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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previously, type C RNA tumor virus-related components have been described in blood leukocytes from patients with acute myelogenous leukemia. These components, for example, reverse transcriptase, have been shown to be most closely related to those from two oncogenic subhuman primate type C viruses (woolly monkey sarcoma virus and gibbon ape leukemia virus). Now, we report the continuous production of budding type C viruses with the same characteristic reverse transcriptase by three separate culturings of leukocytes from a single bleeding from a patient with acute myelogenous leukemia. These isolations were made possible by the discovery of a source of conditioned media which sustains exponential growth of human myelogenous leukemia cells in liquid suspension culture.
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PMID:Type C RNA tumor virus isolated from cultured human acute myelogenous leukemia cells. 4 23

The salient biologic and morphologic characteristics of RNA tumor (oncornavirus) virus are reviewed. The ultrastructure of replicating oncornaviruses is illustrated in detail. C-type particles wide spread in at least three orders of animals were sighted in human sarcomas and leukemias. One case, an infantile fibrosarcoma, is presented from our cases surveyed for the presence of C-type particles. Tissue cultures derived from this tumor contained viral particles and had an elevated reverse transcriptase activity associated with the presence of 70 S RNA. The particles were larger (125 to 150nm) than those of the murine or avian Type C particles.
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PMID:Search for C-type particles in human neoplasia. 4 42

Purified reverse transcriptase from avian myeloblastosis virus or Rous sarcoma virus consists of two subunits of average mol wt of 100,000 and 60,000. The lower-molecular-weight subunit, alpha, has been isolated from avian myeloblastosis virus, Rous sarcoma virus and a temperature-sensitive mutant of Rous sarcoma virus, LA337. Subunit alpha manifests both the DNA polymerase and RNase H activities associated with purified reverse transcriptase of avian RNA tumor viruses. The thermal inactivation of these enzymatic activities of alpha subunit from the wild-type virus. The results show that both DNA polymerase and RNase H activities associated with the alpha subunit of LA337 are five to seven times more thermolabile then the corresponding alpha subunit from the wild-type virus. It is concluded that (i) both the polymerase and nuclease activities reside on the same polypeptide chain, and (ii) at least the lower-molecular-weight subunit alpha is coded for by the viral RNA.
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PMID:Studies on reverse transcriptase of RNA tumor viruses. I. Localization of thermolabile DNA polymerase and RNase H activities on one polypeptide. 4 81

The RNA-dependent DNA polymerase present in intracisternal A-type particles from mouse myeloma tumor cells has been studied. This polymerase can use either endogenous A particle RNA or an exogenous synthetic polynucleotide [poly (rA)] as a template. The DNA reaction product is small (4S-10S) and over 90% of it hybridizes to A particle RNA, whereas up to 50% of it hybridizes to murine sarcoma-leukemia virus RNAs. The RNA isolated from purified A particles is generally of low molecular weight (5S-15S) but contains small amount of 70S and 35S components. These results suggest that A-type particles may be related to C-type oncornaviruses.
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PMID:Characterization of DNA polymerase and RNA associated with A-type particles from murine myeloma cells. 4 84

A new method for the analysis and purification of the RNA-directed DNA polymerase of RNA tumor viruses has been developed. This nucleic acid affinity chromatography system utilizes an immobilized oligo (dT) moiety annealed with poly (A). The alpha and alphabeta DNA polymerases of avain myeloblastosis virus bound effectively to poly (A) oligo (dT)-cellulose. Alpha DNA polymerase did not bind effectively to poly (A) oligo (dT)-cellulose, poly (A)-cellulose, or to cellulose. Alphabeta bound to oligo (dT)-cellulose and cellulose at the same extent (approximately 30%), indicating that this enzyme did not bind specifically to the oligo (DT) moiety only. However, alphabeta bound to poly (A)-cellulose two to three times better than to cellulose itself, showing that alphabeta could bind to poly (A) without a primer. Alphabeta DNA polymerase also bound to poly (C)-cellulose, whereas alpha did not. These data show that the alpha DNA polymerase is defective in binding to nucleic acids if the beta subunit is not present. Data is presented which demonstrates that the alphabeta DNA polymerase bound tighter to poly (A). oligo (DT)-cellulose and to calf thymus DNA-cellulose than the alpha DNA polymerase, suggesting that the beta subunit or, at least part of it is responsible for this tighter binding. In addition, alphabeta DNA polymerase is able to reversibly transcribe avian myeloblastosis virus 70S RNA approximately fivefold faster than alpha DNA polymerase in the presence of Mg2+ and equally efficient in the presence of Mn2+. alpha DNA polymerase transcribed 9S globin m RNA slightly better than alphabeta with either metal ion.
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PMID:Binding properties of avian myeloblastosis virus DNA polymerases to nucleic acid affinity columns. 4 87

Nonionic detergents stimulate purified RNA-directed DNA polymerase (reverse transcriptase) activity from various RNA tumor viruses ranging from avian to primate species. The stimulatory effect of the nonionic detergent is dependent on the type and amount of template-primer. The greatest stimulation is obtained when high concentrations of (dT)12-18-(rA)n or activated salmon sperm DNA are used as template-primers. Little stimulation is obtained with viral 70S RNA or with (dT)12-18- (dA)n. The detergent stimulation appears to be specific for viral reverse transcriptase since this effect is not observed with purified bacterial DNA polymerase or with three known mammalian cellular DNA polymerases. This finding may, therefore, be a useful additional criterion for distinguishing viral reverse transcriptase isolated from cells from other cellular DNA polymerases. Nonionic detergent also has a stabilizing effect on viral DNA polymerase against thermal inactivation. This stabilizing effect is further enhanced by the presence of template-primer.
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PMID:On the stimulation of viral DNA polymerase activity by nonionic detergent. 4 56

Particulates with the properties of cores and/or ribonucleoproteins of RNA tumor viruses have been isolated from Sterox-SL-treated fractions of murine and human mammary adenocarcinomas. These particulates have an RNA-directed DNA polymerase, a 60 to 70 S RNA, and a density of 1.26 g/ml or greater in sucrose equilibrium density gradients. Their uniquely higher densities lead to banding in regions comparatively free of cellular contaminants. These circumstances minimize some of the technical complications of performing the simultaneous detection assay in the presence of cell debris.
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PMID:Biochemical characterization of putative subviral particulates from human malignant breast tumors. 4 81

Microwave-induced emission spectrometry combined with gel-exclusion chromatography provides a microanalytical system capable of precisely measuring 10 minus 10 to 10 minus 13 g of metal in microgram amounts of enzyme. Such sensitivity greatly exceeds that of other, more conventional methods. Metal quenching agents and low-molecular-weight protein contaminants were removed from the enzyme by Sephadex G-100 chromatography in microbore columns (0.03 times 25 cm). Droplet fractions were analyzed for zinc by the present method, for enzyme activity, and for protein content. With this analytical system we could demonstrate that stoichiometric amounts of zinc are present in the RNA-dependent DNA polymerase, the reverse transcriptase, from wooly monkey type C RNA tumor virus. The precision of the method for zinc was demonstrated by the coefficient of variation of 4.4 percent for 10 mug of zinc per liter. Validity and accuracy of the method were established by determining zinc in a series of zinc metalloenzymes of known metal content and stoichiometry.
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PMID:Microanalytical system for determination of picogram quantities of metals in metalloenzymes, as illustrated with zinc-containing enzymes. 4 97

The results of molecular hybridization experiments with high-molecular-weight RNA isolated from RNA tumor viruses and DNA from normal cells suggest that RNA tumor virus genomes originate from cell genes. Some RNA tumor viruses (here called class 1) appear to have been generated in recent times in that their RNA is closely related in nucleotide sequence to certain cell genes (class 1 genes). A second class of RNA tumor viruses (here called class 2) is more distantly related to genomic information of normal cells. Structural properties of the RNA of RNA tumor viruses lead us to propose that the tumor virus RNA is originated when RNA transcripts of class 1 genes are processed by a mechanism we call "paraprocessing." We postulate that RNA paraprocessing is normally used only at particular times during differentiation and is characterized by the cytoplasmic appearance of high-molecular-weight RNA chains containing terminal polyadenylic acid (200 residues). Paraprocessing of class 1 gene transcripts in committed or differentiated cells is considered to be aberrant in transcription that can lead to the generation of an RNA tumor virus genome. If the paraprocessed class 1 gene transcript codes for a reverse transcriptase, replication of the RNA becomes possible. Transfer of the replicating RNA to a new cell can result in genetic change such that the virus genome mutates, differing from the original progenitor genes. We propose that this genetic change causes class 1 viruses to become class 2. These ideas are applied to evidence concerning the biology of infection of RNA tumor viruses and concerning the involvement of RNA tumor viruses in human cancer. Genetic change can also occur during the origination of an RNA tumor virus genome by repeated reverse transcription and recombination (45) or by genetic alteration of particularly changeable cell genes ("hot spots") (43).
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PMID:RNA processing and RNA tumor virus origin and evolution. 4 50

The properties of murine oncornavirus produced by cells of spontaneous lymphosarcroma of CC57Br mice are described. In addition to the properties common for C-type RNA tumor viruses such as 60-70 S high molecular weight RNA, the presence of RNA-directed DNA polymerase and murine gs I (intraspecies) antigen and typical morphology in electron microscope, etc., the virus under study is characterized by instability of virions, unusual features of the DNA polymerase system and by the absence of demonstrable oncogenicity either in laboratory animals or in tissue cultures.
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PMID:[Biochemical and physiocochemical characteristics of a type C virus isolated from spontaneous lymphosarcoma of CC57Br strain mice]. 4 66


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