Mutants of nonproducer cell lines transformed by murine sarcoma virus. 3. Detection and characterization of RNA specific for helper and sarcoma viruses

BALB/3T3 cells transformed by the Kirsten sarcoma virus (nonvirus producer BALB/3T3 cells) and mutant cell lines derived therefrom by treatment with bromodeoxyuridine (BrdU) were analyzed for expression of virus-specific RNA using single-stranded DNA transcripts of Rauscher leukemia virus (RLV), a virus activated in one of the cell lines (58-2T), and Ki-SV-specific DNA transcript; the latter transcript after removal of all sequences cross-reactive with RLV RNA. The Rauscher virus DNA detected multiple copies of viral RNA in virus-producing cells ( approximately 2.5 x 10(3)/cell) whether infected with RLV or activated to produce virus with BrdU. Nonproducer (NP) cells and normal BALB cells showed small numbers of RNA genomes (70-250/cell) and only partial saturation of the transcript. The intracellular RNA sedimented at 35S (main peak) with a variable minor peak at 20S with the exception of one mutant cell, M-43-2 (main peak at 26-27S). The 58-2T transcript reacted preferentially in NP cells and their derivatives with biphasic kinetics suggesting the possibility of sequences specific for the original transforming virus. The size of Ki-SV specific sequences were 30S in mutant cells whether or not complete virus was being produced and independent of in vivo transplantability.

Primate and murine type-C viral nucleic acid association kinetics: analysis of model systems and natural tissues

Hybridization studies employing single-stranded (3)H-DNA transcripts of type-C viruses isolated from a woolly monkey or gibbon ape failed to detect nucleic acid sequences homologous to these viruses in the DNA from a variety of uninfected primate species. The possible significance of these results for the epidemiology of type-C viruses in primates is discussed.

Specificity of the DNA product of RNA-dependent DNA polymerase in type C viruses. II. Quantitative analysis

A number of mammalian Type C viruses were analyzed for relatedness by the technique of DNA.RNA hybridization. Viral DNAs were prepared in single-stranded form from complexes with 70S viral RNA formed during endogenous polymerase reactions. Extent of hybridization was assayed with the single-strand nuclease (S-1) from Aspergillus oryzae. Results obtained indicated a high degree of viral specificity, with significant cross-reactions being observed only with viruses obtained from within a species, as in the case of mouse and cat viruses, or in the special case of woolly monkey-gibbon comparisons. Comparisons of RD-114 virus, recently determined to be of feline origin, and conventional feline Type C viruses (FeLV), revealed minimal relatedness, especially when feline virus was grown on human cells, thus indicating the possibility of coexistence of greatly disparate Type C viruses within one species. A rat-specific virus, recovered from tumors induced by murine sarcoma virus, was found to contain genetic material common to both the original mouse virus and viruses indigenous to the rat, even though only rat-specific proteins have been detected during infection by this virus.

RD 114 virus-specific sequences in feline cellular RNA: detection and characterization

RNA extracted from cat cells contains sequences homologous to RD-114 viral RNA. The sequences are measured by molecular hybridization with a single-stranded DNA probe synthesized by the virion polymerase using the endogenous viral RNA as template. Viral-specific RNA has been detected in all cells of cat origin tested thus far, but not in cells of other animals, except for the virus-producing human rhabdomyosarcoma cell, RD-114. The extent of hybridization of the DNA probe to cellular RNA was equivalent to that obtained with viral 70S RNA indicating that an equal extent of viral specific sequences is present in all cat cells as well as in RD-114 cells. The amounts of this viral RNA reach approximately 100 copies per cell in cat cells, while virus-producing RD-114 cells contain about 1,000 copies per cell. The viral RNA is present in cat cells in two distinct sizes of about 35S and 18S, whereas in RD-114 cells virus-specific RNA is quite heterogeneous in size.

Mutants of nonproducer cell lines transformed by murine sarcoma virus. II. Relationship of tumorigenicity to presence of viral markers and rescuable sarcoma genome

Tumorigenic and nontumorigenic mutants induced by a single 5'-bromodeoxyuridine (BrdU) treatment of a nonproducer (NP) tumorigenic cell line were isolated and characterized. Among the cloned derivatives were examples of virus-free and sarcoma virus-producing cell lines. Oncogenicity did not correlate with production of virus or ease of rescue of the sarcoma genome. All lines, including nononcogenic derivatives, retained the sarcoma genome. Phenotypic reversion of some cell mutants was observed after in vivo inoculation or long term in vitro cultivation. The M-50T cell line, obtained from a tumor induced by M-50 cells, had a sarcoma genome rescuable by direct superinfection; this was only achieved with parental M-50 cells by a cell fusion rescue technique. The M-43-2T cell, obtained from a single small static tumor induced by otherwise nononcogenic M-43-2 cells, shed sarcoma virus and became tumorigenic. M-58-4-48 became tumorigenic after passage 48 of the M-58-4 line, which was originally nontumorigenic. These observations of phenotypic reversion demonstrate that the presence of the sarcoma gene in cells is an essential but not sufficient condition of tumorigenesis.

Mutants of nonproducer cell lines transformed by murine sarcoma viruses. I. Induction, isolation, particle production, and tumorigenicity

A variety of cell mutants were obtained by a single 5'-bromodeoxyuridine (BrdU) treatment of an nonproducer (NP) cell line transformed by the Kirsten strain of murine sarcoma virus (Ki-MSV). Isolation procedures of these cell See PDF for Structure mutants are described. The cell mutants obtained were classified by tumorigenic potential and shedding of Type C virus particles. The cell mutants were classified into four groups: (A) tumorigenic, without particles; (B) tumorigenic, with Type C particles; (C) nontumorigenic, without particles; and (D) nontumorigenic, with Type C particles. The tumorigenic cell lines showed variability in morphology with both flat and typical transformed appearing cell lines showing equal transplantability.

Sugar effects on murine sarcoma virus transformation

Transformation of NIH Swiss mouse fibroblasts by a murine sarcoma virus was influenced by the type of carbohydrate in the culture medium. Exposure to D-mannose and 2-deoxy-D-glucose caused a reduction in the number of transformed colonies in vitro and tumor formation in vivo. This is a new type of interference in the transformation process, manifested also by the absence of the pronounced enhancement of hexose entry into transformed cells, characteristic of a sarcoma virus infection. The uptake of D-glucose, D-mannose, and D-galactose, was repressed by normal mouse cells grown in the presence of D-mannose and D-glucose in the medium, while uptake of the same sugars was derepressed in cells grown in media containing D-xylose, L-xylose, or L-arabinose. D-Galactose had an intermediate effect on hexose uptake and permitted derepression. In every case, enhancement of the primary transport by sarcoma virus transformation was consistently beyond that observed at any time in the derepressed control cells, demonstrating the occurrence of another mechanism of enhancement of hexose uptake after sarcoma virus infection.

Specific inhibition of mammalian ribonucleic acid C-type virus deoxyribonucleic acid polymerases by rat antisera

Inhibition of the ribonucleic acid (RNA)- and deoxyribonucleic acid (DNA)-dependent DNA polymerase activities of mammalian C-type viruses was obtained with sera from rats bearing murine leukemia virus-induced transplant tumors. Polymerase activities of nonmammalian (viper) C-type virus and murine mammary tumor virus were not inhibited by such sera nor by serum from a rat immunized with the DNA polymerase of feline leukemia virus purified by isoelectric focusing. The latter serum appeared to inhibit preferentially the DNA-dependent DNA polymerase activity of mammalian C-type viruses showing no inhibition of RNA-dependent DNA synthesis.

The 3'-terminal nucleosides of the high molecular weight RNA of C-type viruses

Tumor virus RNAs from several mammalian and one reptilian species were purified; their 3'-terminal nucleoside was identified by separation of the trialcohols produced by periodate oxidation followed by reduction and tritiation with NaB(3)H(4). Each virus contained uridine as the predominant terminal nucleoside. Molecular weight estimations based on the tritiation reactions were consistent with a structure consisting of four subunits.