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miRISC and the CCR4-NOT complex silence mRNA targets independently of 43S ribosomal scanning

Duygu Kuzuoğlu-Öztürk1, Dipankar Bhandari1, Eric Huntzinger1

  • 1Department of Biochemistry, Max Planck Institute for Developmental Biology, Tübingen, Germany.

The EMBO Journal
|March 25, 2016
PubMed

Insights

MicroRNAs (miRNAs) and Argonaute (AGO) proteins silence gene expression by degrading mRNA targets. This study reveals a common silencing mechanism involving GW182, CCR4-NOT, and DDX6/Me31B, independent of eIF4A function.

Area of Science:

  • Molecular Biology
  • Gene Regulation
  • RNA Biology

Background:

  • MicroRNAs (miRNAs) regulate gene expression post-transcriptionally by associating with Argonaute (AGO) proteins.
  • Established models propose distinct mechanisms for miRNA-mediated silencing, involving translation inhibition, mRNA deadenylation, and degradation.
  • A debate exists regarding the role of eIF4A in miRNA-mediated translational repression.

Purpose of the Study:

  • To investigate the conserved mechanism of miRNA-mediated mRNA silencing across species.
  • To determine the roles of GW182, CCR4-NOT complex, and DDX6/Me31B in miRNA-mediated gene silencing.
  • To clarify the involvement of eIF4A in scanning-independent mRNA repression.

Main Methods:

  • Utilized human and Drosophila melanogaster (Dm) cell lines.
  • Investigated the function of miRNAs, AGO proteins, GW182, CCR4-NOT complex, and DDX6/Me31B in mRNA regulation.
  • Analyzed the impact on polyadenylated mRNA targets translated via scanning-independent mechanisms.

Main Results:

  • Demonstrated that miRNAs, AGOs, GW182, CCR4-NOT complex, and DDX6/Me31B cooperate to repress and degrade polyadenylated mRNA targets.
  • Showed this common silencing mechanism operates in both human and Dm cells.
  • Provided evidence that this mechanism is independent of eIF4A function during ribosomal scanning.

Conclusions:

  • A conserved mechanism involving miRNAs, AGOs, GW182, CCR4-NOT, and DDX6/Me31B mediates mRNA silencing.
  • This pathway effectively represses and degrades mRNA targets through scanning-independent translation.
  • The findings challenge existing models by highlighting a mechanism independent of eIF4A-mediated ribosomal scanning.
Keywords:
DDX6GW182argonautedeadenylationeIF4A

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