The slicing activity of miRNA-specific Argonautes is essential for the miRNA pathway in C. elegans.
Among the set of Argonautes proteins encoded by metazoan genomes, some have conserved amino acids important for catalytic or slicing activity. The functional significance of these residues in microRNA (miRNA)-specific Argonautes in animals is still unclear since miRNAs do not induce site-specific cleavage of targeted messenger RNAs (mRNAs), unlike small interfering RNAs (siRNAs). Here, we report that miRNA-specific ALG-1 and ALG-2 Argonautes from Caenorhabditis elegans possess the slicing activity normally implicated in the siRNA-silencing pathway. We also find that ALG-1/2 can bind and use a Dicer-processed miRNA duplex to target mRNAs, suggesting an ability to displace RNA strands. Importantly, the slicing activity of ALG-1 or ALG-2 is essential for the miRNA pathway in vivo, as shown by the accumulation of truncated miRNA precursors and altered miRNA-induced silencing complex (miRISC) formation. Taken together, our data demonstrate that the slicing activity of Argonautes contributes to a new and unexpected step in the canonical miRNA pathway that occurs prior to miRISC loading in animals.
Laval University Cancer Research Centre, Hôtel-Dieu de Québec (CHUQ), Quebec City, Québec G1R 2J6, Canada.
Samir
S
Bouasker
Martin J
MJ
Simard
D000818:Animals; D060565:Argonaute Proteins / Q000378:metabolism*; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D035683:MicroRNAs / Q000378:metabolism*; D059367:RNA Cleavage; D016601:RNA-Binding Proteins / Q000378:metabolism*; D034743:RNA-Induced Silencing Complex / Q000378:metabolism; D043244:Ribonuclease III / Q000378:metabolism
C558782:ALG-1 protein, C elegans; C577633:ALG-2 protein, C elegans; D060565:Argonaute Proteins; D029742:Caenorhabditis elegans Proteins; D035683:MicroRNAs; D016601:RNA-Binding Proteins; D034743:RNA-Induced Silencing Complex; D043244:Ribonuclease III