Showing papers by "David Baltimore published in 1973"
TL;DR: Cells from a patient with childhood acute lymphoblastic leukemia contain an apparent DNA polymerase activity that was not found in any other cells except thymus cells, which may be a marker for the origin of leukemic cells.
Abstract: Cells from a patient with childhood acute lymphoblastic leukemia contain an apparent DNA polymerase activity that was not found in any other cells except thymus cells. The enzyme has the properties of terminal transferase, an enzyme known to be found in thymocytes. The cells also contain the three major DNA polymerases found in growing cells. The results suggest that these tumor cells arose from a block in the differentiation of thymocytes. Terminal transferase may be a marker for the origin of leukemic cells.
217 citations
TL;DR: Virus-specific RNA was found to exist in infected cells in three major size classes: 60–70 S RNA, 35 S RNA and 20–30 S RNA; and Messenger RNA was differentiated from other virus-specific RNAs by the criterion that virus- specific messenger RNA must change in sedimentation rate following polyribosome disaggregation.
213 citations
TL;DR: The product of the Fv-1 locus, which restricts growth of murine RNA tumor viruses, must act on an intracellular aspect of tumor virus replication, a step after attachment and penetration.
Abstract: Formation of pseudotypes between murine RNA tumor viruses and vesicular stomatitis virus (VSV) has been confirmed Pseudotypes of VSV genomes coated by the surface envelope from an N-tropic tumor virus grew equally well in cells homozygous for either the Fv-1n or Fv-1b alleles Therefore, the product of the Fv-1 locus, which restricts growth of murine RNA tumor viruses, must act on an intracellular aspect of tumor virus replication, a step after attachment and penetration
143 citations
TL;DR: In this article, it was found that DI particles can carry out most of the standard poliovirus functions including inhibition of cellular macromolecular synthesis, production of viral RNA and production of virus-specific protein.
138 citations
TL;DR: Pulsechase experiments and studies employing the virus-specific inhibitor, guanidine, all indicate that the proviron is formed by combination of newly made RNA with the procapsid, the final step in poliovirus morphogenesis.
Abstract: Poliovirus-infected cells contain a previously unrecognized particle which appears to be an intermediate in virion synthesis and therefore has been named proviron It sediments at about 125S, contains the three procapsid proteins, VP-0, VP-1, and VP-3, and has 35S viral RNA It is disrupted both by sodium dodecyl sulfate and EDTA but the RNA resists digestion by ribonuclease Pulsechase experiments and studies employing the virus-specific inhibitor, guanidine, all indicate that the proviron is formed by combination of newly made RNA with the procapsid Cleavage of VP-0 to form VP-2 and VP-4 follows formation of the provirion and would be the final step in poliovirus morphogenesis
82 citations
TL;DR: In this article, the authors investigated interference with standard poliovirus growth resulting from co-infection of cells with standard virus and defective interfering particles and found that the interference results from equal participation in the intracellular events of the infection cycle by both types of particles.
67 citations
TL;DR: Formation of an apparent virion precursor, the provirion, can be demonstrated in cytoplasmic extracts of poliovirus-infected HeLa cells.
Abstract: Formation of an apparent virion precursor, the provirion, can be demonstrated in cytoplasmic extracts of poliovirus-infected HeLa cells.
39 citations
TL;DR: Study of the cycloheximide effect showed that the drug acted as if to change the input ratio of standard to DI particles, and enrichment due to preferential encapsidation of DI RNA can be explained as aspects of two different phenomena.
Abstract: Infection of HeLa cells by mixtures of standard poliovirus and defective, interfering (DI) poliovirus particles leads to a higher ratio of DI particles in the progeny than in the inoculum The extent of this enrichment could be varied by various manipulations of the co-infected cells At any time during the infection cycle, virions made within short times after addition of radioactive uridine were hyperenriched in DI particles; this transient hyperenrichment fell to the equilibrium enrichment level within 45 min after uridine addition A shift of the temperature of infection from 37 to 31 C also led to a hyperenrichment of DI particles and pulse-labeling revealed a superimposed transient hyperenrichment By contrast, cells continuously infected at 31 C showed a severe decrement in DI particles apparently because poliovirus DI particles behave as cold-sensitive mutants for RNA synthesis Cycloheximide treatment early in the infection cycle also led to hyperenrichment Study of the cycloheximide effect showed that the drug acted as if to change the input ratio of standard to DI particles These effects on enrichment can be explained as aspects of two different phenomena: enrichment due to preferential DI RNA synthesis and enrichment due to preferential encapsidation of DI RNA Both mechanisms probably play a role in the normal level of enrichment
33 citations
TL;DR: Its synthesis relative to the other VSV proteins was studied under conditions of inhibition of initiation of protein synthesis, and its tryptic peptides were compared to those of the other vesicular stomatitis virus proteins.
Abstract: Previous studies have noted the existence of a 190,000-daltoin vesicular stomatitis virus (VSV) protein called the large (L) protein To determine whether this protein is a nonspecific aggregate, a precursor to the other VSV proteins, or a unique viral protein, its synthesis relative to the other VSV proteins was studied under conditions of inhibition of initiation of protein synthesis Also, its tryptic peptides were compared to those of the other VSV proteins In both cases the results were consistent with the identification of the large protein as a unique viral protein
26 citations