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Poly(A)-binding protein modulates mRNA susceptibility to cap-dependent miRNA-mediated repression

Robert W Walters1, Shelton S Bradrick, Matthias Gromeier

  • 1Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA.

RNA (New York, N.Y.)
|November 26, 2009
PubMed

Insights

MicroRNAs (miRNAs) require the 5' cap and 3' poly(A) tail for maximum gene silencing. Poly(A)-binding protein (PABP) antagonizes miRNA function by inhibiting mRNA deadenylation, thus affecting miRNA efficacy.

Area of Science:

  • Molecular Biology
  • Gene Regulation

Background:

  • MicroRNAs (miRNAs) are key regulators of gene expression, mediating post-transcriptional silencing.
  • While miRNA repressive effects are known, the exact mechanisms of gene modulation remain unclear.

Purpose of the Study:

  • To investigate the role of mRNA cis-acting elements (5' cap, 3' poly(A) tail) in miRNA-mediated gene silencing.
  • To elucidate the function of poly(A)-binding protein (PABP) in miRNA activity.

Main Methods:

  • Utilized human cell culture to examine miRNA effects on target transcripts with natural and artificial 3' UTRs.
  • Manipulated PABP levels and activity to assess its impact on miRNA silencing.
  • Evaluated the influence of mRNA 5' UTR structures on miRNA susceptibility.

Main Results:

  • Confirmed that the 5' m(7)G cap and 3' poly(A) tail are crucial for robust miRNA repression.
  • Demonstrated that cap-independent translation initiation structures do not abolish miRNA susceptibility when essential cis-acting elements are present.
  • Observed an inverse correlation between PABP levels/activity and miRNA silencing strength, partly via PABP's antagonism of target mRNA deadenylation.

Conclusions:

  • The 5' cap and 3' poly(A) tail are essential for efficient miRNA-mediated gene silencing.
  • PABP plays a significant role in modulating miRNA efficacy by counteracting mRNA deadenylation.
  • These findings provide a deeper understanding of the factors governing miRNA activity.

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