Porcine polypyrimidine tract-binding protein stimulates translation initiation at the internal ribosome entry site of foot-and-mouth-disease virus

The cDNA for porcine polypyrimidine tract-binding protein (sPTB) was cloned. The sPTB amino acid sequence is highly homologous to the human PTB sequence (97% identity), and the sPTB sequence corresponds to that of the longest human PTB, PTB4. The specificity of binding in the UV-crosslink of sPTB to the internal ribosome entry site (IRES) of foot-and-mouth-disease virus (FMDV) is similar to that of human PTB. Purified recombinant sPTB efficiently stimulates internal translation initiation directed by the FMDV IRES in a rabbit reticulocyte lysate translation system from which the internal PTB had been depleted.