Polypyrimidine tract-binding proteins are cleaved by caspase-3 during apoptosis

J Biol Chem. 2002 Jul 26;277(30):27200-9. doi: 10.1074/jbc.M203887200. Epub 2002 May 9.


The polypyrimidine tract-binding protein (PTB), an RNA-binding protein, is required for efficient translation of some mRNAs containing internal ribosomal entry sites (IRESs). Here we provide evidence that the addition of apoptosis-inducing agents to cells results in the cleavage of PTB isoforms 1, 2, and 4 by caspase-3. This cleavage of PTB separated the N-terminal region, containing NLS-RRM1, from the C-terminal region, containing RRM2-3-4. Our data indicate that there are three noncanonical caspase-3 target sites in PTBs, namely Ile-Val-Pro-Asp(7)Ile, Leu-Tyr-Thr-Asp(139)Ser, and Ala-Ala-Val-Asp(172)Ala. The C-terminal PTB fragments localized to the cytoplasm, as opposed to the nucleus where most intact PTBs are found. Moreover, these C-terminal PTB fragments inhibited translation of polioviral mRNA, which contains an IRES element requiring PTB for its activation. This suggests that translation of some IRES-containing mRNAs is regulated by proteolytic cleavage of PTB during apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Apoptosis*
  • Binding Sites
  • Blotting, Western
  • Caspase 3
  • Caspases / metabolism*
  • Cell Line
  • Cytoplasm / metabolism
  • Epitopes
  • Green Fluorescent Proteins
  • HeLa Cells
  • Humans
  • Jurkat Cells
  • Luminescent Proteins / metabolism
  • Microscopy, Fluorescence
  • Molecular Sequence Data
  • Plasmids / metabolism
  • Poliovirus / metabolism
  • Polypyrimidine Tract-Binding Protein
  • Protein Binding
  • Protein Biosynthesis
  • Protein Structure, Tertiary
  • RNA, Messenger / metabolism
  • RNA-Binding Proteins / metabolism*
  • Recombinant Proteins / metabolism
  • Ribonucleoproteins / metabolism*
  • Sequence Homology, Amino Acid
  • Transcription, Genetic
  • Transfection


  • Epitopes
  • Luminescent Proteins
  • RNA, Messenger
  • RNA-Binding Proteins
  • Recombinant Proteins
  • Ribonucleoproteins
  • Polypyrimidine Tract-Binding Protein
  • Green Fluorescent Proteins
  • CASP3 protein, human
  • Caspase 3
  • Caspases