Two molecular features contribute to the Argonaute specificity for the microRNA and RNAi pathways in C. elegans.
In Caenorhabditis elegans, specific Argonaute proteins are dedicated to the RNAi and microRNA pathways. To uncover how the precise Argonaute selection occurs, we designed dsRNA triggers containing both miRNA and siRNA sequences. While dsRNA carrying nucleotides mismatches can only enter the miRNA pathway, a fully complementary dsRNA successfully rescues let-7 miRNA function and initiates silencing by RNAi. We demonstrated that RDE-1 is essential for RNAi induced by the perfectly paired trigger, yet is not required for silencing by the let-7 miRNA. In contrast, ALG-1/ALG-2 are required for the miRNA function, but not for the siRNA-directed gene silencing. Finally, a dsRNA containing a bulged miRNA and a perfectly paired siRNA can enter both pathways suggesting that the sorting of small RNAs occurs after that the dsRNA trigger has been processed by Dicer. Thus, our data suggest that the selection of Argonaute proteins is affected by two molecular features: (1) the structure of the small RNA duplex; and (2) the Argonautes specific characteristics.
Jannot
Guillaume
G
Laval University Cancer Research Centre, Hôtel-Dieu de Québec (CHUQ), Québec City, Québec G1R 2J6, Canada.
Boisvert
Marie-Eve L
ME
Banville
Isabelle H
IH
Simard
Martin J
MJ
D000818:Animals; D001483:Base Sequence; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism*; D035683:MicroRNAs / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D034622:RNA Interference; D018510:RNA, Helminth / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D043244:Ribonuclease III / Q000378:metabolism
D029742:Caenorhabditis elegans Proteins; D035683:MicroRNAs; D018510:RNA, Helminth; D034741:RNA, Small Interfering; C474488:let-7 microRNA, C elegans; D043244:Ribonuclease III