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:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Conformational changes in the chromatin of the cerebral hemisphere of 3-, 14- and 30-day old developing rats were studied before and after its ADP-ribosylation using DNase I and micrococcal nuclease (MNase). The rate and extent of digestion of chromatin by DNase I are the highest at 3-day and decline progressively thereafter. The rate and extent of digestion by MNase do not change during development. ADP-ribosylation of chromosomal proteins was carried out by incubating nuclei with NAD+ for 30 min and was followed by endonuclease digestion. Both the rate and extent of digestion by DNase I and MNase were enhanced after ADP-ribosylation which was the maximum for 3-day rats.
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PMID:ADP-ribosylation induced changes in the conformation of the chromatin of the brain of developing rats. 396 86

Mitochondrial (mt) DNA from four sibling species within the Paramecium aurelia complex, including stocks of different geographic origin and mutants, were analyzed using four 6-bp recognition site and one 4-bp recognition site endonucleases and the sequence divergence was estimated using Upholt's (1977) statistical procedure. All four species were readily distinguishable regardless of the restriction endonuclease employed. With intraspecies comparisons, no differences were observed which could be accounted for on the basis of geographic origin. Except for species 4, each stock (and mutant) gave a species-specific fragment pattern. For species 4, while the patterns were distinct from the other species, two species-specific type of patterns were found, designated A and B. The sequence divergence between these was estimated to be between 1 and 2 percent. With interspecies comparisons, the sequence divergence ranged from 3.9 to 10.3% with the greatest divergence being between species 1 and 4, and the least between species 1 and 5. The similarity between species 1 and 5 is in accord with other criteria for interspecies comparisons. The degree of sequence divergence measured here in Paramecium mt DNA is well within the range reported for rodents and primates. All four species mt DNA were cleaved to many DNA fragments by DPN II, an enzyme which recognizes non-methylated sites, and not by DPNI, the methyl-site specific counterpart of DPN II, suggesting that mt DNA from Paramecium aurelia is not appreciably methylated, if at all.
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PMID:Evolutionary divergence of mitochondrial DNA from Paramecium aurelia. 625 97

An endodeoxyribonuclease from HeLa cells acting on apurinic/apyrimidinic (AP) sites has been purified to apparent homogeneity as judged by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The presence of Triton X-100 was necessary throughout the purification for stabilization and stimulation of activity. The endonuclease has an apparent native molecular weight of 32,000 determined by molecular sieving and an apparent subunit molecular weight of 41,000 as judged by its electrophoretic mobility in SDS-polyacrylamide gels. The activity has an absolute requirement for Mg2+ or Mn2+ and a broad pH optimum between 6.7 and 9.0 with maximal activity near pH 7.5. The enzyme has no detectable exonuclease activity, nor any endonuclease activity on untreated duplex or single-stranded DNA. It is inhibited by adenine, hypoxanthine, adenosine, AMP, ADP-ribose, and NAD+, but it is unaffected by caffeine, the pyrimidine bases, ADP, ATP, or NADH. The use of a variety of damaged DNA substrates provided no indication that the enzyme acts on other than AP sites. The enzyme appears to cleave AP DNA so as to leave deoxyribose-5-phosphate at the 5' terminus and a 3'-OH at the 3' terminus; it also removes deoxyribose-5-phosphate from AP DNA which has deoxyribose at the 3' terminus. Specific antibody has been produced in rabbits which interacts only with a 41,000-dalton protein present in the purified enzyme (presumably the enzyme itself), as well as with partially purified AP endonuclease fractions from human placenta and fibroblasts.
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PMID:Purification and characterization of an apurinic/apyrimidinic endonuclease from HeLa cells. 625 65

A biphase change in poly (ADP-ribose) polymerase activity of the thymocyte chromatin was observed after 10 Gy irradiation of rats: during the first minutes the incorporation of 14C-NAD increased by 40% then started decreasing to make 110, 60 and 35% after 1, 2 and 3 h, respectively. Irradiation of rat thymus chromatin in vitro sharply decreased poly (ADP-ribose) polymerase activity. The possible role of changes in the poly (ADP-ribose) synthesis in the activation of nuclear Ca/Mg-dependent endonuclease and in the postirradiation degradation of the thymocyte chromatin is discussed.
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PMID:[Mechanism of chromatin degradation in thymocytes of irradiated rats. 6. Postradiation changes in the activity of poly(ADP-riboso)-polymerase]. 630 27

The molecular mechanism of the inhibition of Ca2+, Mg2+-dependent endonuclease by ADP-ribosylation was studied by using purified bull seminal plasma Ca2+, Mg2+-dependent endonuclease, endonuclease-stimulating proteins, and poly-(ADP-ribose) polymerase. The activity of an essentially homogeneous preparation of the endonuclease was markedly suppressed by its preincubation with NAD+, poly-(ADP-ribose) polymerase, DNA, and Mg2+. These four components of the incubation mixture were all essential for the suppression of the activity. Analyses of the initial and the chased reaction product by Sephadex G-100 column chromatography and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis revealed that Ca2+, Mg2+-dependent endonuclease was ADP-ribosylated during the incubation and its activity was markedly inhibited by the elongation of the ADP-ribose polymer covalently attached to the endonuclease. When the suppressed enzymes were mildly treated with an alkaline pH of 10.0, the activity was restored almost to the level of the unmodified control sample. These facts indicate that the linkage between the enzyme and poly(ADP-ribose) is hydrolyzed at this pH, and that the liberated polymer itself does not appreciably affect the endonuclease activity. These results also suggest that an electric repulsion between negative charges on DNA and poly(ADP-ribose) attached to Ca2+, Mg2+-dependent endonuclease is the basis for the observed suppression of the enzyme by ADP-ribosylation. Though histone H2B and H1 are shown to be as good endonuclease-stimulators (1) as they are good acceptors of ADP-ribose in poly(ADP-ribose) polymerase reaction (2), ADP-ribosylation of these two proteins did not affect their endonuclease-stimulating ability appreciably, at least under the conditions used.
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PMID:Ca2+, Mg2+-dependent endonuclease and ADP-ribosylation. 631 36

The activity of purified Ca2+, Mg2+-dependent endonuclease was inhibited when the enzyme was incubated in a system containing poly(ADP-ribose) synthetase, NAD+, Mg2+, and DNA. All four ingredients were essential to mediate ADP-ribosylation and to demonstrate inhibition of the endonuclease. In the absence of Mg2+, ADP-ribose transferring activity of poly(ADP-ribose) synthetase was stimulated by the addition of purified endonuclease to the reaction mixture in a dose-dependent manner. Analysis of the reaction product showed that the endonuclease was ADP-ribosylated. The average chain length of the initial oligo(ADP-ribose) attached to the enzyme was about 5.9 residues. The oligomer was found to be extensively elongated during the chase experiment using unlabeled NAD+ and Mg2+. The present finding suggests that Mg2+ is essential for the extensive elongation of the oligo(ADP-ribose). The DNA-binding affinity of the modified endonuclease was significantly lower than that of unmodified enzyme. Also, free poly(ADP-ribose) was not an effective inhibitor of the endonuclease. These findings suggest that the observed inhibition of the endonuclease induced by ADP-ribosylation is probably due to an electrostatic repulsion between the substrate (DNA) and poly(ADP-ribose) covalently linked to the endonuclease. Histone H1 and H2B stimulated endonuclease activity and were acceptors of ADP-ribose; however, their capacity to stimulate endonuclease activity remained unchanged after ADP-ribosylation.
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PMID:Mechanism of the inhibition of Ca2+, Mg2+-dependent endonuclease of bull seminal plasma induced by ADP-ribosylation. 632 87

We have developed an in vitro system utilizing yeast cell-free extracts to catalyze recombination events between homologous plasmids containing different mutant alleles of the Tet or ARG4 genes. The reaction increased the frequency of Tcr or Arg+ transformants (recombinants) from 2 X 10(-6) to 1-3 X 10(-3). Linearizing one substrate between the two tet mutations stimulated the reaction 2 to 4 fold. The reaction required rATP, Mg++, NAD, and DTT. The rad52-1 mutation decreased the reaction between linear and circular substrates 5 to 6 fold but had little effect with circular substrates. The structures of Tcr plasmids was analyzed by restriction endonuclease mapping and was consistent with a recombination reaction involving crossing-over and gene conversion. Recombination products were also observed directly by subjecting reaction mixtures to electrophoretic analysis. These results indicate that recombination events were catalyzed by the yeast extract.
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PMID:Genetic recombination of homologous plasmids catalyzed by cell-free extracts of Saccharomyces cerevisiae. 636 Mar 80

The nuclei from the control and irradiated (3 h after irradiation at a dose of 10 Gy) thymocytes were preincubated with NAD in conditions optimal for poly (ADP) ribosylation. This was shown to decrease by 6-7- and 2-3 times, respectively, the rate of autolytic cleavage of DNA by Ca/Mg-dependent endonuclease. The inhibitors of poly (ADP-riboso)-polymerase, nicotine amide and thymidine, removed the effect of NAD. The data obtained prompt an assumption that the post-irradiation activation of Ca/Mg-nuclease in thymocytes is associated with the disturbance of its post-translation modification, poly(ADP)ribosylation.
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PMID:[Role of a disorder in poly(ADP-ribosylation) in the activation of Ca/Mg-dependent endonuclease]. 647 18

A DNA ligase has been purified from a subnuclear soluble replication complex isolated from adenovirus type 2-infected human KB cells. DNA ligase activity could not be demonstrated using an exogenous template until the complex was dissociated, suggesting that the ligase activity may be a component of the complex. The purified enzyme was free of endonuclease, exonuclease, 5'-nucleotidase, and phosphatase activities, and had a molecular weight of 105 000, as estimated by sedimentation in a glycerol gradient. The ligase requires ATP and a divalent cation for activity. The optimum of the reaction is at pH 7.8 in 50--100 mM Tris-HCl buffer and 10--20 mM MgCl2. Monovalent salts greatly stimulate ligase activity and the optimum was found at 150 mM. The reaction is very sensitive to high temperature; maximum activity was observed at 25--30 degrees C. ATP is the sole required cofactor and NAD, dATP and GTP could not replace the requirement for ATP. The Km for ATP is 60 microM. The Km for DNA is 250 microgram/ml or 1.6 nmol of terminal phosphate/ml and thus the enzyme shows relatively weak affinity for exogenous DNA. The maximum conversion of 32P into a phosphatase-resistant form is approximately 1.3% of the total, whereas T4 ligase, under the same conditions, can convert more than 25% of phosphate into a resistant form.
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PMID:Purification and properties of a DNA ligase from a soluble DNA replication complex. 735 2

Detergent-lysed BS-C-1, HeLa, and mouse L cells incorporate ADP-ribose from NAD+ into two classes of macromolecules. Metabolically stable products, which appear to be a variety of proteins to which are attached one or a few ADP-ribose residues, predominate when the cellular DNA remains intact. In addition, ghost cells have a potentially much greater capacity to synthesize poly(ADP-ribose), which is completely dependent upon the introduction of strand breaks into their DNA. The initial rate of poly(ADP-ribose) synthesis increases linearly with prior x-ray dose or with the concentration of endonuclease added and, once synthesized, the polymer is rapidly degraded with a half-life of 10 min or less. It appears that sites on the DNA capable of supporting a certain amount of poly(ADP-ribose) synthesis are created as a result of x-irradiation or nucleolytic cleavage and are rapidly eliminated, or "repaired," during subsequent incubation. The sites accumulate if cells are irradiated at 0 degree C; further incubation of the lysed cells with NAD+ at 35 degrees C results in both a burst of poly(ADP-ribose) synthesis and the elimination of the sites. NAD+ enhances the elimination of x-ray-induced sites. Thus, the synthesis of poly(ADP-ribose) may be required for the repair of DNA strand breaks.
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PMID:ADP-ribosylation in mammalian cell ghosts. Dependence of poly(ADP-ribose) synthesis on strand breakage in DNA. 743 Jan 32


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