Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Chicken bone marrow cells transformed by reticuloendotheliosis virus (REV) produce in the cytoplasm a ribonucleoprotein (RNP) complex which has a sedimentation value of approximately 80 to 100S and a density of 1.23 g/cm3. This RNP complex is not derived from the mature virion. An endogenous RNA-directed DNA polymerase activity is associated with the RNP complex. The enzyme activity was completely neutralized by anti-REV DNA polymerase antibody but not by anti-avian myeloblastosis virus DNA polymerase antibody. The DNA product from the endogenous RNA-directed DNA polymerase reaction of the RNP complex hybridized to REV RNA but not to avian leukosis virus RNA. The RNA extracted from the RNP hybridized only to REV-specific complementary DNA synthesized from an endogenous DNA polymerase reaction of purified REV. The size of the RNA in the RNP is 30 to 35S, which represents the subunit size of the genomic RNA. No 60S mature genomic RNA was found within the RNP complex. The significance of finding the endogenous DNA polymerase activity in the viral RNP in infected cells and the maturation process of 60S virion RNA of REV are discussed.
 ...
PMID:Isolation and characterization of a virus-specific ribonucleoprotein complex from reticuloendotheliosis virus-transformed chicken bone marrow cells. 8 19

Two diol epoxides of benzo(a)pyrene (BP), and benzo(a)pyrene 4,5-oxide, have been used to make adducts in the homopolymers polyribocytidylic acid, (rC); polyriboadenylic acid (rA), polydeoxycytidylic acid (dC) and polydeoxyadenylic acid (dA). With appropriate oligomers as primers these modified and unmodified polynucleotides were used as templates for DNA synthesis with avian myeloblastosis virus DNA polymerase (AMV) or E. coli Pol I DNA polymerase. We have found that: (1) the size of the DNA product is not markedly decreased by the presence of these these polycyclic aromatic hydrocarbon adducts in the templates; (2) the presence of adducts does not lead to increased incorporation of erroneous bases. These results, supported by kinetic data, suggest that these polymerases can bypass a site containing an adduct on the template without leaving a gap or causing misincorporation of a base and they imply that mutagenesis by BP may not be attributable to either of these mechanisms.
 ...
PMID:Effects of benzo(a)pyrene adducts of DNA synthesis in vitro. 8 90

An RNA-direct DNA polymerase was purified from human melanoma tissue by successive column chromatography on DEAE-cellulose (DE-23 and DE-52) and phosphocellulose. The purified reverse transcriptase has a mol. wt. of 68,000, a pH optimum of 8.0, a Mn2+ optimum of 0.6 mM, and a KCl optimum of 60 mM. The purified enzyme transcribes (rA)n - (dT)12, (rC)n - (dG)18, (Ome-rC)n - (dG)18 and a 70s RNA from Rauscher leukemia virus (RLV), but failed to transcribe (dA)n - (dT)12. This enzyme has no terminal deoxynucleotidyl transferase activity. Serological studies have shown that the reverse transcriptase from human melanoma tissue is antigenically not related to DNA polymerases from Simian sarcoma virus (SiSV), Avian myeloblastosis virus (AMV), RLV, and human spleen of a patient with myelofibrosis. The purified enzyme showed a close antigenic resemblance to DNA polymerases from baboon endogenous virus (BEV) and rhabdomyosarcoma virus (RD-114), the endogenous virus of the cat.
 ...
PMID:Biochemical and immunological characterization of a reverse transcriptase from human melanoma tissue. 8 88

Highly purified preparations of RNA-directed DNA polymerase from avian myeloblastosis virus (AMV) contain a Mn2+-activated endonuclease activity capable of nicking supercoiled DNA. This endonuclease activity co-sediments in glycerol gradients with the alphabeta form of AMV DNA polymerase, and co-chromatographs with DNA polymerase activity on DEAE-cellulose, phosphocellulose, and heparin-Sepharose. It is also present in AMV alphabeta-DNA polymerase purified by electrophoresis through nondenaturing polyacrylamide gels and subsequently chromatographed on poly(C)-agarose. alphabeta-associated endonuclease is co-immunoprecipitated with DNA polymerase activity by antiserum directed against alphabeta holoenzyme. The alpha form of AMV DNA polymerase lacks this activity. In its enzymatic properties, alphabeta-associated endonuclease resembles the endodeoxyribonuclease activity associated with the AMV p32 protein, which has been shown to be structurally related to the beta (but not the alpha) subunit of AMV DNA polymerase.
 ...
PMID:Endonuclease activity of purified RNA-directed DNA polymerase from avian myeloblastosis virus. 8 98

A recent report (1) presented evidence for allosterism in reverse transcription by Mason-Pfizer monkey virus reverse transcriptase and by E. coli DNA polymerase I. Our experiments also demonstrate these apparent cooperative effects when synthesis is catalyzed by either avian myeloblastosis virus DNA polymerase, feline sarcoma virus DNA polymerase, or E. coli DNA polymerase I (large fragment). We show that the apparent cooperativity depends on the use of oligo(dT)12-18 as primer. However, if the polymerase reaction products are isolated chromatographically, then the polymerases obey classical Michaelis-Menten kinetics with respect to substrate and enzyme concentrations. These results suggest that the cooperative effects are an acid precipitation artifact. The results are also consistent with the enzyme operating by a distributive mechanism with the oligo(dT)12-18 primer.
 ...
PMID:Apparent allosterism by avian myeloblastosis virus reverse transcriptase and E. coli DNA polymerase I. 8 85

A model RNA template-primer system is described for the study of RNA-directed double-stranded DNA synthesis by purified avian myeloblastosis virus DNA polymerase and its associated RNase H. In the presence of complementary RNA primer, oligo(rI), and the deoxyribonucleoside triphosphates dGTP, dTTP, and dATP, 3'-(rC)30-40-poly(rA) directs the sequential synthesis of poly(dT) and poly(dA) from a specific site at the 3' end of the RNA template. With this model RNA template-primer, optimal conditions for double-stranded DNA synthesis are described. Analysis of the kinetics of DNA synthesis shows that initially there is rapid synthesis of poly(dT). After a brief time lag, poly(dA) synthesis and the DNA polymerase-associated RNase H activity are initiated. While poly(rA) is directing the synthesis of poly(dT), the requirements for DNA synthesis indicate that the newly synthesized poly(dT) is acting as template for poly(dA) synthesis. Furthermore, selective inhibitor studies using NaF show that activation of RNase H is not just a time-related event, but is required for synthesis of the anti-complementary strand of DNA. To determine the specific role of RNase H in this synthetic sequence, the primer for poly(dA) synthesis was investigated. By use of formamide--poly-acrylamide slab gel electrophoresis, it is shown that poly(dT) is not acting as both template and primer for poly(dA) synthesis since no poly(dT)-poly(dA) covalent linkages are observed in radioactive poly(dA) product. Identification of 2',3'-[32P]AMP on paper chromatograms of alkali-treated poly(dA) product synthesized with [alpha-32P]dATP as substrate demonstrates the presence of rAMP-dAMP phosphodiester linkages in the poly(dA) product. Therefore, a new functional role of RNase H is demonstrated in the RNA-directed synthesis of double-stranded DNA. Not only is RNase H responsible for the degradation of poly(rA) following formation of a poly(rA)-poly(dT) hybrid but also the poly(rA)fragments generated are serving as primers for initiation of synthesis of the second strand of the double-stranded DNA.
 ...
PMID:Model RNA-directed DNA synthesis by avian myeloblastosis virus DNA polymerase and its associated RNase H. 8 56

An RNA-directed DNA polymerase was purified from a cell line derived from a radiation-induced lymphoma in NIH Swiss mice which produced non-infectious type C virus particles. The enzyme was isolated from a high speed particulate fraction which bands at a density of 1.16--1.19 g/ml in a sucrose gradient, and purified by successive chromatography on DEAE-cellulose, phosphocellulose and hydroxyapatite. The purified DNA polymerase has a molecular weight of 68 000, a pH optimum of 7.5, a KCl optimum of 50 mM, and a Mn2+ optimum of 0.25 mM. It prefers (dT)15 . (A)n to (dT)15 . (dA)n as the primer template and transcribes the poly(C) strand of (dG)15 .(C)n and (dG)15 . (OMeC)n. It transcribes heteropolymeric regions of avian myeloblastosis virus 70 S RNA, and is inhibited by antiserum to Rauscher murine leukemia virus DNA polymerase. Comparison of the properties of DNA polymerase purified from radiation-induced lymphoma cells with the DNA polymerase purified from non-defective murine type C RNA tumor viruses shows that the mouse lymphoma enzyme is both biochemically and immunologically related to murine leukemia virus DNA polymerases.
 ...
PMID:Characterization of an RNA-directed DNA-polymerase from a cell line derived from a radiation-induced lymphoma in mice. 9 May 22

A complex between tRNATrp (beef) and 35 S RNA from avian myeloblastosis virus is obtained when the mixture is preincubated in the presence of reverse transcriptase at 35 degrees C. The tRNA-RNA complex is active in initiating DNA synthesis catalyzed by reverse transcriptase. The interaction of tRNA with reverse transcriptase involves the partial unwinding of the acceptor stem of tRNA, as evidenced by nuclease digestion with RNAase T1 and micrococcal nuclease. When tRNA2Glu (coli), having a high degree of similarity with primer tRNA at the level of the acceptor stem, was used as primer for DNA synthesis, a low but significant level of incorporation was obtained, if the reaction was performed at 35 degrees C, while a high incorporation, similar to the one obtained with tRNATrp was obtained when the annealing between tRNA2Glu and 35 S RNA was performed at 80 degrees C. Our evidences point out to an important role of the viral DNA polymerase in positioning the primer on the RNA genome.
 ...
PMID:Reverse transcriptase mediated binding of primer tRNA to the viral genome. 9 Nov 58

A restriction fragment strand complementary to a sequence near the 3' end of Escherichia coli 16S rRNA has been used to prime reverse transcriptase (avian myeloblastosis virus RNA-directed DNA nucleotidyltransferase; deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, EC 2.7.7.7). In addition to transcripts that were extended to the 5' end of the RNA, two major transcription intermediates were observed. These discrete-sized cDNA intermediates are the result of a kinetic barrier imposed by monomethylation of the amino group on guanine that participates in base-pairing. Both major transcription intermediates correspond to attenuation at the known positions of N2-methylguanine (m2G) in the rRNA sequence. The relaxation time for elongation of the cDNA through m2G is approximately 3 min. No other major kinetic pauses were observed in the 1340 bases transcribed.
 ...
PMID:Reverse transcriptase pauses at N2-methylguanine during in vitro transcription of Escherichia coli 16S ribosomal RNA. 9 Nov 69

RNA-directed DNA polymerase was isolated from the liver, spleen, and myeloblasts of chickens that had been infected with virus of avian myeloblastosis. The enzyme was chromatographically purified from the myeloblasts and brought to about 1,000-fold concentration. The method consisted in cell fractionation, lysis of the microsomal fraction, chromatography on Sephadex G-200 and phosphocellulose, as well as ultracentrifugation in the glycerol gradient. The cellular DNA polymerases alpha and beta were clearly separated from the DNA polymerase of avian myeloblastosis virus and could be distinguished from one another by template-specific reactions. The viral DNA polymerase activities in the microsomal fractions of liver, spleen, and myeloblasts were compared with one another. The amount of avian myeloblastosis virus and related DNA polymerase recorded from the myeloblasts was about six times that in the liver and four times higher than that in the spleen. The procedure described, together with the use of cell fractionation and gel filtration, is an appropriate method for biochemical detection of avian oncorna viruses in cells.
 ...
PMID:[Separation of cellular and viral DNA polymerase from oncornavirus infected chicken cells]. 9 56


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>