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)

Isolated nuclei from HeLa cells can incorporate labeled ADP-ribose from NAD into an acid-precipitable product, poly(ADP-ribose). This reaction is stimulated by 4-6-fold by the addition of deoxyribonuclease I to the complete reaction mixture. If the nuclei are treated first with deoxyribonuclease I, no effect is seen; the stimulation is only apparent when the two enzymes deoxyribonuclease I and poly(ADP-ribose) polymerase, are operating at the same time. After making several minor modifications in the assay mixture, it was found that another endonuclease, micrococcal nuclease, can also stimulate the poly(ADP-ribose) polymerase activity of HeLa nuclei. A comparison of the two stimulatory effects indicated that the two endonucleases activated to the poly(ADP-ribose) polymerase activity of HeLa nuclei in the same way. Overall this evidence suggests that poly(ADP-ribose) polymerase may have a functional role in the process of DNA repair.
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PMID:Stimulation of nuclear poly (adenosine diphosphate-ribose) polymerase activity from HeLa cells by endonucleases. 16 97

The molecular basis for the inhibition of the Ca2+,Mg2+-dependent endonuclease resulting from the formation of poly(adenosine diphosphate ribose) (ADP-Rib) was studies in a simplified system containing purified rat liver or bull semen endonuclease, purified rat liver poly(ADP-Rib) synthetase, [3H]NAD+, and DNA. Poly-(adp-rib) synthetase activity was stimulated when Ca2+, Mg2+-dependent endonuclease was added to the reaction mixture in place of histones, suggesting that the endonuclease can act as an acceptor for ADP-Rib. Evidence was presented to show that the ADP-Rib moiety of [3H]NAD+ was incorporated in the endonuclease fraction. The [3H]ADP-Rib bound to the endonuclease was in the form of monomers and oligomers and not long chain polymers. The present results suggest that the Ca2+,Mg2+-dependent endonuclease was ADP-ribosylated when the endonuclease was incubated with poly(ADP-Rib) synthetase and NAD+.
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PMID:Evidence for adenosine diphosphate ribosylation of Ca2+, Mg2+-dependent endonuclease. 23 25

6-Nitroso-1,2-benzopyrone and 3-nitrosobenzamide, two C-nitroso compounds that inactivate the eukaryotic nuclear protein poly(ADP-ribose) polymerase [NAD+:poly(adenosine diphosphate D-ribose) ADP-D-ribosyltransferase, ADPRT, EC 2.4.2.30] at one zinc-finger site, completely suppressed the proliferation of leukemic and other malignant human cells and subsequently produced cell death. Tumoricidal concentrations of the drugs were relatively harmless to normal bone marrow progenitor cells and to superoxide formation by neutrophil granulocytes. The cellular mechanism elicited by the C-nitroso compounds consists of apoptosis due to DNA degradation by the nuclear calcium/magnesium-dependent endonuclease. This endonuclease is maintained in a latent form by poly(ADP-ribosyl)ation, but inactivation of ADPRT by C-nitroso drugs derepresses the DNA-degrading activity. ADPRT is thus identified as a critical regulatory enzyme component of a DNA-binding multiprotein system that plays a central function in defining DNA structures in the intact cell.
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PMID:Induction of endonuclease-mediated apoptosis in tumor cells by C-nitroso-substituted ligands of poly(ADP-ribose) polymerase. 150 87

NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is a key enzyme involved in the catabolism of the prostaglandins. The cDNA for human placental 15-PGDH has been expressed in Escherichia coli as a catalytically active protein. The polymerase chain reaction was used to introduce restriction endonuclease sites at each end of the 15-PGDH coding sequence. The 15-PGDH DNA was then inserted into the bacterial expression plasmids pUC-18 and pUC-19 which contain the isopropyl-l-thio-beta-D-galactopyranoside (IPTG) inducible lacZ promoter. Extracts from E. coli containing these expression plasmids exhibited 15-PGDH activity which was inducible with (IPTG). Crude extracts from E. coli expressing 15-PGDH activity were found to contain proteins of the predicted sizes in stained SDS-polyacrylamide gels and in Western blots using human placental 15-PGDH antiserum. The specific activity in E. coli extracts was several hundred-fold higher than that seen in extracts from human placenta.
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PMID:Expression of the cDNA for NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase as a catalytically active enzyme in Escherichia coli. 150 55

Endonuclease activity which specifically cleaves baseless (apurinic/apyrimidinic (AP] sites in supercoiled DNA has been purified from mitochondria of the mouse plasmacytoma cell line, MPC-11. Two variant forms separate upon purification; these have small but reproducible differences in catalytic and chromatographic properties, but similar physical properties. Both have a sedimentation coefficient of 4.0, corresponding to a molecular weight of 61,000 (assuming a globular configuration) and a peptide molecular weight of about 65,000 as determined by immunoblot analysis with antiserum raised against the major AP endonuclease from HeLa cells. Thus mitochondrial AP endonuclease appears to be a monomer of about 65 kDa, making it distinguishable from the major AP endonuclease of MPC-11 cells which, like those of other mammalian cells, appears to be a monomer of about 41 kDa. A possible 82-kDa precursor form was also detected by immunoblot analysis of a crude mitochondrial fraction. Mitochondrial AP endonuclease activity is greatly stimulated by divalent cations, has a pH optimum between 6.5 and 8.5, and cleaves the AP site by a class II mechanism to generate a 3'-OH nucleotide residue. These properties resemble those of the major mammalian AP endonucleases but, unlike those enzymes, mitochondrial AP endonuclease activity is neither inhibited by adenine or NAD+ nor stimulated by Triton X-100. Since the mitochondrial activity generates active primer termini for DNA synthesis, it could function in base excision DNA repair; alternatively, it might have a role in eliminating damaged mitochondrial genomes from the gene pool.
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PMID:Mitochondrial endonuclease activities specific for apurinic/apyrimidinic sites in DNA from mouse cells. 245 85

Agents that induce DNA strand breaks evoke a drop in the NAD content in mouse thymocytes. A decrease in the endogenous NAD content that occurs immediately after gamma-irradiation of thymocytes is entirely attributed to the activation of poly(ADP-ribosylation). The addition of 5 mM benzamide before irradiation prevents the postirradiation drop of the NAD level but has no effect on chromatin degradation and cell death. In contrast to liver nuclei, pre-incubation of mouse thymic nuclei with NAD had no effect on the subsequent chromatin endonucleolysis by Ca2+/Mg2+-dependent endonuclease. It is suggested that the NAD-poly(ADP-ribose) polymerase system is probably not the trigger in the radiation-induced programmed death of mouse thymocytes, but may merely be indicative of the radiation response of these cells.
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PMID:Is the NAD-poly (ADP-ribose) polymerase system the trigger in radiation-induced death of mouse thymocytes? 257 Aug 13

Incubation of isolated rat liver nuclei with ATP, NAD+, and submicromolar Ca2+ concentrations resulted in extensive DNA hydrolysis. Half-maximal activity occurred with 200 nM Ca2+, and saturation of the process was observed with 1 microM Ca2+. ATP stimulated a calmodulin-dependent nuclear Ca2+ uptake system which apparently mediated endonuclease activation. Ca2+-activated DNA fragmentation was inhibited by the inhibitor of poly(ADP-ribose) synthetase, 3-aminobenzamide, and was associated with poly(ADP-ribosyl)ation of nuclear protein. The characteristics of this endonuclease activity indicate that it may be responsible for the Ca2+-dependent fragmentation of DNA involved in programmed cell death (apoptosis) and in certain forms of chemically induced cell killing.
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PMID:Calcium-activated DNA fragmentation in rat liver nuclei. 270 97

Nuclear ADP-ribosyltransferase is present in cells from the chick lens throughout embryonic development. The activity does not decrease when the cells become post-mitotic and commence terminal differentiation but declines slowly in both epithelia and fibre cells. At all stages studied the enzyme retains its ability to be activated by DNA strand breaks induced either by X-irradiation or by the action of an endogenous endonuclease. There is no correlation between the enzyme activity or the levels of its substrate NAD+ and the changes in DNA repair capacity which have been observed during the development of the lens.
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PMID:Nuclear ADP-ribosylation in the chick lens during embryonic development. 298 94

The molecular mechanism of activation of Ca2+/Mg2+-dependent endonuclease in thymocytes of irradiated rats was studied. Thymocyte nuclei of control and irradiated rats were pre-incubated with NAD under conditions favourable for poly ADP-ribosylation. Pre-incubation results in a decrease in the rate of autolytic DNA digestion by Ca2+/Mg2+-dependent endonuclease of 6-7- and 2-3-fold for control and irradiated animals, respectively. The activity of Ca2+/Mg2+-nuclease extracted from the nuclei pre-incubated with NAD is also considerably decreased. The presence of nicotinamide and thymidine in the preincubation medium prevents the suppression of Ca2+/Mg2+-nuclease activity. In the experiments performed with isolated nuclei and permeabilized thymocytes the synthesis of poly(ADP-ribose) does not significantly change within 1 h after irradiation at a dose of 10 Gy, whereas 2 and 3 h after the exposure it decreases by 35-40 and 45-55 per cent, respectively. The activity of poly(ADP-ribose) glycohydrolase in this period is similar to that in the controls. The average size of the de novo synthesized chains of poly(ADP-ribose) increases from 11 to 17 ADP-ribose units by the second hour after irradiation. Inhibition of poly(ADP-ribose) polymerase in the postirradiation period preceded the internucleosomal fragmentation of chromatin. The results suggest that activation of Ca2+/Mg2+-nuclease in irradiated thymocytes is accounted for by the disturbance of its poly ADP-ribosylation.
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PMID:Inhibition of poly(ADP-ribose) polymerase as a possible reason for activation of Ca2+/Mg2+-dependent endonuclease in thymocytes of irradiated rats. 312 76

The diminution of NAD level in mouse thymus lymphocytes precedes their death under the effect of various genotoxic agents and manifests itself by the time of the onset of chromatin degradation. At the same time, in vitro, NAD does not influence the activity of micrococcus nuclease of Ca2+,Mg2+-dependent endonuclease from human spleen. Stimulation of protein poly(ADP-ribosylation) by exogenous NAD does not change the sensitivity of chromatin to micrococcus nuclease. In contrast to hepatocytes, in the thymus, no inhibition of Ca2+,Mg2+-endonuclease, resulting from ADP-ribosylation, occurs which may be due to low activity of ADP-ribosyl transferase in thymocytes. Incubation of thymus lymphocytes with benzamide prior to irradiation does not inhibit chromatin degradation. It is suggested that the decrease in the NAD level is one of the indications of the injury to thymocytes which is not related to the induction of their death. In contrast to thymocytes, the pretreatment of Ehrlich ascites tumor cells with benzamide produces a radiosensitizing effect.
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PMID:[Participation of the NAD-poly(ADP ribose) system in the degradation of chromatin in irradiated thymocytes]. 325 28


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