Search PubMed⌕ Search

Biomedical subjects

N R Rice

Publications and source records attributed to N R Rice.

64 records · Page 4Linked to original sources
PubMed1980

Analysis of the nucleic acid components in reticuloendotheliosis virus.

Reticuloendotheliosis virus (REV) is known to be capable of transforming chicken bone marrow cells in vivo and embryo fibroblasts in vitro. As with spleen necrosis virus, we have found that sequences related to REV are found in DNA of several uninfected avian species. For example, about 15% of the [3H]cDNA synthesized in the endogenous reverse transcriptase reaction reassociated with DNA of uninfected chickens. Kinetic analysis revealed only a few (less than five) such sequences per haploid genome, and the thermal stability of the reassociated duplex indicated less than perfect complementarity. Comparison of REV propagated in an avian cell line with REV grown in a canine line has revealed clear differences between the two isolates. Viral RNA and [3H]cDNA of REV isolated from the transformed chicken bone marrow cell line appear to consist of at least three sequence classes. The most numerous of these classes is highly related to REV propagated in canine cells. Only slightly less abundant is a class unrelated to RNA isolated from the canine virus but highly related to sequences found in normal uninfected avian cellular DNA. A third component is present at about 1% the level of the most numerous class. Although REV appears to be unrelated to the other known avian retroviruses, distant relatedness between p30's of REV and various mammalian type C viruses has recently been reported. We have asked whether REV-related sequences can be detected in various mammalian DNAs and viral RNAs. Hybridization experiments performed at low stringency have revealed no such sequences.

Animals↗
PubMed1980

Avian reticuloendotheliosis virus: characterization of the high-molecular-weight viral RNA in transforming and helper virus populations.

Reticuloendotheliosis virus strain T (REV-T) is a type C retrovirus known to transform avian fibroblasts, spleen cells, and bone marrow cells and to produce virulent reticuloendotheliosis in young chicks. Analysis of REV-T high-molecular-weight RNA by electrophoresis in denaturing gels and by electron microscopy revealed the presence of at least two classes of molecules. One class appeared in CH3HgOH gels to have a monomer length of 9.3 kilobases (kb); in electron microscopic spreads under mildly denaturing conditions, it existed as a typical retrovirus dimer, having a monomer length of 8.8 +/- 0.7 kb. The second class also existed as a dimer, with a monomer length of 5.7 kb in CH3HgOH gels. Hybridization with REVA-A 32P-labeled complementary DNA revealed a third size class of molecules (4.7 kb), which were not resolvable from the 5.7-kb class in electron microscope spreads and which comigrated with chicken 28S rRNA in denaturing gels. Only the 9.3-kb class was found in the reportedly nontransforming virus produced after infection of canine thymus cell line with REV-T. Thus, REV-T appears to be similar to the murine and feline sarcoma viruses and the avian acute leukemia viruses in that it consists of a nontransforming helper virus genome and a defective genome responsible for oncogenicity. Our previous results demonstrated the presence in REV-T and in uninfected chicken cellular DNA of some nucleotide sequences not found in virus produced by the canine line (S. Simek and N. Rice, J. Virol. 33:320--329, 1980). In this report we show by hybridization with highly specific 32P-labeled complementary DNAs that REV-T-specific sequences exist within the 5.7-kb genome. Since 32P-labeled complementary DNA synthesized from the canine-derived virus genome hybridized with all three classes of RNAs, we conclude that the 5.7-kb genome is a recombinant between some sequences found in the putative helper and some sequences specific to REV-T. As with the other oncogenic viruses mentioned above, these specific sequences appear to be derived from host DNA.

Base Sequence↗
PubMed1979

Isolation and characterization of an endogenous type C virus of rhesus monkeys.

A type C retrovirus was isolated from a continuous cell line established from a spontaneous esophageal carcinoma of a rhesus monkey (Macaca mulata) by prolonged cocultivation with canine cells. A DNA transcript of the viral RNA hybridized to a high level and kinetic analysis indicated the presence of multiple copies of the viral genome in rhesus monkey DNA, showing that the virus is endogenous in this species. The rhesus monkey virus closely resembles, in several respects, an endogenous type C virus previously isolated from stumptailed macques (Macaca arctoides), aa species closely related to rhesus monkeys.

Animals↗
PubMed1979

Synthesis of long complementary DNA in the endogenous reaction by equine infectious anemia virus.

In the endogenous reverse transcriptase reaction, equine infectious anemia virus is able to synthesize complementary DNA (cDNA) of 8,000 nucleotides in high yield. After 2 h in 50 muM dNTP, about 2.8 mug of cDNA per mg of protein is produced, almost 30% of which is long cDNA. The system thus compares favorably with the other two well-characterized endogenous reaction systems, Moloney murine leukemia virus and avian sarcoma virus. Elongation rates of 100 to 150 nucleotides per min have been observed; these rates are comparable to those seen with purified avian myeloblastosis virus reverse transcriptase and significantly higher than those observed in vivo. In the absence of actinomycin D, equine infectious anemia virus does not require high dNTP levels for either optimal incorporation or long cDNA synthesis. The amount of long cDNA synthesized is maximal at 2 h in 50 muM dNTP; neither longer time nor higher dNTP levels (through 1.8 mM) increased this yield. Half-maximum yield in 2 h was achieved at about 15 muM dNTP, which is very similar to the published K(M)'s for isolated avian and murine reverse transcriptases. Total incorporation, on the other hand, continues to rise slowly through 1 mM dNTP; the half-maximum was 30 to 50 muM dNTP. In the presence of 100 mug of actinomycin D per ml, however, higher dNTP levels are required for long cDNA synthesis. We conclude that equine infectious anemia virus is exceptionally well-suited to studies of the physical organization of the retrovirus genome and to investigations of the mechanism of synthesis of the double-standard cDNA endogenous reaction product.

Cell-Free System↗
PubMed1978

Detection of proviral DNA in horse cells infected with equine infectious anemia virus.

Equine infectious anemia virus (EIAV) recently has been shown to possess a high-molecular-weight RNA genome and a virion reverse transcriptase. We completed the demonstration that EIAV is a retrovirus by showing the presence of proviral DNA in equine cells infected in vitro, but not in normal horse DNA. These studies were performed by using a highly representative cDNA probe synthesized by the virion polymerase. It was found that this cDNA reassociated extensively, and with high thermal stability, with either viral RNA or DNA extracted from infected cells, but showed no detectable reassociation with DNA from uninfected horse cells. Similarly, sequences related to EIAV were neither found in the DNA of four other Equus species, nor in a variety of other mammals including sheep, cows, pigs- dogs, cats, and humans; nor did EIAV cDNA hybridize with a variety of other retrovirus RNAs. These experiments were performed under conditions of very low stringency to enable detection of distantly related sequences, with a sufficient ratio of DAN to cDNA to allow detection of less than one viral copy per haploid genome. We conclude that EIAV is not an endogenous virus of the horse or of the other species tested.

Animals↗
PubMed1973

Relatedness of mouse satellite deoxyribonucleic acid to deoxyribonucleic acid of various Mus species.

Mouse (Mus musculus musculus) satellite DNA is able to reassociate with repeated DNA sequences of Mus caroli and Mus cervicolor, but low thermal stability of the products indicates significant differences between satellite and related DNAs of these two Mus species. There appear to be several satellite-related populations in M. caroli DNA, each of which forms hybrids of low thermal stability with repeated sequences of M. cervicolor DNA. DNAs from the subspecies Mus musculus molossinus and Mus musculus castaneus reassociate with mouse satellite to form hybrids of very high thermal stability, but the satellite content of M. m. musculus DNA is only about 60% that of M. m. musculus DNA. Reassociation of M. m. musculus nonrepeated DNA with M. m. molossinus DNA reveals no detectable differences between them; reassociation with M. caroli (or M. cervicolor) DNA yields a product whose melting temperature depression relative to homologous DNA is about 5 degrees .

Animals↗