Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endonucleases from Micrococcus luteus that induce single-strand breaks in gamma-irradiated DNA have been separated chromatographycally into two groups. The first group involves two different enzymes: AP-endonuclease II (mol. weight 30 000) and AP, UV-endonuclease I (mol. weight 15 000) that recognize alkali-labile lesions in gamma-irradiated DNA and apurinic sites in DNA heated at 70 degrees C, pH 6.08 AP-endonuclease II in cooperation with DNA polymerase from M. luteus and T4 phage-induced polynucleotide ligase is capable of carrying out in vitro complete excision repair of alkali-labile lesins in gamma-irradiated DNA. The second group involves gamma-endonucleases X and Y that act on alkalistable gamma-ray lesions. gamma-endonucleases X and Y can be separated by chromatography on DEAE-cellulose but possess similar properties. Activity of gamma-endonucleases toward gamma-irradiated DNA is inhibited by only heavily UV-irradiated DNA (15 000 ergs/mm2). The data are consistent with the hypothesis that gamma-endonucleases are specific for thymine glycols (t' and tUV) in UV- and gamma-irradiated DNA.
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PMID:[Analysis of the activity of Micrococcus luteus endonucleases with respect to gamma-irradiated DNA]. 2 Jan 61

Full-length, single-stranded rabbit globin cDNA, synthesized by AMV reverse transcriptase, apparently contains a small double-stranded sequence (hairpin) at the 3' terminus. This cDNA can serve as template-primer for E. coli DNA polymerase I, which synthesizes a strand complementary to the cDNA and covalently bound to it. The loop connecting the two strands can be cut by S1 nuclease. Reassociation, hybridization, and restriction endonuclease studies, as well as electrophoretic analyses, indicate that the sequential actions of reverse transcriptase, DNA polymerase 1, and S1 nuclease generate full-length, double-stranded synthetic globin genes.
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PMID:Enzymatic in vitro synthesis of globin genes. 6 Jan 78

The circular DNA of hepatitis B Dane particles, which serves as the primer/template for an endogenous DNA polymerase, was analyzed by electrophoresis before and after a polymerase reaction and after digestion by restriction endonuclease or single-strand-specific endonuclease S1. The unreacted molecules extracted from the particles were electrophoretically heterogeneous, and treatment with S1 nuclease produced double-stranded linear DNA ranging in length from 1,700 to 2,800 base pairs (bp). After an endogenous DNA polymerase reaction, two discrete species of DNA molecules were found: a circular form and a linear form 3,200 bp long. The reaction resulted in a population of molecules with an elongated and more homogeneous double-stranded region. These results suggest that the circular molecules in Dane particles have single-stranded regions of varying lengths that are made double stranded during the DNA polymerase reaction. The endogenous DNA polymerase was found to initiate apparently at random in a region spanning more than a third of the molecule. Analysis of restriction endonuclease cleavage fragments of the fully elongated DNA revealed that although the molecules were of a uniform length, they were somewhat heterogeneous in sequence. The sum of the sizes of the 10 major endonuclease Hae III-generated fragments, detected by ethidium bromide, was 3,880 bp. Two additional fragments (B and G) detected by autoradiography after an endogenous DNA polymerase reaction with (32)P-labeled deoxynucleoside triphosphates made the total 4,910 bp.
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PMID:Structure of hepatitis B Dane particle DNA and nature of the endogenous DNA polymerase reaction. 6 27

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.
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PMID:Endonuclease activity of purified RNA-directed DNA polymerase from avian myeloblastosis virus. 8 98

Hepatitis B virus DNA made fully double stranded by a virion DNA polymerase reaction could be converted from circular to linear molecules by heating in 10 mM NaCl at 77 degrees C or in 100 mM NaCl at 90 degrees C for 15 min. Heat-generated linear hepatitis B virus DNA was reannealed to circular molecules by incubating in higher salt concentrations. The identity of the molecular forms was established by their electrophoretic mobility and appearance in electron micrographs. Recircularization was blocked by reacting linear molecules with nuclease S1 or avian myeloblastosis virus reverse transcriptase. These results suggest that the heated linear DNA had single-stranded ends with complementary nucleotide sequences. It also suggests that a discontinuity or nick is present in each strand of the circular DNA molecule after the single-stranded region is made double stranded by the virion DNA polymerase reaction. The difference in contour length by electron microscopy of circular and linear molecules spread under aqueous conditions suggested that the discontinuities in the two strands were about 270 base pairs apart. The amount of nucleotide incorporated into the ends of heat-generated linear hepatitis B virus DNA by reverse transcriptase suggested that the single-stranded ends were about 305 bases in length. This fully double-stranded linear DNA was cleaved with EcoRI or HpaI restriction endonuclease. The sum of the two fragments generated by each totaled 3,510 base pairs, 310 base pairs greater than the contour length of circular hepatitis B virus DNA which represents a third estimate of the distance between the discontinuities in the two DNA strands of circular DNA. Restriction endonuclease cleavage also indicated that the ends of heated linear DNA which correspond to the discontinuities in the two strands of the circular DNA are at unique sites in the DNA with respect to the restriction sites.
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PMID:Hepatitis B viral DNA molecules have cohesive ends. 9 58

The DNA polymerase induced by Bacillus subtilis bacteriophage PBS2 has a Stokes radius of 7.2 in buffers of high ioninc strength, suggesting a molecular weight in the range 145,000 to 195,000. The polypeptide bands observed on gel electrophoresis in dodecyl sulfate have apparent molecular weights of 78,000 and 69,000 (and possibly another 27,000) in equimolar amounts. In buffers of low ionic strength, the enzyme appears to form large aggregates and even precipitates, with about 90% loss of activity. A nuclease activity co-purifies with the PBS2 DNA polymerase and shows similar responses to changes in pH, MgCl2, N-ethylmaleimide, temperature, and dextran sulfate levels. The nuclease produces deoxyribonucleoside 5'monophosphates from denatured DNA containing thymine or uracil. No endonuclease activity is detectable on supercoiled DNA. The inhibition of nuclease activity by added deoxyribonucleoside triphosphates, the DNA-dependent turnover of triphosphates, to free monophosphates during DNA polymerization, the inhibition of nuclease activity by 3'-phosphates on the DNA template-primer, and the pattern of digestion of 5'-[32P]phosphate-labeled DNA all indicate that the PBS2 DNA polymerase-associated hydrolytic activity is a 3' leads to 5'-exonuclease.
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PMID:Characterization of the Bacillus subtilis bacteriophage PBS2-induced DNA polymerase and its associated exonuclease activity. 10 39

Gene A of the phi X174 genome codes for two proteins, A and A* (Linney, E.A., and Hayashi, M.N. (1973) Nature New Biol. 245, 6-8) of molecular weights 60,000 and 35,000, respectively. The phi X A* protein is formed from a natural internal initiator site within the A gene cistron while the phi X A protein is the product of the entire A gene. These two proteins have been purified to homogeneity as judged by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Previous studies have shown that the phi X A protein is an endonuclease which specifically introduces a discontinuity in the A cistron of the viral strand of supertwisted phi XRFI DNA. In addition to this activity, the phi X A protein also causes relaxation of supertwisted phi XRFI DNA and formation of a phi XRFH DNA . phi X A protein complex which has a discontinuity in the A cistron of the viral strand. This isolatable complex supports DNA synthesis when supplemented with extracts of uninfected Escherichia coli which lack phi X A protein and phi XRFI DNA. The phi XRFII DNA . phi X A protein complex can be attacked by exonuclease III but is not susceptible to attack by E. coli DNA polymerase I, indicating that the 5'-end of the complex is blocked. Attempts to seal the RFII structure generated from the phi XRFII DNA . phi X A protein complex with T4 DNA ligase in the presence or absence of DNA polymerase were unsuccessful. The phi X A protein does not act catalytically in the cleavage of phi XRFI DNA. Under conditions leading to the quantitative cleavage of phi XRFI DNA, the molar ratio of phi XRFI DNA to added phi X A protein was approximately 1:10. At this molar ratio, cross-linking experiments with dimethyl suberimidate yielded 10 distinct protein bands which were multiples of the monomeric phi X A protein. In the absence of DNA or in the presence of inactive DNA (phi XRFII DNA) no distinct protein bands above a trimer were detected. We found it possible in vitro to form a phi XRFII DNA . phi X A protein complex with wild-type phi XRFI DNA (phi X A gene+) and with phi XRFI DNA isolated from E. coli (su+) infected with phage phi X H90 (an am mutant in the phi X A gene). Thus, in vitro, in contrast to in vivo studies, phi X A protein is not a cis acting protein. The purified phi X A* protein does not substitute for the phi X A protein in in vitro replication of phi XRFI DNA nor does it interfere with the action of the phi X A protein which binds only to supertwisted phi XRFI DNA. In contrast, the phi X A* protein binds to all duplex DNA preparations tested. This property prevents nucleases of E. coli from hydrolyzing duplex DNAs to small molecular weight products.
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PMID:Role of polymeric forms of the bacteriophage phi X174 coded gene A protein in phi XRFI DNA cleavage. 15 88

Extracts of Novikoff hepatoma cells contain factors capable of stimulating in vitro DNA synthesis several fold. The activity can be resolved into three separate protein peaks on DEAE-Sephadex. Two of these, factors II and III, have been purified and partially characterized. Both factors increase the initial rate of DNA synthesis and allow synthesis to proceed much longer. If either factor is added after synthesis by the DNA polymerase has reached a plateau, resumption of synthesis occurs. The factors appear to have different modes of action or sites of action since they show an additive effect even when a single one is used at saturating conditions. These factors are present in normal rat liver but at a concentration less than 5% of that found in the tumor cells. When tested with several highly purified DNA polymerases (DNA nucleotidyltransferase, EC 2.7.7.7), the factors show a much greater stimulation of homologous, non-mitochondrial enzymes (rat liver nuclear-, rat liver cytoplasmic-, or Novikoff-DNA polymerases) when compared with rat liver or calf liver mitochondrial-, Escherichia coli I-, or sea urchin nuclear-DNA polymerases. The mechanism of action of these factors is not known at present. No enzymatic activity has been associated with factor III. Highly purified, but not homogeneous, preparations of factor II contain low levels of endonuclease; it has not been established whether endonuclease is a contaminant or is responsible for the stimulating activity.
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PMID:Stimulation of DNA polymerase by factors isolated from Novikoff hepatoma. 16 86

A class of precursor DNA (pDNA) II molecules has been identified as the immediate precursor of simian virus 40 DNA I. A pDNA II molecule contains a strand of newly synthesized DNA with an interruption located in the region where DNA synthesis terminates (4). These pDNA II molecules have been isolated and further characterized. They are converted to covalently closed structures (simian virus 40 DNA I) only when they are treated in vitro with both T4 DNA polymerase and Escherichia coli ligase. After in vitro repair of pDNA II with T4 DNA polymerase and nucleoside triphosphates, approximately 7 mol of alpha-[32P]dATP is incorporated per mol of DNA II. Alkaline sucrose analysis of these gap-filled molecules, after they have been cleaved with Eco RI restriction endonuclease, has demonstrated that gaps are specifically located in the termination region. alpha-[32P]dATP is incorporated equally into the two labeled products that are generated by RI cleavage of these molecules. This indicates the presence of gaps in both the newly synthesized plus the minus strands. Electrophoretic analysis of the gap-filled molecules, after they have been cleaved with endonuclease Hind, has shown that gaps are localized in Hind fragments G and B and to a minor degree in fragment J. pDNA II molecules have the following properties. There is a gap in the newly synthesized linear DNA strand contained in the pDNA II molecule. Nicked pDNA II molecules cannot be detected. The two molecules that arise by segregation contain gaps in both of the complementary strands. Based on the amount of alpha-[32P]dATP incorporated and the rate of exonuclease III digestion of gap-filled molecules, it is estimated that the size of the gaps is between 22 and 73 nucleotides. Models for termination of DNA synthesis are proposed based on these findings.
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PMID:Simian virus 40 DNA replication: characterization of gaps in the termination region. 17 34

Viral DNA molecules were purified from a nontransforming and a transforming strain of Epstein-Barr virus. Each viral DNA was labeled in vitro and renatured in the presence of an excess of either one or the other unlabeled viral DNA. Both viral DNAs were also digested with the Eco R1 restriction endonuclease and subsequently labeled by using avian myeloblastosis virus DNA polymerase to repair either the EcoR1 nuclease-generated single-stranded ends of the DNAs or their single-stranded ends produced by a second digestion with exonuclease III after the first EcoR1 nuclease digestion. The results of these experiments support three general conclusions: (i) the DNAs of these two strains of Epstein-Barr virus share approximately 90% of their nucleotide sequences; (ii) both viral DNA populations are reasonably homogenous; and (iii) both DNAs contain repetitions or inverted repetitions of some of their nucleotide sequences.
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PMID:Nucleic acid renaturation and restriction endonuclease cleavage analyses show that the DNAs of a transforming and a nontransforming strain of Epstein-Barr virus share approximately 90% of their nucleotide sequences. 17 7


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