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Exploring Sequence Space to Identify Binding Sites for Regulatory RNA-Binding Proteins
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Polypyrimidine tract binding protein modulates efficiency of polyadenylation

Pedro Castelo-Branco1, Andre Furger, Matthew Wollerton

  • 1Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom.

Molecular and Cellular Biology
|May 4, 2004
PubMed

Insights

Polypyrimidine tract binding protein (PTB) regulates mRNA levels by affecting 3' end processing. PTB can both inhibit and promote mRNA expression, depending on its interaction with polyadenylation signals.

Area of Science:

  • Molecular Biology
  • RNA Metabolism
  • Gene Regulation

Background:

  • Polypyrimidine tract binding protein (PTB) is a key hnRNP protein involved in mRNA metabolism.
  • PTB plays critical roles in alternative splicing and internal ribosome entry site-driven translation.

Purpose of the Study:

  • To investigate the effect of PTB overexpression on mRNA levels from transfected gene constructs.
  • To elucidate the mechanism by which PTB influences mRNA 3' end processing and polyadenylation.

Main Methods:

  • Transfection of gene constructs with varying polyadenylation signals and PTB overexpression.
  • In vitro analysis to study PTB interaction with polyadenylation signals and CstF.
  • RNA interference (RNAi) to knock down PTB expression.

Main Results:

  • A fourfold overexpression of PTB reduced mRNA levels by 75% due to decreased mRNA 3' end cleavage efficiency.
  • PTB competes with CstF for binding to the pyrimidine-rich downstream sequence element of polyadenylation signals.
  • PTB knockdown reduced C2 complement gene mRNA expression, while PTB overexpression inhibited its polyadenylation.

Conclusions:

  • PTB acts as a dual regulator of mRNA expression through its influence on mRNA 3' end processing.
  • PTB's regulatory role involves both negative effects (inhibiting polyadenylation) and positive effects (promoting expression via specific sequences).
  • The findings highlight PTB's complex role in controlling gene expression at the post-transcriptional level.

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