In mammals, faithful inheritance of genomic methylation patterns ensures proper gene regulation and cell behaviour, impacting normal development and fertility. Following establishment, genomic methylation patterns are transmitted through S-phase by the maintenance methyltransferase Dnmt1. Using a protein interaction screen, we identify Microprocessor component DROSHA as a novel DNMT1-interactor. Drosha-deficient embryonic stem (ES) cells display genomic hypomethylation that is not accounted for by changes in the levels of DNMT proteins. DNMT1-mediated methyltransferase activity is also reduced in these cells. We identify two transcripts that are specifically upregulated in Drosha- but not Dicer-deficient ES cells. Regions within these transcripts predicted to form stem–loop structures are processed by Microprocessor and can inhibit DNMT1-mediated methylation in vitro. Our results highlight DROSHA as a novel regulator of mammalian DNA methylation and we propose that DROSHA-mediated processing of RNA is necessary to ensure full DNMT1 activity. This adds to the DROSHA repertoire of non-miRNA dependent functions as well as implicating RNA in regulating DNMT1 activity and correct levels of genomic methylation.

中文翻译：

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对DROSHA维持哺乳动物CG甲基化的新要求

在哺乳动物中，对基因组甲基化模式的忠实继承可确保适当的基因调节和细胞行为，从而影响正常发育和生育能力。建立后，基因组甲基化模式由维持甲基转移酶Dnmt1通过S期传递。使用蛋白质相互作用筛选器，我们将微处理器组件DROSHA识别为新型DNMT1相互作用器。Drosha缺陷型胚胎干（ES）细胞显示出基因组的低甲基化，这不能通过DNMT蛋白水平的变化来解释。在这些细胞中，DNMT1介导的甲基转移酶活性也降低了。我们确定了两个在Drosha-中而不是在Dicer中特别上调的转录本缺陷的ES细胞。这些转录本中预计会形成茎环结构的区域由微处理器处理，可以在体外抑制DNMT1介导的甲基化。我们的结果突出了DROSHA作为哺乳动物DNA甲基化的新型调节剂，我们建议DROSHA介导的RNA加工对于确保完全DNMT1活性是必要的。这增加了非miRNA依赖性功能的DROSHA库，也暗示RNA调控DNMT1活性和正确的基因组甲基化水平。