The Apaf-1 internal ribosome entry segment attains the correct structural conformation for function via interactions with PTB and unr

Mol Cell. 2003 Mar;11(3):757-71. doi: 10.1016/s1097-2765(03)00093-5.


We have shown previously that polypyrimidine tract binding protein 1 (PTB) binds and activates the Apaf-1 internal ribosome entry segment (IRES) when the protein upstream of N-ras (unr) is prebound. Here we show that the Apaf-1 IRES is highly active in neuronal-derived cell lines due to the presence of the neuronal-enhanced version of PTB, nPTB. The unr and PTB/nPTB binding sites have been located on the Apaf-1 IRES RNA, and a structural model for the IRES bound to these proteins has been derived. The ribosome landing site has been located to a single-stranded region, and this is generated by the binding of the nPTB and unr to the RNA. These data suggest that unr and nPTB act as RNA chaperones by changing the structure of the IRES into one that permits translation initiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptotic Protease-Activating Factor 1
  • Base Sequence
  • Binding Sites
  • Blotting, Western
  • Cell Line
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / metabolism*
  • Dose-Response Relationship, Drug
  • Electrophoresis, Polyacrylamide Gel
  • Gene Deletion
  • HeLa Cells
  • Humans
  • Kinetics
  • Models, Biological
  • Models, Genetic
  • Molecular Sequence Data
  • Mutagenesis
  • Mutation
  • Neurons / metabolism
  • Nucleic Acid Conformation
  • Phenotype
  • Polymerase Chain Reaction
  • Polypyrimidine Tract-Binding Protein / genetics*
  • Polypyrimidine Tract-Binding Protein / metabolism*
  • Protein Binding
  • Protein Biosynthesis
  • Protein Conformation
  • Proteins / metabolism*
  • RNA-Binding Proteins / genetics*
  • RNA-Binding Proteins / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Ribosomes / metabolism*
  • Transcription, Genetic
  • Transfection
  • Ultraviolet Rays


  • APAF1 protein, human
  • Apoptotic Protease-Activating Factor 1
  • CSDE1 protein, human
  • DNA-Binding Proteins
  • Proteins
  • RNA-Binding Proteins
  • Polypyrimidine Tract-Binding Protein