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M A Baluda

Publications and source records attributed to M A Baluda.

At least 37 records · Page 2Linked to original sources
PubMed1985

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 acids including the termination codon are shared by the env protein and AMV transforming protein. The RNA splice acceptor site for the generation of subgenomic v-myb mRNA is located 84 nucleotides downstream from the 5'-recombination site. The AMV transforming protein consists of helper virus-related sequences at both of its amino and carboxyl termini, and all but 84 nucleotides of the cell-derived v-myb sequence. The comparison of MAV gp85 amino acid sequence with those of subgroups B, C, and E indicates that the MAV present in clone lambda 10A2-1 belongs to subgroup B. The high degree of homology among different avian retroviruses of the same subgroup indicates that the amino acid sequence of gp85 is important in determining the conformation of the envelope glycoprotein.

Amino Acid Sequence↗
PubMed1985

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 antibodies raised against the env-encoded carboxyl terminus of p48myb, the transforming protein of avian myeloblastosis virus, specifically immunoprecipitated the gp37env from quail cells transfected with MAV-1 proviral DNA but not from cells infected with MAV-2. This suggests that MAV-1 rather than MAV-2 is the progenitor helper virus from which avian myeloblastosis virus arose by the transduction of cellular proto-oncogene sequences.

Animals↗
PubMed1985

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 deviation] of the total), chromatin (7 +/- 4%), and lamina-nuclear matrix (64 +/- 9%). Also, in myeloblasts analyzed by immunofluorescence during mitosis, p48v-myb appeared to be dispersed through the cell like the lamina-nuclear matrix complex. Strong attachment to the nuclear matrix-lamina complex suggests that p48v-myb may be involved in DNA replication or transcription or both.

Animals↗
PubMed1984

Avian myeloblastosis virus and E26 virus oncogene products are nuclear proteins.

The defective acute leukemia viruses avian myeloblastosis virus (AMV) and E26 virus each contain an inserted cellular sequence related to the same highly conserved cellular gene, proto-amv. The oncogenes of these two retroviruses differ from this cellular proto-oncogene in gene structure, transcript structure, and gene product. The product of the AMV oncogene (myb) is a 48,000 Mr protein, p48myb, encoded by a transduced segment (amv) of proto-amv flanked by short helper-virus-derived terminal sequences. The E26 virus oncogene product is a 135,000 Mr protein, p135gag-amve-ets, encoded by significant portions of a viral structural gene (gag), sequences related to proto-amv (amve), and additional E26-specific sequences (ets) transduced from cellular proto-ets. Both p48myb and p135gag-amve-ets transforming proteins are located in the nucleus of cells transformed by these viruses. A protein of 110,000 Mr which is specifically immunoprecipitated by antisera to amv peptides and may be the product of the normal cellular gene (proto-amv) has been located in the cytoplasm of cells that express proto-amv mRNA.

Animals↗
PubMed1983

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 infected with the AMV helper virus, MAV-1 (myeloblastosis-associated virus type 1). p48amv is not glycosylated or phosphorylated and does not appear to act as a protein kinase in vitro. The same three antisera that recognized p48amv also specifically precipitated a common 110-kilodalton protein from normal uninfected hematopoietic tissue. This normal cellular homologue of the AMV leukemogenic protein, p110proto-amv, was not present in normal fibroblasts, MAV-1 infected fibroblasts, or, interestingly, in some leukemic myeloblasts. We conclude that p48amv is the leukemogenic product of an altered, transduced, partial protooncogene. Short helper-virus sequences provide its carboxyl terminus and also may provide the amino terminus.

Animals↗
PubMed1983

Structural organization and expression of human DNA sequences related to the transforming gene of avian myeloblastosis virus.

Bacteriophage libraries of human DNA were screened for sequences homologous to the transforming gene (v-myb) of avian myeloblastosis virus. The three overlapping clones isolated were shown to contain a total of 1.0 kilobase pair (kbp) of sequence related to v-myb distributed over 6.2 kbp. Restriction enzyme mapping and heteroduplex analysis revealed the presence of five myb-related domains interrupted by four stretches of non-homology. To study the extent of human DNA coding sequences that constitute the myb gene homologue, c-myb (human), probes spanning about 30 kbp were prepared from the clones and used to study transcription in a human hematopoietic cell line (MOLT-4). Each of the probes hybridized a 4.5-kilobase transcript, which suggests that either the c-myb (human) gene encompasses 30 kbp or it contains two or more transcription units that each give rise to a mRNA of 4.5 kilobases.

Avian Leukosis Virus↗
PubMed1983

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 the proto-amv domain, which covers 8 to 9 kilobases of DNA. The cellular genetic elements homologous to the cellular sequence (amv) inserted into the avian myeloblastosis virus genome are contained within six major proto-amv segments which are interrupted by at least five large DNA regions lacking homology with amv.

Animals↗
PubMed1982

Nucleotide sequence of the transforming gene of avian myeloblastosis virus.

Avian myeloblastosis virus is defective in reproductive capacity, requiring a helper virus to provide the viral proteins essential for synthesis of new infectious virus. This virus arose by recombination of the nondefective helper virus and host cellular sequences present within the normal avian genome. These latter sequences are essential for leukemogenic activity. The complete nucleotide sequence of this region is reported. Within the acquired cellular sequences there is an open reading frame of 795 nucleotides starting with the initiation codon ATG (adenine, thymine, guanine) and terminating with the triplet TAG. This open reading frame could code for the putative transforming protein of 265 amino acids with a molecular weight of approximately 30,000.

Animals↗
PubMed1982

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 sequences homologous to AMV was detected in all immature myeloid and lymphoid T cells in addition to the single erythroid cell line examined, but not in mature T cells or in B cells, including lymphoblast cell lines derived from patients with Burkitt lymphoma. In addition, induction of the cell line HL60, a promyelocytic leukemia line, to differentiate with dimethyl sulfoxide or retinoic acid resulted in a reduction of the level of expression of the human cellular gene c-amv homologous to v-amv. There was no detectable c-amv mRNA in any of the solid tumor cell lines examined. Thus, expression of the human c-amv gene could be correlated with the stage of differentiation of different hematopoietic cell types determined by morphologic and marker studies. Expression of c-amv could not be correlated with the extent of methylation in HL60 and in HL60 induced to differentiate with dimethyl sulfoxide.

Carcinoma↗
PubMed1982

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-amv sequences in C/O chicken DNA are interrupted by at least one intervening sequence. A partial arrangement of the proto-amv sequences is presented.

Animals↗
PubMed1982

Nucleotide sequence analysis of the long terminal repeat of avian myeloblastosis virus and adjacent host sequences.

The nucleotide sequence of the integrated avian myeloblastosis virus long terminal repeat has been determined. The sequence is 385 base pairs long and is present at both ends of the viral DNA. The cell-virus junctions at each end consist of a 6-base-pair direct repeat of cell DNA next to the inverted repeat of viral DNA. The long terminal repeat also contains promoter-like sequences, an mRNA capping site, and polyadenylation signals. Several features of this long terminal repeat suggest a structural and functional similarity with sequences of transposable and other genetic elements. Comparison of these sequences with long terminal repeats of other avian retroviruses indicates that there is a great variation in the 3' unique sequence (U3), whereas the 5' specific sequences (U5) and the R region are highly conserved.

Avian Leukosis Virus↗
PubMed1982

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 a long latent period. Filtered (0.22-micrometer pores) supernatant of transformed buffy-coat cell cultures from one leukemic chicken of the lambda 11A1-1 (tdB77) group rapidly transformed yolk sac cells in vitro. Results from an infectivity interference assay and analysis of proviral DNA fragments generated with restriction endonucleases were consistent with the presence in leukemic cells of defective avian myeloblastosis virus and tdB77 as the helper virus.

Animals↗
PubMed1982

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.

Animals↗
PubMed1981

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 amv are present in the genomes of all vertebrates ranging from amphibians to humans but were not detected in fish, sea urchins, or Escherichia coli. In contrast to the preceding findings, nontransforming endogenous proviral nucleotide sequences closely related to the remainder of the avian myeloblastosis virus genome and to the entire myeloblastosis-associated helper virus are present only in chicken DNA. The amv-related cellular sequences appear to be highly conserved during evolution and to be contained at only one or a few locations in the genome of vertebrates. Within closely related species, they appear to share common evolutionary genetic loci. These findings and similar ones obtained with other highly oncogenic retroviruses containing a transforming gene suggest a general mechanism for acquisition of viral oncogenic sequences and an essential role for these sequences in the normal cellular state.

Animals↗
PubMed1980

Identification of a proviral genome associated with avian myeloblastic leukemia.

We have identified and isolated a presumptive leukemogenic provirus from myeloblasts of a chicken in which leukemia had been induced by avian myeloblastosis virus (AMV). Leukemic myeloblasts isolated from peripheral blood or from converted yolk sac cultures of various strains of chickens, regardless of the endogenous proviral content or AMV pseudotype used for infection, contain an EcoRI 2.2-megadalton (MDaI) and a HindIII 2.6-MDal proviral fragment. A proviral genome flanked by chicken DNA sequences on either side and containing both the EcoRI 2.2-MDal and the HindIII 2.6-MDal fragments was inserted by molecular recombination into lambda phage Charon 4A and then cloned. This presumptive AMV proviral genome has a mass of approximately 4.9 MDal and contains terminal redundancies with respect to 3' viral RNA sequences.

Animals↗
PubMed1980

Cellular sequences are present in the presumptive avian myeloblastosis virus genome.

EcoRI restriction endonuclease fragments from a lambda proviral DNA hybrid containing the entire presumptive avian myeloblastosis virus (AMV) provirus, and from a lambda proviral hybrid containing a partial myeloblastosis-associated virus type 1 (MAV-1)-like provirus were compared by heteroduplex analysis. The cloned presumptive AMV provirus was also analyzed by electron microscopy, using R-loop formation with purified 35S RNA isolated from virions of the standard AMV complex. The results indicate that the putative AMV genome contains a segment absent in its MAV-1-like helper virus. This segment represents a substitution in the region of the genome that in MAV-1 virus is occupied by the envelope gene and is approximately 900 +/- 160 nucleotide pairs in length. Hybridization of specific probes from the presumptive AMV genome to Southern blots of EcoRI-digested cellular DNA has revealed that these substituted sequences are homologous to chicken and duck DNA that is not related to chicken endogenous proviral sequences.

Animals↗
PubMed1980

Inhibition of virion-associated reverse transcription by nucleoside triphosphatase in avian myeloblastosis virus.

RNA-dependent DNA polymerase activity of avian myeloblastosis virions as measured by the incorporation of [3H]TTP into trichloroacetic acid-precipitable material was very low. This apparent low polymerase activity was observed with virions isolated either from leukemic chicken plasma or from the supernatant of cultured leukemic myeloblasts. The inhibition of reverse transcriptase activity was caused by nucleoside triphosphatase present in avian myeloblastosis virions and could be reversed by ADP.

Adenosine Diphosphate↗