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PABP and the poly(A) tail augment microRNA repression by facilitated miRISC binding

Francesca Moretti1, Constanze Kaiser, Agnieszka Zdanowicz-Specht

  • 1European Molecular Biology Laboratory, Heidelberg, Germany.

Nature Structural & Molecular Biology
|May 29, 2012
PubMed

Insights

Polyadenylated mRNAs undergo stronger microRNA (miRNA) repression, a process mediated by poly(A)-binding protein (PABP). PABP promotes the association of miRNA-induced silencing complexes (miRISCs) with target mRNAs, enhancing repression.

Area of Science:

  • Molecular Biology
  • Gene Regulation
  • RNA Biology

Background:

  • Polyadenylated mRNAs are generally repressed more effectively by microRNAs (miRNAs) than nonadenylated mRNAs.
  • The poly(A) tail and associated proteins play a role in mRNA regulation and stability.

Purpose of the Study:

  • To investigate the mechanism by which polyadenylation enhances miRNA-mediated translational repression.
  • To elucidate the role of the poly(A)-binding protein (PABP) in this process.

Main Methods:

  • Utilized a cell-free translation system from Drosophila melanogaster.
  • Investigated the correlation between poly(A) tail length and miRNA repression efficiency.
  • Examined the effect of the GW182 silencing domain versus the miRNA-induced silencing complex (miRISC) on repression.
  • Monitored PABP and miRISC association with mRNA.

Main Results:

  • miRNA repression strength positively correlated with poly(A) tail length.
  • The stimulatory effect of the poly(A) tail on repression was dependent on the miRNA-induced silencing complex (miRISC) and not solely on the GW182 silencing domain.
  • Poly(A)-binding protein (PABP) was found to promote the association of miRISC with miRNA-regulated mRNAs.
  • PABP dissociation from mRNA occurred rapidly upon miRISC recruitment and preceding detectable deadenylation.

Conclusions:

  • Poly(A)-binding protein (PABP) is a key mediator of enhanced miRNA repression for polyadenylated mRNAs.
  • PABP facilitates miRISC recruitment to target mRNAs, thereby increasing translational repression efficiency.
  • A revised model for PABP and poly(A) tail function in miRNA-mediated translational repression is proposed.

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