FIG. 6.

Accumulation of NC in the cytoplasm of a subset of mutants. In vitro-transcribed RNA from mutants and wild type were electroporated into BHK cells and incubated at 37°C. Five hours posttransfection, actinomycin D was added to the cells to a final concentration of 1 μg/ml, to block host cell transcription. At 6 h posttransfection, replicating RNA was labeled with [5,6-³H]uridine (40 μCi/ml). Cytoplasmic extracts of the infected cells were prepared at 12 h posttransfection and layered onto a 25% freeze-thaw sucrose gradient. The [³H]uridine profile of intracellular nucleocapsids following sucrose gradient centrifugation fractionation and scintillation counting is shown.