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: EC:2.7.7.49 (reverse transcriptase)
31,746 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

Catalytic properties of terminal riboadenylate transferase from Escherichia coli and the products of the enzymic reaction were investigated. The kinetic analysis revealed that the reaction obeys the sequential ordered bi-bi mechanism. The application of conditions elaborated in this study resulted in the synthesis of products of defined size and efficient primer utilization. The tRNA(rA)n obtained was a good template for the synthesis of complementary DNA with reverse transcriptase.
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PMID:Terminal riboadenylate transferase from Escherichia coli. Characterization and application. 6 60

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

When Rous sarcoma virus RNA is transcribed into DNA by the reverse transcriptase, a tRNA primer is elongated into DNA. The primer is near the 5' end of the virus genome; the first major DNA made is a "run-off" product extending 101 bases from the primer to the 5' end of the template. We have studied this DNA molecule to determine the sequence of the first 101 bases at the 5' end of the Rous sarcoma virus genome (Prague strain, subgroup C). Twenty-one bases at the extreme 5' end are also at the 3' end of the virus genome (see D. E. Schwartz, P. C. Zamecnik, and H. L. Weith, this issue, pp. 994-998), and thus this virus is terminally redundant. The existence of this sequence repetition immediately suggests mechanisms by which the growing DNA copy can jump from the 5' end to a 3' end of the template and become circular. The sequence also displays a possible ribosome binding site and enough secondary structure to permit a possible 5'-5' linkage of viral RNA molecules.
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PMID:Rous sarcoma virus genome is terminally redundant: the 5' sequence. 6 83

The extent of binding of various RNA species to the three forms of avian sarcoma virus B77 RNA-dependent DNA polymerase was determined using a sensitive nitrocellulose filter binding technique which was capable of detecting binding reactions with association constants as low as 3 X 10(6) liters X mole-1. All three enzyme forms, alphabeta, beta2, and alpha, bound to all single-stranded RNA species that were tested, including nonviral RNAs. 70 S viral RNA exhibited the highest association constant (about 10(11) liters X mole-1), and a population of virus-derived tRNA molecules from which tRNATrp had been removed, the lowest (about 3000 times lower). The affinity for other RNAs was roughly proportional to their size. The affinity of RNAs for the alphabeta enzyme form always exceeded that for the two others by a factor that depended on the particular RNA, never exceeded 6 and was sometimes as low as 1.2. The association constant of the alphabeta enzyme form with viral 70 S RNA was about 15-fold higher than that with viral 35 S RNA. 35 S RNA annealed to tRNATrp had an association constant that was only 2.5 times higher than that of 35 S RNA alone. This finding suggests that the tertiary structure of 70 S RNA plays a significant role in its affinity for B77 DNA polymerase.
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PMID:The RNA-dependent DNA polymerase of avian sarcoma virus B77. Binding of viral and nonviral ribonucleic acids to the alpha, beta2, and alphabeta forms of the enzyme. 7 Apr 28

The majority of the mRNA that specifies retrovirus glycoproteins is known to be derived from the 3' half of the genome. To examine whether the glycoprotein mRNA of murine leukemia viruses (MuLVs) might consist of portions derived from both the 5' and 3' ends of the viral genome, we performed hybridization with a 5'-specific probe and heteroduplex analysis with long reverse transcribed DNA. A 5' probe was made by purifying a discrete 50 nucleotide-long reverse transcript attached to its tRNA primer. This probe was found to hybridize to RNA of the size of glycoprotein mRNA--21S, poly(A)-containing RNA--indicating that the mRNA could have a 5' leader sequence. The 5'-specific sequences were studied by electron microscopic examination of hybrids between 21S RNA and the two longest discrete cDNA species synthesized in the endogenous reverse transcriptase reaction. One of these species, 8.8 kb long, is only made in the absence of actinomycin D, but it does not contain any self-complementary sequences, and therefore appears to be a complete transcript of the viral genome. The shorter of the two species, 8.2 kb long, is synthesized whether or not actinomycin D is present; it must terminate 500--600 nucleotides internal to the 5' end of the template RNA. The structures observed in heteroduplexes of 21S RNA and these DNAs indicated the presence of a leader sequence approximately 500 nucleotides long at the 5' end of the 21S RNA. Sequences comprising this leader segment in the 21S RNA mapped at the 5' end of the genome RNA; the rest of the 21S RNA consisted of sequences from the 3' portion of the genome. Analysis of heteroduplexes with 8.2 kb DNA suggested that actinomycin D could block the reverse transcription of most of the sequence in the genome RNA that appears as a leader in the 21S RNA.
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PMID:Analysis of a 5' leader sequence on murine leukemia virus 21S RNA: heteroduplex mapping with long reverse transcriptase products. 7 33

The interaction of tRNA with the reverse transcriptase (RNA-dependent DNA polymerase) of mammalian RNA viruses, such as Moloney murine leukemia virus and simian sarcoma virus, has been studied. Whereas the purified reverse transcriptase of mammalian viruses sedimented in glycerol gradients as a globular protein with a molecular weight of 70,000, after interaction with tRNA the enzyme cosedimented with a protein of 150,000 molecular weight. The twofold increase in molecular weight could be a result of either two reverse transcriptase molecules complexed with a tRNA or, alternatively, several tRNA molecules bound to a single enzyme polypeptide. The enzyme complexes were dissociated in part upon degradation of the tRNA moiety by pancreatic RNase A. The reverse transcriptase released from virions of Moloney murine leukemia virus, simian sarcoma virus, and avian myeloblastosis virus, by nonionic detergent, migrated faster on glycerol gradients than purified enzyme preparation. This phenomenon was probably due to complex formation between part of the virion enzyme and the tRNA, which is endogenous in virions. Addition of exogenous tRNA was needed, however, to quantitatively complex all the virion reverse transcriptase of Moloney murine leukemia virus and simian sarcoma viruses. The reverse transcriptase of Moloney murine leukemia virus did not show tRNA species specificity in the binding reaction when glycerol gradients were used for assay. Thus, several tRNA species of Escherichia coli, yeast, chicken, and rat origin were able to complex with the enzyme. The species specificity in the interaction between tRNA and avian myeloblastosis virus reverse transcriptase was also examined. We demonstrated that under our experimental conditions, this enzyme binds different tRNA species of E. coli and yeast as well as tRNA of chicken origin.
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PMID:Binding of tRNA to reverse transcriptase of RNA tumor viruses. 7 7

We studied the kinetics of the reverse transcription of 70S and 35S RNA of avian myeloblastosis virus in the presence and absence of various tRNA's. All tRNA's inhibited synthesis. tRNA's from Escherichia coli and yeast exhibited a noncompetitive type of inhibition, i.e., they bound reversibly and randomly and did not alter the affinity of the viral RNA for the polymerase. Nonprimer tRNA's obtained from 70S RNA molecules produced a complex pattern of inhibition. The results show that the nonprimer tRNA's which bound to the reverse transcriptase decreased the affinity of the viral RNA for the enzyme. The maximum rate of synthesis with 70S RNA as the template was less than that with 35S RNA, presumably because the former contains nonprimer tRNA's which can interact with the polymerase.
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PMID:Inhibition of reverse transcription of 70S and 35S avian myeloblastosis RNAs by nonprimer tRNA's. 8 Apr 59


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