Interferon induction by viruses. II. Sindbis virus: interferon induction requires one-quarter of the genome--genes G and A.
We have measured the amounts of interferon formed by chick cells 'aged' in vitro in response to different amounts of infectious wild-type Sindbis virus. Our results suggest that one plaque-forming unit is enough to induce maximum interferon formation. With higher m.o.i. the yield of interferon is less. To inactivate the interferon-inducing activity of Sindbis virus, four times more u.v.-radiation was needed than to inactivate the infectivity of the virus. This suggests that only 25% of the virus genome need be intact in order to induce interferon. Temperature-sensitive Sindbis virus mutants from the three RNA+ complementation groups, C. D and E, gave rise to interferon in chick cells incubated at a non-permissive temperature, Similarly, mutants from two of the RNA- groups, B and F, gave rise to interferon, but not mutants from groups G and A. We conclude that no pre-formed inducer of interferon is present in Sindbis virus. It appears, however, that genes G and A represent a special one-quarter of the genome which must be functional in order to synthesize an interferon-inducing moiety. We suggest that this moiety is a double-stranded RNA molecule formed after synthesis of a segment of RNA complementary to the genome.
D000818:Animals; D002642:Chick Embryo; D046508:Culture Techniques; D005814:Genes, Viral; D007369:Interferon Inducers; D007372:Interferons / Q000096:biosynthesis*; D009154:Mutation; D012330:RNA, Double-Stranded / Q000494:pharmacology*; D012367:RNA, Viral / Q000494:pharmacology*; D012845:Sindbis Virus / Q000235:genetics* / Q000254:growth & development / Q000528:radiation effects; D013696:Temperature; D014466:Ultraviolet Rays
D007369:Interferon Inducers; D012330:RNA, Double-Stranded; D012367:RNA, Viral; D007372:Interferons