Viral RNA synthesis in measles virus-infected cells

Sedimentation analysis of measles virus-specific cytoplasmic RNA at different times after infection revealed several size classes. The three specific components found in greatest amount were estimated to have sedimentation coefficients of 20 S, 27 S, and 35 S. A fourth component, 52 S, sedimented with characteristics of viral RNA. 20 S RNA appeared later than the other size classes, and accounted for an increasingly greater proportion of the total. However, with a temperature-sensitive mutant synthesis of all three major components was turned off simultaneously by transfer of infected cultures from permissive to nonpermissive temperature. Subgenomic-size RNA was found in virion preparations made by undiluted passage, but not after serial passage of diluted inoculum.