Primary transcription of the influenza virus genome in permissive cells

The primary transcription of the RNA genome of influenza A 0 WSN was followed by infecting chick embryo cells with 32 P-labeled virus and monitoring the conversion of the labeled virion RNA into a ribonuclease resistant form before and after annealing. Annealing tests showed that unlabeled WSN RNA could successfully compete with at least 75% of the 32 P-labeled nucleic acid fraction extracted from infected cells. In vivo transcription was first detected proceeding at a relatively low rate after 40–60 min of incubation and accelerated rapidly thereafter between 90 and 120 min. The presence of cycloheximide allowed primary transcription to proceed at the same initial rate as in untreated cells but prevented its later amplification. No transcription could be demonstrated by the method employed in infected cells treated with either actinomycin D or interferon.