Showing papers by "David Baltimore published in 1976"
TL;DR: A quantitative Abelson murine leukemia virus (A- MuLV) lymphoid cell transformation assay has been developed using a semisolid agarose culture system and allows study of A-MuLV-lymphoid cell interaction at the level of single cell-single virus particle interaction.
Abstract: A quantitative Abelson murine leukemia virus (A-MuLV) lymphoid cell transformation assay has been developed using a semisolid agarose culture system. Under these conditions lymphoid cell transformation was shown to vary linearly with the dose of A-MuLV used. The susceptibility of bone marrow cells from different strains of mice to A-MuLV-induced transformation can be estimated using the agarose assay. Strains with bone marrow cells of high, medium, and low susceptibility to A-MuLV can be identified. The assay has been used to study the susceptibility of cells from lymphoid organs of fetal and adult mice to A-MuLV. Cell suspensions from fetal liver, adult bone marrow, and adult spleen are susceptible to A-MuLV, while thymocytes are resistant to A-MuLV-induced transformation. Bovine serum albumin gradient fractionation of bone marrow cells before infection with A-MuLV demonstrates that the majority of A-MuLV-sensitive cells are recovered in a broad band partially overlapping the majority of the nucleated cells. The agarose assay system allows study of A-MuLV-lymphoid cell interaction at the level of single cell-single virus particle interaction.
271 citations
TL;DR: The only potential 5'-terminal m7G is pUp as discussed by the authors, which is present in a yield of 1 mole/mole of poliovirus RNA and is not required for translation of at least one RNA species in animal cells.
Abstract: Poliovirus RNA purified from virus-specific polyribosomes does not contain m7G in a 5'-5'-pyrophosphate linkage at its 5'-end The only potential 5'-end found in ribonuclease digests of this RNA is pUp, which is present in a yield of 1 mole/mole of poliovirus RNA We conclude that a 5'-terminal m7G is not required for translation of at least one RNA species in animal cells
223 citations
TL;DR: Analysis of the reaction products on polyacrylamide gels shows that the majority of DNA synthesized, especially at high concentrations of dNTPs, comprised a set of DNA chains of discrete length the longest of which cover a major fraction of the genome.
143 citations
TL;DR: The Fv-l gene product appears to prevent integration of proviral DNA, which is found to be the same in both permissive and resistant cells after infection with N- or B-tropic viruses.
Abstract: The amounts of unintegrated murine leukemia virus-specific DNA detected by molecular hybridization in extracts of Fv-ln/n (strains NIH/3T3, SIM) or Fv-lb/b (strains JLS-V9, SIM.R) mouse cells after infection with N- or B-tropic viruses were found to be the same in both permissive and resistant cells. Therefore, formation of DNA products from the viral RNA template does not appear to be grossly affected by the Fv-l gene product. Integration of virus-specific DNA into chromosomal cellular DNA was assayed by hybridization of radioactive complementary DNA to DNA from infected cells.With either NIH/3T3 or SIM.R cells infected with N- or B-tropic viruses, integration of proviral DNA could be detected in permissive cells but not in nonpermissive cells. The Fv-l gene product therefore appears to prevent integration of proviral DNA.
134 citations
TL;DR: The virion RNA of Moloney murine leukemia virus has been translated in eukaryotic cell-free systems derived from mouse L- and human HeLa cells and fingerprint analysis of tryptic digests indicated that all three contain anino acid sequences in common with each other and with the major methionine-containing structural proteins of the virion.
Abstract: The virion RNA of Moloney murine leukemia virus (MuLV) has been translated in eukaryotic cell-free systems derived from mouse L- and human HeLa cells. In both systems at least three polypeptides, approximately 60,000, 70,000, and 180,000 in apparent molecular weight, were formed in response to the added 35S MuLV RNA. All three polypeptides were precipitable with antiserum to detergent-disrupted MuLV. Fingerprint analysis of tryptic digests indicated that all three contain anino acid sequences in common with each other and with the major methionine-containing structural proteins of the virion.
113 citations
TL;DR: It is found that an elimination after induction with the thymic polypeptide removes a substantial amount of terminal transferase from the bone marrow cell population, suggesting that at least one-half of the marrow cells bearing this enzyme are related to those found in theThymus.
Abstract: Terminal deoxynucleotidyl transferase is an enzyme which has the unique property of polymerizing polydeoxynucleotides onto a primer in the absence of a template (1,2). This enzyme is found both in the thymus and the bone marrow of birds, rodents, and humans (3-7). Whether the marrow cells that contain terminal transferase are related to thymocytes, or are on a separate pathway of differentiation, is not yet known (7,8). To determine the lineage of the murine bone marrow cells that have terminal transferase, we have investigated whether these cells have the antigen Thy-1 induced on the cells by treatment with thymopoietin (9). Thymopoietin is known to induce a set of characteristic T-cell markers including the Thy-1 alloantigen on the surface of a subpopulation of bone marrow cells committed to T-cell differentiation (prothymocytes) (10). Destruction of Thy- 1-positive cells after exposure to thymopoietin allows elimination of a substantial fraction of those bone marrow cells that can repopulate an irradiated thymus (11). We find that such an elimination after induction with the thymic polypeptide removes a substantial amount of terminal transferase from the bone marrow cell population, suggesting that at least one-half of the marrow cells bearing this enzyme are related to those found in the thymus.
109 citations
TL;DR: The ability to make long, representative DNA transcripts of tumor virus RNA provides a source of excellent probes for molecular hybridization.
Abstract: Virions of Moloney murine leukemia virus can synthesize two classes of DNA molecules complementary to their 70S RNA. One class consists of molecules about 200 nucleotides long, which are of limited sequence complexity; these molecules are formed preferentially if the dNTP concentration during the reaction is low. The second class consists of very heterogeneous DNA molecules with weight-average size of about 1,000 nucleotides containing at least 70% of the viral RNA sequences in approximately equal concentration. The longest of these molecules can be 5,000 nucleotides long. This second class of DNA is formed in large amounts only in reactions containing dNTP concentrations of 0.2 mM or higher. In such reactions after 24 h of incubation, at least 35% of the input RNA is represented in DNA copies. The ability to make long, representative DNA transcripts of tumor virus RNA provides a source of excellent probes for molecular hybridization.
101 citations
TL;DR: Mouse antisera against calf terminal deoxynucleotidyltransferase (terminal transferase) indicate that terminal transferase is a tissue-specific enzyme and is not related to other DNA polymerases.
57 citations
TL;DR: My personal involvement in uncovering the different genetic systems of RNA viruses, a story which leads to the recognition of the unique style of retroviruses, is reviewed.
Abstract: The study of biology is partly an exercise in natural esthetics. We derive much of our pleasure as biologists from the continuing realization of how economical, elegant and intelligent are the accidents of evolution that have been maintained by selection. A virologist is among the luckiest of biologists because he can see into his chosen pet down to the details of all of its molecules. The virologist sees how an extreme parasite functions using just the most fundamental aspects of biological behavior. A virus is a form of life with very simple requirements (1). The basic needs of a virus are a nucleic acid to be transmitted from generation to generation (the genome) and a messenger RNA to direct the synthesis of viral proteins. The critical viral proteins that the messenger RNA must encode are those that coat the genome and those that help replicate the genome. One of the great surprises of modern virology has been the discovery of the variety of genetic systems that viruses have evolved to satisfy their needs. Among the animal viruses, at least 6 totally different solutions to the basic requirements of a virus have been found (2). If we look back to virology books of 15 years ago, we find no appreciation yet for the variety of viral genetic systems used by RNA viruses (3). Since then, the various systems have come into focus, the last to be recognized being that of the retroviruses (“RNA tumor viruses”). As each new genetic system was discovered, it was often the identification of an RNA or a DNA polymerase that could be responsible for the synthesis of virus-specific nuclei acids that gave the most convincing evidence for the existence of the new system. Now that the life-styles of different types of viruses have been delineated we can ask what relation there is between a virus’ multiplication cycle and the disease it causes. In general, this question has no simple answer because disease symptoms do not correlate with the biochemical class of the virus. For instance, both poliovirus and rhinovirus are picornaviruses but one causes an intestinal infection with paralysis while the other causes the common cold. One class of RNA viruses, however, does have a unique symptom associated with it: the biochemically-defined group of viruses called the retroviruses are the only RNA viruses known to cause cancer. For a virologist interested in cancer, the problem is to first understand the molecular biology of retroviruses and then to understand how they cause the disease. In what follows, I will review my personal involvement in uncovering the different genetic systems of RNA viruses, a story which leads to the recognition of the unique style of retroviruses. I will then consider what is known
48 citations
TL;DR: The data show that virus-specific RNA levels are reduced in cells nonpermissive at the Fv-1 locus, suggesting that restriction of the F v-1 gene product occurs at the level of transcription of the viral genome or at a pre-integration step, or that the RNA transcripts are rapidly degraded after their synthesis.
44 citations
TL;DR: The 5'-terminal sequence m(7)G( 5') ppp(5') GmpCp was isolated from Moloney murine leukemia virus 35S RNA after digestion of (32)P-labeled RNA with RNases T1, T2, and A followed by pH 3.5 ionophoresis on DEAE paper.
Abstract: The 5'-terminal sequence m7G5' ppp5' GmpCp was isolated from Moloney murine leukemia virus 35S RNA after digestion of 32P-labeled RNA with RNases T1, T2, and A followed by pH 3.5 ionophoresis on DEAE paper.
TL;DR: The size distribution of virus-specific RNA was determined before and after denaturation, and it was found that most of the virus- Specific RNA had a sedimentation coefficient of 35S or lower, but a small fraction of the nuclear virus- specific RNA sedimented more rapidly than 35S RNA even afterDenaturation.
Abstract: About 1% of the total RNA of cell lines producing murine leukemia virus is virus-specific RNA About one-third of the virus-specific RNA is located within the nucleus The size distribution of virus-specific RNA was determined before and after denaturation Before denaturation, virus-specific RNA sequences sedimented as a heterogeneous population of RNA molecules, some of which sedimented very rapidly After denaturation, most of the virus-specific RNA had a sedimentation coefficient of 35S or lower, but a small fraction of the nuclear virus-specific RNA sedimented more rapidly than 35S RNA even after denaturation
01 Jan 1976
TL;DR: The finding of terminal deoxynucleotidyl transferase in the circulating leukemic cells of a child with acute lymphoblastic leukemia suggested that the thymus might play a role in the pathogenesis of this disease in man.
Abstract: In 1973 we first reported our finding of terminal deoxynucleotidyl transferase (TdT) in the circulating leukemic cells of a child with acute lymphoblastic leukemia (1). Until that time this unique DNA synthetic enzyme had been thought to be a special biochemical property of cells undergoing maturation in the thymus (2). Its presence in circulating lymphoblastic leukemia cells suggested that the thymus might play a role in the pathogenesis of this disease in man, analogous to the central position it plays in the pathogenesis of lymphoblastic leukemia in the AKR mouse (3, 4, 5). In addition, it appeared to have potential clinical utility as a new biochemical leukemia cell marker (1, 6).
01 Jan 1976
TL;DR: Terminal deoxynucleotidyltransferase activity in mice, as in other animals, is normally confined to the thymus and the bone marrow, but in leukemic AKR mice, terminal transferase activity was also detected inLeukemic cells.
TL;DR: Rodent cells were found to contain a high level of alcohol dehydrogenase activity which was not inducible, and other hepatoma and nonhepatoma cell lines were tested and found to contained lower but measurable levels of alcohol dehydration enzyme.
Abstract: Rodent cells were found to contain a high level of alcohol dehydrogenase activity which was not inducible. Other hepatoma and nonhepatoma cell lines were tested and found to contain lower but measurable levels of alcohol dehydrogenase.
01 Jan 1976
TL;DR: Two transformation systems for the study of Abelson murine leukemia virus-lymphoid cell interaction are discussed and quantitation of transformation and study of cells arising from single transformation events are discussed.
Abstract: . Abelson murine leukemia virus transforms lymphoid cells in vitro . Two transformation systems for the study of Abelson murine leukemia virus-lymphoid cell interaction are discussed in this paper. One system, in which mass cultures of hematopoietic cells are infected with Abelson virus, allows rapid isolation of large numbers of transformed cells. The second system allows quantitation of transformation and study of cells arising from single transformation events.