Abstract
The virus-specific, RNase-resistant RNA appearing in vaccinia virus-infected cells was directly shown to be an RNA duplex. After its melting and subsequent banding on Cs(2)SO(4) or incubation with DNase, the RNA could be reannealed and then hybridized with vaccinia virus DNA.The double-stranded virus-specific RNA appears to exist in the cell in the form of heterogeneous partially double-stranded RNA's sedimenting between 9 and 22S. The kinetics of the appearance of the double-stranded RNA in the cell show a dependence on the multiplicity of infection and suggest that the double-stranded RNA is a "late" product of viral intracellular biosynthesis. The synthesis of the double-stranded RNA is inhibited by actinomycin D.