Studies on the nature of dengue viruses. III. RNA synthesis in cells infected with type 2 dengue virus.

Infection of KB cells with type 2 dengue virus results in stimulation of "actinomycin D-resistant" RNA synthesis. The newly synthesized intracellular RNA produces plaques on monolayers of BHK21 cells as does RNA extracted from virus. The intracellular RNA is composed predominantly of two species with sedimentation coefficients of 45 S and 20 S. An intermediate (26 S) form may be present occasionally, but then only in barely detectable amounts. The 45 S species corresponds to viral RNA. The 20 S RNA is resistant to RNase treatment; after denaturation by dimethylsulfoxide its sedimentation coefficient changes to about 45 S. It is concluded that the 20 S RNA is a double-stranded replicative form. If infected cells are exposed to 32P inorganic phosphate early in the viral growth cycle, the base composition of the labeled 20 S RNA approaches that expected for a double-stranded RNA. If the 32P labeling is done at later periods, however, the labeled 20 S base composition is similar to that of the 45 S RNA. It is concluded that both strands of the 20 S RNA are synthesized in the early period after infection, whereas at later times only the positive or viral strand is synthesized.