Transcription of human respiratory syncytial virus genome RNA in vitro: requirement of cellular factor(s).

Extracts made from human respiratory syncytial virus (RSV)-infected Hep-2 cells synthesized mRNAs encoded by all known viral genes. In contrast, RSV ribonucleoproteins purified from infected cells failed to transcribe in vitro; transcription was restored by addition of a cytoplasmic extract of uninfected Hep-2 cells, demonstrating that a cellular factor(s) has a role in RSV gene expression. Quantitation of the individual gene mRNAs transcribed in vitro revealed polarity of transcription of the genome.