BACKGROUND: MicroRNAs (miRNAs) are ~22 nucleotide (nt) small RNAs that control development, physiology, and pathology in animals and plants. Production of miRNAs involves the sequential processing of primary hairpin-containing RNA polymerase II transcripts by the RNase III enzymes Drosha in the nucleus and Dicer in the cytoplasm. miRNA duplexes then assemble into Argonaute proteins to form the RNA-induced silencing complex (RISC). In mature RISC, a single-stranded miRNA directs the Argonaute protein to bind partially complementary sequences, typically in the 3' untranslated regions of messenger RNAs, repressing their expression. RESULTS: Here, we show that after loading into Argonaute1 (Ago1), more than a quarter of all Drosophila miRNAs undergo 3' end trimming by the 3'-to-5' exoribonuclease Nibbler (CG9247). Depletion of Nibbler by RNA interference (RNAi) reveals that miRNAs are frequently produced by Dicer-1 as intermediates that are longer than ~22 nt. Trimming of miRNA 3' ends occurs after removal of the miRNA* strand from pre-RISC and may be the final step in RISC assembly, ultimately enhancing target messenger RNA repression. In vivo, depletion of Nibbler by RNAi causes developmental defects. CONCLUSIONS: We provide a molecular explanation for the previously reported heterogeneity of miRNA 3' ends and propose a model in which Nibbler converts miRNAs into isoforms that are compatible with the preferred length of Ago1-bound small RNAs.
BACKGROUND: MicroRNAs (miRNAs) are ~22 nucleotide (nt) small RNAs that control development, physiology, and pathology in animals and plants. Production of miRNAs involves the sequential processing of primary hairpin-containing RNA polymerase II transcripts by the RNase III enzymes Drosha in the nucleus and Dicer in the cytoplasm. miRNA duplexes then assemble into Argonaute proteins to form the RNA-induced silencing complex (RISC). In mature RISC, a single-stranded miRNA directs the Argonaute protein to bind partially complementary sequences, typically in the 3' untranslated regions of messenger RNAs, repressing their expression. RESULTS: Here, we show that after loading into Argonaute1 (Ago1), more than a quarter of all Drosophila miRNAs undergo 3' end trimming by the 3'-to-5' exoribonuclease Nibbler (CG9247). Depletion of Nibbler by RNA interference (RNAi) reveals that miRNAs are frequently produced by Dicer-1 as intermediates that are longer than ~22 nt. Trimming of miRNA 3' ends occurs after removal of the miRNA* strand from pre-RISC and may be the final step in RISC assembly, ultimately enhancing target messenger RNA repression. In vivo, depletion of Nibbler by RNAi causes developmental defects. CONCLUSIONS: We provide a molecular explanation for the previously reported heterogeneity of miRNA 3' ends and propose a model in which Nibbler converts miRNAs into isoforms that are compatible with the preferred length of Ago1-bound small RNAs.
Authors: Young Sik Lee; Kenji Nakahara; John W Pham; Kevin Kim; Zhengying He; Erik J Sontheimer; Richard W Carthew Journal: Cell Date: 2004-04-02 Impact factor: 41.582
Authors: Stefan L Ameres; Michael D Horwich; Jui-Hung Hung; Jia Xu; Megha Ghildiyal; Zhiping Weng; Phillip D Zamore Journal: Science Date: 2010-06-18 Impact factor: 47.728
Authors: Joseph A Karam; Rasesh Y Parikh; Dhananjaya Nayak; David Rosenkranz; Vamsi K Gangaraju Journal: J Biol Chem Date: 2017-02-13 Impact factor: 5.157
Authors: Simone Backes; Jillian S Shapiro; Leah R Sabin; Alissa M Pham; Ismarc Reyes; Bernard Moss; Sara Cherry; Benjamin R tenOever Journal: Cell Host Microbe Date: 2012-08-16 Impact factor: 21.023