Fate of Sendai Virus Ribonucleoprotein in Virus-infected Cells

Abstract

The cytoplasmic extracts of Ehrlich ascites tumor cells infected with 32 PO 4 and 3 H-leucine-labeled Sendai virus have been examined during the course of infection with respect to sedimentation behavior and buoyant densities of input virus radioactivity. It was found that 32 P and 3 H radioactivities were coincident, and, at 30 min after infection, the bulk of radioactivity was recovered in the polysome region of a sucrose gradient in the position of Sendai virus ribonucleoprotein (210 S ). The heterogeneity of radioactivity profiles appeared at 1 hr after infection and increased during 6 hr of incubation. The buoyant densities of input virus components were determined by banding in CsCl gradient. Here again the bulk of coincident 32 P and 3 H radioactivity at 30 min after infection banded at the same density as Sendai virus ribonucleoprotein (1.31 g/cm 3 .) This component disappeared at 3 hr after infection, and 32 P and 3 H radioactivities were now found in components banded at densities 1.38, 1.41, 1.45, 1.49, and 1.55 g/cm 3 . The results presented are consistent with the idea that virus ribonucleoprotein is retained in the cytoplasm of infected cells during at least 6 hr of incubation, being partly deproteinized in the course of infection. The nature of components which banded at ρ = 1.41, 1.45, 1.49, and 1.55 as complexes of partly deproteinized ribonucleoprotein with ribosomes will be described in a separate paper.