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:2.7.7.48 (transcriptase)
9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The alkoxybenzophenanthridine alkaloids (coralyne acetosulfate, fagaronine chloride, and nitidine chloride) have been reported to possess antileukemic activity in mice. These compounds were tested for inhibition of reverse transcriptase activity of an RNA tumor virus and DNA polymerase, RNA polymerase, and polyadenylic acid polymerase activities of NIH-Swiss mouse embryos. Reverse transcriptase and DNA polymerase activities were strongly inhibited by these antileukemic alkaloids, whereas RNA polymerase and polyadenylic acid polymerase activities were only moderately affected. Viral and cellular DNA polymerase activities were potently diminished by the alkaloids when poly[d(A-T)], poly(dA)-oligo(dT), and poly(rA)-oligo(dT) template primers were used in the reaction mixture; however, no inhibition of enzyme activity was obtained with poly(rC)-oligo(dG) as template primer. These results suggest that alkoxybenzophenanthridine alkaloids inhibit DNA polymerase activity by interaction with A:T base pairs of the template primer.
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PMID:Inhibition of mammalian and oncornavirus nucleic acid polymerase activities by alkoxybenzophenanthridine alkaloids. 5 19

Samples of three nonmalignant and seven leukemic human cells were examined for DNA polymerase activity that could be identified as RNA tumor virus reverse transcriptase. Experiments on virus-infected model animal cells provided the basis for cell fractionation procedures, and reconstituted systems of known virus, added to human cells, established a threshold of virus detection by enzyme assay at 1 to 10 particles/cell. DNA polymerase activity with some properties similar to a reverse transcriptase was detected in some of the human leukemic cells. However, parallel analyses of nonmalignant cells showed sufficient similarities to raise serious questions about the specificity of the criteria. Reverse transcriptase activity has been reported to be present in white blood cells from a proportion of cases of leukemia; however, it is concluded from the present study that the usual enzymatic criteria using synthetic template primers, which were used in most of the studies reported, are not sufficient to identify a DNA polymerase activity as viral reverse transcriptase.
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PMID:Detection of reverse transcriptase activity in human cells. 8 60

The free 4S RNA of avian RNA tumor viruses is greatly enriched in one of the four methionine tRNAs of the host cells, tRNA4Met. On the assumption that viral tRNAMet forms are identical to the corresponding tRNAs of mouse or chick cells, the following conclusions were drawn concerning the tRNAMet content of oncornaviruses: (1) tRNAMet species may be compartmentalised within the host cells, and the viral tRNA pool could reflect the cellular compartment in which viral maturation takes place since tRNAMet forms distribute unevenly between different fractions of a cell homogenate. (2) tRNA4Met appears to have no special role in the modulation of protein synthesis in as much as no functional difference between tRNA2Met and tRNA3Met, tRNA4Met could be demonstrated in in vitro protein synthesising systems. (3) tRNA4Met differs in nucleotide sequence from all other host cell tRNAMet forms except possibly tRNA2Met. The nucleotide sequences of two tRNAMet species, tRNA1Met and tRNA4Met, have already been determined and the sequence of another host cell tRNAMet, tRNA3Met, was derived from the analogy of its sequence to that of tRNA4Met since the two molecules differ in only 6 nucleotides out of 76. (4) Avian myeloblastosis virus reverse transcriptase has been shown to bind specifically tRNA4Met and tRNATrp in whole cell tRNA and therefore the free tRNA4Met in the virion particle may exist substantially bound to virion-associated transcriptase.
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PMID:Selection of methionine tRNAs by avian oncornaviruses. 21 69

Eight cases of Philadelphia positive acute leukemia (Ph+AL) were compared with 13 cases of Ph+ chronic myelogenous leukemia in blast crisis (BC) and 10 cases of Ph negative acute lymphoblastic leukemia (Ph-ALL) based on the clinical and molecular biological findings. Distinguishing clinical features were a high leukocyte count (median; 147.9 x 10(3)/microliters) for Ph+AL, and a high incidence of tumor formation and basophilia for BC. A cytogenetic study demonstrated the disappearance or marked reduction of Ph+ metaphases in Ph+AL in remission, while Ph+ cells persisted in BC. The major bcr gene was not rearranged in 4 Ph+AL cases, whereas it was found rearranged in 4 other cases of Ph+ AL and 6 cases of BC. Reverse transcriptase polymerase chain reaction technique demonstrated the presence of minor bcr/abl mRNA in the former three cases, and major bcr/abl mRNA in the latter 4 cases. Remission rates were 63% for Ph+AL, 38% for BC, and 100% for Ph-ALL, and the 50% survival were 12, 5 and 29 months, respectively. It was concluded that Ph+AL can be differentiated from BC by a marked reduction of Ph+ cells at remission, and that the prognosis of Ph+AL is better than BC, but worse than Ph-ALL.
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PMID:[Clinical and molecular biological study of Ph positive acute leukemia: comparison with blast crisis of chronic myelogenous leukemia and Ph negative acute lymphoblastic leukemia]. 163 16

Operator-induced biological contamination in cell cultures is a multifaceted problem involving the unexpected introduction of other animal cells, microbial and viral contaminants. Detailed studies on animal cell cross contaminations have been performed and published. The frequency of detection of problem cultures has been as high as 36% for one service performed in the USA, with interspecific cross contamination accounting for 25% and human intraspecific contamination representing 11%. Awareness of the potential of this problem plus the application of several characterizations are key factors for its control. For example, fluorescent antibody staining, isoenzyme analyses, cytogenetic evaluations and DNA fingerprinting using molecular probes are needed for quality assurance on master seed stocks. Detection of microbial contamination is relatively straightforward, but the prevalence of mycoplasmal infections in cell cultures used in general research is still a significant problem. Detection services report frequencies of infection varying from 10% upwards, depending upon the country and laboratory of origin. The utilization of prescreened reagents and antibiotic-free cultivation, plus the application of improved procedures, such as fluorescent dyes and molecular probes for detection, provide effective means of avoiding mycoplasma infection and facilitating control. For many viruses, the presence of mycoplasma reduces immunoreactivity, suppresses transcriptase and other enzyme activities, reverses viral neutralization etc. The introduction of viral contaminants into cell cultures is perhaps the most problematic, especially where no cytopathic effect is produced. Few cases are documented where technicians infected with specific viruses have introduced these unwittingly into cultures in their care. The potential exists, however, as reports have appeared documenting the considerable stability of rhinoviruses, respiratory syncytial virus, rotaviruses and others, in aerosols on workers' hands and safety hood surfaces. The infection of cell cultures via other contaminated cells or reagents such as sera is a related problem. In this regard, the infection of transplantable tumor cell lines with lymphocytic choriomeningitis virus from host animals led to an outbreak of the disease in medical center personnel. Similar infection of rat cell lines exposed to animals harboring hantaviruses has been reported. Technical staff in US government laboratories have been infected with human immunodeficiency virus produced in cultured cells. Such serious public health hazards warrant repeated emphasis. The use of multiple cell lines in a given laboratory, including cultures known to be virally infected, compounds the problems and necessitates application of preventive methods both to avoid cross-infections and to document freedom from contamination.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Operator-induced contamination in cell culture systems. 179 20

Assays are described that permit one to distinguish the reverse transcriptase of RNA tumor viruses from known normal cellular DNA-instructed DNA polymerases. Template responses of purified reverse transcriptase were compared with those of similar preparations of the DNA polymerase I of Escherichia coli and of calf-thymus polymerase. All three enzymes responded well to the synthetic duplexes poly(dT).poly(A), poly(U).poly(A), and poly(dT).poly(dA). Hence, these duplexes can detect, but cannot distinguish reverse, transcriptase from the known normal DNA polymerases. However, certain oligomer-homopolymer complexes serve as excellent distinguishing agents. The reverse transcriptase responds very well to (dT)(10).poly(A) and very poorly to (dT)(10).poly(dA), whereas both cellular DNA polymerases do not exhibit this behavior.Purified single-stranded RNA also serves as a diagnostic device, since only reverse transcriptase gives a detectable response. To be definitive, a positive response to RNA must be accompanied by a demonstration via molecular hybridization that the DNA product is complementary to the RNA and not to some minor DNA contaminant.
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PMID:Distinguishing reverse transcriptase of an RNA tumor virus from other known DNA polymerases. 433 48

Purified wound tumor virus was found to possess an associated ribonucleic acid (RNA) transcriptase. The product of transcriptase synthesis was shown to be single-stranded RNA which annealed specifically to wound tumor viral RNA.
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PMID:Ribonucleic acid transcriptase acitvity in purified wound tumor virus. 550 58

The present study describes the separation and purification of a reverse transciptiase from an orbital tumor of a patient with acute myelomonocytic leukemia. Specific reaction conditions with respect to ionic requirements and template-primers are reported. The purified enzyme was able to transcribe (rA)n . (dT)12, (rC)n . (dG)12, (OMeC)n . (dg)12 and the 70 S RNA from R(Mu)LV. Serological studies that the reverase transcriptase is antigenically related to reverse transcriptase from the type C woolly monkey virus-gibbon ape leukemia virus group.
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PMID:RNA-dependent DNA polymerase activity in ocular granulocytic sarcoma associated to acute myelomonocytic leukemia in Turkish children. Biochemical and immunological characterization of the enzyme. 615 28

Variant double-stranded RNAs are often associated with the genome of transmission-defective isolates of wound tumor virus. These RNAs are replicated and packaged into virus particles in systemically infected plants and are transcribed in vitro by the virion-associated transcriptase. Direct physical evidence that the variant RNAs are remnants of particular WTV genome segments was provided by molecular hybridization studies. Subsequently, ribonuclease T1 digestion products of 3'-end-labeled genome and remnant RNAs were analyzed by one- and two-dimensional electrophoretic techniques. One-dimensional partial and complete digestion patterns were indistinguishable, indicating that the guanosine positions relative to the 3' terminus of the corresponding strands of a particular genome segment and its remnant RNA are the same for at least 40 nucleotides from each end. Fingerprints of the 3' terminal ribonuclease T1-resistant fragments were identical, showing that the nucleotide composition of the 3' terminal ends of the corresponding strands of a particular genome segment and its remnant RNA are also identical. These results indicate that variant RNAs associated with transmission-defective WTV isolates are formed by deletion of an internal portion (as much as 85%) of genomic RNA segments yielding terminally conserved genomic remnants that are functional with respect to transcription, replication, and packaging.
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PMID:Variant dsRNAs associated with transmission-defective isolates of wound tumor virus represent terminally conserved remnants of genome segments. 671 Aug 65

Peptides of melanosomal proteins have recently been shown to be recognized in an HLA-restricted mode by specific cytolytic T lymphocytes in melanoma patients. Dendritic antigen-presenting cells (DC) are considered to be the most effective stimulators of T cell responses, and the use of these cells has therefore been proposed to generate therapeutic responses to tumor antigens in cancer patients. We, therefore, generated DC from peripheral blood of normal donors in the presence of granulocyte/macrophage colony-stimulating factor and interleukin-4. Flow cytometric analysis of the cells during a 2-week culture revealed a loss of CD14 and CD34 expression, a concomittent increase of CD1a, CD11a,b and c, CD44, CD45, CD54, HLA-class I and II, and intermediate levels of CD26, CD80 and CD86. Cultured DC stimulated proliferation of allogeneic T cells and induced a marked, up to 20-fold, stimulation of T cell proliferation after pulsing with tetanus toxoid. To achieve independence of already-identified antigenic peptides presented in HLA class I-restricted fashion, which limits the general applicability of such peptides for vaccination of melanoma patients, we tested whether DC are transfectable with eukaryotic expression plasmids. DC transfected with two reporter genes (CAT, beta-galactosidase) using a liposome-based transfection technique, exhibited only low levels of enzymatically active proteins, but were able to degrade rapidly intracellular proteins and to process peptides efficiently. Chloramphenicol acetyltransferase as well as tyrosinase mRNA were detectable after transfection by reverse-transcriptase-polymerase chain reaction, and enzyme activities became measurable. Furthermore, DC transfected with the tyrosinase gene were able to induce specific T cell activation in vitro, indicating appropriate peptide processing and presentation in DC after transfection. These data suggest new approaches to future tumor vaccination strategies.
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PMID:Dendritic cells generated from peripheral blood transfected with human tyrosinase induce specific T cell activation. 748 49


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