Two initiation sites for translation of poliovirus RNA in vitro: comparison of LSc and Mahoney strains

Abstract

Previous studies showed that the initiation of translation by the Mahoney strain of poliovirus type 1 RNA in vitro occurs at 2 unique sites. This study shows that the LSc strain of poliovirus type 1, a multistep, temperature-sensitive mutant of the Mahoney strain, also utilizes 2 sites for the initiation of translation in vitro. Incorporation of formyl-[35S]methionine into the amino terminus of newly synthesized polypeptides revealed the production of 2 labeled tryptic peptides which are identical in size and electrophoretic mobility with those produced by Mahoney virus. The polypeptides containing amino-terminal label showed similar patterns on sodium dodecyl sulfate-acrylamide gels, although 1 of the LSc polypeptides had a slightly faster mobility. The relative proportion of initiation at each site varied with the Mg concentration for both viruses, but the LSc strain favored initiation at 1 site more so than did the Mahoney strain.