Conditional-Lethal Mutants of an Animal Virus: Identification of Two Cistrons

Abstract

Two different temperature-sensitive conditional-lethal mutants of Sindbis virus, an animal virus that contains RNA, have been isolated. When cultured in chick fibroblast monolayers at 42°C, these mutants yield less than 0.05 percent as much virus as does the wild type, whereas at 27°C they grow normally. One mutant appears to be altered in the synthesis of a protein that is produced early in the infection and is required for viral RNA synthesis. The other mutant produces as much infectious RNA as the wild type at 42°C and appears to be altered in the synthesis of a protein produced late in the infection.