and maintenance methylation of CG dinucleotides
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DOI：
10.1007/s11103-004-0179-1
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发表时间：
2004-04-01
影响因子：
5.1
通讯作者：
Matzke, M
中科院分区：
文献类型：
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作者：
Aufsatz, W;Mette, MF;Matzke, M
对拟南芥中RNA引导的DNA甲基化缺陷突变和组成性诺帕林合成酶(NOS)启动子转录沉默的遗传筛选发现，编码DNA甲基转移酶MET1的基因有两个独立的突变。这两个突变的等位基因在MET1催化域的结构上都发生了破坏，表明它们是完全丧失功能的等位基因。旨在测试MET1突变对目标NOS启动子的RNA引导的从头开始和维持甲基化的影响的实验显示，在每个病例中，非CG甲基化水平接近野生型水平，CG甲基化水平显著降低。这些结果证实了MET1需要维持由RNA诱导的CG甲基化。此外，尽管在其他序列环境中Cs的RNA指示的从头甲基化正常，但在MET1突变体中未能建立完全的CG甲基化，这表明MET1是CG二核苷酸完全从头甲基化所必需的。我们讨论了MET1作为一种位点特异的DNA甲基转移酶，它能够在DNA复制过程中维持CG甲基化，并有助于响应RNA信号的CG从头开始甲基化。
A genetic screen for mutants defective in RNA-directed DNA methylation and transcriptional silencing of the constitutive nopaline synthase'(NOS) promoter in Arabidopsis identified two independent mutations in the gene encoding the DNA methyltransferase MET1. Both mutant alleles are disrupted structurally in the MET1 catalytic domain, suggesting that they are complete loss of function alleles. Experiments designed to test the effect of a met1 mutation on both RNA-directed de novo and maintenance methylation of the target NOS promoter revealed in each case approximately wild type levels of non-CG methylation together with significant reductions of CG methylation. These results confirm a requirement for MET1 to maintain CG methylation induced by RNA. In addition, the failure to establish full CG methylation in met1 mutants, despite normal RNA-directed de novo methylation of Cs in other sequence contexts, indicates that MET1 is required for full de novo methylation of CG dinucleotides. We discuss MET1 as a site-specific DNA methyltransferase that is able to maintain CG methylation during DNA replication and contribute to CG de novo methylation in response to RNA signals.