A MicroRNA Precursor Surveillance System in Quality Control of MicroRNA Synthesis

• Published in: Molecular cell 2014-09, Vol.55 (6), p.868-879
• Main Authors: Liu, Xuhang, Zheng, Qi, Vrettos, Nicholas, Maragkakis, Manolis, Alexiou, Panagiotis, Gregory, Brian D., Mourelatos, Zissimos
• Format: Article
• Language: English
• Subjects: Argonaute Proteins - metabolism; Exosome Multienzyme Ribonuclease Complex - chemistry; Exosome Multienzyme Ribonuclease Complex - metabolism; Exosomes - metabolism; Genome; HEK293 Cells; High-Throughput Nucleotide Sequencing; Humans; MicroRNAs - genetics; RNA Nucleotidyltransferases - metabolism; Uridine - metabolism
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2014.07.017

MicroRNAs (miRNAs) are essential for regulation of gene expression. Though numerous miRNAs have been identified by high-throughput sequencing, few precursor miRNAs (pre-miRNAs) are experimentally validated. Here we report a strategy for constructing high-throughput sequencing libraries enriched for full-length pre-miRNAs. We find widespread and extensive uridylation of Argonaute (Ago)-bound pre-miRNAs, which is primarily catalyzed by two terminal uridylyltransferases: TUT7 and TUT4. Uridylation by TUT7/4 not only polishes pre-miRNA 3′ ends, but also facilitates their degradation by the exosome, preventing clogging of Ago with defective species. We show that the exosome exploits distinct substrate preferences of DIS3 and RRP6, its two catalytic subunits, to distinguish productive from defective pre-miRNAs. Furthermore, we identify a positive feedback loop formed by the exosome and TUT7/4 in triggering uridylation and degradation of Ago-bound pre-miRNAs. Our study reveals a pre-miRNA surveillance system that comprises TUT7, TUT4, and the exosome in quality control of miRNA synthesis. [Display omitted] •A strategy for identifying full-length pre-miRNAs bound to Agos•Uridylation by TUT7/4 polishes pre-miRNAs and facilitates degradation by the exosome•Distinct features recognized by DIS3 and RRP6 in pre-miRNA degradation•A positive feedback loop formed by the exosome and TUT7/4 in pre-miRNA degradation Liu et al. report a strategy for constructing high-throughput sequencing libraries enriched for pre-miRNAs and find that there is extensive uridylation of Agonaute-bound pre-miRNAs, which they find are generated as part of a pre-miRNA quality control system involving uridylyltransferases and the exosome.