ARGONAUTE10 promotes the degradation of miR165/6 through the SDN1 and SDN2 exonucleases in Arabidopsis.
ARGONAUTE10 promotes the degradation of miR165/6 through the SDN1 and SDN2 exonucleases in Arabidopsis.
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ARGONAUTE10 通过拟南芥中的 SDN1 和 SDN2 核酸外切酶促进 miR165/6 的降解。
DOI：
10.1371/journal.pbio.2001272
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发表时间：
2017-02
期刊：
影响因子：
9.8
通讯作者：
Chen X
中科院分区：
文献类型：
--
作者：
Yu Y;Ji L;Le BH;Zhai J;Chen J;Luscher E;Gao L;Liu C;Cao X;Mo B;Ma J;Meyers BC;Chen X
植物和动物中小RNA的降解与小RNA 3 '截短和3'尿苷化有关，因此依赖于核酸外切酶和核苷酸转移酶。Argonaute（AGO）蛋白在体内与小RNA结合，不仅对小RNA的活性而且对小RNA的稳定性都是必需的。AGO 1是拟南芥中的microRNA（miRNA）效应子，其最接近的同源物AGO 10通过螯合miR 165/6（一种通过AGO 1起作用的保守miRNA）来维持分生组织中的干细胞稳态。在这里，我们发现小RNA降解核酸酶（SDNs）通过作用于AGO 1结合的miRNA，导致其3′端截短，从而启动miRNA降解，截短的种类被尿苷酸化和降解。我们报道了AGO 10通过增强其在体内被SDN 1和SDN 2降解来减少miR 165/6的积累。在体外，AGO 10结合的miR 165/6比AGO 1结合的miR 165/6更容易受到SDN 1介导的3′截短。因此，AGO 10促进miR 165/6的降解，这与AGO 1的稳定作用相反。我们的工作确定了一类负责体内miRNA 3′截短的核酸外切酶，并揭示了miRNA周转的特异性决定机制。这项工作，加上以前对AGO 10的研究，表明空间调控的miRNA降解是植物干细胞维持的基础。microRNAs（miRNAs）是一类由21-24个核苷酸组成的调控RNA，影响动植物的几乎所有生物过程。miRNA的丰度由其生物发生和降解决定。miRNA的降解与其3′端的修剪和加尾有关。拟南芥中3′端修剪与3′端加尾的关系以及3′端修剪的相关酶尚不清楚。保护miRNAs免于降解的机制包括3′端甲基化和与ARGONAUTE（AGO）蛋白的结合。在本研究中，我们发现小RNA降解核酸酶（SDN）家族的两个成员，SDN 1和SDN 2，部分负责拟南芥中的miRNA 3′修剪活动。我们进一步阐明了3′修剪和3′加尾之间的关系--miRNA首先被SDNs修剪，而3′修剪和未甲基化的miRNA被核苷酸转移酶HESO 1加尾。此外，我们证明了SDN 1能够作用于AGO 1结合和甲基化的miRNA。我们还揭示了AGO 10的特殊功能，其在体内对miR 165/6具有最高的亲和力。我们发现，AGO 10结合的miR 165/6比AGO 1结合的miR 165/6更容易受到SDN介导的降解。本研究为miRNA降解提供了一个通用的分子框架，并为miRNA降解的特异性测定提供了一个实例。
The degradation of small RNAs in plants and animals is associated with small RNA 3′ truncation and 3′ uridylation and thus relies on exonucleases and nucleotidyl transferases. ARGONAUTE (AGO) proteins associate with small RNAs in vivo and are essential for not only the activities but also the stability of small RNAs. AGO1 is the microRNA (miRNA) effector in Arabidopsis, and its closest homolog, AGO10, maintains stem cell homeostasis in meristems by sequestration of miR165/6, a conserved miRNA acting through AGO1. Here, we show that SMALL RNA DEGRADING NUCLEASES (SDNs) initiate miRNA degradation by acting on AGO1-bound miRNAs to cause their 3′ truncation, and the truncated species are uridylated and degraded. We report that AGO10 reduces miR165/6 accumulation by enhancing its degradation by SDN1 and SDN2 in vivo. In vitro, AGO10-bound miR165/6 is more susceptible to SDN1-mediated 3′ truncation than AGO1-bound miR165/6. Thus, AGO10 promotes the degradation of miR165/6, which is contrary to the stabilizing effect of AGO1. Our work identifies a class of exonucleases responsible for miRNA 3′ truncation in vivo and uncovers a mechanism of specificity determination in miRNA turnover. This work, together with previous studies on AGO10, suggests that spatially regulated miRNA degradation underlies stem cell maintenance in plants. MicroRNAs (miRNAs) are 21–24 nucleotide regulatory RNAs that impact nearly all biological processes in plants and animals. The abundance of miRNAs is determined by their biogenesis and degradation. miRNA degradation is associated with trimming and tailing of their 3′ ends. The relationship between 3′ trimming and 3′ tailing as well as the enzyme(s) responsible for 3′ trimming was unknown in Arabidopsis. Mechanisms that protect miRNAs from degradation include 3′ terminal methylation and association with ARGONAUTE (AGO) proteins. In this study, we show that two members of the SMALL RNA DEGRADING NUCLEASE (SDN) family, SDN1 and SDN2, are partly responsible for the miRNA 3′ trimming activities in Arabidopsis. We further elucidate the relationship between 3′ trimming and 3′ tailing—miRNAs are first trimmed by SDNs, and the 3′ trimmed-and-unmethylated miRNAs are tailed by the nucleotidyl transferase HESO1. Furthermore, we demonstrate that SDN1 is able to act on AGO1-bound and methylated miRNAs. We also reveal a special function of AGO10, which has the highest affinity for miR165/6 in vivo. We show that AGO10-bound miR165/6 is more susceptible to SDN-mediated degradation than AGO1-bound miR165/6. This study provides a general molecular framework for miRNA degradation and an example of specificity determination in miRNA degradation.