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)

Particles with the density and enzymatic activity characteristic of known oncornavirus have been previously described in bone marrow cells from patients with leukemia in relapse and in remission. We have confirmed these findings and studied two patients in whom preleukemia was among the diagnostic considerations. Following cultivation of bone marrow from these patients for 1 week in conditioned media with dexamethasone, a high-speed pellet of the supernatant fluid and disrupted cells was prepared and analyzed on a sucrose gradient for enzymatic activity characteristic of RNA-directed DNA polymerase (reverse transcriptase). Peaks of endogenous DNA polymerase activity showing ribonuclease sensitivity and/or stimulation with the synthetic template poly(rC)-(dG)12-18 were demonstrated in both patients at densities of 1.15 to 1.19 and 1.21 to 1.24 g/ml. Subsequently, diagnosis 2 and 4 months after initial evaluation revealed acute myelogenous leukemia and malignant histiocytosis, respectively. Prior studies have suggested a possible etiological significance of such particles in human leukemia. The demonstration of similar particles preceding clinically overt disease in these patients supports this hypothesis and offers the possibility of early diagnosis and treatment.
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PMID:Oncornavirus-like particles from cultured bone marrow cells preceding leukemia and malignant histiocytosis. 5 58

Rifamycins and distamycins were assayed in vitro for their effects on the activity of a reverse transcriptase derived from the plasma of a patient with breast cancer. The inhibitory effect observed was compared with that of a human placental substance with a molecular weight of approximately 10 000. The latter substance is apparently also capable of affecting reverse transcriptase activity in vitro.
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PMID:In-vitro inhibition of RNA-instructed DNA polymerase. 5 62

The DNA product of the endogenous reverse transcriptase reaction of Gibbon ape lymphoma virus has been analyzed and characterized. Data show that in simultaneous detection assays in which the type and/or concentration of divalent cation is varied the best yield of rapidly-sedimenting DNA was obtained from reactions containing 1.5 mM Mn2+. This yield is ten-fold better than the yield observed at the optimal Mg2+ concentration (5.0mM). Evidence is presented to show that DNA synthesized at the optimal concentration of either of these cations consists of large pieces varying in size from 4 to 12S. This DNA hybridizes efficiently to homologous viral RNA (greater than 60 percent annealing) and protects at least two-thirds of GALV 70S [32P]RNA from ribonuclease digestion. The hybrids formed with homologous viral RNA are stable as evidenced by their thermal elution patterns from hydroxylapatite columns. In contrast, DNA synthesized in reactions in which the concentration of Mn2+ or Mg2+ was greater than optimal was predominantly 4S or smaller in size and displayed a low level of hybridization (less than 10 percent) to homologous viral RNA.
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PMID:The endogenous reverse transcriptase activity of Gibbon ape lymphoma virus: characterization of the DNA product. 5 76

Revistin, a substance that strongly inhibits the reverse transcriptase activity of murine leukemia virus in our screening system, was obtained from a cultured broth of a soil streptomyces which was closely related to Streptomyces filipinensis. The assay method for the activity was based on the inhibition by a test material of the incorporation of 3H-dTMP into DNA synthesized by the reverse transcriptase of an oncogenic RNA virus. Crude revistin was isolated by serial procedures of salting out with ammonium sulfate and precipitation with cetylpyridinium chloride. The crude material showed neither antibacterial nor antifungal activity. It exhibited against splenomegaly in mice caused by Rauscher leukemia virus infection.
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PMID:Revistin found by screening for inhibitors of reverse transcriptase of an oncogenic virus. 5 48

We isolated a type-C RNA virus from the Japanese field mouse, Mus musculus molossinus. M. musculus musculus and M. musculus molossinus are two different subspecies of Mus and thus only distantly related. The virus grew only on cells foreign to the host, was xenotropic, and readily rescued the murine sarcoma (MuSV) genome from a normal rat kidney cell line transformed nonproductively by the Harvey strain of MuSV. The virus banded at a density of 1.16 g/ml and contained an RNA-dependent DNA polymerase.
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PMID:Isolation of an endogenous C-type RNA virus from Mus musculus molossinus. 5 16

The host range of the C particle produced by FLOPC-1 myeloma cells, FLOPC-1 murine myeloma-associated virus (FL-MuMAV), was assessed in terms of its ability to productively infect and/or induce new viral antigens in a variety of different cell lines. Production of C particle-like structures by cells exposed to FL-MuMAV) was determined by incorporation of [3H]uridine into particles with a density of 1.16 g/ml and/or measurement of RNA-dependent DNA polymerase activity in concentrated culture medium. to FL-MuMAV was capable of infecting NIH/3T3, normal rat kidney (NRK) cell, BALB/c 3T3, and the A31 clone of BALB/3T3 cells but not rabbit cell line, SIRC. Thus, it is an N, B-tropic murine virus as replication in NRK cells has been shown not to delineate a group of murine viruses with a separate host range (M. M. Lieber, C. J. Sherr, and G. J. Todero, 1974). Further neoantigens, reactive with anti-FL-MuMAV serum, were detected on infected cells. Production of the MuMAV-like particle and MuMAV-associated cell antigens in infected NIH/3T3 and NRK cells persisted for three subcultures. The limited production could not be explained by the lack of an RNA-dependent DNA polymerase or high-molecular-weight RNA as the particles possessed both of these properties. The particles produced by infected NIH/3T3 or NRK cells were antigenically and physicochemically similar to FL-MuMAV and not K-MuLV. The MuMAV-like particles produced by infected NIH/3T3 were capable of limited replication in NIH/3T3 and and BALB/3T3 cells, whereas NRK-MuMAV replicated for a limited period in NIH/3T3, NRK, and SIRC cells; i.e., they had a different host range than FL-MuMAV. The particles produced by infected BALB/3T3 and A31 cells had the same host range as FL-MuMAV. In certain situations, isotopically labeled particles with a density of 1.16 g/ml were produced which appeared to lack RNA-dependent DNA polymerase.
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PMID:Host range studies of FLOPC-1 murine myeloma C particles. 5 24

DNA transcripts, ranging from 1,500 to 4,500 nucleotides in length, can be identified in the DNA product synthesized in vitro by the Rous sarcoma virus-associated RNA-directed DNA polymerase. Although these DNA transcripts are considerably larger than the size classes of the DNA product previously reported, they only represent a minor proportion (less than 5%) of the total DNA synthesized in standard reaction mixtures containing rate-limiting concentration of one of the four deoxynucleoside triphosphates. However, the proportion of these larger transcripts relative to the total DNA product increases substantially when the enzymatic synthesis of DNA is performed in the presence of equimolar concentrations of deoxynucleoside triphosphate precursors. Both rate-zonal sedimentation in alkaline sucrose and nucleic acid hybridization techniques have confirmed the length and genetic complexity of these larger DNA transcripts. The identification of large DNA chains in the DNA product synthesized in vitro by the avian oncornavirus RNA-directed DNA polymerase provides an explanation for the paradox that exists between the limited number of primer sites per 70S RNA genome, the small size of the bulk of the DNA product, and the extent of the Rous sarcoma virus genome represented by the DNA product.
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PMID:In vitro transcription of DNA from the 70S RNA of Rous sarcoma virus: identification and characterization of various size classes of DNA transcripts. 5 25

We have studied the effect of protein phosphokinase (EC 2.7.1.37; ATP:protein phosphotransferase) and phosphoprotein phosphatase (EC 3.1.3.16; phosphoprotein phosphohydrolase) on reverse transcriptase (RNA-dependent DNA nucleotidyltransferase) activity of Rous sarcoma virus. Protein kinase from Rous sarcoma virus-transformed chick embryo fibroblasts was purified by DEAE-cellulose chromatography, Sephadex gel filtration, and isoelectric focusing. Purified reverse transcriptase from Rouse sarcoma virus was preincubated with protein kinase and ATP under conditions allowing incorporation of phosphate into substrate protein. After the preincubation, reverse transcriptase activity was assayed in the presence of poly(rA).oligo(dT) as template. A 2- to 5-fold increase of reverse transcriptase activity was found after the preincubation of reverse transcriptase with protein kinase and ATP. Incubation of reverse transcriptase with heat-treated, inactive protein kinase and ATP had no effect on transcriptase activity. When the transcriptase preparation was incubated with protein kinase and [gamma-32P]ATP and subsequently purified by chromatography on phosphocellulose and Sephadex gel filtration, significant amounts of 32P-labeled proteins were found in the fractions exhibiting reverse transcriptase activity, suggesting 32P incorporation into transcriptase or transcriptase-associated proteins. A 20-60% decrease of reverse transcriptase activity was observed after incubation of reverse transcriptase with phosphatase. The results suggest that phosphorylative modification of reverse transcriptase may be critical in the regulation of reverse transcriptase-catalyzed DNA synthesis.
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PMID:Protein kinase and its regulatory effect on reverse transcriptase activity of Rous sarcoma virus. 5 72

A high-molecular-weight RNA encapsulated with an RNA-instructed DNA polymerase in particles possessing the density characteristic of the RNA tumor viruses has been detected in 13 out of 14 human malignant melanomas. The [3H]DNA synthesized by these particles in an endogenous reaction hybridizes to RNA extracted from the human melanoma particulate structures, but not to RNA from normal skin. Similar particles containing RNA and enzyme have been found in basal cell and squamous cell carcinomas of the skin. The RNA of the melanoma particles is easily distinguishable by hybridization from the RNAs found in the particles of the basal and squamous cell carcinomas.
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PMID:Oncornavirus-like particles in human skin cancers. 5 74

Many bovine leukemic lymphocytes produce virus particles when kept in survival cultures in Eagle's Minimum Essential Medium supplemented with 20 percent of inactivated fetal calf serum. Virus particles equilibrate at a density of 1.16 g/ml in sucrose gradients and at a density of 1.12 g/ml in metrizamide gradients. Simultaneous detection tests show that a high molecular weight RNA-reverse transcriptase complex exists in these viruses. Hybridizations between total RNA from bovine leukemic lymphocytes and C-DNA prepared in various known RNA oncogenic viruses show that the virus associated with bovine leukosis is unrelated to RLV, SSV-1, MSV-Ki, FSV-Ga and FLV-Ri.
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PMID:Biochemical approach to bovine leukemia. 5 80


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