Role of CG and non-CG methylation in immobilization of transposons in arabidopsis
Role of CG and non-CG methylation in immobilization of transposons in arabidopsis
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DOI：
10.1016/s0960-9822(03)00106-4
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发表时间：
2003-03-04
期刊：
影响因子：
9.2
通讯作者：
Kakutani, T
中科院分区：
文献类型：
--
作者：
Kato, M;Miura, A;Kakutani, T
真核生物基因组中胞嘧啶残基的甲基化通常与包括转座子及其衍生物的重复序列相关[1，2]。甲基化与这些重复序列的两种潜在有害作用的控制有关：（1）不受控制的转录[2-4]，这通常会干扰附近宿主基因的正确表达[5，6]，以及（2）通过转座和异位重组改变基因组结构[2，7]。拟南芥提供了一个遗传上易于处理的系统来检查这些可能性，因为DNA甲基转移酶的可行突变体是可用的。拟南芥MET 1（甲基转移酶1，哺乳动物DNA甲基转移酶Dnmt 1的直系同源物）是维持基因组胞嘧啶甲基化在5 '-CG-3'位点所必需的[8，9]。拟南芥另外使用染色体甲基化酶3（CMT 3）甲基化非CG位点[10，11]。我们检查了Met 1、cmt 3和cmt 3-Met 1突变体中内源性CACTA转座子的迁移率。在cmt 3-met 1双突变体中检测到CACTA元件的高频转座。无论是met 1或cmt 3的单一突变体的动员效果差得多，尽管显着诱导CACTA转录积累。这些结果使我们得出结论，CG和非CG甲基化系统冗余的转座子的固定功能。植物中的非CG甲基化可能已经进化为专用于转座子控制的附加表观遗传标签。这一观点与最近发现CMT 3优先甲基化转座子相关序列一致[12]。
Methylation of cytosine residues in eukaryotic genomes is often associated with repeated sequences including transposons and their derivatives [1, 2]. Methylation has been implicated in control of two potential deleterious effects of these repeats: (1) uncontrolled transcription [2-4], which often disturbs proper expression of nearby host genes [5, 6], and (2) changes in genome structure by transposition and ectopic recombination [2, 7]. Arabidopsis thaliana provides a genetically tractable system to examine these possibilities, since viable mutants in DNA methyltransferases are available. Arabidopsis MET1 (METHYLTRANSFERASE 1, ortholog of mammalian DNA methyltransferase Dnmt1) is necessary for maintaining genomic cytosine methylation at 5'-CG-3' sites [8, 9]. Arabidopsis additionally methylates non-CG sites using CHROMO-METHYLASE3 (CMT3) [10, 11]. We examined the mobility of endogenous CACTA transposons in met1, cmt3, and cmt3-met1 mutants. High-frequency transposition of CACTA elements was detected in cmt3-met1 double mutants. Single mutants in either met1 or cmt3 were much less effective in mobilization, despite significant induction of CACTA transcript accumulation. These results lead us to conclude that CG and non-CG methylation systems redundantly function for immobilization of transposons. Non-CG methylation in plants may have evolved as an additional epigenetic tag dedicated to transposon control. This view is consistent with the recent finding that CMT3 preferentially methylates transposon-related sequences [12].