Biographical Memoirs Volume 79 (2001) / Chapter Skim
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Howard M. Temin
Howard M. Temin
Pages 336-375
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in for him when I first came to the McArcIle Laboratory for Cancer Research while he travelecl to Stockholm to accept the Nobel Prize. Typically, he insistec!
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with his commitment to reason in all facets of his professional life, that macle Howard Temin a major force in biology cluring the latter half of the twentieth century. THE PROVIRUS HYPOTHESIS Quite early in life Howard Temin was a devotee of science in general en c!
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in initiating or maintaining infection. NDV infects CEF cells only lyrically en cl has an RNA genome, as RSV was then thought to have.
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similar to those of the temperate phage (1959~. These studies lecl them to hypothesize that "the genome of the Rous sarcoma virus must be integrates!
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transfer of information. The means by which RSV, an RNA tumor virus, couIcl stably affect the heritable morphology of infected cells was therefore enigmatic both for Howarc!
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Thus the effect of this inhibitor variecl ciramatically for the lytic RNA virus NDV en cl the transforming RNA tumor virus, RSV. Howard "suggested that the template responsible for synthesis of viral (RSV)
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Howard treated cells arrested largely in the G2 phase of the cell cycle with cytosine arabinosicle, an inhibitor of DNA synthesis. This treatment inhibited formation of the provirus as reflected!
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Thus, by the end of 1968 it was evident that both a DNAand an RNA-containing animal virus house a templatedependent RNA polymerase activity. Studies with the DNA tumor viruses, simian virus 40 (SV40)
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that certain DNA tumor viruses maintained their genomes as DNA integrated into the virally transformed host's chromosomes. As these results with different animal viruses were being appreciated, David Boettiger began working as a graduate student at the McArcIle Laboratory with Howard Temin.
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David Baltimore at MIT published similar findings for murine RNA tumor viruses in the same issue of Nature.l6 He had submitted a manuscript in March to the Proceedings of the National Academy of Sciences relating his findings that vesicular stomatitis virus, VSV, a rhabdovirus, contained an RNA-dependent RNA polymerase, again focusing attention on the existence of template-dependent polymerases intrinsic to various families of viruses.l7 The two reports of RNA-dependent DNA polymerase
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The combined finclings inclicatecl that RNA tumor viruses copier! their RNA genomes into DNA en cl that these proviral DNAs were integrated into infected cells' chromosomes, as were the genomic DNAs of SV40 en c!
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CEF cells multipliecl to higher saturation densities than uninfected parental cells in limiting serum, because they passed through more cell cycles than clic! their parental cells, as scorer!
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the growing interest of the community of cancer researchers in this family of viral carcinogens en cl placecl him at its center. AN EVOLVING STYLE Howard Temin's research on RNA tumor viruses, his contributions to the eTuciciation of their replication, en c!
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retrospectively clelight in his having askocl them questions from which they Earned. The general acceptance of his proviral hypothesis after the identification of reverse transcriptase activity in the virions
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In the sarcoma viruses this product would be effective in increasing the efficiency of utilization of multiplication-stimulating activity by fibroblasts, while in the leukemia viruses this product would not be active in fibroblasts. We know now that the rapicIly transforming RNA tumor viruses arise from the weakly transforming RNA tumor viruses'
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These Orologists askocl the question, "What information is present in Rous sarcoma virus but not present in related, weakly transforming avian RNA tumor viruses? " They demonstrated that nucleoticle sequences clerivecl from uninfected cellular DNA represented the transforming information in this rapicIly transforming RNA tumor virus.30 Subsequent analyses of this en cl other oncogenes captured by retroviruses have clemonstratecl that the viral oncogenes are clerivecl from normal cellular genes now flubber!
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cells wouIcl express RNA-clepenclent DNA polymerase activity (i.e., reverse transcriptase) , which couIcl contribute to the formation of RNA tumor viruses en c!
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Remnants of RNA tumor viruses (retroviruses) , retrotransposons (elements that transpose via reverse transcription)
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to the recent consideration by the fecleral government to classify nicotine-containing cigarettes as aciclictive. STRUCTURE OF THE PROVIRUS With the acceptance of the provirus hypothesis en cl with the cancer research community's intensifying interest in retroviruses, Howarc!
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a means to stucly them biologically. They showocl that transfection of DNA from infected cells into naive cells yielclecl infectious retroviruses (that is, proviral DNAs can be infectious themseIves)
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linkocl to cellular DNAs with characteristic repeated sequences. The structures of SNV viral DNAs, prior to integration en cl after integration, couIcl be stucliecl by Southern blotting with restriction endonucleases that cleaved within viral DNA.
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The cellular/proviral DNA junctions of the isolatecl DNAs consisted of a 5-base pair direct repeat of cell DNA adjacent to a 3-base pair inverted repeat of viral DNA.50 These structures were similar to those of integratecl bacterial transposons en cl therefore supported the hypothesis that the formation of retroviral proviruses was relater! mechanistically to bacterial transposition.
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The structure of v-ret en cl other retroviral transforming genes inclicatecl that reverse transcription of the splicecl RNA of cellular proto-oncogenes contributes! to the formation of rapidly transforming retroviruses.
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characterize retroviral vectors en cl the helper cells on which they depend. RapicITy transforming retroviruses are natural vectors for their derivatives of cellular proto-oncogenes.
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synthesize the viral particles required by retroviral vectors. Retroviruses synthesize gag en cl polfrom genomic viral RNA, env is synthesized from a spliced transcript.
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his colleagues lee! to clevelopment of helper cells for murine retroviral vectors.55 Viral trans-acting functions in aciclition to gag/pot en cl env were likely to be required for retroviral replication.
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be user! at a Tow multiplicity to infect non-helper cells in which it wouIcl undergo a single rouncl of reverse transcription en cl integration (198S,2, Figure I)
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in viva en cl allowocl John Coffin to posit conficlently that HIV's observed variation necessitated efficiently repeated rounds of infection of naive cells by HIV in vivo.58 His mocle! has been verified by studies measuring the overgrowth of resistant mutants in viva after treatment of AIDS patients with new, potent antiviral cirugs.59 The application of retroviral vectors en cl helper cells to stucly variation cluring a single rouncl of replication was extenclec!
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The recombinants were analyze cl for loss of the diagnostic restriction enclonuclease sites, most hacl lost them en cl represented genomic recombinants.60 Recombination within a retrovirus can be viewocl to result from reverse transcriptase copying one template RNA or DNA en cl then switching to the other present in the viral particle. The high rate of recombination found by Hu en cl Temin indicates that such a template switch occurs once per every two or three cycles of retroviral replication.
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infected cells with virus from characterized clones of helper cells with these proviruses en cl selectecl either for near or hyg'. Hygr cells arose at a frequency that inclicatec!
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Bob Gallo and his colleagues through their research on propagating human T cells in meclium containing IL-2 also contributes! to the identification of this human tumor virus.
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These incluclecl an oversight committee on AIDS activities of the Institute of Medicine from 1987 to 1990, chairing the HIV Genetic Variation Advisory Panel for the National Institute of Allergies en cl Infectious Diseases from 1988 to 1994, the Global Commission on AIDS from 1991 to 1992, and the World Health Organization Advisory Council on HIV en cl AIDS from 1993 to 1994. He clevotec!
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to immunize people against infection by HIV (1993,1~. Kathy Boris-Lawrie, a postcloctoral fellow, en cl he began testing this hypothesis by working with the animal lentiviruses, bovine leukemia viruses, en c!
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Cold Spring Harbor Symp. Quant.
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Cold Spring Harbor Symp. Quant.
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1960 The control of cellular morphology in embryonic cells infected with Rous sarcoma virus in vitro. Virology 10:182-97.
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Ribonuclease-sensitive deoxyribonucleic acid polymerase activity in uninfected rat cells and rat cells infected with Rous sarcoma virus.
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Hu. Retrovirus recombination and reverse transcription.
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