Translation from the internal ribosome entry site of bovine viral diarrheavirus is independent of the interaction with polypyrimidine tract-binding protein

Translation of the pestiviral polyprotein is initiated cap independently at an internal site of the: viral RNA, the internal ribosome entry site ORES) . We investigated the translation from the IRES of bovine viral diarrhea vi rus (BVDV) and the possible interaction of the unconventional cellular RNA- binding proteins, particularly of polypyrimidine tract-binding protein (PTB ). The BVDV IRES is translationally active in rabbit reticulocyte lysate (R RL), and it is translated most efficiently at low concentrations of Mg2+- a nd K+-ions. In the UV cross-link assay, several proteins from RRL bind to t he BVDV IRES, including proteins of 50, 65 and 72 kDa, but no protein of 57 kDa possibly corresponding to PTB, although PTB is endogenously present in RRL. However, the BVDV IRES can bind PTB weakly under certain conditions. Interestingly, in a functional depletion and add-back translation system, P TB does not enhance translation of BVDV, although PTB enhances translation of a picornavirus in this translation stimulation assay. These results indi cate that PTB can bind the BVDV IRES RNA, but translation is independent of the: action of PTB. (C) 2000 Elsevier Science B.V. All rights reserved.