A key step in microRNA biogenesis is the processing of a primary precursor RNA by the microprocessor into a precursor miRNA (pre-miRNA) intermediate. In plants, little is known about the processes that act on pre-miRNAs to influence miRNA biogenesis. Here, we performed 3' rapid amplification of complementary DNA ends sequencing to profile pre-miRNA 3' ends in Arabidopsis. 3' end heterogeneity was prevalent, and the three microprocessor components promoted 3' end precision. Extensive cytidylation and uridylation of precise and imprecise pre-miRNA 3' ends were uncovered. The nucleotidyl transferase HESO1 uridylated pre-miRNAs in vitro and was responsible for most pre-miRNA uridylation in vivo. HESO1, NTP6 and NTP7 contribute to pre-miRNA cytidylation. Tailing of pre-miRNAs tended to restore trimmed pre-miRNAs to their intact length to promote further processing. In addition, HESO1-mediated uridylation led to the degradation of certain imprecisely processed pre-miRNAs. Thus, we uncovered widespread cytidylation and uridylation of pre-miRNAs and demonstrated diverse functions of pre-miRNA tailing in plants.

中文翻译：

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拟南芥中前体 miRNA 的普遍胞苷化和尿苷化。

microRNA生物发生的一个关键步骤是微处理器将初级前体RNA加工成前体miRNA（pre-miRNA）中间体。在植物中，对作用于前 miRNA 以影响 miRNA 生物发生的过程知之甚少。在这里，我们进行了互补 DNA 末端测序的 3' 快速扩增，以分析拟南芥中的 pre-miRNA 3' 末端。3'端异质性普遍存在，三个微处理器组件提升了3'端精度。发现了精确和不精确的 pre-miRNA 3' 末端的广泛胞苷酸化和尿苷酸化。核苷酸转移酶 HESO1 在体外对 pre-miRNA 进行尿苷化，并负责体内大多数 pre-miRNA 尿苷化。HESO1、NTP6 和 NTP7 有助于前 miRNA 胞苷化。pre-miRNA 的加尾倾向于将修剪后的 pre-miRNA 恢复到其完整长度，以促进进一步加工。此外，HESO1 介导的尿苷酸化导致某些未精确加工的前 miRNA 降解。因此，我们发现了 pre-miRNA 的广泛胞苷化和尿苷化，并证明了植物中 pre-miRNA 拖尾的多种功能。