RNA Mediated Gene Regulation Section; RNA Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA.
School of Basic Medicine, Zhejiang Chinese Medical University, Hangzhou, 310053, China.
Nat Commun. 2020 Jun 2;11(1):2765. doi: 10.1038/s41467-020-16533-w.
MicroRNAs (miRNAs) associated with Argonaute proteins (AGOs) regulate gene expression in mammals. miRNA 3' ends are subject to frequent sequence modifications, which have been proposed to affect miRNA stability. However, the underlying mechanism is not well understood. Here, by genetic and biochemical studies as well as deep sequencing analyses, we find that AGO mutations disrupting miRNA 3' binding are sufficient to trigger extensive miRNA 3' modifications in HEK293T cells and in cancer patients. Comparing these modifications in TUT4, TUT7 and DIS3L2 knockout cells, we find that TUT7 is more robust than TUT4 in oligouridylating mature miRNAs, which in turn leads to their degradation by the DIS3L2 exonuclease. Our findings indicate a decay machinery removing AGO-associated miRNAs with an exposed 3' end. A set of endogenous miRNAs including miR-7, miR-222 and miR-769 are targeted by this machinery presumably due to target-directed miRNA degradation.
微 RNA（miRNA）与 Argonaute 蛋白（AGO）相关，在哺乳动物中调节基因表达。miRNA 3' 末端经常发生序列修饰，这些修饰被认为会影响 miRNA 的稳定性。然而，其潜在机制尚不清楚。在这里，通过遗传和生化研究以及深度测序分析，我们发现 AGO 突变破坏 miRNA 3' 结合足以在 HEK293T 细胞和癌症患者中引发广泛的 miRNA 3' 修饰。在 TUT4、TUT7 和 DIS3L2 缺失细胞中比较这些修饰，我们发现 TUT7 比 TUT4 更能有效地使成熟 miRNA 寡聚化，进而导致其被 DIS3L2 外切酶降解。我们的研究结果表明存在一种降解机制，可以去除具有暴露 3' 末端的 AGO 相关 miRNA。一组内源性 miRNA，包括 miR-7、miR-222 和 miR-769，可能是由于靶向导向的 miRNA 降解而成为该机制的靶标。
