Analysis of the C. elegans Argonaute family reveals that distinct Argonautes act sequentially during RNAi
Graduate School of Biomedical Sciences; Program in Molecular Medicine
Medical Subject Headings
Amino Acid Sequence; Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Embryo, Nonmammalian; Models, Genetic; Molecular Sequence Data; Mutation; Phylogeny; Protein Binding; *RNA Interference; RNA, Helminth; RNA, Small Interfering; Recombinant Fusion Proteins
Life Sciences | Medicine and Health Sciences
Argonaute (AGO) proteins interact with small RNAs to mediate gene silencing. C. elegans contains 27 AGO genes, raising the question of what roles these genes play in RNAi and related gene-silencing pathways. Here we describe 31 deletion alleles representing all of the previously uncharacterized AGO genes. Analysis of single- and multiple-AGO mutant strains reveals functions in several pathways, including (1) chromosome segregation, (2) fertility, and (3) at least two separate steps in the RNAi pathway. We show that RDE-1 interacts with trigger-derived sense and antisense RNAs to initiate RNAi, while several other AGO proteins interact with amplified siRNAs to mediate downstream silencing. Overexpression of downstream AGOs enhances silencing, suggesting that these proteins are limiting for RNAi. Interestingly, these AGO proteins lack key residues required for mRNA cleavage. Our findings support a two-step model for RNAi, in which functionally and structurally distinct AGOs act sequentially to direct gene silencing.
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Citation: Cell. 2006 Nov 17;127(4):747-57. Link to article on publisher's site