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

---

Query: EC:3.1.27.4 (ribonuclease)
6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An RNA-directed DNA polymerase was isolated from the peripheral blood leukocytes of a patient with acute myelomonocytic leukemia by successive purification of a particulate cytoplasmic fraction with endogenous, ribonuclease-sensitive DNA polymerase activity. Like RNA-directed DNA polymerase from mammalian type-C virus, the human leukemic cell enzyme efficiently utilized (A)(n).(dT)(12-18) and (C)(n).(dG)(12-18) and had an approximate molecular weight of 70,000. Further, the leukemic cell enzyme was strongly inhibited by antisera to RNA-directed DNA polymerase of primate type-C virus in a fashion similar to that noted with an extensively purified RNA-directed DNA polymerase from a person with acute myelogenous leukemia [Todaro, G.J. & Gallo, R.C. (1973), Nature 244, 206]. By these biochemical and immunological results the leukemic cell enzyme could be differentiated from all other known cellular DNA polymerases but could not be distinguished from RNA-directed DNA polymerase of primate type-C virus. We interpret these data, combined with observations published elsewhere, to indicate that human acute myelogenous leukemia cells contain components related to primate type-C virus. The parameters used in this study may provide the specificity and sensitivity required for determining the presence or absence and (if present) the relatedness of RNA-directed DNA polymerase in other cases and types of human leukemia.
...
PMID:Relationship between RNA-directed DNA polymerase (reverse transcriptase) from human acute leukemic blood cells and primate type-C viruses. 413 50

Rat cells infected with the B77 strain of avian sarcoma virus [R(B77) cells] produced no virus-like particles but contained information for the production of infectious B77 virus. (3)H-labeled deoxyribonucleic acid (DNA) product of the B77 virus endogenous DNA polymerase system was used to determine the relative amounts of B77 virus-specific ribonucleic acid (RNA) in B77 virus-infected chicken and R(B77) cells. R(B77) cells were found to contain much less B77 virus RNA than did B77 virus-infected chicken cells. Ribonuclease-sensitive DNA polymerase activity was present in high-speed pellet fractions from Nonidet extracts of B77 virus-infected rat cells. Similar preparations from some uninfected rat cells contained lesser amounts of a similar ribonuclease-sensitive DNA polymerase activity. The endogenous template for the DNA polymerase activity in high-speed pellet fractions from R(B77) cells was not related to B77 virus RNA or to RNA of a rat C-type virus. The DNA product of the endogenous DNA polymerase in high-speed pellet fractions of R(B77) cells hybridized to a small extent with RNA from the same fraction and to a similar extent with RNA from uninfected rat cells.
...
PMID:Ribonuclease-sensitive deoxyribonucleic acid polymerase activity in uninfected rat cells and rat cells infected with Rous sarcoma virus. 433 35

Early chicken embryos that are either positive or negative for group-specific antigens of avian leukosis viruses contained endogenous RNA-directed DNA polymerase activity. This endogenous DNA polymerase activity was not increased after mixture of soluble DNA polymerases isolated from chicken embryos with disrupted chicken embryo cells. The endogenous activity was resistant to treatment with deoxyribonuclease, and the initial rate of DNA synthesis was partially resistant to actinomycin D. In contrast, over 90% of the endogenous polymerase activity was destroyed by ribonuclease in medium with high salt concentration. The DNA product of the endogenous DNA polymerase activity from chicken embryos did not hybridize with RNA of Rous sarcoma virus or reticuloendotheliosis virus, whereas about 40% of this DNA product hybridized with the RNA from the same chicken-cell fraction. Antibody against DNA polymerase of avian myeloblastosis virus did not neutralize the chicken endogenous DNA polymerase activity. These results demonstrate that uninfected chicken embryo cells contain endogenous RNA-directed DNA polymerase activity that is not derived from avian leukosis or reticuloendotheliosis viruses.
...
PMID:Endogenous RNA-directed DNA polymerase activity in uninfected chicken embryos. 433 97

The presence is reported of an RNA-instructed DNA polymerase in visna virus, the causative agent of a "slow" neurological disease in sheep. The product synthesized by the RNA-directed reaction has been shown to be a DNA heteropolymer by the following criteria: synthesis requires the presence of all four deoxyriboside triphosphates; the product is resistant to ribonuclease and alkali but is degraded by DNase; and the product has a density of 1.420 in Cs(2)SO(4) solution, characteristic of DNA.Visna virions, like those of the oncogenic RNA viruses, contain DNA polymerase activities that respond to a variety of double-stranded DNAs and to synthetic DNA.RNA hybrids.
...
PMID:DNA polymerase activities in varions of visna virus, a causative agent of a "slow" neurological disease. 499 14

The effect of the ribonuclease inhibitor polyvinyl sulfate on the activity of retroviral DNA polymerase and terminal c transferase was examined. This substance was found to be a potent inhibitor of these enzymes by virtue of competition between the sulfated sidechains of the molecule and the template primer for a site on the enzyme. The significance of these findings in relation to searching for reverse transcriptase is discussed.
...
PMID:Inhibition of reverse transcriptase by polyvinyl sulfate (PVS). 616 65

The nascent DNA synthesized by permeable cells of Bacillus subtilis in the presence of 5'-mercurideoxycytidine triphosphate and 2',3'-dideoxyATP has been isolated and characterized. The newly synthesized DNA was isolated free from other cellular nucleic acids by affinity chromatography on thiol-substituted agarose. The number average chain length of the nascent DNA synthesized in one minute at 25 degrees C was 33 nucleotide residues, due to the chain-terminating action of 2',3'-dideoxyATP. Several lines of evidence indicated that at least 90% of the DNA thus isolated carried a terminally phosphorylated RNA moiety at its 5'-end: (1) the nascent DNA was resistant to exonucleolytic degradation by spleen phosphodiesterase unless first hydrolyzed by strong alkali or ribonuclease; (2) the 5'-termini of nascent DNA could not be phosphorylated by polynucleotide kinase unless first treated with alkaline phosphatase or subjected to hydrolysis by strong alkali or ribonuclease; (3) alkaline hydrolysis of nascent DNA labeled with 32P at the 5'-end released unlabeled DNA with a free 5'-terminus and 32P-labeled ribonucleoside 3',5'-bisphosphates; (4) ribonuclease degradation of similarly labeled material produced an unlabeled DNA-containing polynucleotide fraction and 32P-labeled ribo-oligonucleotides; (5) chromatography on dihydroxyboryl cellulose showed that the RNA moiety lacked a 3'-terminal cis-diol grouping (even after treatment with alkaline phosphatase) unless first subjected to the 3'-exonucleolytic action of bacteriophage T4 DNA polymerase. The sequence of the ribonucleotide chains was elucidated by end-group labeling with polynucleotide kinase and digestion with various ribonucleases. The ribonucleotide moiety was primarily three and four residues in length with the predominant sequence (pp)pApG(pC)1-2pDNA. The possibility that it represents a primer for discontinuous DNA synthesis is discussed.
...
PMID:Analysis of the 5'-termini of nascent DNA chains synthesized in permeable cells of Bacillus subtilis. 618 36

Short-term cultures of cells from human rain tumours have been reported to synthesise RNA particles of density in the range characteristic of C type RNA retroviruses, with associated DNA polymerase activity. Fresh tumour cells obtained from 6 children with astrocytoma and 7 children with medulloblastoma, together with one sample of normal brain tissue and normal leukocytes from brain tumour patients were assayed by several characteristics for the primate retrovirus. 1 or 6 (17%) astrocytomas and 4 of 7 (57%) medulloblastomas released RNA particles which banded in sucrose gradients at a density of 1.16-1.18 g/cm3 together with a short segment of DNA, which was eliminated by prior ribonuclease treatment and two proteins of 28k and 16k daltons. These findings were compatible with the presence of a primate retrovirus. Immune coprecipitation of 125I-labelled proteins from the 1.16-1.18 g/cm3 gradient region failed to show any reactivity with antisera to p28 core antigens or the p70 reverse transcriptase antigens of simian sarcoma virus, baboon endogenous virus or Mason Pfizer virus. Assays for DNA polymerase activity in culture supernatant fluid showed only a low amount of activity with template preferences not characteristic of the retroviral reverse transcriptase enzyme.
...
PMID:Children's brain tumour cells produce RNA particles with incomplete retrovirus characteristics. 628 9

Adenovirus DNA replication was studied in a partially reconstituted system consisting of purified viral proteins (DNA-binding protein, precursor terminal protein and Ad DNA polymerase) and a nuclear extract from uninfected HeLa cells. Optimal DNA replication required the presence of a heat-stable, ribonuclease-sensitive fraction from the cytosol of uninfected cells. This fraction stimulated the initiation about 3-fold and the replication of origin fragments 5-10-fold. Sedimentation analysis indicated the presence of a fast-sedimenting and a slow-sedimenting component which complemented each other. At least part of the stimulation was caused by low-molecular-mass RNA.
...
PMID:Adenovirus DNA replication in vitro is stimulated by RNA from uninfected HeLa cells. 672 75

RNases H are traditionally thought to degrade RNA only in RNA-DNA hybrid form. We found that the wild-type Moloney murine leukemia virus (M-MuLV) reverse transcriptase (RT) was capable of degrading RNA in RNA-RNA duplexes as well as in RNA-DNA hybrids, as assayed by in situ gel techniques. Escherichia coli RNase H does not degrade the RNA-RNA duplex in this assay, while E. coli RNase III, a double-strand-specific ribonuclease, does. The apparent specific activity of M-MuLV RT on RNA-RNA duplexes is similar to that on RNA-DNA hybrids. Neither the DNA polymerase domain nor the RNase H domain of RT expressed individually exhibited this RNA-RNA activity. We have generated a series of mutations in the RNase H domain of M-MuLV RT, expressed the mutant enzymes in E. coli, and assayed these mutants for various activities. All RTs were as active as the wild type in the oligo(dT):poly(rA) DNA polymerase assay, and many retained both nuclease activities. Two enzymes with mutations at the carboxyl terminus of the RNase H domain retained RNA-DNA activity, but not RNA-RNA activity. Another mutant enzyme showed the opposite phenotype, retaining RNA-RNA, but not RNA-DNA, nuclease activity. Thus, we were able to genetically separate the two activities. These results may be helpful in defining enzyme-substrate interactions.
...
PMID:Nuclease activities of Moloney murine leukemia virus reverse transcriptase. Mutants with altered substrate specificities. 769 92

We examined whether the allegedly aberrant expression of the lymphoid lineage associated DNA polymerase, terminal deoxynucleotidyl transferase (TdT), in acute myeloid leukaemia (AML) is associated with alterations of the enzyme at the cellular, biochemical or transcriptional level when compared to lymphoid leukaemia (ALL), either lacking or expressing myeloid antigens. By flowcytometric analysis, the intensity of TdT staining with monoclonal anti-TdT antibody was considerably weaker in TdT+ AML and myeloid+ ALL (M+ ALL) than in myeloid- ALL (M- ALL). TdT enzyme activity in TdT+ AML was on an average 10%, and in M+ ALL 25% of that measured in M- ALL. Anti-TdT antibodies precipitated a major specific protein of identical relative molecular mass (58 kD) from metabolically labelled TdT+ myeloblasts and lymphoblasts. By Northern blot analysis and ribonuclease protection assay, TdT transcript levels were significantly lower in TdT+ myeloblasts and M+ lymphoblasts than in M- ALL (P < 0.0001). The level of TdT transcription in AML was independent of the simultaneous expression of lymphoid-specific antigens, such as CD2 and CD19. Our data demonstrate that TdT expression is downregulated in association with myeloid features, not only in AML but also in ALL. This observation may provide the molecular basis for the differential therapeutic responsiveness, particularly to glucocorticoids, in these various leukaemia subtypes.
...
PMID:Differential expression of terminal transferase (TdT) in acute lymphocytic leukaemia expressing myeloid antigens and TdT positive acute myeloid leukaemia as compared to myeloid antigen negative acute lymphocytic leukaemia. 821 92


<< Previous 1 2 3 Next >>

---