FIG. 4.

Analysis of plus-strand RNA synthesis in BHK cells infected with wild-type (SINV) or mutant viruses. (A) The infected cells were maintained at the permissive (30°C) or nonpermissive temperature (37°C) and radiolabeled with inorganic ³²P in medium containing actinomycin D. At 10 h postinfection, cytoplasmic RNA was extracted. Approximately 2 μg of total RNA was subjected to denaturing gel electrophoresis on a formaldehyde-agarose gel, and the gel was dried and autoradiographed on a Molecular Imager FX Phosphorimager. (B) The radioactivity counts in bands corresponding to the genomic and subgenomic RNA were quantitated using Quantity One software (Bio-Rad) and used to evaluate the percent RNA levels for the mutants with respect to wild-type virus at 37°C.