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Nucleic Acids Res. 2016 Jul 8;44(12):5924-35. doi: 10.1093/nar/gkw276. Epub 2016 Apr 19.

Poly(A)-binding proteins are required for microRNA-mediated silencing and to promote target deadenylation in C. elegans.

Author information

1
Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada Goodman Cancer Research Center, McGill University, Montreal, QC H3A 1A3, Canada.
2
Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada Division of Experimental Medicine & Goodman Cancer Research Center, McGill University, Montreal, QC H3A 1A3, Canada.
3
Department of Biological Chemistry David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
4
St-Patrick Research Group in Basic Oncology, Centre Hospitalier Universitaire de Québec-Université Laval (Hôtel-Dieu de Québec), Laval University Cancer Research Centre, Quebec City, QC G1R 2J6, Canada.
5
Department of Biochemistry and Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, NC 27834, USA.
6
Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada Division of Experimental Medicine & Goodman Cancer Research Center, McGill University, Montreal, QC H3A 1A3, Canada thomas.duchaine@mcgill.ca.

Abstract

Cytoplasmic poly(A)-binding proteins (PABPs) link mRNA 3' termini to translation initiation factors, but they also play key roles in mRNA regulation and decay. Reports from mice, zebrafish and Drosophila further involved PABPs in microRNA (miRNA)-mediated silencing, but through seemingly distinct mechanisms. Here, we implicate the two Caenorhabditis elegans PABPs (PAB-1 and PAB-2) in miRNA-mediated silencing, and elucidate their mechanisms of action using concerted genetics, protein interaction analyses, and cell-free assays. We find that C. elegans PABPs are required for miRNA-mediated silencing in embryonic and larval developmental stages, where they act through a multi-faceted mechanism. Depletion of PAB-1 and PAB-2 results in loss of both poly(A)-dependent and -independent translational silencing. PABPs accelerate miRNA-mediated deadenylation, but this contribution can be modulated by 3'UTR sequences. While greater distances with the poly(A) tail exacerbate dependency on PABP for deadenylation, more potent miRNA-binding sites partially suppress this effect. Our results refine the roles of PABPs in miRNA-mediated silencing and support a model wherein they enable miRNA-binding sites by looping the 3'UTR poly(A) tail to the bound miRISC and deadenylase.

PMID:
27095199
PMCID:
PMC4937315
DOI:
10.1093/nar/gkw276
[Indexed for MEDLINE]
Free PMC Article

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