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:3.1.31.1 (micrococcal nuclease)
2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Control of the rate of cardiac cell division by oxygen occurs most probably by altering the redox state of a control substance, e.g. NAD(+)right harpoon over left harpoonNADH. NAD(+) (and not NADH) forms poly(ADP-ribose), an inhibitor of DNA synthesis, in a reaction catalysed by poly(ADP-ribose) polymerase. Lower partial pressure of oxygen, which increases the rate of division, would shift NAD(+)-->NADH, decrease poly(ADP-ribose) synthesis, and increase DNA synthesis. Chick-embryo heart cells grown in culture in 20% O(2) (in which they divide more slowly than in 5% O(2)) did exhibit greater poly(ADP-ribose) polymerase activity (+83%, P<0.001) than when grown in 5% O(2). Reaction product was identified as poly(ADP-ribose) by its insensitivity to deoxyribonuclease, ribonuclease, NAD glycohydrolase, Pronase, trypsin and micrococcal nuclease, and by its complete digestion with snake-venom phosphodiesterase to phosphoribosyl-AMP and AMP. Isolation of these digestion products by Dowex 1 (formate form) column chromatography and paper chromatography allowed calculation of average poly(ADP-ribose) chain length, which was 15-26% greater in 20% than in 5% O(2). Thus in 20% O(2) the increase in poly(ADP-ribose) formation results from chain elongation. Formation of new chains also occurs, probably to an even greater degree than chain elongation. Additionally, poly(ADP-ribose) polymerase has very different K(m) and V(max.) values and pH optima in 20% and 5% O(2). These data suggest that poly(ADP-ribose) metabolism participates in the regulation of heart-cell division by O(2), probably by several different mechanisms.
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PMID:Poly(adenosine dephosphate ribose) metabolism and regulation of myocardial cell growth by oxygen. 2 65

When HeLa cell nuclei were treated with micrococcal nuclease (nucleate 3-oligonucleotidohydrolase, EC 3.1.4.7), lysed, and centrifuged, the supernatant from early digests contained two predominant classes of polynucleosomes of repeat size 8N and 16N. With increasing digestion time, the 16 N polynucleosome appeared to be cleaved to the 8N species and finally to the basic subunit of chromatin. The size of the polynucleosomes has been determined by DNA analysis and on polyacrylamide electrophoretic gels of native chromatin particles. The 16N polynucleosome appears to be a unique higher ordered structural component of HeLa cell chromatin. Our recent report, showing that the nuclear protein-modifying enzyme poly(ADP-ribose) polymerase increases in specific activity progressively with increasing nucleosome repeat size up to 8-10N, has been extended in the present study. Activity was also elevated in the polynucleosomes of the 16N structure preferentially cleaved by micrococcal nuclease, although specific activity of the enzyme was highest in octanucleosomes. Acceptors for poly(ADP-ribose) have also been determined in these particles.
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PMID:Nucleosome periodicity in HeLa cell chromatin as probed by micrococcal nuclease. 10 31

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 distribution of a chromatin-bound, nuclear protein modifying enzyme, poly (adenosine diphosphate-ribose) polymerase, and its product, poly(ADP-ribose), among various fractions of sheared and nuclease-digested HeLa cell chromatin has been examined. Epichlorohydrin-tris(hydroxymethyl)aminomethane-cellulose and glycerol gradient fractionation of solubilized chromatin indicated that poly(ADP-ribose)polymerase activity was associated primarily with the template active regions (euchromatin), whereas the transcriptionally inert chromatin fractions were found to contain relatively low levels of ADP-ribosylating activity. When isolated HeLa cell nuclei were digested in situ with micrococcal nuclease and the resultant chromatin was fractionated into nucleosome monomers (v bodies) and oligomers by sucrose gradient centrifugation, only material sedimenting faster than the 11S monomers was found to contain appreciable poly(ADP-ribose) polymerase activity. If, on the other hand, isolated HeLa cell nuclei were first incubated with labeled NAD, the substrate for poly(ADP-ribose) polymerase, prior to the preparation and fractionation of nuclease-digested chromatin, it was found that those chromatin fractions which possess significant poly(ADP-ribose) polymerase activity (nucleosome oligomers) are relatively deficient in the labeled product of this enzyme, and that a considerable portion of the homopolymeric product is ultimately associated with the 11S v bodies. Additional evidence is presented which indicates that the absence of nucleosome monomer-associated poly(ADP-ribose) polymerase activity is not due to the absence of a suitable acceptor on these structures, and that the activity of this enzyme within the chromatin is most probably dependent upon the physical integrity of the oligomeric structures themselves.
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PMID:Poly(adenosine diphosphate-ribose) polymerase: the distribution of a chromosome-associated enzyme within the chromatin substructure. 18 3

Poly(ADP-ribosylation) of histones and several other nuclear proteins seem to participate in nuclear processes involving DNA strand breaks like repair, replication, or recombination. This is suggested from the fact that the enzyme poly(ADP-ribose) polymerase responsible for this modification is activated by DNA strand breaks produced in these nuclear processes. In this article I provide three lines of evidence supporting the idea that histone poly(ADP-ribosylation) is involved in chromatin replication. First, cellular lysates from rapidly dividing mouse or human cells in culture synthesize a significant number of oligo- in addition to mono(ADP-ribosylated) histones. Blocking the cells by treatment of cultures with 5 mM butyrate for 24 h or by serum or nutrient depletion results in the synthesis of only mono- but not of oligo(ADP-ribosylated) histones under the same conditions. Thus, the presence of oligo(ADP-ribosylated) histones is related to cell proliferation. Second, cellular lysates or nuclei isolated under mild conditions in the presence of spermine and spermidine and devoid of DNA strand breaks mainly synthesize mono(ADP-ribosylated) histones; introduction of a small number of cuts by DNase I or micrococcal nuclease results in a dramatic increase in the length of poly(ADP-ribose) attached to histones presumably by activation of poly(ADP-ribose) polymerase. Free ends of DNA that could stimulate poly(ADP-ribosylation) of histones are present at the replication fork. Third, putatively acetylated species of histone H4 are more frequently ADP-ribosylated than nonacetylated H4; the number of ADP-ribose groups on histone H4 was found to be equal or exceed by one the number of acetyl groups on this molecule. Since one recognized role of tetraacetylated H4 is its participation in the assembly of new nucleosomes, oligo(ADP-ribosylation) of H4 (and by extension of other histones) may function in new nucleosome formation. Based on these results I propose that poly(ADP-ribosylated) histones are employed for the assembly of histone complexes and their deposition on DNA during replication. Modified histones arise at the replication fork by activation of poly(ADP-ribose) polymerase by unligated Okazaki fragments.
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PMID:Poly(ADP-ribosylated) histones in chromatin replication. 238 72

The nuclear location of NMN adenylytransferase, which catalyses the formation of NAD and pyrophosphate from ATP and NMN, has been examined to ascertain if the enzyme is bound to the domains of chromatin which undergo poly(ADP-ribos)ylation. This latter reaction utilizes much of the cellular NAD. A radioisotope assay using [alpha-32P]ATP was developed to enable precise measurement of picomole amounts of NAD. With this assay, it appeared that the reaction catalysed by NMN adenylyltransferase proceeded with a rapid, early 'burst' of NAD before steady-state velocities were established. From this it was calculated that there could be 10- active sites of NMN adenylyltransferase per HeLa nucleus in asynchronously growing cells: that is, approximately one per 10-20 nucleosomes. Very little enzyme activity was liberated by digesting HeLa nuclei with micrococcal nuclease in 80 mM NaCl, and the enzyme which was solubilized was not bound to oligonucleosomes separated by electrophoresis on polyacrylamide gels. In contrast, poly(ADP-ribose) polymerase activity was clearly demonstrated on these particles. The enzyme was readily liberated by DNase I digestion, especially when the digestion was carried out in low-ionic-strength buffer. The results demonstrated that the enzyme was neither bound to oligonucleosomes nor part of the nuclear envelope or matrix. Preliminary results suggested that there could be some direct channelling of NAD between the two enzymes in intact nuclei. It appears that NMN adenylyltransferase is bound within rather than to chromatin.
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PMID:NMN adenylyltransferase: its association with chromatin and with poly(ADP-ribose) polymerase. 629 57

Nucleosomal chains of various repeat unit lengths were generated by a mild micrococcal nuclease digestion of purified pancreatic nuclei. Maximal nucleosome associated poly(ADP-ribose) polymerase activity was recovered in trimeric to tetrameric chromatin fragments, after which the enzyme activity gradually decreased and stabilized towards oligomeric periodicities of 11 to 16 nucleosomes. Electrophoresis of [32P]ADP-ribosylated histones on first-dimension acid-urea or acid-urea-Triton gels and on second-dimension acid--urea--cetyltriammonium bromide gels revealed that, of all histones, only histone H1 could be significantly poly(ADP-ribosyl)ated while only minimal modification could be recovered with histone H1(0). Furthermore, the extent of ADP-ribosylation present on pancreatic histone H1 is shown to proportionally retard this protein's electrophoretic mobility in all gel systems and to consist of a distinct series of at least 12 modification intermediates which can be evidenced, in nuclei or nucleosomes, and fully recovered along with histone H1 upon its selective extraction with 5% perchloric acid. The generation of these increasingly ADP-ribosylated forms of histone H1 is also demonstrated to be time dependent and the more complex ADP-ribosylated forms of this histone are favored at high NAD+ concentrations. Moreover, the electrophoretic mobilities of all intermediates are unaffected by the presence of the nonionic detergent Triton X-100.
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PMID:Hyper(ADP-ribosyl)ation of histone H1. 629 82

A hyperthermic shift in the hyperchromicity curve of thermally denatured swine aortic-smooth-muscle-cell chromatin solubilized by digestion of nuclei with micrococcal nuclease was observed after the chromatin was incubated under conditions to allow poly-(ADP-ribose) synthesis by the endogenous poly(ADP-ribose) polymerase. When the order of solubilization and poly(ADP-ribosyl)ation was reversed, a smaller proportion of the solubilized chromatin exhibited greater thermal stability. Nuclease digestion of nuclei preincubated for poly(ADP-ribose) synthesis revealed no difference in kinetics of digestion or fragment size distribution compared to that of control nuclei. Poly(ADP-ribose) synthesis in these nuclei was proportionately greater in the chromatin fraction most resistant to solubilization by micrococcal nuclease treatment.
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PMID:Increased thermal stability of solubilized chromatin after poly(ADP-ribose) synthesis. 664 81

The biochemical role of poly(ADP-ribosyl)ation on internucleosomal DNA fragmentation associated with apoptosis was investigated in HL 60 human premyelocytic leukemia cells. It was found that UV light and chemotherapeutic drugs including adriamycin, mitomycin C, and cisplatin increased poly(ADP-ribosyl)ation of nuclear proteins, particularly histone H1. A poly(ADP-ribose) polymerase inhibitor, 3-aminobenzamide, prevented both internucleosomal DNA fragmentation and histone H1 poly(ADP-ribosyl)ation in cells treated with the apoptosis inducers. When nuclear chromatin was made accessible to the exogenous nuclease in a permeabilized cell system, chromatin of UV-treated cells was more susceptible to micrococcal nuclease than the chromatin of control cells. Suppression of histone H1 poly(ADP-ribosyl)ation by 3-aminobenzamide reduced the micrococcal nuclease digestibility of internucleosomal chromatin in UV-treated cells. These results suggest that the poly(ADP-ribosyl)ation of histone H1 correlates with the internucleosomal DNA fragmentation during apoptosis mediated by DNA damaging agents. This suggestion is supported by the finding that xeroderma pigmentosum cells which are defective in introducing incision at the site of DNA damage, failed to induce DNA fragmentation as well as histone H1 poly(ADP-ribosyl)ation after UV irradiation. We propose that poly(ADP-ribosyl)ation of histone H1 protein in the early stage of apoptosis facilitates internucleosomal DNA fragmentation by increasing the susceptibility of chromatin to cellular endonuclease.
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PMID:Poly(ADP-ribosyl)ation of histone H1 correlates with internucleosomal DNA fragmentation during apoptosis. 862 64

Activation of endothelial cell integrins inhibits DNA breakage by diverse agents, including the DNA-damaging agent bleomycin. DNA breaks activate nuclear poly(ADP-ribose) polymerase (PARP), which regulates chromatin structure and DNA repair. We determined the role of PARP in suppression of bleomycin genotoxicity by integrins using wild-type and PARP knockout mouse lung endothelial cells (MLEC), and the PARP inhibitor, 3-aminobenzamide (3AB). Activation of beta1 integrins by antibody clustering enhanced the sensitivity of wild-type nuclei to digestion with micrococcal nuclease and deoxyribonuclease I, indicating that chromatin structure was altered. 3AB blocked this effect. Knockout and 3AB-treated wild-type MLEC were hypersensitive to deoxyribonuclease I compared with wild-type cells, demonstrating that PARP regulates chromatin structure. Integrin clustering reduced the hypersensitivity of knockout cells, suggesting additional, PARP-independent mechanisms that inhibit nuclease interaction with chromatin. Bleomycin caused DNA breakage in wild-type and knockout MLEC. Breaks were eliminated after 60 min incubation of wild-type cells in drug-free medium, whereas 3AB or PARP knockout inhibited DNA repair. Integrin clustering protected wild-type cells from DNA breakage, and 3AB and PARP knockout inhibited this protection. Bleomycin caused large increases in PARP activity in wild-type but not knockout MLEC, and integrin clustering inhibited the activation of PARP. The results indicate that the antigenotoxic effects of integrin activation require PARP and that integrins alter chromatin structure by PARP-dependent and -independent mechanisms.
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PMID:Regulation of bleomycin-induced DNA breakage and chromatin structure in lung endothelial cells by integrins and poly(ADP-ribose) polymerase. 1112 26


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