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[dna polymerase in the microsomal fraction of the myeloblasts of chickens infected with avian myeloblastosis virus].only one dna polymerase is present in the microsomal fraction of the cells producing amv. chromatographically purified enzyme shows the properties of revertase, that is it transcribes in dna the information encoded in natural rna. the enzyme possesses identical chromatographic characteristics and the same template specificity as the enzyme isolated from pure amv virus. thus the virus enzyme and the cellular dna polymerase from the microsomal fraction cannot be differentiated on the basis of cert ...19807293688
virus-mediated abrogation of chicken lymphocyte responsiveness to mitogenic stimulus.we have found that various sorts of virus particles, including avian leukosis and sarcoma viruses, sendai virus, friend leukemia virus and murine mammary tumor virus, are able, upon coincubation with chicken peripheral lymphocytes and either concanavalin a (con a) or phytohemagglutinin (pha), to inhibit the mitogenic responses that normally follow. such inhibition is not dependent on the use of infectious virus, and can be documented by using particles whose infectivity has been abolished by irr ...19806255923
purification and characterization of the rna-directed dna polymerase of a primate type-d retrovirus: mason-pfizer virus.the rna-directed dna polymerase of the primate type-d retrovirus mason-pfizer virus was purified using ion-exchange and affinity chromatography, and molecular sieving. the enzyme was shown to have a molecular weight of approx. 80 000 as determined by sedimentation analysis, molecular sieving and sodium dodecyl sulfate polyacrylamide gel electrophoresis. the purified rna-directed dna polymerase retained its ability to use a heteropolymeric rna as a template. the mason-pfizer virus rna-directed dn ...19806772221
a cloned calmodulin structural gene probe is complementary to dna sequences from diverse species.calmodulin mrna has been partially purified from a total nucleic acid extract of the electroplax of electrophorus electricus by oligo(dt)-cellulose chromatography and sucrose gradient centrifugation. a 9- to 10s fraction was determined to contain 39% calmodulin mrna by translation in a reticulocyte lysate followed by immunoprecipitation with antibodies to calmodulin. double-stranded cdna was synthesized from the rna fraction by using reverse transcriptase from avian myeloblastosis virus. the dou ...19816941292
collagen and noncollagen protein synthesis in chick limb bud cells infected with a virus that causes osteoblastoma.infection of cultured stage 24 (day 4.5) chick limb cells (spot cultures) with myeloblastosis-associated virus 2-(osteo) (mav-2(0)) produces cell density-dependent alterations of collagen and noncollagen protein synthesis over the course of 8 days in culture. collagen synthesis in infected, low density cultures (100 k cells/spot) was maximal on day 4 and increased 12 fold compared with maximal values on days 5-6 for uninfected counterparts. the patterns of collagen synthesis were similar in unin ...19817289876
replicating, differentiated macrophages can serve as in vitro targets for transformation by avian myeloblastosis virus.pure cultures of chicken macrophages were characterized functionally and transformed by avian myeloblastosis virus. transformed cells exhibited an altered function. the efficiency of transformation was limited by the mitotic activity of the macrophages.19816260997
histone h5 in the immature blood cells of chickens with leukosis induced by avian leukosis virus strain e26.whole histone was isolated from the immature cells of the peripheral blood of white leghorn chickens, line 151, with leukosis experimentally induced by avian leukosis virus, strain e26 (alv-e26). histone h5 was demonstrated in all samples of these cells and was characterized by electrophoresis in polyacrylamide gel, extraction with perchloric acid, amino acid analysis, and immunodiffusion in agarose gel. histone h5 was not detected in the myeloblasts of chickens with myeloblastosis caused by the ...19816264195
vertebrate dnas contain nucleotide sequences related to the transforming gene of avian myeloblastosis virus.avian myeloblastosis virus contains a continuous sequence of approximately 1,000 nucleotides which may represent a gene (amv) responsible for acute myeloblastic leukemia in chickens. this sequence appears to have been acquired from chicken dna and to be substituted for the envelope gene in the viral genome. we used hybridization probes enriched for the amv sequences and conditions that facilitate annealing of partially homologous nucleotide sequences to show that cellular sequences related to am ...19816275098
characterization of reticuloendotheliosis virus strain t dna and isolation of a novel variant of reticuloendotheliosis virus strain t by molecular cloning.reticuloendotheliosis virus strain t (rev-t) is a highly oncogenic avian retrovirus which causes a rapid neoplastic disease of the lymphoreticular system. upon infection, this virus gives rise to two species of unintegrated linear viral dna, which are 8.3 and 5.5 kilobase pairs long and represent the helper virus (rev-a) and the oncogenic component (rev-t), respectively. restriction endonuclease cleavage maps of these two dna components indicate that rev-t dna has a large portion of the genome d ...19816275117
characterization of an inhibitor of granulocyte/monocyte colony formation in leukemic chicken plasma.the plasma of chicks with myeloblastic leukemia (induced by avian myeloblastosis virus, amv) contained an inhibitor which blocked colony formation in vitro by marrow cells. it eluted in the second protein peak obtained by sephadex g-200 gel filtration and was found in the diafiltrate following defiltration through a um 10 membrane under acidic conditions. it was not extractable with chloroform, was heat-stable (65 degrees c, 30 min), pronase-sensitive and had a molecular weight less than or equa ...19816165604
reverse transcriptase associated with avian sarcoma-leukosis viruses. i. comparison of intra-virion content of multiple enzyme forms.the rna-dependent dna polymerase (the reverse transcriptase) was solubilized from three related strains of avian sarcoma virus (asv b77, asv tsla334, and asv qv2) as well as avian myeloblastosis virus (amv) and a chicken endogenous virus (rav-o), by a combination of non-ionic detergent treatment and cscl step-gradient centrifugation, and was subsequently separated into individual enzyme forms by poly(c)-agarose column chromatography. the newly developed two-step method allowed us to purify the t ...19826175623
lymphoid leukosis: detection of group specific viral antigen in chicken spleens by immunofluorescence and complement fixation.monospecific antiserum obtained from rabbits hyperimmunized against homogeneous p27 group specific protein purified from avian myeloblastosis virus was commercially procured and was then conjugated with fluorescein isothiocyanate. the conjugate was applied to spleens from naturally or experimentally infected chickens that had no evidence of lymphoid tumors. fluorescence was usually localized in connective tissue of sheathed capillaries giving it a ring-like appearance. sites of fluorescence corr ...19826184143
studies on the structure of avian myeloblastosis virus (amv) rna. ii. integrity of the rna in dependence on rna isolation and virus propagation.while sedimentation analysis revealed no basic changes in the sedimentation characteristics of 60-70 s avian myeloblastosis virus (amv) rna isolated under different conditions from two sources, electron microscopy exhibited differences in the length distributions of this rna. based on the length distribution profiles, phenol extraction showed a higher degradation effect in comparison with direct gradient centrifugation of viral lysates. proteinase k appeared to be a more suitable nuclease inhibi ...19826124106
helper viruses associated with avian acute leukemia viruses inhibit the cellular immune response. 19826278717
modulation of atpase activity of avian myeloblastosis virus with ca2+, atp & its reaction products. 19826299931
changes in the expression of membrane antigens during the differentiation of chicken erythroblasts.chicken erythroblasts can be transformed by the avian retrovirus, avian erythroblastosis virus (aev). earlier studies have shown that the mechanism of transformation appears to involve a "block" in differentiation, in that when erythroblasts are transformed by a temperature-sensitive mutant of ts34 aev and incubated at the nonpermissive temperature, the cells start to differentiate and produce hemoglobin. we have decided to use this system to isolate pure populations of chicken erythroblasts and ...19827040433
differential expression of the amv gene in human hematopoietic cells.total cellular rnas from a variety of fresh and culture-derived human hematopoietic neoplastic cell types at various stages of differentiation and human sarcoma, carcinoma, melanoma, and glioblastoma cell lines were enriched for poly(a)- containing sequences, fractionated by gel electrophoresis, and blot hybridized to a cloned dna probe containing the transforming sequences (v-amv) of avian myeloblastosis virus (amv), a virus known to cause myeloid leukemias in chickens. expression of rna sequen ...19826954533
levels of colony-stimulating and inhibiting activities in chicks with myeloblastic leukemia are related to disease progression.chicks with myeloblastic leukemia induced by avian myeloblastosis virus (amv) exhibited increased levels of plasma granulocyte/monocyte (gm) colony-stimulating activity (csa). chromatography of plasma from amv-infected chicks revealed that this csa eluted in the first protein peak from a column of sephadex g-200. a second protein peak from the same column contained an inhibitor of gm colony-formation. the presence of the inhibitor and the increased csa was studied during the development of myelo ...19826978259
myeloblasts transformed by the avian acute leukemia virus e26 are hormone-dependent for growth and for the expression of a putative myb-containing protein, p135 e26.avian leukemia virus e26 contains the myb oncogene and transforms erythroid and myeloid hematopoietic cells in vivo and in vitro. e26-transformed nonproducer myeloblasts but not avian erythroleukemia virus (aev)-transformed erythroblasts nor mc29-transformed macrophages were shown to be dependent for growth on factor(s) present in supernatants from concanavalin a-stimulated chicken spleen cells. the same factor enhanced the synthesis of p135 e26, the candidate transforming protein of e26, but di ...19826329725
transcription of the chicken alpha 2 (type i) collagen gene by homologous cell-free extracts.we have used two methods to detect specific transcription of the chicken alpha 2 (type i) collagen gene in cell-free extracts derived from rous sarcoma virus-transformed chicken embryo fibroblasts. the first method is a modification of the s1 nuclease mapping procedure which utilizes a dna probe labeled with 32p at the 5' end of the hindiii linker originally used to clone the collagen promoter region into pbr322. the probe distinguishes newly made, specific rna from endogenous rna and nonspecifi ...19826282836
avian myeloblastosis virus transforming gene is related to unique chicken dna regions separated by at least one intervening sequence.identification of several additional restriction endonuclease sites within the cellular substitution (amv) inserted into the avian myeloblastosis virus proviral genome has permitted us to isolate different regions of the amv sequence. these subsets of the avian myeloblastosis virus transforming gene have been cloned in the plasmid pbr322 and used as hybridization probes to investigate the topology of homologous (proto-amv) normal chicken dna sequences. the results showed that the cellular proto- ...19826283118
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 ...19826283142
acute leukemia viruses e26 and avian myeloblastosis virus have related transformation-specific rna sequences but different genetic structures, gene products, and oncogenic properties.replication-defective acute leukemia viruses e26 and myeloblastosis virus (amv) cause distinct leukemias although they belong to the same subgroup of oncogenic avian tumor viruses based on shared transformation-specific (onc) rna sequences. e26 causes predominantly erythroblastosis in chicken and in quail, whereas amv induces a myeloid leukemia. however, upon cultivation in vitro for >1 month, a majority of surviving hemopoietic cells of e26-infected animals bear myeloid markers similar to those ...19826285358
immune stimulation of sensitized chicken lymphocytes by avian retrovirus proteins.peripheral blood lymphocytes of chickens bearing tumours induced by avian sarcoma virus can be specifically stimulated to divide by the crude culture fluids of virus-infected cells. in this communication, we show that relevant antigenic activity apparently resides in each of the internal virus proteins p15 and p27. the ability of infectious culture fluids to be mitogenic for sensitized lymphocytes is greatly reduced following treatment with antibodies specific for either total avian myeloblastos ...19826286858
avian myeloblastosis provirus cloned in a lambda bacteriophage is leukemogenic.the avian myeloblastosis virus provirus inserted in a lambda bacteriophage, recombinant clone 11a1-1 (souza et al., proc. natl. acad. sci. u.s.a. 77:3004-3008, 1980), was transfected into chicken embryo fibroblasts which had been preinfected with either rous-associated virus type 61 or the transformation-defective avian sarcoma virus tdb77. within 4 to 5 h after transfection, the cells were injected into 16-day-old chicken embryos or 1-day-old chicks. acute myeloblastic leukemia developed after ...19826292502
organization of chicken dna sequences homologous to the transforming gene of avian myeloblastosis virus. i. restriction enzyme analysis of total dna from normal and leukemic cells.hybridization probes consisting of cloned dna recombinants which represent different regions of the leukemogenic sequence (amv) from avian myeloblastosis virus were used to carry out a more detailed restriction endonuclease analysis of the homologous sequences (proto-amv) present in normal and leukemic chicken dna. the results show that four large introns interrupt the normal cellular proto-amv sequences and that there is no major rearrangement of these sequences in leukemic myeloblasts.19826292519
transformation of both erythroid and myeloid cells by e26, an avian leukemia virus that contains the myb gene.e26 and avian myeloblastosis virus are replication-defective avian retroviruses that contain the myb oncogene and cause leukemia in chickens with short periods of latency. animals infected with e26 develop erythroleukemia and also contain low numbers of transformed myeloid cells, while avian myeloblastosis virus induces a purely myeloid leukemia. in both cases the type of leukemia induced is independent of the subgroup of the helper virus used. e26-transformed erythroid and myeloid cells can eac ...19826297778
a monoclonal antibody with specificity for leukemic cells transformed by defective avian leukemia viruses.mouse anti-chicken monoclonal antibodies were raised against an avian myeloblastosis virus (amv)-transformed myeloblastic leukemic cell line. one monoclonal antibody, s1-37 (igg2a), reacted with producer and nonproducer myeloblastic leukemia cell lines transformed by amv and by e-26 virus, but it did not react with chicken fibroblasts infected with rav-2, mav-2, mav-1, or rav-7. s1-37 also did not react with normal chicken hemopoietic cells, except for yolk sack macrophages and a small populatio ...19826302112
nucleotide sequence and organization of the transforming region and large terminal redundancies (ltr) of avian myeloblastosis virus (amv).avian myeloblastosis virus (amv) is a replication-defective acute leukemia virus, requiring a helper virus to provide the viral proteins essential for synthesis of new infectious virus. the genome of the amv has undergone a sequence substitution in which a portion of the region normally coding for the "env" protein has been replaced by chicken cellular sequences. these latter sequences are essential for the transforming activity of the virus. we have determined the complete nucleotide sequence o ...19826302118
identification of the leukemogenic protein of avian myeloblastosis virus and of its normal cellular homologue.the genome of the replication-defective avian myeloblastosis virus (amv) contains an inserted cellular sequence (amv) that is part of the oncogene responsible for acute myeloblastic leukemia in chickens infected with amv. three antisera raised against distinct synthetic peptides predicted from the long open reading frame of amv specifically precipitated the same 48-kilodalton protein (p48amv) from leukemic myeloblasts but not from normal hematopoietic tissue, fibroblasts, or from fibroblasts inf ...19836304685
the product of the retroviral transforming gene v-myb is a truncated version of the protein encoded by the cellular oncogene c-myb.avian myeloblastosis virus (amv) is an oncogenic retrovirus that rapidly causes myeloblastic leukemia in chickens and transforms myeloid cells in culture. amv carries an oncogene, v-myb, that is derived from a cellular gene, c-myb, found in the genomes of vertebrate species. we constructed a plasmid vector that allows expression of a portion of the coding region for v-myb in a procaryotic host. we then used the myb-encoded protein produced in bacteria to immunize rabbits. the antisera obtained p ...19836305504
tripartite structure of the avian erythroblastosis virus e26 transforming gene.only two avian oncogenic viruses specifically cause acute leukaemias yet do not transform chicken fibroblasts in culture: e26, which causes erythroblastosis and a low level of concomitant myeloblastosis in chickens, and avian myeloblastosis virus (amv), which causes myeloblastosis exclusively. both viruses are replication-defective and share a sequence termed myb (also known as amv) which is unrelated to essential virion genes and is therefore thought to be part of the transforming onc genes of ...19836316155
structure and transcription of the cellular homolog (c-myb) of the avian myeloblastosis virus transforming gene (v-myb).we isolated and characterized molecular clones containing the chicken cellular homolog (c-myb) of the avian myeloblastosis virus oncogene (v-myb). mapping of the c-myb clones using restriction endonucleases and hybridization to radiolabeled v-myb probes revealed that the sequences homologous to v-myb are contained within four separate regions, which have since been shown by nucleotide sequencing (klempnauer et al., cell 31:453-463, 1982) to carry seven exons. analysis of c-myb transcripts showed ...19836298458
isolation and characterization of a temperature-sensitive mutant of avian myeloblastosis virus.a temperature-sensitive (ts) mutant, ga 907/7, was isolated after mutagen treatment of avian myeloblastosis virus. when bone marrow cells or secondary yolk sac macrophages were infected with ga 907/7, the expression of transformation was greatly reduced at 41 degrees c. the results of temperature-shift experiments suggest that in ga 907/7 the putative v-myb gene product is functional only at 35.5 degrees c. moreover, when ts-induced transformed cells were shifted to 41 degrees c, a partial morph ...19836298790
detection of avian hematopoietic cell surface antigens with monoclonal antibodies to myeloid cells. their distribution on normal and leukemic cells of various lineages.the isolation and characterization of monoclonal antibodies reacting with cell surface antigenic determinants of normal and leukemic avian hematopoietic cells is described. the antibodies were produced by immunizing mice with normal macrophages, as well as with myeloid cells transformed with the avian acute leukemia viruses mc29, amv and e26. eleven antibodies were characterized for their reactivity with a variety of normal and leukemic cells of the myeloid, b- and t-lymphoid and of the erythroi ...19836299767
organization of chicken dna sequences homologous to the transforming gene of avian myeloblastosis virus. ii. isolation and characterization of lambda proto-amv dna recombinant clones from a library of leukemic chicken dna.several lambda proto-amv recombinants isolated from a lambda charon 4a library of leukemic chicken dna were analyzed by using various restriction endonucleases and hybridization with specific probes representing different regions of the transforming gene of avian myeloblastosis virus. the position of 30 sites for 11 different restriction endonucleases was established in the proto-amv region of chicken dna. identical restriction endonuclease maps were obtained for the normal and leukemic dnas in ...19836300463
transforming ability of avian defective leukemia viruses in early embryogenesis.the response to infection of chicken hemopoietic cells derived from the early stages of embryogenesis by avian myeloblastosis virus (amv) and avian erythroblastosis virus (aev) was investigated. it was found that erythroid progenitor cells were present in the blastoderm at a higher frequency than that of myeloid progenitor cells. these results correlate with the observation that target cells for aev were found to be more numerous than those for amv. therefore, blastoderm cells are of potential v ...19836297153
a putative second cell-derived oncogene of the avian leukaemia retrovirus e26.the acute avian leukaemia retroviruses amv and e26 both induce myeloblastosis in vivo and transform myeloblasts in vitro. both viruses contain the oncogene v-myb first described for amv. unlike amv, e26 has the additional capacity to induce erythroblastosis in vivo and to transform erythroblasts. previous analyses indicated that the genome of e26 also contained nucleotide sequences distinct from v-myb and unrelated to viral replicative genes. using a molecularly cloned e26 provirus, we have now ...19836316156
the use of elisa for detection of exogenous and endogenous avian leukosis viral antigens in basic breeding flocks.an enzyme-linked immunosorbent assay (elisa) for avian leukosis/ sarcoma virus (alv) group-specific (gs) antigens was used to study the identification of hens which congenitally excrete exogenous alv. the sensitivity of this assay was compared with that of the phenotypic mixing test (pmt) and the direct complement fixation test (cft) by testing limiting dilutions of purified avian myeloblastosis virus (amv), embryo homogenates and albumens. about 0.4 ng/ml of purified amv protein could be detect ...198318766804
avian myeloblastosis virus: a model for the generation of viral oncogenes from potentially oncogenic cellular genetic elements. 19836301896
mechanism of action of the endonuclease associated with the alpha beta and beta beta forms of avian rna tumor virus reverse transcriptase.preparations of the alphabeta and the betabeta forms of reverse transcriptase from the prague c strain of rous sarcoma virus grown in chicken embryo fibroblasts, the alphabeta and the betabeta forms of the enzyme from the b77 strain of rous sarcoma virus grown in duck embryo fibroblasts, and the alphabeta form of reverse transcriptase from avian myeloblastosis virus have been analyzed. all these enzyme preparations contain a mn(2+) -activated endonuclease activity. the betabeta form of enzyme, i ...19836187936
the human dna locus related to the oncogene myb of avian myeloblastosis virus (amv): molecular cloning and structural characterization.chicken and human cell dna contains sequences homologous to the avian myeloblastosis virus oncogene, v-myb. these cellular sequences, c-myb (human) and c-myb (chicken), were isolated from libraries of human or chicken cell dna fragments, generated by partial digestion with the restriction enzymes alui and haeiii, and compared. the chicken c-myb locus isolated from two distinct overlapping recombinant phages, contained five contiguous ecori fragments of 5.4, 1.1, 2.1, 2.2 and 9 kbp, accounting fo ...19836194989
induced differentiation of avian myeloblastosis virus-transformed myeloblasts: phenotypic alteration without altered expression of the viral oncogene.cells of a clone of avian myeloblastosis virus-transformed myeloblasts were induced to differentiate to adherent myelomonocytic cells by treatment with lipopolysaccharide. these adherent cells were subcultured and maintained as a line for more than 6 months with lipopolysaccharide present. cells of this line were induced to differentiate to nondividing macrophage-like cells by the addition of the tumor promoter 12-o-tetradecanoylphorbol-13-acetate. in this way, the following homogeneous cell pop ...19846098812
in vitro translation of fractionated rna isolated from chicken leukaemic plasma virus (amv). a 76k pol-related polypeptide.the 60s rna was isolated from amv-chicken leukaemic plasma virus. it was poly(a) selected, sized on sucrose gradients, and each fraction of rna translated in vitro in the rabbit reticulocyte lysate. it was shown by immunoprecipitation and peptide mapping that p76gag was translated from genome-length rna, a 76k pol-related polypeptide from 24-26s rna and a 34k protein, not related to any virion proteins, from 14s rna. the possible relationship of these in vitro translated proteins to known genome ...19846083884
avian erythroblastosis virus e26: nucleotide sequence of the tripartite onc gene and of the ltr, and analysis of the cellular prototype of the viral ets sequence.an intact 5.7-kb provirus of the avian erythroblastosis virus e26 has been molecularly cloned for comparisons with avian myeloblastosis virus (amv) and other avian tumor viruses. e26 and amv transform hemopoietic cells exclusively. both cause myeloblastosis, but e26 also causes erythroblastosis. sequence analysis of the proviral dna showed that: the tripartite transforming gene of e26 forms a contiguous reading frame of 1046 codons, including 272 gag, 283 mybe, and 491 ets codons. no subgenomic ...19846097027
[isolation of reverse transcriptase from the avian myeloblastosis virus in preparative quantities].inverse transcriptase of bird myeloblastosis virus is a unique instrument for artificial synthesis of structural genes of viruses, plants, animals. methods for the virus production in preparative amounts are developed due to selection of the corresponding line of chickens, conditions of their maintenance, diet infection methods and myeloblastosis diagnostics. main demands to the inverse transcriptase preparations (their high activity, absence of nuclease impurities, high concentration of the enz ...19846209836
presence of actin in oncornaviruses.a 43k protein present in avian myeloblastosis virus has been identified as actin by 2d gel electrophoresis and peptide mapping proteolysis. electron microscopy of chicken embryo fibroblasts infected with different pseudotypes of oncornaviruses treated with anti-actin antibody showed positive staining at the level of the virions especially on buds. our results indicate that this actin is unlikely to have been artefactually absorbed at the virion surface during its preparation. it may therefore pl ...19846322753
target cells for avian myeloblastosis virus in embryonic yolk sac and relationship of cell differentiation to cell transformation.the yolk sac of the 12-day chicken embryo retains the blast stage progenitors to cells of the myeloid lineages with a very low level of contamination by more mature myeloid cells which have begun to express the characteristic myeloid cell markers. both in vivo and in vitro experiments have supported the hypothesis that target cells for the bai-a strain of avian myeloblastosis virus are contained within the myeloid lineages. an assay system for avian myeloblastosis virus was developed which utili ...19846699939
subcellular localization of proteins encoded by oncogenes of avian myeloblastosis virus and avian leukemia virus e26 and by chicken c-myb gene.analysis of the subcellular location of the proteins encoded by the oncogenes of avian myeloblastosis virus and avian leukemia virus e26 ( p45v -myb and p135gag -myb-ets, respectively) and by the chicken c-myb gene ( p75c -myb) shows that all three proteins are located in the nucleus. in amv-infected (but not transformed) chicken fibroblasts p45v -myb also resides in the nucleus, indicating that a nuclear location of p45v -myb in these cells is not sufficient to achieve transformation. in amv-tr ...19846327074
chromosomal localization of the human proto-oncogene c-ets.e26 is an acute leukaemia avian retrovirus which induces myeloblastosis and erythroblastosis in vivo and transforms erythroblasts and myeloblasts in vitro. it contains the oncogene v-myb (ref. 4), first described for avian myeloblastosis virus (amv), as well as a second specific nucleotide sequence, v-ets located 3' to v-myb (refs 5,6). we have reported that v-ets has a cellular counterpart (c-ets) in chicken and human dna. now, using two independent methods--hybridization with human c-ets probe ...19846462246
[mechanism of virus-induced leukemogenesis in an animal model system].retroviruses can cause different types of leukemias in chickens. a small group of virus strains induce acute leukemias and transform hematopoietic cells in vitro. we have shown that cells transformed in vitro by erythroblastosis and myeloblastosis viruses resemble in vivo transformed cells in their phenotype of differentiation. the erythroblastosis virus aev carries two cell-derived oncogenes termed erba and erbb. the analysis of aev using deletion mutants showed that erbb is the main oncogene w ...19846471771
avian monocytic leukemia cells release fibroblast growth factor: implications to associated myelofibrosis.the marrow of chicks with leukemia induced by avian 'myeloblastosis' virus (amv) exhibited a 5-10-fold increase in the number of fibroblast colony-forming cells (cfu-f). the increased cfu-f correlated with a mild fibrosis which can be seen in the marrow of these animals. fibroblast proliferation likely was not simply due to the presence of leukemic cells because addition of formaldehyde-fixed peripheral leukemic cells failed to initiate cfu-f growth. conditioned medium (cm) from day-4 cultures o ...19853866125
induction of colony-stimulating factor from quiescent fibroblasts by avian macrophages and monocytic leukemic cells.confluent, quiescent chick embryo fibroblasts maintained in protein-free medium released csf(s) active on granulocyte and monocyte progenitors and on monocytic leukemia cells induced by avian 'myeloblastosis' virus (amv) when exposed to formaldehyde-fixed amv leukemic cells. the csf was assayed under serum-free conditions. of several normal cell types tested including populations enriched for blast cells, only macrophages exhibited this capacity.19853935882
biologically active proviral clone of myeloblastosis-associated virus type 1: implications for the genesis of avian myeloblastosis virus.a biologically active myeloblastosis-associated virus (mav) provirus was cloned from a bacteriophage recombinant library constructed from leukemic chicken myeloblast dna. the restriction endonuclease map of this clone was consistent with that of a type 1 mav (mav-1). interference assays of virus recovered from cultured chicken embryo fibroblasts after dna transfection established that the provirus was infectious and confirmed that it belonged to avian retrovirus subgroup a (type 1). antipeptide ...19852993653
nucleotide sequence of cdna clones of the murine myb proto-oncogene.we have isolated cdna clones of murine c-myb mrna which contain approximately 2.8 kb of the 3.9-kb mrna sequence. nucleotide sequencing has shown that these clones extend both 5' and 3' to sequences homologous to the v-myb oncogenes of avian myeloblastosis virus and avian leukemia virus e26. the sequence contains an open reading frame of 1944 nucleotides, and could encode a protein which is both highly homologous, and of similar size (71 kd), to the chicken c-myb protein. examination of the dedu ...19852998780
sites of recombination between the transforming gene of avian myeloblastosis virus and its helper virus.the sites of recombination between the transforming gene of avian myeloblastosis virus (amv) and its natural helper myeloblastosis-associated virus (mav) have been determined. in amv, the cellular sequence substituting for the viral envelope (env) gene gives rise to a different carboxyl terminus of the dna polymerase. the 5'-recombination site coincides with the rna splice acceptor site for the production of env mrna in mav-infected cells. the 3'-recombination site reveals that the last 11 amino ...19852992154
transformation of brown leghorn chicken embryo fibroblasts by avian myeloblastosis virus proviral dna.brown leghorn chicken embryo fibroblasts were transfected with a mixture of avian myeloblastosis virus (amv) and myeloblastosis-associated virus type 1 (mav1) proviral dna purified from lambda-charon 4a recombinant clones. a transformed cell line (t1am) able to grow without anchorage in semisolid medium was obtained. the presence of both proviral amv and mav sequences was detected in t1am dna by hybridization with v-myb- and mav1-specific probes. altered amv and mav1 proviral genomes were found ...19852989555
developmental regulation of c-myb in normal myeloid progenitor cells.hematopoietic tissues and some leukemic cell lines express elevated levels of c-myb transcripts. we have separated a subpopulation of chicken embryo yolk sac cells that represents about 5% of the yolk sac hematopoietic cells and appears to contain all of the detectable c-myb transcripts. the level of myb expression in this cell population is higher than previously reported for any normal cell population and is in the range of that found in cells transformed by avian myeloblastosis virus and e26 ...19852413449
the proto-oncogene c-ets is preferentially expressed in lymphoid cells.the transforming sequences of the avian acute leukemia virus, e26, contain two distinct oncogenes, v-mybe and v-ets, fused together. by using a probe containing v-ets sequences, polyadenylated transcripts of the c-ets proto-oncogene were detected in avian tissues; they included a major 7.0-kilobase and a minor 2.0-kilobase species. these c-ets mrnas were detected at high levels only in lymphoid organs and in avian t and b lymphoid cell lines. a similar pattern of c-ets transcription was observed ...19853018492
nuclear compartmentalization of the v-myb oncogene product.nuclei obtained from chicken leukemic myeloblasts transformed by avian myeloblastosis virus were fractionated into various subnuclear compartments, which were then analyzed by specific immunoprecipitation for the presence of the leukemogenic product, p48v-myb, of the viral oncogene. in cells labeled for 30 or 60 min with l-[35s]methionine and in unlabeled exponentially dividing leukemic cells analyzed by western blotting, p48v-myb was detected within the nucleoplasm (29 +/- 9% [standard deviatio ...19853018495
[involvement of bone tissue in chicken infected with the myeloblastic mav 2-0 virus. generalized cortical hyperostosis].an affection of osseous tissue appears in chicken have been injected at the embryonic state with retrovirus myeloblastic mav 2-0 in solution. the structural lesions are different from these examined in human or murine osteopetrosis, considered to be an general cortical hyperostosis.19853919885
dna-binding activity is associated with purified myb proteins from amv and e26 viruses and is temperature-sensitive for e26 ts mutants.oncogene protein products from avian myeloblastosis virus, p48v-myb, and from avian leukemia virus e26, p135gag-myb-ets, are located predominantly in the nucleus of nonproducer bone marrow cell clones, as revealed by indirect immunofluorescence. both oncogene proteins were purified by immunoaffinity chromatography using monoclonal antibodies against p19 and immunoglobulins specific for myb, which was expressed in bacteria for antibody production. the purified proteins bind to dna in vitro. in co ...19852985272
structure of the protein encoded by the chicken proto-oncogene c-myb.the retroviral oncogene v-myb arose by transduction of the chicken proto-oncogene c-myb. we isolated and sequenced cdna that represents the entire coding domain of chicken c-myb. by transcribing the cdna into mrna in vitro and then translating the rna, we were able to document the integrity of the cdna and to identify the codon responsible for initiation of translation from c-myb. two different alleles of v-myb are extant, one in the genome of avian myeloblastosis virus (amv) and the other in th ...19863025608
detection of antibodies to avian reverse transcriptase by indirect elisa.an improved indirect elisa test for detection of antibodies to the reverse transcriptase (revertase) is described. the sensitivity of the revertase elisa test was compared to that of the revertase inhibition test. serum samples of various origin and sera of specific pathogen free (spf) hens were examined for the revertase antibodies. the presence of these antibodies in the sera of spf chickens is discussed.19862425612
transforming potential of the v-myb oncogene from avian myeloblastosis virus: alterations in the oncogene product may reveal a new target specificity.transfection of brown leghorn chicken embryo fibroblasts by dna containing v-myb sequences cloned either in a complete amv proviral dna or in a retroviral derived vector has led to the isolation of two kinds of transformed cells. a characterization of the proviral sequences retained and expressed in these transformed cells revealed that they contained either new or altered v-myb-related rna species. the experiments presented in this paper also show that both types of transformants expressed trun ...19862427128
identification in chicken macrophages of a set of proteins related to, but distinct from, the chicken cellular c-ets-encoded protein p54c-ets.using an antiserum to a bacterially expressed polypeptide corresponding to 56 amino acids of v-ets, we previously identified in chicken tissues a protein of 54 kd (p54c-ets) which shares extensive sequence homology to the v-ets-encoded domain of the e26-transforming protein p135gag-myb-ets and is thus apparently encoded by the c-ets proto-oncogene. we report here that the anti-ets serum specifically identifies in chicken cells a second set of proteins of 60 kd (p60), 62 kd (p62) and 64 kd (p64) ...19863536486
nucleotide sequence of chicken c-myb complementary dna and implications for myb oncogene activation.avian myeloblastosis virus (amv), like other acute transforming viruses, arose by recombination between its helper virus and host cellular sequences. the latter sequences, termed v-myb, are responsible for the oncogenic properties of the virus. amv causes acute myeloblastic leukaemia in chickens and transforms a specific class of haematopoietic cells in vitro, but does not induce morphological transformation of cultured fibroblasts, suggesting that only a restricted target-cell population is res ...19863753748
characterization of monoclonal antibodies to avian leukosis viruses.hybridoma cell lines secreting monoclonal antibody (mca) to avian leukosis virus (alv) structural proteins p27 and p19 have been established. in an indirect enzyme-linked immunosorbent assay (elisa), mca 6al20 (igg1 isotype) reacted with rpl-40 (alv subgroup a), avian myeloblastosis virus (amv) (a mixture of subgroups a and b), rous-associated virus (rav)-2 (subgroup b), and carr-zilber strain of rous sarcoma virus (cz-rsv) (subgroup d) but not with prague strain of rsv (prc-rsv) (subgroup c) or ...19863015099
antibodies to the evolutionarily conserved amino-terminal region of the v-myb-encoded protein detect the c-myb protein in widely divergent metazoan species.antibodies directed against a bacterial fusion protein that contains the domain encoded by the highly evolutionarily conserved 5' one-third of the v-myb oncogene of avian myeloblastosis virus (amv) detect the protein products of various members of the myb gene family. immunoprecipitation or immunoblot analyses with these antibodies yielded the following information. first, the products of the v-myb oncogenes of amv (p48v-myb) and of e26 virus (p135gag-myb-ets) contain this highly conserved amino ...19863088565
association of persistent synthesis of viral dna with macrophage accessory cell dysfunction induced by avian retrovirus myeloblastosis-associated virus of subgroup b inducing osteopetrosis in chickens.this investigation concentrates on a regenerative anemia and immunosuppression occurring in the absence of osteopetrosis. polyclonal activation of t-cells was used as an in vitro test system to study immunosuppression induced by the avian myeloblastosis-associated virus of subgroup b inducing osteopetrosis [mav-2(o)]. t-cell unresponsiveness in vitro was attributed to a defect in an accessory cell function of the macrophage. counterflow centrifugation fractionation followed by mixing experiments ...19872444336
env-encoded residues are not required for transformation by p48v-myb.the v-myb oncogene of avian myeloblastosis virus induces acute myeloblastic leukemia in chickens and transforms avian myeloid cells in vitro. the protein product of this oncogene, p48v-myb, is partially encoded by the retroviral gag and env genes. we demonstrated that the env-encoded carboxyl terminus of p48v-myb is not required for transformation. our results showed, in addition, that a coding region of c-myb which is not essential for transformation was transduced by avian myeloblastosis virus ...19873027417
a sequential study of bone lesions caused by isolates of an avian osteopetrosis virus, mav-2(0).the pathogenesis of avian osteopetrosis caused by rapid and slow-onset isolates of myeloblastosis associated virus, mav-2(0), was studied by inoculation of 10-day-old chick embryos with virus. femur and calvarium were examined at 15, 17 and 19 days in ovo and 7 and 25 days after hatching by histologic and immunoperoxidase techniques. femur and calvarium were also examined by electron microscopy at 17 and 19 days in ovo and at 7 days after hatching. avian osteopetrotic bone lesions were character ...19873446259
expression of a truncated v-myb product in transformed chicken embryo fibroblasts.transformed cells have been isolated after transfection of chicken embryo fibroblasts (cef) with the dna of a recombinant clone (kxa 3457) in which the v-myb sequences are flanked by the two amv-ltrs. abnormal myb-specific rna species and myb-related polypeptides were found to be expressed in these cells, suggesting that transformation of cef by v-myb might require alterations of the oncogene product.19873032682
two exons specific for the myb proto-oncogene found upstream from the avian myeloblastosis virus-transduced myb sequences.a partial restriction map of cloned 5.42-kb chicken dna (clone p542, perbal et al. 1983), covering a portion of the c-myb locus, is presented. the 5' end of the v-myb gene (approximately 0.5 kb) is located at the 3' end of p542 dna, the remainder are the cellular sequences not transduced by avian myeloblastosis virus. two non-contiguous dna segments were detected within these cellular sequences which code for the 5' end of c-myb mrna. these two exons, designated e1 and e2, are separated by a app ...19873032698
[the effect of 3'-azido-2',3'-dideoxythymidine on experimental viral infections].3'-azido-2',3'-dideoxythymidine (az-t) inhibited effectively the reproduction of some retroviruses; among these viruses were the four serological subgroups of sarcoma raus virus in chicken embryo, avian myeloblastosis virus and erythroblastosis virus in chicken. this inhibition was specific towards retroviruses and practically was not observed in the case of infections dna- and rna-genome model viruses of vaccinia and influenza, at whose reproduction reverse transcriptase is not involved. three ...19872821379
immunoblotting with polyclonal and monoclonal antibody to avian myeloblastosis protein p27: studies of liver proteins in chickens with erythroblastosis.an antigen detected by complement fixation with polyclonal antibody to avian myeloblastosis virus (amv) antigen p27, appears in the livers of chickens inoculated with avian erythroblastosis virus (aev). it can be demonstrated at the 30,000 dalton (30k) molecular weight level by western immunoblotting of electropherograms of aev infected liver extracts. the 30k protein reacted strongly with this polyclonal antibody but only weakly with a monoclonal antibody to the same viral antigen and possible ...19872836998
[tumors of the brain vascular plexuses caused by the avian myeloblastosis virus].a series of experiments on the induction of tumours in the central nervous system with the help of avian myeloblastosis virus was carried out. 142 highly sensitive and inbred chickens, 1 or 2 days of age, were used. the intracerebral virus dose was 0.01-0.02 ml. the titer was 10(9)--10(12) pfu/ml. 25 tumours of choroid plexus were induced during the experiments, 3 tumours developed in the control after intravenous inoculation. out of 33 chickens highly sensitive to amv tumours of choroid plexus ...19873620686
avian nephroblastomas induced by a retrovirus (mav-2) lacking oncogene. ii. search for common sites of proviral integration in tumour dna.to demonstrate the existence of a common site of integration in independent tumour clones, restriction mapping of the vicinity of integrated mav-2 proviruses in nephroblastoma dna was performed, using southern hybridization with an mav-2 specific probe u3(pat). the results have shown that (1) nephroblastomas are of semiclonal origin. (2) nephroblastoma cells contain an average of 5 clonally located integrated proviruses per diploid genome; they do not contain any detectable amount of non-integra ...19882849568
[induction of tumors of the meningeal membranes in chicks by the avian myeloblastosis virus].the meningiomas could be easily produced by intracerebral injection of the avian myeloblastosis virus (0.01 ml of virus suspension with titer 10(9)-10(12) pfu/ml) into highly susceptible (white leghorn anya cross) or randomly bred newborn (24-48 hours) chicken. tumours were observed in 66.7% highly susceptible chickens and in 33.73% of randomly bred chickens. first clinical signs of disease appeared on the 7-9th days after infection. death occurred on the 3-4th days after beginning of the diseas ...19882832019
sequential study of visceral lesions caused by isolates of an avian osteopetrosis virus (myeloblastosis-associated virus).ten-day-old chicken embryos were inoculated with isolates of myeloblastosis-associated virus that induced osteopetrosis of slow or rapid onset. bursa of fabricius, thymus, spleen, bone marrow, kidney, liver, and lung were examined at 15, 17, and 19 days in ovo and at 7 and 25 days after hatching by histologic and immunoperoxidase techniques. tissues from 19-day-old in ovo embryos also were examined by electron microscopy. the lymphoid organs of embryos inoculated with all isolates manifested cha ...19883223670
proto-oncogene expression in chicken leukemic cells induced by avian myeloblastosis virus.sixteen proto-oncogenes which have generated retroviral oncogenes were tested for their expression in chicken leukemic cells induced by avian myeloblastosis virus (amv) and five were found to be expressed (c-ets, c-fps, c-mht, c-myc, and c-rel). the size of the c-fps transcript (4.0 kb) was not in good agreement with the size (approximately 3.0 kb) previously reported but was uniform in the leukemic cells from 10 different chickens. the size of the other proto-oncogene transcripts appeared norma ...19883226723
mapping of a small phosphopeptide at the carboxyterminus of the viral myb protein by monoclonal antibodies.several myb-specific monoclonal antibodies were produced and their antigen recognition sites characterized using a series of bacterially expressed truncated myb proteins. the monoclonal antibodies were used for analysing the in vivo phosphorylation site of the oncogene protein from avian myeloblastosis virus (amv), p48v-myb. the p48v-myb protein labeled metabolically with [32p]orthophosphate was isolated from the amv-transformed chicken myeloblast cell line bm-2 by immunoaffinity chromatography. ...19892464784
avian retroviral long terminal repeats bind ccaat/enhancer-binding protein.dna-protein interactions involving enhancer and promoter sequences within the u3 regions of several avian retroviral long terminal repeats (ltrs) were studied by dnase i footprinting. the rat ccaat/enhancer-binding protein, c/ebp, bound to all four viral ltrs examined. the rous sarcoma virus binding site corresponded closely to the 5' limit of the ltr enhancer; nucleotides -225 to -188 were protected as a pair of adjacent binding domains. the fujinami sarcoma virus ltr bound c/ebp at a single si ...19892725492
the ets sequence is required for induction of erythroblastosis in chickens by avian retrovirus e26.e26 is a replication-defective avian retrovirus that causes an erythroblastic leukemia in vivo and transforms hematopoietic precursor cells of both the erythroid and the myeloid lineages in vitro. the e26 genome contains two sets of cell-derived sequences, ets and myb. myb sequences are also present in avian myeloblastosis virus, which transforms myeloblasts exclusively. to determine whether the ets sequence is responsible for the erythroid specificity of e26, we analyzed the transforming activi ...19892535740
the v-myb oncogene product binds to and activates the promyelocyte-specific mim-1 gene.the v-myb oncogene induces myeloid leukemias in chickens, transforms myeloid cells in vitro, and encodes a sequence-specific dna binding protein. we used differential hybridization to screen for v-myb-regulated genes in cells transformed by a temperature-sensitive mutant of the oncogene and identified a new gene, mim-1, which encodes a specifically expressed, secretable protein contained in the granules of both normal and v-myb-transformed promyelocytes. the promoter of the mim-1 gene contains t ...19892688896
transformation by v-myb correlates with trans-activation of gene expression.the v-myb oncogene of avian myeloblastosis virus causes acute myelomonocytic leukemia in chickens and transforms avian myeloid cells in vitro. its protein product p48v-myb is a nuclear, sequence-specific, dna-binding protein which activates gene expression in transient dna transfection studies. to investigate the relationship between transformation and trans-activation by v-myb, we constructed 15 in-frame linker insertion mutants. the 12 mutants which transformed myeloid cells also trans-activat ...19902160580
binding properties of avian retroviral proteins. iii. binding of protein aslv ma(p19) to viral rna and proviral dna.the binding of the avian retroviral matrix protein aslv ma(p19) to homologous viral ssrna and proviral dsdna was analysed using electron microscopic methods combined with a special computer evaluation. no binding affinity of ma(p19) to homologous nondenatured or denatured viral rna was found. in contrast, aslv ma(p19) was shown to have one specific binding site on mav-1 proviral dsdna at position 6795 +/- 345 bp from the 5' end of the molecule. a second specific binding site was found in a cellu ...19902160895
heterogeneities in vertebrate trnas(trp) avian retroviruses package only as a primer the trna(trp) lacking modified m2g in position 7.bovine, rabbit and chicken trna(trp) species and trna(trp) packaged in avian myeloblastosis virus were separated and purified using two-dimensional gel electrophoresis and their primary structures were determined. two major trna(trp) species (1 and 2) were identified in beef and rabbit, two minor ones (3 and 4) in beef and only one minor in rabbit. their structures differ by 4 nucleotide substitutions located in the d, s and t loops (positions 16, 47, 57 and 59). species 3 and 4 differ from one ...19902156227
protein truncation is required for the activation of the c-myb proto-oncogene.the protein product of the v-myb oncogene of avian myeloblastosis virus, v-myb, differs from its normal cellular counterpart, c-myb, by (i) expression under the control of a strong viral long terminal repeat, (ii) truncation of both its amino and carboxyl termini, (iii) replacement of these termini by virally encoded residues, and (iv) substitution of 11 amino acid residues. we had previously shown that neither the virally encoded termini nor the amino acid substitutions are required for transfo ...19912072904
proto-oncogene expression in avian hematopoietic tissues.previous findings from this laboratory (kim & baluda, 1988) have shown that the proto-oncogenes ets, fps, mht (raf), myc and rel are expressed in avian myeloblastosis virus (amv)-transformed cells, whereas the myb gene is repressed. in this study five different chicken hematopoietic tissues which contained varying concentrations of target cells for amv transformation were analyzed to determine whether the expression of these proto-oncogenes resulted from, or was altered by, v-myb-induced leukemo ...19911886713
v-myb transformation of xeroderma pigmentosum human fibroblasts: overexpression of the c-ha-ras oncogene in the transformed cells.human xeroderma pigmentosum "normal" fibroblasts as16 (xp4 vi) were transformed after transfection with a recombinant v-myb clone. in this clone (pkxa 3457) derived from avian myeloblastosis virus (amv), the expression of the oncogene sequences is driven by the amv u-5 ltr promoter. the transformed cells (askxa), which have integrated a rearranged v-myb oncogene, grow in agar, are not tumorigenic in nude mice, and express a 45-kda v-myb protein. the hmw dna of these cells transform chicken embry ...19911893942
cdna cloning of a homeobox-containing gene expressed in avian myeloblastic virus-transformed chicken monoblastic leukaemia cells.by combining the polymerase chain reaction and differential library screening, a cdna for an mrna expressed in chicken avian myeloblastosis virus (amv)-transformed monoblasts was isolated. this mrna is not expressed in erythroblast or t-lymphoblast cell lines. induced differentiation of the cells of the amv-transformed bm2 line was associated with reduced levels of this transcript. the predicted protein product of chox m was a homeodomain factor similar to murine hox-4.3.19911674560
v-src enhances phosphorylation at ser-282 of the rous sarcoma virus integrase.the rous sarcoma virus (rsv) integrase (in) and the beta polypeptide (beta) of the reverse transcriptase are posttranslationally modified by phosphorylation on ser at amino acid position 282 of in. when in was immunoprecipitated from rsv (prague a strain) virions, approximately 30 to 40% of the in molecules were phosphorylated. when in was immunoprecipitated from a v-src deletion mutant (delta mst-a) of rsv or from avian myeloblastosis virus (amv), the percentage of in molecules that were phosph ...19921312616
transformation of chicken myelomonocytic cells by a retrovirus expressing the v-myb oncogene from the long terminal repeats of avian myeloblastosis virus but not rous sarcoma virus.to test the effect of long terminal repeat (ltr) regulatory sequences on the transforming capability of the v-myb oncogene from avian myeloblastosis virus (amv), we have constructed replication-competent avian retroviral vectors with nearly identical structural genes that express v-myb from either amv or rous sarcoma virus (rsv) ltrs. after transfection into chicken embryo fibroblasts, virus-containing cell supernatants were used to infect chicken myelomonocytic target cells from preparations of ...19921323701
protein truncation is not required for c-myb proto-oncogene activity in neuroretina cells.the v-myb oncogene of avian myeloblastosis virus (amv) differs from its normal cellular counterpart by a truncation at both its amino and carboxyl termini and by a substitution of 11 amino acid residues. we had previously shown that v-myb-containing amv, in the presence of basic fibroblast growth factor, transformed chicken neuroretina (cnr) cells. to understand the mechanism of c-myb activation, we have tested whether avian retroviruses that express the full-length c-myb are also active on cnr ...19921404616
[the technology for isolating the avian myeloblastosis virus in high titers from leukosis-free chicks].in order to enhance the outcome of high-quality reverse transcriptase enzyme, an efficient biotechnology was developed of accumulating and isolating the avian myeloblastosis virus (amv) in high titres from blood plasma of leukosis-free chickens. when commercial chickens are infected in most sensitive one-day age, the virus titre does not exceed the value of 10(12) particles per 1 ml of plasma. we used 3-4-day old leukosis free chickens and achieved a stable average titre of the virus of 5.10(12) ...19921430580
transforming potential of truncated v-myb and stimulation of replication by gag-myb fusion products.we have previously reported that truncated forms of the v-myb oncogene of avian myeloblastosis virus (amv) are expressed in transformed chicken embryo fibroblasts (cef). in this paper, we show that deletion mutants encoding v-myb products altered in either the dna-binding or the negative regulatory domains are able to induce cef transformation. in addition, we report that recombinant plasmids expressing gag-myb fusion proteins are maintained as extrachromosomal forms in transfected cells. this o ...19921549366
extension of the dna binding consensus of the chicken c-myb and v-myb proteins.the chicken c-myb gene and the v-myb oncogene transduced by avian myeloblastosis virus (amv) encode dna binding transcription activators. the dna binding domain of amv v-myb displays a number of amino acid changes relative to c-myb; v-myb proteins in which one or more of three crucial residues in the dna binding domain are mutated to resemble the c-myb sequence display altered transformation phenotypes. in order to establish whether the spectrum of dna binding sites which amv v-myb can recognise ...19921620600
definition of functional domains in p135gag-myb-ets and p48v-myb proteins required to maintain the response of neuroretina cells to basic fibroblast growth factor.the v-myb- and v-ets-containing e26 retrovirus induces the proliferation of chicken neuroretina (cnr) cells in minimal medium. proliferation of e26 cnr cells is strongly stimulated by basic fibroblast growth factor (bfgf). the v-myb-containing avian myeloblastosis virus also induces the proliferation of infected cnr cells stimulated by bfgf. both e26 cnr and avian myeloblastosis virus cnr cells are able to form colonies in soft agar in the presence of bfgf. this suggests that the v-myb product, ...19921727478
proviral rearrangements and overexpression of a new cellular gene (nov) in myeloblastosis-associated virus type 1-induced nephroblastomas.histological and anatomopathological studies performed on 152 independent myeloblastosis-associated virus type 1 (mav1)-induced nephroblastomas allowed us to precisely define the chronology of tumor development in chickens. three tumors representing increasing developmental stages were used to construct genomic libraries and to study both the state of proviral genomes and the sites of mav1 integration in genomic dna. we established that increasing levels of proviral rearrangement, eventually lea ...19921309586
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