Reversible inactivation of the deoxyribonucleic acid polymerase of Rauscher leukemia virus.

Rauscher leukemia virus deoxyribonucleic acid polymerase is reversibly inactivated by 6 m guanidine-hydrochloride. Gel filtration in 6 m guanidine-hydrochloride reveals that the viral deoxyribonucleic acid polymerase consists of a single polypeptide chain of approximately 70,000 molecular weight.

Isolation of temperature-sensitive mutants of murine sarcoma virus.

Three separate murine sarcoma virus nonproducer cell lines have been isolated which are temperature sensitive for the maintenance of transformation. In each case, a viral rather than a cellular genetic mutation is the reason for the temperature-sensitive effect. Superinfection of one of the mutants with murine leukemia virus overcomes the temperature-sensitive change in the transformed state.

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.

Radioimmunoassay of mammalian type-C viral proteins: interspecies antigenic reactivities of the major internal polypeptide.

Mammalian type-C viruses contain a major internal polypeptide of about 30,000 daltons that is characterized by both intraspecies and interspecies antigenic reactivities. Radioimmunoprecipitation assays were used for measurement of this protein; the assay was based upon interspecies reactivities of the protein. As little as 5 ng of the group-specific antigen of murine leukemia virus can be measured by radioimmunoprecipitation assays, thus providing an approximate 10,000-fold increase in sensitivity over the standard immunodiffusion procedure.

Affinity chromatography of RNA-dependent DNA polymerase from RNA tumor viruses on a solid phase immunoadsorbent.

A solid phase immunoadsorbent specific for RNA-dependent DNA polymerase from murine and feline RNA tumor viruses has been prepared. The enzymes from murine and feline virus but not from avian virus bind to columns of this material. Bound enzymes can be eluted in active form.

Immunological relationships of reverse transcriptases from ribonucleic acid tumor viruses.

Antiserum to partially purified reverse transcriptase from the Schmidt-Ruppin strain of Rous sarcoma virus has been prepared and characterized. Antibody to the avian polymerase inhibited the reverse transcriptase activity of avian C-type viruses but had no effect on the polymerase activity from C-type viruses of other classes. The known mammalian C-type viral polymerases were significantly inhibited only by the antiserum to murine C-type viral polymerases; reverse transcriptases from four other mammalian viruses were immunologically distinct from both avian and mammalian C-type viral polymerases.

In vitro synthesis of DNA complementary to purified rabbit globin mRNA (RNA-dependent DNA polymerase-reticulocyte-hemoglobin-density gradient centrifugation-oligo(dT) primer).

Several properties of the viral RNA-dependent DNA polymerases and of rabbit globin mRNA make it possible to consider synthesis of the globin gene in vitro. These enzymes copy an RNA template using a short sequence of complementary nucleotides as a primer. Furthermore, globin mRNA has a 3'-terminal sequence of adenylic acid residues that make it particularly suitable as a template, since oligo(dT) can be annealed to a specific site on the mRNA.

Hydrolysis of fMet-tRNA by peptidyl transferase.

Escherichia coli and rabbit reticulocyte (f[(3)H]Met-tRNA.AUG.ribosome) intermediates undergo hydrolysis, with release of f[(3)H]methionine, upon addition of tRNA or CpCpA in the presence of acetone.

Induction of murine C-type viruses from clonal lines of virus-free BALB-3T3 cells.

Each clone of BALB/c mouse embryo cells that has been tested can be induced to form C-type virus. The individual cells therefore contain a complete copy of the genetic information for making the murine RNA tumor viruses.

Antibody to the RNA-dependent DNA polymerase of mammalian C-type RNA tumor viruses.

Sera from rats bearing transplantable tumors induced by murine C-type tumor viruses contain an inhibitor of the activity of the viral RNA-dependent DNA polymerase. The inhibitor is shown to be an immunoglobulin (IgG) directed against the enzyme. Antiserum made in rabbits against partially purified murine leukemia virus polymerase also inhibits the polymerases of other mammalian C-type RNA-containing tumor viruses.

RNA-dependent DNA polymerase activity in five RNA viruses: divalent cation requirements.

The RNA-dependent DNA polymerase(s) in murine leukemia, murine mammary tumor, and avian myeloblastosis viruses require maganese for optimal activity. The transcription of added synthetic polyribonucleotides is greatly enhanced when manganese is used in place of magnesium. A soluble RNA-dependent DNA polymerase activity has been released from murine leukemia particles in the presence of manganese and high detergent concentrations.

DNA synthesis by RNA-containing tumor viruses.

Murine leukemia (Rauscher and Moloney strains) and sarcoma (Kirsten strain) virions, as well as the mammary tumor virus of mice, contain an RNA-dependent DNA polymerase. Optimal incorporation of deoxyribonucleoside triphosphates occurs at a critical detergent (Triton X-100) concentration (0.010-0.