首页> 外文OA文献 >The De Novo Cytosine Methyltransferase DRM2 Requires Intact UBA Domains and a Catalytically Mutated Paralog DRM3 during RNA–Directed DNA Methylation in Arabidopsis thaliana
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The De Novo Cytosine Methyltransferase DRM2 Requires Intact UBA Domains and a Catalytically Mutated Paralog DRM3 during RNA–Directed DNA Methylation in Arabidopsis thaliana

机译:De Novo胞嘧啶甲基转移酶DRM2需要完整的UBA域和拟南芥中RNA定向DNA甲基化过程中的催化突变的Paralog DRM3。

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摘要

Eukaryotic DNA cytosine methylation can be used to transcriptionally silence repetitive sequences, including transposons and retroviruses. This silencing is stable between cell generations as cytosine methylation is maintained epigenetically through DNA replication. The Arabidopsis thaliana Dnmt3 cytosine methyltransferase ortholog DOMAINS REARRANGED METHYLTRANSFERASE2 (DRM2) is required for establishment of small interfering RNA (siRNA) directed DNA methylation. In mammals PIWI proteins and piRNA act in a convergently evolved RNA–directed DNA methylation system that is required to repress transposon expression in the germ line. De novo methylation may also be independent of RNA interference and small RNAs, as in Neurospora crassa. Here we identify a clade of catalytically mutated DRM2 paralogs in flowering plant genomes, which in A.thaliana we term DOMAINS REARRANGED METHYLTRANSFERASE3 (DRM3). Despite being catalytically mutated, DRM3 is required for normal maintenance of non-CG DNA methylation, establishment of RNA–directed DNA methylation triggered by repeat sequences and accumulation of repeat-associated small RNAs. Although the mammalian catalytically inactive Dnmt3L paralogs act in an analogous manner, phylogenetic analysis indicates that the DRM and Dnmt3 protein families diverged independently in plants and animals. We also show by site-directed mutagenesis that both the DRM2 N-terminal UBA domains and C-terminal methyltransferase domain are required for normal RNA–directed DNA methylation, supporting an essential targeting function for the UBA domains. These results suggest that plant and mammalian RNA–directed DNA methylation systems consist of a combination of ancestral and convergent features.
机译:真核DNA胞嘧啶甲基化可用于转录沉默重复序列,包括转座子和逆转录病毒。这种沉默在细胞世代之间是稳定的,因为通过DNA复制表观遗传地维持胞嘧啶甲基化。拟南芥Dnmt3胞嘧啶甲基转移酶直系同源物DOMAINS重新排列的甲基转移酶2(DRM2)是建立小干扰RNA(siRNA)指导的DNA甲基化所必需的。在哺乳动物中,PIWI蛋白和piRNA在聚合进化的RNA指导的DNA甲基化系统中起作用,该系统是抑制种系中转座子表达所必需的。从头甲基化也可能与RNA干扰和小RNA无关,例如在Neurospora crassa中。在这里,我们确定了开花植物基因组中催化突变的DRM2旁系同源进化枝,在拟南芥中,我们称其为DOMAINS重新排列的甲基转移酶3(DRM3)。尽管被催化突变,DRM3对于正常维持非CG DNA甲基化,由重复序列触发的RNA定向DNA甲基化的建立以及与重复相关的小RNA的积累是必需的。尽管哺乳动物的催化失活的Dnmt3L旁系同源物以类似的方式起作用,但系统发育分析表明DRM和Dnmt3蛋白质家族在植物和动物中独立地分化。我们还通过定点诱变表明,正常的RNA定向DNA甲基化需要DRM2 N末端UBA结构域和C末端甲基转移酶结构域,从而支持UBA域的基本靶向功能。这些结果表明,植物和哺乳动物RNA定向的DNA甲基化系统由祖先和会聚特征组成。

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