Polypyrimidine tract binding protein and poly r(C) binding protein 1 interact with the BAG-1 IRES and stimulate its activity in vitro and in vivo

Nucleic Acids Res. 2003 Jan 15;31(2):639-46. doi: 10.1093/nar/gkg146.


The 5'-untranslated region of Bag-1 mRNA contains an internal ribosome entry segment (IRES) and the translation of Bag-1 protein can be initiated by both cap-dependent and cap-independent mechanisms. In general, cellular IRESs require non-canonical trans-acting factors for their activity, however, very few of the proteins that act on cellular IRESs have been identified. Proteins that interact with viral IRESs have also been shown to stimulate the activity of cellular IRESs and therefore the ability of a range of known viral trans-acting factors to stimulate the Bag-1 IRES was tested. Two proteins, poly r(C) binding protein 1 (PCBP1) and polypyrimidine tract binding protein (PTB), were found to increase the activity of the Bag-1 IRES in vitro and in vivo. The regions of the Bag-1 IRES RNA to which they bind have been determined, and it was shown that PCBP1 binds to a short 66 nt section of RNA, whilst PTB interacts with a number of sites over a larger area. The minimum section of the RNA that still retained activity was determined and both PCBP1 and PTB interacted with this region suggesting that these proteins are essential for Bag-1 IRES function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites / genetics
  • COS Cells
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Line
  • DNA-Binding Proteins
  • Electrophoretic Mobility Shift Assay
  • HeLa Cells
  • Heterogeneous-Nuclear Ribonucleoproteins / genetics
  • Heterogeneous-Nuclear Ribonucleoproteins / metabolism*
  • Humans
  • Luciferases / genetics
  • Luciferases / metabolism
  • Polypyrimidine Tract-Binding Protein / genetics
  • Polypyrimidine Tract-Binding Protein / metabolism*
  • Protein Binding
  • Protein Biosynthesis
  • RNA-Binding Proteins
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Ribosomes / metabolism
  • Transcription Factors
  • Transcription, Genetic
  • Transfection
  • Tumor Cells, Cultured


  • BCL2-associated athanogene 1 protein
  • Carrier Proteins
  • DNA-Binding Proteins
  • Heterogeneous-Nuclear Ribonucleoproteins
  • PCBP1 protein, human
  • RNA-Binding Proteins
  • Recombinant Fusion Proteins
  • Transcription Factors
  • Polypyrimidine Tract-Binding Protein
  • Luciferases