GW182-Free microRNA Silencing Complex Controls Post-transcriptional Gene Expression during Caenorhabditis elegans Embryogenesis

• Published in: PLoS genetics 2016-12, Vol.12 (12), p.e1006484-e1006484
• Main Authors: Jannot, Guillaume, Michaud, Pascale, Quévillon Huberdeau, Miguel, Morel-Berryman, Louis, Brackbill, James A, Piquet, Sandra, McJunkin, Katherine, Nakanishi, Kotaro, Simard, Martin J
• Format: Article
• Language: English
• Subjects: Animals; Biology and life sciences; Caenorhabditis elegans; Caenorhabditis elegans - genetics; Caenorhabditis elegans - growth & development; Caenorhabditis elegans Proteins - chemistry; Caenorhabditis elegans Proteins - genetics; Cancer; Carrier Proteins - genetics; Colleges & universities; Embryonic Development - genetics; Funding; Gene expression; Gene Expression Regulation, Developmental; Humans; Medical research; MicroRNAs; MicroRNAs - biosynthesis; MicroRNAs - genetics; Mutation; Nematodes; Oncology; Proteins; Research and Analysis Methods; RNA Interference; RNA-Binding Proteins - biosynthesis; RNA-Binding Proteins - chemistry; RNA-Binding Proteins - genetics; RNA-Induced Silencing Complex - genetics
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.1006484

MicroRNAs and Argonaute form the microRNA induced silencing complex or miRISC that recruits GW182, causing mRNA degradation and/or translational repression. Despite the clear conservation and molecular significance, it is unknown if miRISC-GW182 interaction is essential for gene silencing during animal development. Using Caenorhabditis elegans to explore this question, we examined the relationship and effect on gene silencing between the GW182 orthologs, AIN-1 and AIN-2, and the microRNA-specific Argonaute, ALG-1. Homology modeling based on human Argonaute structures indicated that ALG-1 possesses conserved Tryptophan-binding Pockets required for GW182 binding. We show in vitro and in vivo that their mutations severely altered the association with AIN-1 and AIN-2. ALG-1 tryptophan-binding pockets mutant animals retained microRNA-binding and processing ability, but were deficient in reporter silencing activity. Interestingly, the ALG-1 tryptophan-binding pockets mutant phenocopied the loss of alg-1 in worms during larval stages, yet was sufficient to rescue embryonic lethality, indicating the dispensability of AINs association with the miRISC at this developmental stage. The dispensability of AINs in miRNA regulation is further demonstrated by the capacity of ALG-1 tryptophan-binding pockets mutant to regulate a target of the embryonic mir-35 microRNA family. Thus, our results demonstrate that the microRNA pathway can act independently of GW182 proteins during C. elegans embryogenesis.