MEM1 participates in ROS1-mediated DNA demethylation pathway, and acts functionally as ROS3 to counteract the effects of RdDM pathway.mem1mutation leads to large numbers of hyper-DMRs inArabidopsisgenome. In higher plants, DNA methylation performs important functions in silencing transcribed genes and transposable elements (TEs). Active DNA demethylation mediated by REPRESSOR OF SILENCING 1 (ROS1) is able to antagonize the action of DNA methylation caused by RNA-directed DNA methylation (RdDM) pathway, which plays critical roles in keeping DNA methylation at a proper level. In this study, a new mutant named mem1 (for methylation elevated mutant 1) was isolated from a genetic screen of T-DNA insertional mutant population for lines with elevated DNA methylation at a particular locus through Chop-PCR method. MEM1 possesses a Zf-C3HC domain, and is localized in nucleus as well as highly expressed in cotyledons. Whole-genome bisulfite sequencing data showed that knockout mutation of MEM1 leads to 4519 CG, 1793 CHG and 12739 CHH hyper-DMRs (for differentially methylated regions). Further analysis indicated that there are 2751, 2216 and 2042 overlapped CG hyper-DMRs between mem1-1and three mutants, i.e. ros1-4, rdd and ros3-2, respectively; 797, 2514, and 6766 overlapped CHH hyper-DMRs were observed between mem1-1 and three such mutants, respectively; mem1 nrpd1-3 and mem1 rdm1 double mutants showed nearly complete or partial loss of hypermethylation at 4 tested loci, suggesting that MEM1 performs similar functions as DNA glycosylase/lyases in counteracting excessive DNA methylation, and MEM1 plays important roles as REPRESSOR OF SILENCING 3 (ROS3) in erasing CHH methylation caused by the RdDM pathway. Together, these data demonstrate the involvement of MEM1 in ROS1-mediated DNA demethylation pathway and functional connections between MEM1 and ROS3.

中文翻译：

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MEM1 参与拟南芥 DNA 去甲基化。

MEM1 参与 ROS1 介导的 DNA 去甲基化途径，并在功能上作为 ROS3 来抵消 RdDM 途径的影响。mem1 突变导致拟南芥基因组中大量的超 DMR。在高等植物中，DNA 甲基化在沉默转录基因和转座因子 (TE) 方面发挥重要作用。REPRESSOR OF SILENCING 1 (ROS1) 介导的活性 DNA 去甲基化能够拮抗由 RNA 指导的 DNA 甲基化 (RdDM) 途径引起的 DNA 甲基化作用，这在将 DNA 甲基化保持在适当水平方面起着关键作用。在这项研究中，通过 Chop-PCR 方法从 T-DNA 插入突变体群体的遗传筛选中分离出一个名为 mem1 的新突变体（用于甲基化升高的突变体 1），用于在特定基因座处具有升高的 DNA 甲基化的系。MEM1 拥有一个 Zf-C3HC 结构域，并且定位于细胞核以及在子叶中高度表达。全基因组亚硫酸氢盐测序数据显示 MEM1 的敲除突变导致 4519 个 CG、1793 个 CHG 和 12739 个 CHH 超 DMR（用于差异甲基化区域）。进一步分析表明，mem1-1与ros1-4、rdd和ros3-2三个突变体之间分别有2751、2216和2042个重叠的CG hyper-DMR；在 mem1-1 和三个这样的突变体之间分别观察到 797、2514 和 6766 个重叠的 CHH hyper-DMR；mem1 nrpd1-3 和 mem1 rdm1 双突变体在 4 个测试位点显示几乎完全或部分高甲基化丧失，表明 MEM1 在抵消过度 DNA 甲基化方面与 DNA 糖基化酶/裂解酶具有相似的功能，并且 MEM1 作为 REPRESSOR OF SILENCING 3 (ROS3) 在消除由 RdDM 途径引起的 CHH 甲基化中起重要作用。总之，这些数据证明了 MEM1 参与 ROS1 介导的 DNA 去甲基化途径以及 MEM1 和 ROS3 之间的功能联系。