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At least 127 records · Page 7Linked to original sources

PubMed1975

Characterization of endogenous RNA-directed DNA polymerase activity of reticuloendotheliosis viruses.

Reticuloendotheliosis viruses (REV) contain an endogenous RNA-directed DNA polymerase activity. The endogenous DNA polymerase activity can be elicited in purified preparations of REV by treatment with nonionic detergents. The enzyme activity has a strong preference for manganous ions. Therefore, appreciable endogenous DNA polymerase activity can be demonstrated only if the reaction mixture contains appropriate concentrations of manganous ions. Enzyme activity can be inhibited by pretreatment with RNase or deletion of one or more deoxyribonucleoside triphosphates from the reaction mixture. In contrast, actinomycin D has little effect in initial DNA synthesis. The results from both velocity and equilibrium centrifugation indicate that the nascent chains of product DNA are associated with 60S viral RNA. The DNA product of the endogenous DNA polymerase reaction is hybridizable to REV RNA, but not to avian leukosis virus RNA.

Avian Leukosis Virus↗

PubMed1976

Effect of medium of lowered NaCl concentration on virus release and protein synthesis in cells infected with reticuloendotheliosis virus.

When cultures producing reticuloendotheliosis virus were incubated for 24 h in medium of lowered NaCl concentration, virus production was inhibited. The extent of inhibition increased as the salt concentration of the medium was decreased. The inhibition was rapidly reversed by replacement of low-salt medium with normal medium. During the first hour after the inhibited cultures were returned to normal medium, virus was released at an accelerated rate, making the total amount of virus released by inhibited and control cultures the same. After 1 h in normal medium, the rate of virus production in the previously inhibited cultures was the same as in the control cultures. Incubation of infected cells in low-salt medium resulted in a 60% decrease in the overall rate of protein synthesis. Although returning the cells to normal medium rapidly reversed the inhibition of virus production, it did not rapidly increase the rate of protein synthesis. These results suggest that host cell-directed protein synthesis is preferentially inhibited by the low-ionic-strength medium, whereas that required for virus production continues.

Animals↗

PubMed1976

Group-specific antigen shared by the members of the reticuloendotheliosis virus complex.

The polypeptides of reticuloendotheliosis virus (REV) were separated by gel filtration in the presence of guanidine hydrochloride. The eight peaks obtained by gel filtration were then analyzed by polyacrylamide gel electrophoresis and four appeared to contain single polypeptides. The material identified as p29 was used to prepare antiserum. This protein constitutes the major internal non-glycosylated polypeptide in the virion. Double immunodiffusion indicated that the antiserum was specific for p29. Using this antiserum, cross-reactivity was demonstrated between REV, chick syncytial virus, duck infectious anemia virus, and spleen necrosis virus. Antiserum to p29 failed to cross-react with Rous sarcoma virus. This indicates that p29 is a group-specific antigen shared by the viruses of the REV complex. A microcomplement fixation test was developed with this antiserum that will be useful in the quantitation of REV and the identification of other members of this newly defined group.

Animals↗

PubMed1976

RNA polymerase activity in purified virions of avian reticuloendotheliosis viruses.

An RNA polymerase activity that synthesizes a U-rich RNA hydrogen bonded to a large viral RNA molecule was found in the cores of virions of avian reticuloendotheliosis viruses (REV). The RNA polymerase activity was separable from the DNA polymerase activity of REV virions. The 5'-terminus of the newly synthesized RNA was A. In addition, a tRNA nucleotidyl transferase activity, which added -CpCpA ends to tRNA, appears to be present in the REV virions.

Animals↗

PubMed1977

Pseudotypes of vesicular stomatitis virus with the mixed coat of reticuloendotheliosis virus and vesicular stomatitis virus.

Vesicular stomatitis virus (VSV) forms pseudotypes with envelope components of reticuloendotheliosis virus (REV). The VSV pseudotype possesses the limited host range and antigenic properties of REV. Approximately 70% of the VSV, Indiana serotype, and 45% of VSV, New Jersey serotype, produced from the REV strain T-transformed chicken bone marrow cells contain mixed envelope components of both VSV and REV. VSV pseudotypes with mixed envelope antigens can be neutralized with excess amounts of either anti-VSV antiserum or anti-REV antiserum.

Antigens, Viral↗

PubMed1977

Formation of reticuloendotheliosis virus pseudotypes of Rous sarcoma virus.

Superinfection of chicken embryo fibroblasts transformed by the defective Bryan strain of Rous sarcoma virus (BH-RSV) with two different reticuloendotheliosis viruses (REVs), REV strain T (REV-T) or spleen necrosis virus (SNV), resulted in the production of infectious sarcoma virus pseudotypes. These pseudotypes were neutralized by antiserum prepared against SNV and were unable to infect chicken cells preinfected with either REV-T or SNV. These results suggest that defective BH-RSV is able to use the glycoprotein from REV to form infectious pseudotypes. On the other hand, neither REV-T nor SNV was able to supply a functional reverse transcriptase to the polymerase-negative mutant BH-RSValpha, nor was REV-T or SNV able to complement the defect in the internal protein gene of the temperature-sensitive avian sarcoma virus mutant NY45.

Animals↗

PubMed1978

High-molecular-weight RNAs of AKR, NZB, and wild mouse viruses and avian reticuloendotheliosis virus all have similar dimer structures.

Several 50 to 70S tumor viral RNAs have previously been shown by electron microscopy to be dimers, with the two monomer subunits joined near their 5' ends. Five additional naturally occurring type C RNA tumor viruses have now been examined: AKR, and endogenous murine ecotropic virus; NZB, an endogenous murine xenotropic virus; and ecotropic and an amphotropic virus isolated from a wild mouse; and the avian reticuloendotheliosis virus (REV). All five 50 to 70S RNAs have similar 5'-to-5' dimer structures. Therefore, the observations support the hypothesis that the dimer linkage is a structural feature common to all type C mammalian viruses. REV is the first example of an avian virus with a clear 5'-to 5' dimer linkage. All of the mammalian viral RNAs, but not REV, showed symmetrically placed loops in each subunit of the dimer. Possible molecular structures and biological functions of the dimer linkages and loops are discussed.

AKR murine leukemia virus↗

PubMed1978

Isolation and characterization of a virus-specific ribonucleoprotein complex from reticuloendotheliosis virus-transformed chicken bone marrow cells.

Chicken bone marrow cells transformed by reticuloendotheliosis virus (REV) produce in the cytoplasm a ribonucleoprotein (RNP) complex which has a sedimentation value of approximately 80 to 100S and a density of 1.23 g/cm3. This RNP complex is not derived from the mature virion. An endogenous RNA-directed DNA polymerase activity is associated with the RNP complex. The enzyme activity was completely neutralized by anti-REV DNA polymerase antibody but not by anti-avian myeloblastosis virus DNA polymerase antibody. The DNA product from the endogenous RNA-directed DNA polymerase reaction of the RNP complex hybridized to REV RNA but not to avian leukosis virus RNA. The RNA extracted from the RNP hybridized only to REV-specific complementary DNA synthesized from an endogenous DNA polymerase reaction of purified REV. The size of the RNA in the RNP is 30 to 35S, which represents the subunit size of the genomic RNA. No 60S mature genomic RNA was found within the RNP complex. The significance of finding the endogenous DNA polymerase activity in the viral RNP in infected cells and the maturation process of 60S virion RNA of REV are discussed.

Animals↗

PubMed1979

Reticuloendotheliosis virus: detection of immunological relationship to mammalian type C retroviruses.

Reticuloendotheliosis virus (REV) p30 shares cross-reactive determinants and a common NH2-terminal tripeptide with mammalian type C viral p30's. An interspecies competition radioimmunoassay was developed, using iodinated REV p30 and a broadly reactive antiserum to mammalian virus p30's. The avian leukosis-sarcoma viruses and mammalian non-type C retroviruses did not compete in this assay. Previous data indicating that the REV group is not represented completely in normal avian cell DNA lead us to speculate that this may be the first example of interclass transmission, albeit in the remote past, among the Retroviridae.

Animals↗

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

Low-molecular-weight RNAs and initiation of RNA-directed DNA synthesis in avian reticuloendotheliosis virus.

The small RNAs of avian reticuloendotheliosis virus (REV) were analyzed by two-dimensional polyacrylamide gel electrophoresis and compared with those of murine leukemia virus and avian sarcoma virus. Although there were some similarities among the three virus types, the patterns of small RNAs were distinct. By characterizing the small RNA which is most tightly associated with REV genome RNA and which can be labeled in limited DNA synthesis reactions, the primer for REV reverse transcription was identified as tRNAPro. This is consistent with previous reports that REV is more closely related to retroviruses of mammalian origin than to other avian viruses. In contrast, REV strong-stop complementary DNA is longer than any previously characterized strong-stop products of avian or mammalian retroviruses. The REV group may, therefore, have been derived from an as yet unidentified mammalian type C virus.

Avian Sarcoma Viruses↗

PubMed1980

Specific antigenic relationships between the RNA-dependent DNA polymerases of avian reticuloendotheliosis viruses and mammalian type C retroviruses.

Immunoglobulin G directed against the DNA polymerase of Rauscher murine leukemia virus (R-MuLV) could bind to 125I-labeled DNA polymerase of spleen necrosis virus (SNV), a member of the reticuloendotheliosis virus (REV) species. Competition radioimmunoassays showed the specificity of this cross-reaction. The antigenic determinants common to SNV and R-MuLV DNA polymerases were shared completely by the DNA polymerases of Gross MuLV, Moloney MuLV, RD 114 virus, REV-T, and duck infectious anemia virus. Baboon endogenous virus and chicken syncytial virus competed partially for antibodies directed against the common antigenic determinants of SNV and R-MuLV DNA polymerases. DNA polymerases of avian leukosis viruses, pheasant viruses, and mammalian type B and D retroviruses and particles with RNA-dependent DNA polymerase activity from the allantoic fluid of normal chicken eggs and from the medium of a goose cell culture did not compete for the antibodies directed against the common antigenic determinants of SNV and R-MuLV DNA polymerases. We also present data about a factor in normal mammalian immunoglobulin G that specifically inhibits the DNA polymerases of REV and mammalian type C retrovirus DNA polymerases.

AKR murine leukemia virus↗

PubMed1981

Avian reticuloendotheliosis virus: characterization of genome structure by heteroduplex mapping.

The genome structure of defective, oncogenic avian reticuloendotheliosis virus (REV) was studied by heteroduplex mapping between the full-length complementary DNA of the helper virus REV-T1 and the 30S REV RNA. The REV genome (5.5 kilobases) had a deletion of 3.69 kilobases in the gag-pol region, confirming the genetic defectiveness of REV. In addition, REV lacked the sequences corresponding to the env gene but contained, instead, a contiguous stretch (1.6 to 1.9 kilobases) of the specific sequences presumably related to viral oncogenicity. Unlike those of other avian acute leukemia viruses, the transformation-specific sequences of REV were not contiguous with the gag-pol deletion. Thus, REV has a genome structure similar to that of a defective mink cell focus-inducing virus or a defective murine sarcoma virus. An additional class of heteroduplex molecules containing the gag-pol deletion and two other smaller deletion loops was observed. These molecules probably represented recombinants between the oncogenic REV and its helper virus.

Base Sequence↗

PubMed1981

Chemical and Immunological characterization of the major structural protein (p28) of MMC-1, a rhesus monkey endogenous type C virus: homology with the major structural protein of avian reticuloendotheliosis virus.

The major core protein (p28) of MMC-1, an endogenous type C virus of the rhesus monkey (Macaca mulatta), was purified and subjected to structural and immunological analyses. The NH2-terminal amino acid sequence of MMC-1 p28 showed extensive homology to the sequences of the major structural proteins (p30) of known mammalian type C viruses. Similarly, interspecies antigenic determinants shared by all the above viral proteins were detected in MMC-1 p28. Competition radioimmunoassays together with the results of statistical analysis of the primary structure data provided evidence that MMC-1 p28 is not more closely related to primate type C viruses of the Papio genus than to those isolated from rodents, cats, or New World monkeys. MMC-1 p28 was found to be closely related structurally to the p30 protein of the avian reticuloendotheliosis virus (REV-A), a horizontally transmitted type C virus of putative mammalian origin. In addition, MMC-1 p28 and REV-A p30 shared a specific subset of antigenic determinants not present in any of the other avian or mammalian type C viruses studied. These findings suggest that MMC-1 and REV may have a common evolutionary origin.

Amino Acid Sequence↗

PubMed1983

Structure and expression of c-rel, the cellular homolog to the oncogene of reticuloendotheliosis virus strain T.

The cellular homolog of the onc sequences in the avian retrovirus reticuloendotheliosis virus strain T (v-rel) was studied by molecular cloning and nucleic acid hybridization. In contrast to v-rel sequences, which are 1.4 kilobase pairs long, the cellular homolog, c-rel, from line 15B chickens is at least 25 kilobase pairs long, with multiple apparent introns. A 4.0-kilobase polyadenylic acid-containing RNA transcript is the primary species of c-rel RNA present in uninfected chicken cells. Sequences at the 3' end of this c-rel RNA are not present in v-rel.

Animals↗

PubMed1984

Structure and dimorphism of c-rel (turkey), the cellular homolog to the oncogene of reticuloendotheliosis virus strain T.

A locus has been identified in turkey DNA that contains nucleotide sequences homologous to the oncogene (v-rel) in the avian retrovirus, reticuloendotheliosis virus strain T. This locus, c-rel, has been molecularly cloned from an apparently heterozygous turkey. c-rel is approximately 23 kilobase pairs in length, with at least seven apparent introns, and contains sequences sufficient to account for all of v-rel. Nucleic acid sequence differences exist between v-rel and homologous regions of c-rel. We examined a population of turkeys to determine whether these sequence differences are the result of polymorphism in the population. Within the turkey population, c-rel is dimorphic in apparent introns and 3' flanking sequences, but polymorphism has not been detected within the regions of the c-rel locus that are homologous to v-rel. Additionally, no nucleic acid sequence differences have been detected between the regions of c-rel in turkeys that are homologous to v-rel and the sequences related to v-rel of a homologous locus in chickens (Chen et al., J. Virol. 245:104-113, 1983). The general organization of introns and flanking sequences is conserved for both c-rel in turkeys and this locus in chickens, indicating that c-rel, like other proto-oncogenes, may have an important development or metabolic function.

Animals↗

PubMed1985

Insertional activation of c-myc by reticuloendotheliosis virus in chicken B lymphoma: nonrandom distribution and orientation of the proviruses.

Chicken syncytial virus, a member of the reticuloendotheliosis virus family, can induce chicken B lymphomas indistinguishable from those caused by avian leukosis virus. Previously, we have demonstrated that the chicken syncytial virus proviruses in these tumors are linked to the proto-oncogene c-myc. We have now determined the arrangement of chicken syncytial virus proviruses in 22 tumors. The results indicate that these proviruses, without exception, are integrated upstream from the second c-myc exon. At least 70% of these insertion sites are clustered in a 0.5-kilobase region immediately preceding the exon. The proviruses are all arranged in the same transcriptional orientation as c-myc. This type of provirus organization bears strong resemblance to that of the avian leukosis virus proviruses involved in c-myc activation.

Animals↗

PubMed1986

Oncogene expression in reticuloendotheliosis virus-transformed lymphoid cell lines and avian tissues.

The genome of reticuloendotheliosis virus (REV-T) contains a unique oncogene, designated v-rel, which is inserted into the env region. Employing a cloned rel DNA probe, a single 2.9- to 3.0-kilobase v-rel mRNA was identified in poly(A)+ RNA from REV-T-transformed lymphoid cell lines. A 4.0-kilobase rel-specific transcript corresponding to the cellular homolog of the v-rel oncogene was identified in MSB-1 cells, a herpesvirus-transformed lymphoid cell line. Cytodot hybridization was used to quantitate the levels of rel, c-rel, c-myc, c-myb, c-abl, c-fms, c-Ha-ras, c-Ki-ras, c-src, c-yes, c-mos, and c-sis mRNA in REV-T-transformed cells. The levels of rel transcription in REV-T-transformed cells were elevated only two to eightfold over levels found in the transformed immature avian lymphoid cell line MSB-1. The relatively modest levels of rel transcription in REV-T-transformed cells and the significant differences between the lengths of the v-rel and c-rel mRNA suggest that REV-T transformation is the result of the production of an altered rel protein. The c-rel proto-oncogene is expressed in all avian hematopoietic tissues but is not expressed at significant levels in brain and muscle. The transcription of other proto-oncogenes is not enhanced in REV-T-transformed lymphoid cell lines.

Animals↗