Wade P. Parks

Reverse Transcriptases of Primate Viruses as Immunological Markers

Antibodies were prepared against the DNA polymerases (reverse transcriptases) of three potentially oncogenic RNA viruses of primates. Two type C viruses, isolated from a woolly monkey fibrosarcoma and from a gibbon ape lymphosarcoma, have polymerases that are immunologically related to each other and are distinct from the type C viruses isolated from other mammals.

Murine mammary tumor cell clones with varying degrees of virus expression.

Single cell clones were derived from Sykes′ CCL-51, a type-B particle positive, type-C virus negative murine mammary tumor cell line. Two of the clones had similar growth properties—they formed “dome-like” structures, grew in soft agar, and had abundant microvilli by electron microscopy—but differed markedly in their expression of type-B viral information. One clone, clone 11, had morphological type-B particles, type-B specific sl antigen (3500 ng/mg protein), and cellular RNA which hybridized with MTV [ 3 H]DNA product. The other clone, clone 6 did not have detectable particles by electron microscopy, antigen levels were below the limits of sensitivity or barely detectable (∽30 ng/mg protein), and RNA hybridizable to MTV DNA product was less than 5% of the reaction noted with the positive clone. Measurement of the cellular MTV-related DNA sequences by DNA-DNA hybridization using the same single-stranded MTV DNA product revealed comparable levels of MTV DNA sequences in both clones. Type-C viral expression (gs antigen and RNA levels) in both clones was comparable and not significantly higher than noted in other “normal” murine cell lines.

Distribution of murine type B and type C viral nucleic acid sequences in template active and template inactive chromatin.

Template active chromatin and template inactive chromatin have been fractionated from mouse cells infected with the Moloney strain of murine leukemia virus. In vivo the cells produce abundant Rna homologous to Moloney leukemia virus, but do not produce either globin mRNA or RNA homologous to type B mouse mammary tumor virus. The DNA extracted from the template active chromatin or template inactive chromatin contained equal amounts of sequences homologous to Moloney type C virus, to type B virus, or to globin mRNA. The results are discussed with regard to the in vivo structure of chromatin and the difficulties in fractionating chromatin in vitro.

Affinity chromatography of avian type C viral reverse transcriptase: Studies with Rous sarcoma virus transformed rat cells

Abstract An affinity chromatographic procedure is described for the purification of avian type C viral reverse transcriptase. Partially purified viral enzyme specifically binds to and can be eluted in active form from Sepharose coupled to an antibody prepared against the Schmidt-Ruppin reverse transcriptase. Crude extracts of non-virus-producing, RSV-transformed rat tumor cells (XC cells), which contain detectable avian viral gs antigens, have no detectable RSV reverse transcriptase. Mixing experiments indicate that the XC cell extracts do not contain soluble inhibitor(s) of the viral enzyme. These findings suggest that the synthesis or formation of active viral polymerase is depressed in these cells.

Host range studies on xenotropic type C viruses in somatic cell hybrids

Abstract A selection system is described for the isolation of somatic cell hybrids which does not require mutagenesis or Budr treatment of either parental cell. Thioguanine-resistant Kirsten sarcoma virus transformed nonproducer rat cells have been fused to contact-inhibited mouse cells and the hybrids selected in soft agar containing hypoxanthine, aminopterin, and thymidine. The somatic cell hybrids obtained by this procedure between mouse and rat cells have been used to study the host range of xenotropic type C viruses. The restriction by murine cells to the growth of certain xenotropic murine type C viruses was found to be dominant in such hybrids.