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A specific Argonaute phosphorylation regulates the binding to microRNAs during C. elegans development.

ABSTRACT: Argonaute proteins are at the core of the microRNA-mediated gene silencing pathway essential for animals. In C. elegans, the microRNA-specific Argonautes ALG-1 and ALG-2 regulate multiple processes required for proper animal developmental timing and viability. Here, we identified a new phosphorylation site, serine 642, on ALG-1 that modulates microRNA association. Mutating ALG-1 serine 642 into a phospho-mimicking residue impairs microRNA binding and causes embryonic lethality and post-embryonic phenotypes that are common with alteration of microRNA functions. Monitoring microRNA levels in alg-1 phosphorylation mutant animals reveal that miRNA passenger strands strongly increase but are not preferentially loaded into ALG-1, indicating that the miRNA binding defects could also lead to miRNA duplexes accumulation. Our genetic and biochemical experiments support the protein kinase A KIN-1 as the putative kinase that phosphorylates ALG-1 serine 642. Altogether, our data indicate that PKA triggers the ALG-1 phosphorylation to regulate its microRNAs association during C. elegans development.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE198352 | GEO | 2022/09/10

REPOSITORIES: GEO

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Project description:MicroRNAs are regulators of gene expression whose functions are critical for normal development and physiology. We have previously characterized mutations in a Caenorhabditis elegans microRNA-specific Argonaute ALG-1 (Argonaute-like gene) that are antimorphic [alg-1(anti)]. alg-1(anti) mutants have dramatically stronger microRNA-related phenotypes than animals with a complete loss of ALG-1. ALG-1(anti) miRISC (microRNA induced silencing complex) fails to undergo a functional transition from microRNA processing to target repression. To better understand this transition, we characterized the small RNA population associated with ALG-1(anti) complexes in vivo. alg-1(anti) mutants dramatically overaccumulated microRNA* (passenger) strands, and immunoprecipitated ALG-1(anti) complexes contained nonstoichiometric yields of mature microRNA and microRNA* strands, with some microRNA* strands present in the ALG-1(anti) Argonaute far in excess of the corresponding mature microRNAs. We show complex and microRNA-specific defects in microRNA strand selection and microRNA* strand disposal. For certain microRNAs (for example mir-58), microRNA guide strand selection by ALG-1(anti) appeared normal, but microRNA* strand release was inefficient. For other microRNAs (such as mir-2), both the microRNA and microRNA* strands were selected as guide by ALG-1(anti), indicating a defect in normal specificity of the strand choice. Our results suggest that wild-type ALG-1 complexes recognize structural features of particular microRNAs in the context of conducting the strand selection and microRNA* ejection steps of miRISC maturation. Deep-sequencing was performed on cDNA libraries made from total RNA and RNA immunoprecipitated with ALG-1 from mixed-staged populations of three strains: three biological replicates from wild-type animals and two biological replicates each from alg-1(ma192) and alg-1(ma202) mutant animals. In addition, deep-sequencing was performed on cDNA libraries made from L2-staged total RNA in two biological replicates from wildtype and alg-1(ma202) animals and one biological replicate of alg-1(ma192).

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A specific Argonaute phosphorylation regulates the binding to microRNAs during C. elegans development.

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