Graduation date: 1971RNA tumor viruses, such as avian myeloblastosis virus (AMV)\ud and MC29 virus, cause malignant transformation of the cells they infect.\ud Transformed cells are able to continually produce progeny virus\ud particles.\ud Evidence is given that RNA-dependent RNA polymerase is present\ud in virus infected cells. RNA-dependent RNA polymerase isolated\ud from AMV-infected myeloblasts had an absolute requirement for\ud heteropolymer RNA, and 64S RNA from AMV was the preferred primer\ud for RNA synthesis. Under assay conditions where ribonuclease activity\ud was inhibited by polyvinylsulfate, the RNA-dependent RNA polymerase\ud synthesized RNA in vitro which had the velocity sedimentation\ud properties of 64S RNA from AMV.\ud RNA-dependent RNA polymerase was separated by CM-Sephadex\ud chromatography into two polymerase activities which did not incorporate\ud all four ribonucleoside monophosphates equally into RNA product. In particular, a polymerase fraction was obtained which incorporated\ud only UMP into RNA product, but maintained the specificity\ud for high molecular weight RNA as primer.\ud An RNA polymerase activity was also obtained by detergent\ud solubilization procedures which synthesized RNA from a template\ud associated with the enzyme fraction. The activity was largely resistant\ud to deoxyribonuclease. Under appropriate assay conditions the detergent-\ud solubilized RNA polymerase also synthesized RNA product which\ud had velocity sedimentation properties of 64S RNA from AMV.\ud RNA tumor virus particles contain DNA polymerase. Evidence\ud is presented that both RNA and DNA will serve as templates for DNA\ud synthesis by DNA polymerase from AMV and MC29 virus. AMV\ud particles and MC29 virus were banded isopycnically in preformed\ud glycerol density gradients. DNA polymerase activity was located at a\ud buoyant density (1.16 gm/cc) characteristic of tumor virus particles.\ud Virus-associated DNA polymerase was also isolated from chick\ud myeloblasts infected with AMV and from chick embryo culture (CEC)\ud cells infected with MC29 virus. The virus-associated DNA polymerasE\ud banded isopycnically at a buoyant density of 1.16 gm/cc. RNA polymerase\ud also banded at the same buoyant density. RNA polymerase\ud activity was stimulated by both DNA and RNA primers.\ud Human leukemia blood samples were examined for DNA polymerase\ud activity which would fit the criteria for tumor virus DNA polymerase. Blood samples from patients with chronic lymphocytic\ud leukemia, acute lymphocytic leukemia, and chronic myelogenous\ud leukemia contained DNA polymerase in particulates which were obtained\ud from the blood plasmas. Plasmas from healthy individuals and\ud from a patient with nonmalignant lymphocytosis did not contain DNA\ud polymerase. DNA polymerase from chronic lymphocytic leukemia\ud banded isopycnically at a buoyant density similar to RNA tumor virus\ud nucleocapsids.\ud Preliminary studies on chronic lymphocytic leukemia lymphocytes\ud revealed DNA polymerase activity in postnuclear supernatant\ud fractions with specific activity and buoyant density characteristics\ud very similar to the virus-associated DNA polymerase obtained from\ud myeloblasts and MC29 infected CEC.\ud Possible mechanisms for RNA tumor virus replication are discussed.\ud Evidence for human tumor virus etiology of human leukemia\ud is presented
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