Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UMLS:C0679427 (myeloblastosis)
982 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Selected species of 4S RNA of chick embryo cells will hybridize in vitro with 35S RNA of avian myeloblastosis virus. A major tRNA component of the hybridizable 4S RNA is tryptophan tRNA. A hybrid prepared from purified tryptophan tRAN and 35S RNA of avian myeloblastosis virus in vitro is an efficient templateprimer for DNA synthesis catalyzed by reverse transcriptase (RNA-dependent DNA polymerase).
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PMID:Ability of tryptophan tRNA to hybridize with 35S RNA of avian myeloblastosis virus and to prime reverse transcription in vitro. 4 54

The ability of tryptophan tRNA (tRNATrp) to initiate reverse transcription of the 70S RNA of avian RNA tumor viruses suggested that the reverse transcriptase (RNA-dependent DNA polymerase; deoxynucleosidetriphosphate: DNA deoxynucleotidyltransferase; EC 2.7.7.7) might have a specific binding site for the tRNA. A complex of tRNATrp and the avian myeloblastosis virus reverse transcriptase has been demonstrated using chromatography on Sephadex G-100 columns. Of all the chicken tRNAs, only tRNATrp and a tRNA4Met bind to the enzyme with high enough affinity to be selected from a mixture of the chicken cell tRNAs. The ability of tRNATrp to change the sedimentation rate of the enzyme indicates that tRNATrp is not binding to a contaminant in the enzyme preparation. Treatment of the enzyme with monospecific antibody to reverse transcriptase prevented binding of tRNA as well as inhibited the DNA polymerase activity of the enzyme. The ability of reverse transcriptase to utilize tRNATrp aa a primer for DNA synthesis, therefore, appears to involve a highly specific site on the enzyme.
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PMID:Specific binding of tryptophan transfer RNA to avian myeloblastosis virus RNA-dependent DNA polymerase (reverse transcriptase). 5 56

The RNA-directed DNA polymerase (deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase EC 2.7.7.7) of avian oncornavirus requires a tryptophan tRNA (tRNATrp) primer molecule located close to the 5' end of the viral RNA genome for the initiation of DNA synthesis in vitro. In this communication we demonstrate that the DNA product, transcribed from avian myeloblastosis virus (AMV) 35S RNA containing only tRNATrp as primer, is located also at the 5' end of the RNA genome. More importantly, we demonstrate that these 5' terminal DNA transcripts contain nucleotide sequences complementary to the 3' end of the genome. We have interpreted these results to mean that the genome. We have interpreted these results to mean that the 3' and 5' termini of the AMV 35S RNA genome become juxtaposed with each other either before or immediately after DNA synthesis has begun. These results are discussed in regard to the mechanism for synthesis of the circular forms of oncornavirus proviral DNA.
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PMID:Evidence for circularization of the avian oncornavirus RNA genome during proviral DNA synthesis from studies of reverse transcription in vitro. 5 20

Tryptophanyl-tRNA was specifically labeled at the 3' end with [3H]tryptophan and cleaved in half with RNase under denaturing conditions, and the 3' half was shown to hybridize exclusively at the 5' end of avian myeloblastosis virus RNA. The RNA-dependent DNA polymerase of avian myeloblastosis virus is capable of efficiently binding the 3' half of the primer molecule.
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PMID:Primer recognition by avian myeloblastosis virus RNA-directed DNA polymerase. 6 28

The immunoglobulin G (IgG) fraction of the antiserum from rabbits immunized with homogeneous beef pancreas tryptophanyl-tRNA synthetase inhibits the enzyme activity in the reactions of both tRNATrp aminoacylation and tryptophan activation. Fab fragments of IgG act in a similar way. Common antigenic determinants have been detected in tryptophanyl-tRNA synthetases from beef, pig, chicken and rat livers using pure antibodies against beef pancreas tryptophanyl-tRNA synthetase. This observation indicates the evolutional stability of certain structural features of tryptophanyl-tRNA synthetases. The interaction of antibodies with the fragments of beef tryptophanyl-tRNA synthetase produced by endogenous and tryptic proteolysis of the enzyme has been studied. On third of the antiserum antibodies interacting with the C-terminal fragment of the enzyme (Mr approximately equal to 40000) inhibits its activity whereas the antibodies to the N-terminal fragment (Mr approximately equal to 20000) have no effect on the enzyme activity. The immunochemical identity of the two synthetase fragments differing in their enzymatic activity supports the assumption that the loss of enzymatic activity of the tryptic fragment is caused by lack of a small peptide which is retained in case of endogenous proteolysis; probably the amino acid residues of this peptide participate in formation of active centre of tryptophanyl-tRNA synthetase. A radioimmunochemical method is described for determining the number of antigenic determinants. One molecule of tryptophanyl-tRNA synthetase was found to bind 9 (+/- 1) molecules of Fab fragments. Antibodies against tryptophanyl-tRNA snythetase from beef pancreas do not inhibit noticeably the activity of reverse transcriptase from avian myeloblastosis virus. No antigenic determinants in common have been detected in reverse transcriptase and tryptophanyl-tRNA synthetase by radioimmunochemical assays.
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PMID:Immunochemical studies of beef pancreas tryptophanyl-tRNA synthetase and its fragments. Determination of the number of antigenic determinants and a comparison with tryptophanyl- tRNA synthetases from other sources and with reverse transcriptase from avian myeloblastosis virus. 8 31

The distribtuion of various amino acid tRNA's in the 4S RNA components of avian myeloblastosis virus (AMV) and in 4S RNA prepared from chicken cmbryo cells, chicken myeloblasts, and chicken livers was determined. This was done by aminoacylating the 4S RNA samples with a mixture of 17 radioactive amino acids and subsequently identifying the tRNA-accepted amino acids on an amino acid analyzer after deacylation. In embryo cells, myeloblasts, and liver, tRNA's accepting all 1m amino acids were demonstrated. "Free" AMV 4S RNA was characterized by very low quantities of glutamate, valine, and tyrosine tRNA's. RNAs accepting all 17 amino acids, with the exception of tyrosine, were shown to be present in the "70S-associated" 4S RNA which dissociates at 60 C. The bulk of the 70S-associated 4S RNA was dissociated at 60 C at low ionic strength with a concomitant conversion of 70S RNA to 35S RNA. The residual associated 4S RNA was dissociated by further heating of the 35S RNA to 80 C; tryptophan tRNA accounted for greater than 90% of the total amino acid accepting activity in this fraction. The results support other studies in suggesting that tryptophan tRNA may serve as a primer for DNA synthesis in AMV, as has been shown in Rous sarcoma virus.
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PMID:tRNA's associated with the 70S RNA of avian myeloblastosis virus. 17 60

The structural and functional properties of the nucleocapsid (NC) protein of the avian myeloblastosis virus were examined by steady-state fluorescence and fluorescence anisotropy measurements of the complex between the NC and the extrinsic fluorophore 4,4'-bis(phenylamino)(1,1'-binaphthalene)-5,5'-disulfonic acid (bis-ANS). The intrinsic fluorescence of bis-ANS is enhanced many fold upon forming a complex with the NC. Between 2 and 10 molecules of bis-ANS bind strongly to the NC, with an overall Kd of less than 10(-6) M. The emission of bis-ANS in the complex can also be induced by excitation at 298 nm, indicating that energy is transferred from Trp 80, the sole tryptophan in the NC protein, to bis-ANS. The energy transferred between the Trp 80 and bis-ANS was analyzed to yield a calculated distance of separation between these fluorophores of 28 +/- 3 A; thus, Trp 80 is well removed from the nearest bound bis-ANS. The fluorescence emission of bis-ANS in the NC.bis-ANS complex is efficiently quenched by added salts and by poly(A), suggesting that salt (presumably anions), nucleic acid, and bis-ANS bind to the same, positively charged region on the NC protein. A site size of six nucleotides was determined for nucleic acid binding to the NC protein, with an estimated Kd of less than 10(-6) M. Salt (anion) binding is strong, but nonspecific, with a Kapp of 4 mM, raising the possibility that anion binding to the NC protein might regulate the interaction of the NC with viral RNA inside the host cell.
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PMID:Interactions at the nucleic acid binding site of the avian retroviral nucleocapsid protein: studies utilizing the fluorescent probe 4,4'-bis(phenylamino)(1,1'-binaphthalene)-5,5'-disulfonic acid. 226 56

Avian myeloblastosis virions purified by conventional techniques were shown to be associated with or to contain transfer ribonucleic acid synthetase activity. Arginine, tryptophan, cystine, and lysine synthetase activities were observed.
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PMID:Transfer ribonucleic acid synthetase activity associated with avian myeloblastosis virus. 433 17

The basis of the specific binding of tRNATrp by avian myeloblastosis virus reverse transcriptase was studied by chemical and enzymatic modification of the RNA. Binding does not depend on recognition of the tryptophan anticodon since molecules cleaved in the anticodon are stably bound by the enzyme. Modification of pseudouridine residues in the tRNA destroys binding to reverse transcriptase. These results are consistent with a model in which reverse transcriptase-tRNATrp interaction occurs not at the anticodon, but at regions in the tRNA which contain or are stabilized by pseudouridine residues.
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PMID:Structural features required for the binding of tRNATrp to avian myeloblastosis virus reverse transcriptase. 619 93

c-Myb is the founder member of a class of transcription factors with tryptophan-rich repeats responsible for DNA binding. Activated oncogenic forms of Myb are encoded by the avian retroviruses, avian myeloblastosis virus (AMV) and E26. AMV v-Myb encodes a truncated protein with 11 point mutations relative to c-Myb. The mutations in the DNA binding domain (DBD) were reported to impose distinct phenotypes of differentiation on transformed myeloid cells (Introna, M., Golay, J., Frampton, J., Nakano, T., Ness, S. A., and Graf, T. (1990) Cell 63, 1287-1297). The molecular mechanism operating has remained elusive since no change in sequence specificity has been found. We introduced AMV-specific point mutations in the minimal DBD of chicken c-Myb and studied their effect on structure and function of the purified protein. Fluorescence emission spectra and fluorescence quenching experiments showed that the AMV-specific point mutations had a significant effect on the conformation of the DBD, giving rise to a more compact structure, a change that was accompanied by a reduced sensitivity toward cysteine-specific alkylation and oxidation. The DNA binding properties were also altered by the AMV-specific point mutations, leading to protein-DNA complexes with highly reduced stability. This reduction in stability was, however, more severe with certain subtypes of binding sequences than with others. This differential behavior was also observed in an in vivo model system where DBD-VP16 fusions were coexpressed with various reporters. These findings imply that different subsets of Myb-responsive promoters may react differentially toward the AMV-specific mutations, a phenomenon that could contribute to the altered patterns of gene expression induced by the AMV v-Myb relative to wild type c-Myb.
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PMID:Oncogenic point mutations induce altered conformation, redox sensitivity, and DNA binding in the minimal DNA binding domain of avian myeloblastosis virus v-Myb. 902 Jan 67


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