Characterization of the in vitro system for the synthesis of mRNA from human respiratory syncytial virus.

An in vitro transcription system for human respiratory syncytial virus (RSV) is described. Purified viral nucleocapsid (RNP) isolated from virus-infected cells was shown to support transcription of all 10 genes encoded by the virus as determined by Northern blot hybridization. The mRNAs synthesized were polyadenylated and comigrated with the corresponding mRNAs synthesized in virus-infected cells when analyzed in agarose-urea gel electrophoresis. The in vitro-synthesized mRNAs are functional as determined by their capacity to synthesize protein in vitro. The transcriptional reaction was significantly stimulated by the uninfected host cell lysate, indicating a requirement of host factor(s) in mRNA synthesis. Preliminary results suggest that cellular actin is involved in this process.