Poly(A)-binding proteins are required for microRNA-mediated silencing and to promote target deadenylation in C. elegans.
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.
Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada Goodman Cancer Research Center, McGill University, Montreal, QC H3A 1A3, Canada.
Mathieu N
MN
Flamand
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.
Edlyn
E
Wu
Department of Biological Chemistry David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
Ajay
A
Vashisht
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.
Guillaume
G
Jannot
Department of Biochemistry and Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, NC 27834, USA.
Brett D
BD
Keiper
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.
Martin J
MJ
Simard
Department of Biological Chemistry David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
James
J
Wohlschlegel
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.
Thomas F
TF
Duchaine
D020413:3' Untranslated Regions; D000249:Adenosine Monophosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism; D004625:Embryo, Nonmammalian; D020868:Gene Silencing; D007814:Larva / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D011061:Poly A / Q000235:genetics* / Q000378:metabolism; D039122:Poly(A)-Binding Protein I / Q000235:genetics* / Q000378:metabolism; D039103:Poly(A)-Binding Protein II / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis; D034743:RNA-Induced Silencing Complex / Q000235:genetics / Q000378:metabolism
D020413:3' Untranslated Regions; D029742:Caenorhabditis elegans Proteins; D035683:MicroRNAs; D039122:Poly(A)-Binding Protein I; D039103:Poly(A)-Binding Protein II; D034743:RNA-Induced Silencing Complex; D011061:Poly A; D000249:Adenosine Monophosphate