Purification of a factor that restores translation of vesicular stomatitis virus mRNA in extracts from poliovirus-infected HeLa cells.

Abstract

The poliovirus-induced inhibition of translation of capped mRNA in [human cervical carcinoma] HeLa cells can be reversed by a protein found in preparations of the eukaryotic initiation factor eIF-4B. This restoring factor was purified from a high-salt wash of rabbit reticulocyte ribosomes by taking advantage of its tight association with factor eIF-3 at low salt concentrations. It did not copurify with the major MW 80,000 polypeptide of eIF-4B preparations but did copurify with a MW 24,000 polypeptide previously shown to bind to the cap structures of mRNA. Both the electrophoretic mobility and the tryptic peptide pattern of the restoring factor were indistinguishable from those of the capbinding protein, and the restoring factor could be crosslinked to the 5''-terminal cap on mRNA. Thus, it appears that poliovirus inhibits cellular protein synthesis by inactivation of some crucial property of the cap-binding protein.