RNA Virus Particles Research Articles

The presence of C-type RNA virus particles in a rat embryo cell line spontaneously transformed in tissue culture.

SUMMARY Two established rat cell lines, WERC and TWERC, were studied for the presence of C-type RNA virus particles. WERC cells, spontaneously transformed in vitro, continuously released C-type RNA virus (WERC virus) by budding from the plasma membrane. Some of these virus particles (diameter about 100 nm.) showed an electron-lucent nucleoid of diameter 75 to 80 nm. and represented immature C-type virus. Others showed dense nucleoids of about 65 to 70 nm. diameter and looked like mature forms of murine leukaemia virus. Each cell showed 60 to 100 virus particles. The buoyant density of the virus particles in sucrose gradients was that expected for avian or murine RNA virus particles (1.16 g./ml.). No virus particles were observed in the subline of cells (TWERC) originating from the malignant transformation with avian sarcoma virus (the prague strain of Rous sarcoma virus) of parental WERC cells.

Newcastle disease virus RNA: II. Preferential synthesis of RNA complementary to parental viral RNA by chick embryo cells

Following infection by strain “C” of Newcastle disease virus, and during incubation in the presence of actinomycin D, chick embryo cells synthesized RNA which had a base composition complementary to the base composition of RNA from virus particles. Evidence for base-sequence complementarity between RNA from virus particles and RNA synthesized by infected cells was obtained by in vitro hybridization. Of the total radioisotopically labeled RNA synthesized by infected cells in the presence of actinomycin D, 80% or more became insensitive to pancreatic ribo-nuclease after annealing with RNA from virus particles. The ribonuclease-resistant RNA had properties of a double-stranded polynucleotide. RNA from chick embryo cells or from Escherichia coli cells did not render labeled RNA from Newcastle disease virus-infected cells resistant to ribonuclease, and RNA from virus particles did not confer ribonuclease resistance on RNA from uninfected chick embryo cells. From 18 to 40% of the labeled RNA obtained from infected cells became RNase-resistant when annealed in the absence of RNA from virus particles. Cells infected by any of four other strains of Newcastle disease virus synthesized RNA, which was complementary in base composition to RNA from strain “C” virus particles. Virus particle RNA from all of these strains hybridized with RNA from cells infected by the “C” strain.