| purification and properties of spleen necrosis virus dna polymerase. | dna polymerase was purified to apparent electrophoretic homogeneity from virions of spleen necrosis virus (snv). (snv is a member of the reticuloendotheliosis group of avian ribodeoxyviruses). the snv dna polymerase appears to consist of a single polypeptide with a molecular weight of 68,000. the snv dna polymerase has a preference for mn2+ for dna synthesis with an rna template and mg2+ for dna synthesis with a deoxyribohomopolymer template. at the optimum concentrations of divalent cation, the ... | 1975 | 51934 |
| rna-directed dna polymerase activity of reticuloendotheliosis virus: characterization of the endogenous and exogenous reactions. | reticuloendotheliosis virus (rev) contains an endogenously instructed, rna-directed dna polymerase activity. both the endogenous and exogenous dna polymerase activities exhibited up to 10-fold greater activity at the optimum concentration of manganous ion (0.025 mm for exogenous; 0.25 mm for endogenous) than at any concentration of magnesium ion. antiserum to the dna polymerase of an rev group virus (spleen necrosis virus) inhibited both endogenous and exogenous dna polymerase activity of rev, w ... | 1975 | 51935 |
| 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 ... | 1976 | 56462 |
| rna-directed dna polymerase from particles released by normal goose cells. | cells from a goose embryo were shown to release particle-associated rna-directed dna polymerase and rnase h activities that required the presence of nonidet p-40 for detection. the particles were not infectious and did not have endogenous dna synthesis. the goose particle dna polymerase was related to the dna polymerase of spleen necrosis virus with respect to size and was inhibited by immunoglobulin g to spleen necrosis virus dna polymerase. however, goose cells producing dna polymerase-contain ... | 1979 | 87517 |
| pheasant virus dna polymerase is related to avian leukosis virus dna polymerase at the active site. | the dna polymerase from amherst pheasant virus (apv), a member of the pheasant virus species of retroviruses, was compared to the dna polymerases of avian leukosis viruses (alv) and a reticuloendotheliosis virus (spleen necrosis virus (snv)). immunoglobulin inhibition tests and competition immunoassays showed that apv and alv dna polymerases are closely related at their active sites. the determinants common to their active sites are not shared by snv dna polymerase. bu using a species-specific r ... | 1979 | 94361 |
| comparative ultrastructural study of four reticuloendothelias viruses. | the morphology and development of four members of the reticuloendotheliosis virus group were studied by transmission electron microscopy. virions of duck spleen necrosis virus, duck infectious anemia virus, chicken syncytial virus, and reticuloendotheliosis virus strain t are sperical with a diameter of approximately 110 nm. they are covered with surface projections about 6 nm long and 10 nm in diameter. the center-to-center distance of surface projections is about 14 nm. the budding virions con ... | 1975 | 170410 |
| infectious dna of spleen necrosis virus is integrated at a single site in the dna of chronically infected chicken fibroblasts. | the infectious dnas of a number of avian leukosis-sarcoma and reticuloendotheliosis viruses were digested with six nucleotide-specific restriction endonucleases, and the digests were tested for infectivity. all of the enzymes inactivated the viral infectivities except for ecori, which did not inactivate the infectivity of the dna of two of the reticuloendotheliosis viruses, spleen necrosis and chick syncytial viruses. the infectious dna of spleen necrosis virus after digestion with ecori had a b ... | 1977 | 189309 |
| 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 us ... | 1977 | 195082 |
| complement-fixation test for reticuloendotheliosis viruses: limits of sensitivity in infected avian cells. | a specific micro-complement-fixation procedure for assay of avian reticuloendotheliosis viruses (rev), designated by use as the cofar test, was compared with an assay based on immunofluorescent (if) antibody staining of infected chick embryo fibroblasts. endpoint titrations in which rev strain t, chick syncytial virus, and spleen necrosis virus were used indicated that cultures infected with limiting dilutions of each strain were positive by both procedures within 6 days. depending on cell densi ... | 1977 | 204281 |
| sites of integration of reticuloendotheliosis virus dna in chicken dna. | the pattern of integration of spleen necrosis virus (snv) dna in dna from a large population of snv-infected chicken cells was studied by nucleic acid hybridization with iodinated viral rna by the blotting technique of southern. snv dna was found to be integrated at multiple sites in acutely infected chicken cells. concomitant with the transition from acute to chronic infection, a shift in the pattern of integration was observed. the majority of integrated snv dna found in acutely infected cells ... | 1978 | 210459 |
| dna of noninfectious and infectious integrated spleen necrosis virus (snv) is colinear with unintegrated snv dna and not grossly abnormal. | the cleavage sites of eight restriction endonucleases in linear spleen necrosis virus (snv) dna were mapped, and the map was oriented with respect to viral rna. with the aid of this map, several structural features of the viral dna were elucidated: unintegrated linear snv dna is terminally redundant; the majority of snv dna molecules integrated in chicken dna, which were previously shown to be present in many sites in cellular dna, are colinear with unintegrated viral dna; no tandem integration ... | 1979 | 217546 |
| cell killing by spleen necrosis virus is correlated with a transient accumulation of spleen necrosis virus dna. | spleen necrosis virus productively infects avian and rat cells. the average number of molecules of unintegrated and integrated viral dna in cells at different times after infection was determined by hybridization and transfection assays. shortly after infection, there was a transient accumulation of an average of about 150 to 200 molecules of unintegrated linear spleen necrosis virus dna per chicken, turkey, or pheasant cell. no such accumulation was seen in infected rat cells. soon after infect ... | 1979 | 225560 |
| formation and structure of infectious dna of spleen necrosis virus. | the kinetics of formation and the structure of infectious dna of spleen necrosis virus were determined. nonintegrated infectious viral dna first appeared 18 to 24 h after infection of dividing cells and persisted for more than 14 days. the nonintegrated infectious viral dna was in the form of either a double-stranded linear dna with a molecular weight of 6 x 10(6), detected in both the cytoplasm and nucleus, or a closed circular dna of the same molecular weight, detected primarily in the nucleus ... | 1977 | 556779 |
| inhibition of viral dna synthesis in stationary chicken embryo fibroblasts infected with avian retroviruses. | previously, we reported (fritsch and temin, j. virol. 21:119-130, 1977) that infectious viral dna was not present in spleen necrosis virus-infected stationary chicken cells. however, a stable intermediate was present in such infected stationary cells as evidenced by the appearance of infectious viral dna shortly after serum stimulation of these cells. after serum stimulation of infected stationary cells, the infectious viral dna appeared first in the nucleus. in contrast, in infected dividing ce ... | 1977 | 916025 |
| polypeptide composition of spleen necrosis virus, a reticuloendotheliosis virus. | the polypeptide composition of virions of spleen necrosis virus, a reticuloendotheliosis virus, was determined using electrophoresis on sodium dodecyl sulfate-containing, 10 percent polyacrylamide gels. ten polypeptides were resolved. four of these were present in minor and somewhat variable amounts. two proteins, gp71 and gp22, contained d-glucosamine and were located on the outer surface of the lipid envelope, as demonstrated by lactoperoxidase-catalyzed iodination and by bromelain digestion. ... | 1975 | 1142473 |
| clonal analysis of cardiac morphogenesis in the chicken embryo using a replication-defective retrovirus. iii: polyclonal origin of adjacent ventricular myocytes. | replication-incompetent variants of the avian spleen necrosis virus (snv) encoding cytoplasmic or nuclear-directed beta-galactosidase (beta-gal) have been used to trace the clonal growth of myocytes during left ventricular free-wall formation. tubular-stage hearts were infected with a mixed suspension of both retroviruses and, after hatching, the progeny of marked cells in the ventricular wall were examined by x-gal histochemistry. when a small number of virions was introduced individual blue pa ... | 1992 | 1297456 |
| novel gacg-hairpin pair motif in the 5' untranslated region of type c retroviruses related to murine leukemia virus. | we searched for the presence of common rna structural motifs in mammalian type c retroviruses related to murine leukemia viruses and the closely related avian spleen necrosis virus. a novel motif consisting of a pair of hairpins, called hairpin pair motif, was detected in the 5' untranslated regions of the genomes of these retroviruses. a combination of computational analyses that included the assessment of phylogenetic sequence conservation by multiple alignment, the search for regions with unu ... | 1992 | 1309906 |
| a spleen necrosis virus-based retroviral vector which expresses two genes from a dicistronic mrna. | we have investigated a novel strategy for coexpressing two genes from a retroviral vector. the 5' nontranslated leader region of at least some picornavirus rnas contains a sequence that can act as an internal ribosome entry site allowing initiation of translation at a downstream aug codon in a 5' cap-independent manner. to investigate whether such a sequence can function in the context of a retroviral vector, we constructed a spleen necrosis virus-based vector carrying two selectable marker gene ... | 1992 | 1310190 |
| spleen necrosis virus, an avian immunosuppressive retrovirus, shares a receptor with the type d simian retroviruses. | the reticuloendotheliosis viruses (rev) are a family of highly related retroviruses isolated from gallinaceous birds. on the basis of sequence comparison and overall genome organization, these viruses are more similar to the mammalian type c retroviruses than to the avian sarcoma/leukemia viruses. the envelope of a member of the rev family, spleen necrosis virus (snv), is about 50% identical in amino acid sequence to the envelope of the type d simian retroviruses. although snv does not productiv ... | 1992 | 1313915 |
| direct determination of the point mutation rate of a murine retrovirus. | the point mutation rate of a murine leukemia virus (mulv) genome (akv) was determined under conditions in which the number of replicative cycles was carefully controlled and the point mutation rate was determined by direct examination of the rna genomes of progeny viruses. a clonal cell line infected at a low multiplicity of infection (2 x 10(-3)) was derived to provide a source of virus with high genetic homogeneity. virus stocks from this cell line were used to infect cells at a low multiplici ... | 1992 | 1316475 |
| complementation studies with rous sarcoma virus gag and gag-pol polyprotein mutants. | avian retroviruses (with the notable exception of spleen necrosis virus) express their protease (pr) both in their gag and their gag-pol polyprotein precursors, in contrast to other retroviruses, notably, the mammalian retroviruses, in which pr is encoded in the gag-pol polyprotein or in a separate reading frame as a gag-pro product. the consequence is that the avian pr is expressed in stoichiometric rather than catalytic amounts. to investigate the significance of the particular genome organiza ... | 1992 | 1316486 |
| multiple sequence elements are involved in rna 3' end formation in spleen necrosis virus. | the function of the poly(a) signal in spleen necrosis virus (snv) is dependent upon the distance between the cap site and the poly(a) site, while the function of the sv40 late poly(a) signal is independent of the distance. deletions in the snv poly(a) sequence do not alter the distance-dependent function. snv/sv40 chimeric poly(a) signals show intermediate behavior between the snv and sv40 poly(a) signals. these results indicate that multiple sequence elements are involved in the functions of ei ... | 1992 | 1319783 |
| effect of gamma radiation on retroviral recombination. | to elucidate the mechanism(s) of retroviral recombination, we exposed virions to gamma radiation prior to infecting target cells. by using previously described spleen necrosis virus-based vectors containing multiple markers, recombinant proviruses were studied after a single round of retrovirus replication. the current models of retroviral recombination predict that breaking virion rna should promote minus-strand recombination (forced copy-choice model), decrease or not affect plus-strand recomb ... | 1992 | 1602553 |
| development and testing of a packaging cell line for avian retroviral vectors. | a new helper cell line designated l3.07, has been used to package spleen necrosis virus (snv)-based vectors, resulting in the production of high titres of replication defective retroviruses. one of these vectors, vsno21 has been shown to infect avian primordial germ cells (pgcs). | 1991 | 1652237 |
| the u3 region is not necessary for 3' end formation of spleen necrosis virus rna. | primary transcripts of retroviruses contain two poly(a) sites, one near the 5' and one near the 3' end of the transcript, but only the 3' poly(a) site is used for 3' end formation of viral rna. it was hypothesized on the basis of experiments with u3-deleted vectors of spleen necrosis virus that the u3 region contains sequences required for this rna 3' end formation: the titer of a u3-deleted vector was 150 times lower than that of the parental vector, and the addition of the simian virus 40 poly ... | 1990 | 1700836 |
| the efficiency of rna 3'-end formation is determined by the distance between the cap site and the poly(a) site in spleen necrosis virus. | the efficiency of rna 3'-end formation of spleen necrosis virus (snv) is determined by the distance between the cap site and the poly(a) site. when the distance between the cap site and the poly(a) site was shorter than 500 bases, only 3-9% of the rna was polyadenylated at the snv poly(a) site. however, when the distance between the cap site and the poly(a) site was 1400 bases or more, 70% of the total rna was polyadenylated at the snv poly(a) site. in contrast, the poly(a) signal sequences of t ... | 1990 | 1703980 |
| characterization of large deletions occurring during a single round of retrovirus vector replication: novel deletion mechanism involving errors in strand transfer. | retroviruses mutate at a high rate during replication. we used a spleen necrosis virus-based vector system and helper cell line to characterize mutations occurring during a single round of retrovirus replication. the vector used, jd216hyneo, codes for two drug resistance genes, hygromycin resistance (hygro) and neomycin resistance (neo). the downstream neo gene is expressed only when a mutation alleviates a block to splicing which is located in the upstream hygro gene. the mutations allowing spl ... | 1991 | 1714517 |
| spleen necrosis virus, an avian retrovirus, can infect primate cells. | spleen necrosis virus (snv) is an avian retrovirus that can infect some mammalian cells such as dog cells as well as all avian cells tested to date. we were interested in testing whether snv could also infect primate cells. for these experiments, we used hela and cos-7 cells. initially, we determined whether the snv long terminal repeat promoter was functional in hela and cos-7 cells. in transient transfection assays, the snv promoter efficiently directed chloramphenicol acetyltransferase gene e ... | 1991 | 1870201 |
| determination of retroviral mutation rates using spleen necrosis virus-based vectors and helper cells. | | 1991 | 2007191 |
| in vivo analysis of a new lacz retrovirus vector suitable for cell lineage marking in avian and other species. | to obtain a replication-defective retrovirus vector well suited for cell lineage marking in early avian embryos, we have constructed and tested a derivative of the avian spleen necrosis virus (snv) carrying the marker gene lacz. consistently high titers of this virus, designated cxl, were produced from retroviral packaging cells with no evidence of contaminating helper virus even after 12 months of continuous culture. cxl expresses lacz strongly and stably in avian cells and has a host range tha ... | 1991 | 2070832 |
| presence of a retroviral encapsidation sequence in nonretroviral rna increases the efficiency of formation of cdna genes. | we showed previously that retrovirus vector particles can encapsidate rnas without retroviral cis-acting sequences, that such rnas are reverse transcribed in infected target cells, and that the cdna copies are inserted into the host genome resulting in cdna genes (r. dornburg and h. m. temin, mol. cell. biol. 8:2328-2334, 1988). to provide further evidence that this retrovirus-mediated gene transfer occurred through an rna intermediate, we constructed retroviral vectors containing an intron from ... | 1990 | 2153250 |
| n myristoylation of the spleen necrosis virus matrix protein is required for correct association of the gag polyprotein with intracellular membranes and for particle formation. | to determine whether myristoylation is required for spleen necrosis virus replication, we constructed a substitution mutation in the gag gene that alters the putative myristate acceptor glycine residue. this single amino acid change was lethal for virus replication, resulted in aberrant proteolytic processing, and interrupted virion assembly and the release of virus from cells. immunofluorescence analysis indicated that the amount of gag polyprotein at the cell periphery and in golgi-associated ... | 1990 | 2164607 |
| broad spectrum of in vivo forward mutations, hypermutations, and mutational hotspots in a retroviral shuttle vector after a single replication cycle: deletions and deletions with insertions. | in the preceding paper we described an experiment that determined the in vivo forward mutation rate in a single replication cycle for spleen necrosis virus. in addition to substitutions, frameshifts, and hypermutations, the mutated proviruses contained two classes of deletions. one class of deletions contained short direct repeats at the deletion junctions. another class of deletions had short stretches of sequences inserted at the deletion junctions. in this report, we describe the deletion mut ... | 1990 | 2166940 |
| n-linked glycosylation and reticuloendotheliosis retrovirus envelope glycoprotein function. | different properties of the spleen necrosis virus (snv) envelope glycoprotein were analyzed following biosynthesis in the presence of glycosylation inhibitors. tunicamycin, which inhibits all asparagine n-linked glycosylation, prevented intracellular processing and translocation to the cell surface of the envelope protein. in contrast, castanospermine or deoxymannojirimycin, which block glycosidase trimming of the early high-mannose chains and subsequent complex type n-glycosylation, did not inh ... | 1990 | 2173257 |
| spleen necrosis virus gag polyprotein is necessary for particle assembly and release but not for proteolytic processing. | the nature of spleen necrosis virus pol gene expression and the role of gag and gag-pol polyproteins in virion assembly was investigated. the dna sequence of the gag-pol junction revealed that the two genes occupy the same open reading frame but are separated by an in-frame amber stop codon. biochemical analysis of gag-pol translational readthrough in vitro and in escherichia coli suggests that, in a manner similar to that in other mammalian type c retroviruses, amber stop codon suppression is r ... | 1990 | 2186174 |
| broad spectrum of in vivo forward mutations, hypermutations, and mutational hotspots in a retroviral shuttle vector after a single replication cycle: substitutions, frameshifts, and hypermutations. | we determined the in vivo forward mutation rate in a single replication cycle for spleen necrosis virus (snv). a method was developed to clone integrated proviruses of retroviral shuttle vectors by exploiting the tight binding of the lac operator to the lac repressor protein. the vectors contained the lacz alpha gene as a reporter of mutations. thirty-seven of the 16,867 proviruses recovered contained five classes of mutations, including substitutions and frameshifts. runs of 9 and 10 identical ... | 1990 | 2201018 |
| structure and autoregulation of the c-rel promoter. | precise regulation of proto-oncogene expression appears to be essential for the proper growth and development of multi-cellular organisms. one aspect of this regulation is at the level of transcription from the proto-oncogene promoter(s). in order to characterize the promoter for the chicken c-rel proto-oncogene, we have isolated and sequenced genomic dna containing the first exon of the chicken c-rel proto-oncogene. the c-rel promoter is structurally similar to the promoters of the so-called ho ... | 1990 | 2284104 |
| genetic consequences of packaging two rna genomes in one retroviral particle: pseudodiploidy and high rate of genetic recombination. | retroviruses contain two complete viral genomic rnas in each virion. a system to study in a single round of replication the products of virions with two different genomic rnas was established. a spleen necrosis virus-based splicing vector containing both the neomycin-resistance gene (neo) and the hygromycin b phosphotransferase gene (hygro) was used. two frameshift mutants were derived from this vector such that the neo and the hygro genes were inactivated in separate vectors. thus, each vector ... | 1990 | 2304918 |
| transcription from a spleen necrosis virus 5' long terminal repeat is suppressed in mouse cells. | to determine the block(s) to spleen necrosis virus (snv) replication in mouse cells, we studied the expression of a dominant selectable marker, neo, or a gene whose product is easily assayed, the chloramphenicol acetyltransferase (cat) gene, in snv-derived and murine leukemia virus-derived vectors. using transient (cat) and stable (neor phenotype) transfection assays, we showed that the snv promoter was used in mouse cells only when the 3' snv long terminal repeat (ltr) was absent. infection of ... | 1987 | 2444716 |
| new retrovirus helper cells with almost no nucleotide sequence homology to retrovirus vectors. | we prepared retrovirus packaging cell lines containing gag-pol genes from spleen necrosis virus (expressed from a cytomegalovirus promoter and the simian virus 40 (sv40) polyadenylation sequences) and, on a separate vector, either the env gene from spleen necrosis virus (expressed from the rous sarcoma virus promoter and the sv40 polyadenylation sequences) or the env gene from amphotropic murine leukemia virus (expressed from a cytomegalovirus promoter and the sv40 polyadenylation sequences). th ... | 1989 | 2524600 |
| bovine leukaemia virus packaging cell line for retrovirus-mediated gene transfer. | retroviral packaging cell lines were constructed by using the gag-pol gene of spleen necrosis virus, the gag-pol gene of moloney murine leukaemia virus and the env gene of bovine leukaemia virus. the plasmids containing the gag-pol genes and the plasmid containing the env gene were cotransfected into nih/3t3 and d17 cells. the cells containing the helper virus constructs were tested for their ability to package replication-defective murine leukaemia and avian reticuloendotheliosis retrovirus vec ... | 1989 | 2549178 |
| expression of avian reticuloendotheliosis virus envelope confers host resistance. | we constructed two reticuloendotheliosis virus (rev) envelope gene expression plasmids, one containing the rev-a envelope gene, the other the spleen necrosis virus (snv) envelope gene. cell lines were generated by transfecting each of the rev envelope plasmids into d17 cells, a canine cell line. the levels of rev envelope glycoprotein in the cell lines were assayed by immunoprecipitating the envelope glycoproteins from lysates of cells that were labeled with [35s]methionine. virological challeng ... | 1989 | 2554569 |
| a rapid, quantitative bioassay based on the human immunodeficiency virus trans-activator. | we constructed a human immunodeficiency virus (hiv) trans-activator cdna (tat) encoding the n-terminal 76 amino acids of the viral trans-activator followed by two additional amino acids (val and pro). this cdna encoded a functional trans-activator (tat) as shown by cotransfection into murine cells with a hiv promoter-chloramphenicol acetyltransferase dna construct. the tat cdna was cloned into an avian retroviral expression vector, a modified spleen necrosis virus (snv), and high-titer infectiou ... | 1989 | 2590554 |
| sequence instability in the long terminal repeats of avian spleen necrosis virus and reticuloendotheliosis virus. | sequence divergence between the 3' long terminal repeats (ltr) of avian reticuloendotheliosis virus (rev), deletion variant proviral clone 2-20-4, and spleen necrosis virus (snv)-proviral clones 14-44, 60, and 70-was found to involve two classes of base substitutions: low-frequency interspersed and high-frequency clustered substitutions. clones 2-20-4 and 14-44 have diverged 4.4% owing to low-frequency substitutions. in contrast, two high-frequency substitution segments have diverged by 30% and ... | 1987 | 2822937 |
| determination of the rate of base-pair substitution and insertion mutations in retrovirus replication. | we recently described a protocol for determination of retrovirus mutation rates, that is, the mutation frequency in a single cycle of retrovirus replication (j.p. dougherty and h.m. temin, mol. cell. biol. 6:4378-4395, 1987; j.p. dougherty and h.m. temin, p. 18-23, in j. h. miller and m. p. calos, ed., gene transfer vectors for mammalian cells, 1987). we used this protocol to determine the mutation rates for defined mutations in a replicating retrovirus by using a spleen necrosis virus-based vec ... | 1988 | 2839703 |
| purification and chemical and immunological characterization of avian reticuloendotheliosis virus gag-gene-encoded structural proteins. | five gag-gene-encoded structural proteins, designated p12, pp18, pp20, p30, and p10 were purified from replication-competent avian reticuloendotheliosis-associated virus (rev-a) by high-performance liquid chromatography complemented with chloroform-methanol extraction and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. based on amino acid composition and nh2- and cooh-terminal sequence analysis p12, pp18, p30, and p10 are distinct from one another, whereas pp20 is likely identical to ... | 1985 | 2982236 |
| in vitro transcription analysis of the viral promoter involved in c-myc activation in chicken b lymphomas: detection and mapping of two rna initiation sites within the reticuloendotheliosis virus long terminal repeat. | chicken syncytial virus, a member of the reticuloendotheliosis virus family, induces b-cell lymphomas in chickens that arise by transcriptional activation of the chicken c-myc gene. in vitro transcription studies on cloned tumor dna containing a deleted chicken syncytial virus provirus integrated upstream from, and in the same transcriptional orientation as, the chicken c-myc coding region were utilized to map possible transcriptional promoters and initiation sites. in vitro transcripts extendin ... | 1985 | 2983111 |
| nondefective spleen necrosis virus-derived vectors define the upper size limit for packaging reticuloendotheliosis viruses. | we constructed a nondefective retrovirus vector based on spleen necrosis virus (snv), a replication-competent reticuloendotheliosis virus. we introduced different dna sequences into this vector and studied the ability of the resulting viruses to replicate in chicken embryo fibroblasts. the replication efficiency of snv-derived viruses decreased with increasing virus size. viruses larger than 9.4 kilobases (kb) were rapidly overgrown by replication-competent deletion mutants. the size restriction ... | 1986 | 3024171 |
| comparison of promoter suppression in avian and murine retrovirus vectors. | previously, we described "promoter suppression" in infectious retrovirus vectors with two genes and an internal promoter. here, we examined several parameters of promoter suppression and found that the amount of suppression in an integrated retrovirus vector was dependent both on whether the vector was derived from spleen necrosis virus or murine leukemia virus and on which internal promoter was present in the vector. murine leukemia virus vectors showed less suppression than analogous spleen ne ... | 1986 | 3025812 |
| secretion of enzymatically active human renin from mammalian cells using an avian retroviral vector. | recombinant plasmid-based retroviral expression vectors were constructed using a modified spleen necrosis virus (snv) containing the herpes simplex virus thymidine kinase gene promoter controlling the expression of the tn5 neomycin phosphotransferase ii gene (nptii gene). the human renin (hrn) gene (hrn) was inserted into the 5' end of the snv sequences such that in concatemeric plasmid dna its expression was controlled by the strong promoter in the snv long terminal repeat (ltr). dog cells tran ... | 1986 | 3026901 |
| transformation of normal rat kidney (nrk) cells by an infectious retrovirus carrying a synthetic rat type alpha transforming growth factor gene. | we synthesized a gene for rat type alpha transforming growth factor (tgf-alpha) consisting of the leader sequence and the sequence coding for the mature 50-amino acid peptide without the c-terminal processed region. this gene was inserted into the retrovirus vector psw272, which is derived from spleen necrosis virus, to obtain an infectious recombinant virus carrying the rat tgf-alpha gene. this recombinant virus can infect normal rat kidney (nrk) cells and allow these cells to grow in soft agar ... | 1987 | 3469667 |
| the spleen necrosis virus int gene product expressed in escherichia coli has dna binding activity and mediates att and u5-specific dna multimer formation in vitro. | to facilitate the in vitro study of the spleen necrosis virus (snv) int gene product, we expressed the viral int locus in an escherichia coli expression vector. antiserum made against the protein produced in bacteria precipitated a 44-kda polypeptide from virus-infected chicken embryo fibroblasts. this result is consistent with the expected size of the snv int polypeptide. in a protein blotting assay, the expressed protein binds strongly to dna and was able to complex nonspecifically with both s ... | 1987 | 3548033 |
| high mutation rate of a spleen necrosis virus-based retrovirus vector. | spleen necrosis virus (snv) is an avian retrovirus that efficiently infects some mammalian cells (e.g., dog and rat cells). we constructed an snv-based vector, which contains less than 1 kilobase (kb) of the retrovirus sequence, and a number of derivatives containing selectable markers. we obtained high-titer virus stocks, over 10(6) transforming units per ml, with a vector whose genomic rna consists of 1,850 bases (full-length snv rna is 7.7 kb). we also studied two vectors that both carry two ... | 1986 | 3796606 |
| heparin-treated, v-myc-transformed chicken heart mesenchymal cells assume a normal morphology but are hypersensitive to epidermal growth factor (egf) and brain fibroblast growth factor (bfgf); cells transformed by the v-ha-ras oncogene are refractory to egf and bfgf but are hypersensitive to insulin-like growth factors. | chicken heart mesenchymal cells do not proliferate in culture medium containing heat-defibrinogenated plasma but proliferate briskly when incubated with epidermal growth factor (egf) or brain fibroblast growth factor (bfgf) plus insulin-like growth factors (igfs) or when infected with sarcoma or erythroblastosis viruses. when infected with the retrovirus mc29, which bears a v-myc oncogene, chicken heart mesenchymal cells proliferate at a more modest rate and become morphologically transformed. h ... | 1985 | 3898072 |
| replication of reticuloendotheliosis viruses in cell culture: acute infection. | replication of reticuloendotheliosis viruses (rev) in cultures of chicken and duck fibroblasts leads to some cell death soon after infection. this cell killing was used to develop a plaque assay for trager duck spleen necrosis virus (tdsnv) on duck embryo fibroblasts. a normal replicative cell cycle was required for normal virus production and the development of cytopathic effects in chicken cells exposed to tdsnv. the latent period was about two days. stationary chicken embryo fibroblasts could ... | 1974 | 4855738 |
| the retrovirus pol gene encodes a product required for dna integration: identification of a retrovirus int locus. | we mutagenized cloned spleen necrosis virus dna to identify a region of the retrovirus genome encoding a polypeptide required for integration of viral dna. five plasmids bearing different lesions in the 3' end of the pol gene were examined for the ability to integrate or replicate following transfection of chicken embryo fibroblasts. transfection with one of these dnas resulted in the generation of mutant virus incapable of integrating but able to replicate at low levels; this phenotype is ident ... | 1984 | 6083562 |
| tau, sigma, and delta. a family of repeated elements in yeast. | we report here the isolation and structure of a new repeated dna element, tau. this element, from saccharomyces cerevisiae, is 371 base pairs long and is flanked on either end by the same invertedly repeated sequence found at the ends of some ty and sigma elements in yeast, copia elements in drosophila and spleen necrosis virus. the tau inverted repeats are themselves flanked by a 5-base pair directly repeated genomic sequence that is present only once in a cognate tau-allele. these structural c ... | 1984 | 6088502 |
| the location of v-src in a retrovirus vector determines whether the virus is toxic or transforming. | we prepared infectious stocks of an avian retrovirus, a modified spleen necrosis virus, containing the herpes simplex virus type 1 thymidine kinase gene and the avian sarcoma virus v-src gene. viruses were recovered after cotransfection of chicken cells with dna of recombinants between cloned spleen necrosis virus thymidine kinase and v-src and with dna of cloned reticuloendotheliosis virus strain a. when v-src was inserted near the 5'end of the viral genome, only low titers of recombinant virus ... | 1984 | 6098817 |
| radioimmunological comparison of the dna polymerases of avian retroviruses. | 125i-labeled dna polymerases of avian myeloblastosis virus and spleen necrosis virus were used in a radioimmunological characterization of avian retrovirus dna polymerases. it was shown that avian leukosis virus and reticuloendotheliosis virus dna polymerases do not cross-react in radioimmunoassays. within the avian leukosis virus species, species-specific and type-specific antigenic determinants of the dna polymerase were defined. the previous finding of genus-specific antigenic determinants in ... | 1980 | 6154153 |
| 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 vir ... | 1980 | 6154804 |
| 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 geno ... | 1980 | 6245235 |
| infectious and noninfectious recombinant clones of the provirus of snv differ in cellular dna and are apparently the same in viral dna. | ten clones of charon 4a containing proviruses of spleen necrosis virus, an avian retrovirus, and flanking chicken dna sequences were isolated and characterized. some clones gave rise to progeny with viral dna sequences deleted or duplicated, probably as a result of crossing-over in the 600 bp terminal redundancy in viral dna. the cellular sequences are different in each clone, indicating that all the proviruses are integrated in different sites in cellular dna. six clones are infectious and four ... | 1980 | 6248244 |
| terminal repeats of the drosophila transposable element copia: nucleotide sequence and genomic organization. | we have determined the nucleotide sequence of the terminal regions of two members of the copia sequence family of d. melanogaster. the first 276 bp at one end of a copia element are repeated in direct orientation at its other end. the direct repeats on a single copia element are identical to each other, but they differ by two nucleotide substitutions between the two elements which were examined; this suggests that during transposition only one direct repeat of the parent element is used as a tem ... | 1980 | 6250726 |
| no apparent nucleotide sequence specificity in cellular dna juxtaposed to retrovirus proviruses. | the sequences of the virus-cell junctions of seven dna clones of spleen necrosis virus provirus were analyzed to determine the nucleotide sequence specificity of the cellular integration sites. as previously reported for one provirus, all clones contain a 5-base-pair direct repeat of cellular dna at the cell-virus junctions and a 3-base-pair inverted repeat at both ends of the provirus dna. the sequences of the 5-base-pair direct repeats are different in each clone and have no apparent homology ... | 1980 | 6261252 |
| mapping of alterations in noninfectious proviruses of spleen necrosis virus. | ten recombinant lambda phage containing proviruses of spleen necrosis virus (snv) were previously obtained. six of the proviruses are infectious and four are not infectious in infectious dna assays. in this paper, we show that these noninfectious proviruses are not infectious because of alterations in the viral dna. we constructed recombinants between infectious and noninfectious proviruses and tested these recombinants in an infectious dna assay. in addition, we carried out cotransfection of a ... | 1981 | 6268804 |
| 5'-terminal nucleotide noncoding sequences of retroviruses: relatedness of two old world primate type c viruses and avian spleen necrosis virus. | computer-assisted comparison of the 5'-terminal regions of mammalian type c viruses serves as a useful model of evolutionary divergence of noncoding nucleic acid sequences. it has led to the concept that regions of conserved nucleic acid sequences, the slowly divergent sequences, contain signals of translational, transcriptional, or integrative significance. interspersed among the conserved regions are rapidly divergent sequences in which base changes, insertions, and deletions are especially pr ... | 1981 | 6268813 |
| formation of infectious progeny virus after insertion of herpes simplex thymidine kinase gene into dna of an avian retrovirus. | we have prepared several infectious stocks of an avian retrovirus, spleen necrosis virus, containing the herpes simplex virus type 1 thymidine kinase (tk) gene. the viruses were produced after cotransfection of chicken cells with dna from recombinants between cloned spleen necrosis virus and tk dnas and dna of cloned reticuloendotheliosis virus strain a. removal of sequences in the tk gene for the end of tk mrna increased a thousand fold the yield of infectious recombinant virus. infection of ch ... | 1981 | 6276009 |
| spontaneous variation and synthesis in the u3 region of the long terminal repeat of an avian retrovirus. | recombinant dna clones of a viral clone of spleen necrosis virus, an avian retrovirus, were found to have long terminal repeats of different sizes. the variation was in the u3 region of the long terminal repeats, and any one clone had u3 of the same size in both long terminal repeats. the u3 regions in the 5' and 3' long terminal repeat were shown both to be derived from the 3' long terminal repeat of parental virus dna. | 1982 | 6283110 |
| establishment of infection by spleen necrosis virus: inhibition in stationary cells and the role of secondary infection. | the relationship of two early events in the establishment of infection by avian retroviruses, the inhibition of viral dna synthesis in stationary avian cells and the secondary infection which occurs after infection of replicating cells, was investigated. when neutralizing antibody to spleen necrosis virus was used to prevent secondary infection, the amount of unintegrated linear spleen necrosis virus dna detected was much lower in infected stationary cells than in infected replicating cells. the ... | 1982 | 6283112 |
| genome of reticuloendotheliosis virus: characterization by use of cloned proviral dna. | reticuloendotheliosis virus is an avian type c retrovirus that is capable of transforming fibroblasts and hematopoietic cells both in vivo and in vitro. this virus is highly related to the three other members of the reticuloendotheliosis virus group, including spleen necrosis virus, but it is apparently unrelated to the avian leukosis-sarcoma virus family. previous studies have shown that it consists of a replication-competent helper virus (designated rev-a) and a defective component (designated ... | 1982 | 6283142 |
| encapsidation sequences for spleen necrosis virus, an avian retrovirus, are between the 5' long terminal repeat and the start of the gag gene. | the minimal cis-acting sequences outside the long terminal repeat (ltr) required for formation of an infectious retrovirus cloning vector were determined with recombinants of spleen necrosis virus (snv) dna and herpes simplex virus type 1 thymidine kinase gene. the 3' end of snv dna was removed to within 40 base pairs (bp) from the 3' ltr with only a 2-fold effect on the recovery of infectious recombinant virus. however, when the 5' end of snv dna was removed to within 100 bp from the 5' ltr, in ... | 1982 | 6310558 |
| the terminal nucleotides of retrovirus dna are required for integration but not virus production. | deletion of specific nucleotides at either end of the long terminal repeat of the avian retrovirus, spleen necrosis virus, results in replication-competent but integration-defective virus. this result supports two conclusions: (1) the 5-base pair terminal inverted repeats and three to seven adjacent nucleotides are required for integration; (2) integration of retrovirus dna is not required for retrovirus gene expression. | 1983 | 6316141 |
| construction of a helper cell line for avian reticuloendotheliosis virus cloning vectors. | we wished to construct cell lines that supply the gene products of gag, pol, and env for the growth of replication-defective reticuloendotheliosis retrovirus vectors without production of the helper virus. to do this, first we located by s1 mapping the donor and acceptor splice sites of reticuloendotheliosis virus strain a. the donor splice site is ca. 850 base pairs from the 5' end of proviral dna. it is close to or overlaps the encapsidation sequences for viral rna. the splice acceptor site is ... | 1983 | 6318091 |
| high-frequency deletion in recovered retrovirus vectors containing exogenous dna with promoters. | we previously described infectious retrovirus vectors constructed from spleen necrosis virus which contain the herpes simplex virus thymidine kinase gene and the mouse alpha-globin gene (k. shimotohno and h. m. temin, nature [london] 299:255-268, 1982). in the present study we report that when tk- chicken cells infected with a virus containing the mouse alpha-globin promoter and other 5' noncoding sequences in addition to the alpha-globin coding sequences were selected for thymidine kinase (tk) ... | 1984 | 6321798 |
| expression from an internal aug codon of herpes simplex thymidine kinase gene inserted in a retrovirus vector. | we identified structural features that affect the expression of an exogenous gene inserted into a retrovirus vector constructed by using spleen necrosis virus, an avian retrovirus. the thymidine kinase gene from herpes simplex virus type 1 containing deletions in the promoter and terminal sequences of the mrna was inserted into spleen necrosis virus. we found that synthesis of thymidine kinase by the recovered virus was apparently initiated from internal aug residues. at least in some cases, how ... | 1984 | 6325894 |
| expression of complete chicken thymidine kinase gene inserted in a retrovirus vector. | the chicken thymidine kinase (tk) gene was inserted into spleen necrosis virus. thymidine kinase activity was expressed even when the promoter and terminator sequences for tk rna synthesis were retained. when the promoter was present in the same orientation as the promoter in the long terminal repeat of the virus, deletions occurred both in the virus and in the tk gene, and the thymidine kinase-transforming activity of the recovered virus was low. splicing of apparent intervening sequences in th ... | 1984 | 6325895 |
| tau, a repeated dna sequence in yeast. | we have found a 371-base-pair (bp) repeated dna element, tau, in saccharomyces cerevisiae. the ends of tau are composed of a 5-bp inverted repeat, similar in sequence to those reported for the ty, sigma, copia, and spleen necrosis virus elements. these inverted repeats are flanked by 5-bp direct repeats of a target sequence that occurs only once in an allele that lacks the tau element. this overall structure is characteristic of transposable elements. like sigma, tau elements have been found (in ... | 1984 | 6328481 |
| cellular dna surrounding integration sites of an avian retrovirus. | the size of the direct repeats of cellular dna next to a spleen necrosis virus (snv) provirus from infected rat cells and the nature of the cellular dna surrounding snv integration sites in chicken dna were studied. a five-base pair repeat, atttt, was observed at the snv-rat cell junctions. five of ten snv proviruses from chicken cells were flanked by unique dna and five others were flanked by repetitive dna. no large rearrangements of cellular dna at snv integration sites were observed. a clone ... | 1983 | 6834001 |
| spontaneous changes in nucleotide sequence in proviruses of spleen necrosis virus, an avian retrovirus. | we determined the nucleotide sequence of about 1 kilobase of dna 3' to the 5' long terminal repeat of three noninfectious ad one infectious proviral dna clones of spleen necrosis virus, an avian retrovirus, to determine if the types of nucleic acid changes involved in retrovirus mutation shed light on special features of retrovirus replication. an open reading frame was found starting 411 base pairs from the end of the long terminal repeat. it contained sequences coding for the 36 amino acids at ... | 1982 | 6951170 |
| isolation and characterization of retrovirus-like elements from normal human fetuses. | retrovirus-like particles have been isolated from normal fetal human plasma and from different embryonic organs collected from late first-trimester fetuses. the majority of the virus-like particles banded at a density region of of 1.19-1.22 g/ml, although lighter particles having a density of 1.15-1.17 g/ml were observed in some fetal tissues. the particles appeared similar to retroviruses when viewed electron-microscopically. they contained reverse transcriptase (rt) which accepted oligo (dg)-p ... | 1982 | 7129678 |
| ribonucleotides in unintegrated linear spleen necrosis virus dna. | the structure of unintegrated spleen necrosis virus dna was characterized by using various chemical and enzymatic treatments in conjunction with denaturing gels and nucleic acid hybridization probes. throughout the course of the viral infection, the predominant species of viral dna was that of a linear double-stranded molecule containing ribonucleotides covalently joined to the dna. the majority of both - and + strands were continuous. the ribonucleotide linkages appeared to be relatively short, ... | 1980 | 7365874 |
| e- vectors: development of novel self-inactivating and self-activating retroviral vectors for safer gene therapy. | we have developed novel self-inactivating and self-activating retroviral vectors based on the previously observed high-frequency deletion of direct repeats. we constructed spleen necrosis virus (snv)-based viral vectors that contained large direct repeats flanking the viral encapsidation sequence (e). a large proportion of the proviruses in the target cells had e and one copy of the direct repeat deleted. direct repeats of 1,333 and 788 bp were deleted at frequencies of 93 and 85%, respectively. ... | 1995 | 7474097 |
| genetic rearrangements occurring during a single cycle of murine leukemia virus vector replication: characterization and implications. | retroviruses evolve at rapid rates, which is presumably advantageous for responding to selective pressures. understanding the basic mutational processes involved during retroviral replication is important for comprehending the ability of retroviruses to escape immunosurveillance and antiviral drug treatment. moreover, since retroviral vectors are important vehicles for somatic cell gene therapy, knowledge of the mechanism of retroviral variation is critical for anticipating untoward mutational e ... | 1995 | 7494312 |
| high rates of frameshift mutations within homo-oligomeric runs during a single cycle of retroviral replication. | homo-oligomeric runs were inserted into a spleen necrosis virus-based retrovirus vector to determine the nature and rate of mutations within runs of 10 to 12 identical nucleotides during a single replication cycle. clones of helper cells containing integrated copies of retroviral vectors were used to produce virus for infection of target (nonhelper) cells. proviral sequences from target cell clones were compared with proviral sequences from helper cell clones to study mutations that occurred dur ... | 1994 | 7515970 |
| high rate of mismatch extension during reverse transcription in a single round of retrovirus replication. | we made spleen necrosis virus-based retroviral vectors with mutations at the 3' end of the primer binding site region to observe the effects of terminal mismatches on retroviral replication. these vectors, when compared to a vector with the wild-type primer binding sequence, allowed us to assay the effects of the mutations on the viral titer during a single cycle of replication. the mutant vectors had titers that were comparable to the wild-type vector, indicating that reverse transcriptase has ... | 1994 | 7524077 |
| lower in vivo mutation rate of human immunodeficiency virus type 1 than that predicted from the fidelity of purified reverse transcriptase. | the level of genetic variation of human immunodeficiency virus type 1 (hiv-1), a member of the lentivirus genus of the retroviridae family, is high relative to that of retroviruses in some other genera. the high error rates of purified hiv-1 reverse transcriptase in cell-free systems suggest an explanation for this high genetic variation. to test whether the in vivo rate of mutation during reverse transcription of hiv-1 is as high as predicted by cell-free studies, and therefore higher than that ... | 1995 | 7541846 |
| cell targeting with retroviral vector particles containing antibody-envelope fusion proteins. | retroviral vectors are the most efficient tool to introduce genes into vertebrate cells. however, their use is limited by the host range of the retrovirus from which they were derived. to alter the host range of the vector particle, we developed a method to substitute the receptor-binding domain of the envelope protein of a retrovirus with an antigen-binding site of an antibody. to test whether such particles are competent for infection, we established a model system using an antigen-binding sit ... | 1994 | 7584094 |
| replication of the retroviral terminal repeat sequence during in vivo reverse transcription. | there is a copy of a short terminal repeat segment, r, at each end of the retroviral rna genome. during reverse transcription, r is copied from the genomic rna to form the r component of the long terminal repeat in viral dna. although our current model for reverse transcription suggests that the 5' r is copied, it is not known whether the 5' copy, the 3' copy, or part of each r in the genomic rna serves as the template for the r region in the progeny viral dna. to assess the relative contributio ... | 1993 | 7685409 |
| high rate of genetic rearrangement during replication of a moloney murine leukemia virus-based vector. | a protocol was designed to measure the forward mutation rate over an entire gene replicated as part of a moloney murine leukemia virus-based vector. for these studies, the herpes simplex virus thymidine kinase (tk) gene under the control of the spleen necrosis virus u3 promoter was used as target sequence since it allows selection for either the functional or the inactivated gene. our results indicate that after one round of retroviral replication, the tk gene is inactivated at an average rate o ... | 1993 | 7692080 |
| mapping of receptor binding domains in the envelope protein of spleen necrosis virus. | spleen necrosis virus (snv) is an amphotropic retrovirus originally isolated from a duck. although of avian origin, it also replicates on some mammalian cells. snv-derived retroviral vectors work with high efficiency and have a high potential for various gene transfer applications. however, little is known about the envelope-receptor interactions of this virus. we constructed a series of recombinant envelope proteins to characterize the su peptide of snv. we found that, in contrast to the envelo ... | 1995 | 7769695 |
| intrachromosomal recombination mediated by the polyomavirus large t antigen. | we used a spleen necrosis virus-based retroviral vector to introduce the polyomavirus replication origin into rat cells and developed a system to analyze homologous recombination events that do not reconstitute a selectable marker. introduction of the gene coding for the polyomavirus large t antigen into the cell lines by dna transfection promoted high-frequency recombination between the two retroviral ltrs, leading to amplification and excision of dna sequences. to analyze homology requirements ... | 1995 | 7831777 |
| genetically simpler bovine leukemia virus derivatives can replicate independently of tax and rex. | retrovirus genomes have a conserved modular organization that consists of trans-acting gag, pol, and env genes that function through cis-acting sequences to replicate the rna genome to the dna provirus. genetically more complex retroviruses also encode regulatory genes and cis-acting sequences that are essential for their replication. we sought to convert a more complex retrovirus into a simpler retrovirus derivative that can replicate. we constructed novel, hybrid retrovirus vectors to replicat ... | 1995 | 7853535 |
| mapping the origin of the avian enteric nervous system with a retroviral marker. | the enteric nervous system is largely formed from the vagal neural crest which arises from the neuroaxis between somites 1-7. in order to evaluate the contribution of different regions of the vagal crest to the enteric nervous system, we marked crest cells by injecting somites 1-10 with a replication-defective spleen necrosis virus vector which contains the marker gene lacz. after incubation in x-gal, lacz-positive blue cells were found in the wall of the gut in three locations. most were found ... | 1994 | 7881127 |
| retroviral vector particles displaying the antigen-binding site of an antibody enable cell-type-specific gene transfer. | retroviral vectors are the most efficient tool for stably introducing genes into vertebrate cells. however, their use is limited by the host range of the retrovirus from which they are derived. to alter the host range, we recently constructed retrovirus vector particles, derived from spleen necrosis virus, that display a single-chain antigen-binding site of an antibody (sca) on the viral surface (t.-h. t. chu, i. martinez, w. sheay, and r. dornburg, gene ther. 1:292-299, 1994). using a hapten (2 ... | 1995 | 7884919 |
| improved self-inactivating retroviral vectors derived from spleen necrosis virus. | self-inactivating (sin) retroviral vectors contain a deletion spanning most of the right long terminal repeat's (ltr's) u3 region. reverse transcription copies this deletion to both ltrs. as a result, there is no transcription from the 5' ltr, preventing further replication. many previously developed sin vectors, however, had reduced titers or were genetically unstable. earlier, we reported that certain sin vectors derived from spleen necrosis virus (snv) experienced reconstitution of the u3-del ... | 1994 | 7933088 |
| one retroviral rna is sufficient for synthesis of viral dna. | we used previously characterized spleen necrosis virus-based retroviral vectors and helper cells to study the strand transfers that occur during the reverse-transcription phase of a single cycle of retroviral replication. the conditions used selected only for formation of an active provirus rather than for expression of multiple drug resistance markers. in nonrecombinant proviruses the minus- and plus-strand dna primer transfers were almost completely intramolecular. however, as previously repor ... | 1994 | 8254730 |
| lower mutation rate of bovine leukemia virus relative to that of spleen necrosis virus. | genetic variation of the more complex retroviruses in the human t-cell leukemia virus/bovine leukemia virus (htlv/blv) group is less than in some other retroviral genera. to test whether reverse transcription of htlv/blv group members is less error prone than that of members of other groups, we developed an assay for detecting forward mutations in blv, similar to that developed for the simpler spleen necrosis virus (snv). we used this system to study the rates and types of mutations that occur d ... | 1994 | 8254760 |
| a short sequence upstream of the 5' major splice site is important for encapsidation of hiv-1 genomic rna. | a series of linker scanning and deletion mutations has been constructed in the 5' leader sequence of hiv-1. one virus with a 13-base-linker substitution upstream of the 5' major splice site was as impaired in its ability to replicate as a virus with a large deletion, which included these 13 bases, and was less efficient in packaging its genomic rna than viruses carrying mutations between the 5' major splice site and the gag translation initiation site. these observations have led to the identifi ... | 1994 | 8259668 |
| a double hairpin structure is necessary for the efficient encapsidation of spleen necrosis virus retroviral rna. | we conducted a mutational analysis within the previously defined encapsidation sequence (e) for spleen necrosis virus (snv), an avian retrovirus. we found that two regions are necessary for efficient snv replication. the first region is a double hairpin structure as proposed by konings et al. (1992, j. virol., 66, 632-640); the second region is located downstream of the hairpins. we showed further that the double hairpin structure is required for efficient snv rna encapsidation. our work is the ... | 1994 | 8313915 |
| retroviral expression of fgf-2 (bfgf) affects patterning in chick limb bud. | to investigate the role of fibroblast growth factor-2 (basic fibroblast growth factor) in chick limb development, we constructed a replication-defective spleen necrosis virus to ectopically express fibroblast growth factor-2 in stage 20-22 chick limb bud. because infecting cells in vivo proved to be inefficient, limb bud cells were dissociated, infected in vitro, and then grafted back into host limbs. this procedure caused duplications of anterior skeletal elements, including proximal humerus, d ... | 1993 | 8375342 |