Interferon Induction by Viruses. III. Vesicular Stomatitis Virus: Interferon-inducing Particle Activity Requires Partial Transcription of Gene N

Abstract

The interferon-inducing particle (i.f.p.) activity of a ts mutant, G11(I), of vesicular stomatitis virus (VSV) and a non-ts revertant, R1 (T1026) in aged chick embryo cells and mouse L(Y) cells at 40.5 and 37.5.degree. C, respectively, were measured. A single i.f.p. suffices to induce a quantum yield of interferon and there are several times more i.f.p. than plaque-forming particles (p.f.p.) in stock preparations of VSV. Furthermore, while virus replication or amplified RNA synthesis is not required for a particle of VSV to induce interferon, there is a requirement for primary transcription. About 1/10 of the genome must remain intact and be transcribed to synthesize an interferon-inducer moiety. (This represents transcription of about 2/3 of the N protein gene.) VSV apparently does not contain a preformed inducer of interferon; a model for its formation is proposed. There is a cumulative loss of N (and/or NS and L) protein from the ribonucleoprotein complex during primary transcription, leading ultimately to extensive base-pairing between the genome RNA and its complementary transcript. The ds[double-stranded]RNA thus formed constitutes the interferon inducer moiety of VSV.