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)

The endonuclease DNase II preferentially attacks a limited and tissue-specific portion of chromosomal DNA. This material may be separated from the bulk of chromatin DNA by virtue of its solubility in 2 mM MgCl2. The Mg2+ soluble fraction forms a specific subset of DNA sequences and is enriched four to sevenfold in sequences coding for cytoplasmic poly(A)-containing RNA and globin messenger RNA (in globin-producing cells). The bulk (70--90%) of rapidly labelled RNA is found associated with the Mg2+-soluble fraction. Transcriptionally active, Mc2+-soluble chromatin is organized into repeating subunits of DNA (200 +/- 5 base pairs) and histone. Mc2+-soluble active subunits differ from the subunits or nucleosomes of non-transcribed regions in many respects: namely, chemical composition (non-histone protein and RNA), sedimentation properties, differential sensitivity to DNase I and the single-strand-specific nuclease S1, and optical melting behaviour. These results suggest that chromatin subunits adopt a new configuration during the process of transcription.
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PMID:Organization of transcribed regions of chromatin. 2 80

The action of micrococcal nuclease, DNase I and DNase II on mouse TLT hepatoma chromatin revealing the periodicity of its structure as visualized by denaturing and non-denaturing gel electrophoresis, was consistent with the action of these enzymes on other chromatins. Micrococcal nuclease showed a complex subnucleosome fragment pattern based on multiples of 10 base pairs with a prominant couplet at 140/160 base pairs and the absence of the 80 base pair fragment. This couplet of the core and minimal nucleosome fragments was conspicuously present in the mononucleosomes found in the 11S fractions of a glycerol gradient centrifugation. DNase I and II produced a fairly even distribution of a 10 base pair increasing series of fragments to about 180 base pairs, a pattern also repeated in the DNA of nucleosome glycerol-gradient fractions. In limited digestions by these nucleases multinucleosomic DNA fragments are pronounced. These fragment lengths are multiples of an estimated average repeat length of nucleosome DNA of 180 base pairs. The action of the endogenous Mg/Ca-stimulated endonuclease produced only limited cuts in the hepatoma chromatin resulting primarily in multi-nucleosomic DNA fragment lengths and only upon lengthy digestion limited subnucleosomic, 10-base-pair multiple fragments are produced. The putative euchromatin-enriched fractions (50-75S) of the glycerol gradient centrifugation of autodigested chromatin, similarly, contained primarily the multinucleosomic DNA fragment lengths. These results are consistent with our previous electron microscopic demonstration that autodigested chromatin as well as the putative euchromatin-enriched fractions were composed of multi-nucleosomic chromatin segments containing a full complement of histones.
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PMID:Periodicity and fragment size of DNA from mouse TLT hepatoma chromatin and chromatin fractions using endogenous and exogenous nucleases. 20 20

Rat-liver chromatin has bee fractionated into transcriptionally active and inactive regions [Gottesfeld et al. (1974) Proc. Nat. Acad. Sci. USA 71, 2193-2197] and the distribution of nuclease-resistant complexes in these fractions has been investigated. About half of the DNA of both fractions is resistant to attack by tne endonuclease DNase II. The nuclease-resistant structures of inactive chromatin are DNA-histone complexes (v-bodies) which sediment at 11-13 S. Template-active chromatin yields two peaks of nuclease-resistant nucleoprotein. These complexes sediment at 14 and 19 S, and contain DNA, RNA, histone, and nonhistone chromosomal proteins. Polyacrylamide gel electrophoresis reveals a complex pattern of chromatin proteins, suggesting that the complexes are heterogeneous in composition.
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PMID:Structure of transcriptionally active chromatin. 106 Jan 19

Oligodeoxynucleotides with different arrangements of methylphosphonate linkages were examined for nuclease sensitivity in vitro, stability in tissue culture, and ability to form RNase H-sensitive substrates with complementary RNA. After nuclease treatment, resistance was demonstrated by the ability to alter the electrophoretic mobility of a labeled complementary phosphodiester oligodeoxynucleotide. Both 5'- and 3'-exonuclease activities were retarded by methylphosphonate linkages. Methylphosphonate-containing oligodeoxynucleotides with 1-5 adjacent phosphodiester linkages were tested as substrates for the endonucleases DNase I and DNase II. The results indicated that a span of three or fewer contiguous internal phosphodiester linkages led to the greatest resistance to endonuclease. However, in serum-supplemented culture medium half-lives of these oligodeoxynucleotides were independent of the number of contiguous phosphodiester linkages. Methylphosphonate-containing oligodeoxynucleotides were hybridized to RNA runoff transcripts and tested as substrates for RNase H. The results indicated that a span of three internal phosphodiester linkages in the oligodeoxynucleotide was necessary and sufficient to direct cleavage of the RNA in the duplex.
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PMID:Number and distribution of methylphosphonate linkages in oligodeoxynucleotides affect exo- and endonuclease sensitivity and ability to form RNase H substrates. 247 96

The histones isolated from the siliceous sponge Geodia cydonium have been separated using two electrophoretic techniques. A comparison of their mobilities with those of calf thymus and rat liver show that some Geodia histone species (H3, H1 and H1(0) exhibit electrophoretic variance. The results show, that as in other eukaryotic systems the sponge chromatin contains the core histones (H2A, H2B, H3 and H4) and the linker histone (H1). ADP-ribosylation of Geodia histones and separation of the individual histones by electrophoresis resulted in four histones being radiolabeled. Digestion of Geodia chromatin with endogenous endonuclease is shown to result in the formation of nucleosome particles containing approximately 200 base pairs of DNA. A major product of endogenous endonuclease digestion is a relatively stable 110 base pair intermediate. Incubation of chromatin with DNase II and separation of the products under denaturing conditions reveals 20 bands migrating at 10 base intervals.
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PMID:Chromatin structure from the marine sponge Geodia cydonium. 631 75

Some characteristics of the postirradiation degradation of chromatin in the thymuses of mice were studied. The results proved that the main wave of chromatin degradation becomes evident between 2 and 4 h postirradiation, when considerable amounts of degradation products leach from nuclei during their isolation and are solubilized by lysis of nuclei. Similarly the degradation is manifested in the increase of salt-soluble chromatin fraction as well as of the fractions released from chromatin by various solutions (EDTA, heparin, deoxycholate, alkaline buffer). Later on, within 24 h after irradiation, only little changes in the relative amounts of the degradation products take place. Evidently only a certain thymocyte population is involved. Electrophoretic analyses of DNA fragments from various fractions in native and denatured state demonstrated that chromatin was degraded into nucleosomes and their oligomers by an endonuclease activity. The DNA bears, however, no signs of intranucleosomal regular single-strand fragmentation. This fact makes improbable the participation in this process of DNase I, DNase II and Ca,Mg-dependent endonuclease. No appreciable amount of smaller DNA fragments (products of further degradation of nucleosomes) were found even at 24 h postirradiation interval. Thus the nucleosomes and their oligomers must be considered as the only "long-lived" chromatin fragments in damaged lymphoid cells.
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PMID:On the degradation of chromatin to nucleosomes in the thymocytes of X-irradiated mice. 637 91

A hallmark of apoptosis is internucleosomal DNA fragmentation resulting from the activation of endonucleases. We characterized the endonuclease activity of human myeloid cell nuclei that cleaved their own nuclear chromatin to oligonucleosomal length fragments. Polymorphonuclear leukocytes (PMNs) of normal peripheral blood contained both Ca2+/Mg(2+)-dependent and DNase II-like acidic endonuclease activities in their nuclei. Immature myeloid cells of normal bone marrow at various stages of granulocytic maturation had similar nuclease activities. In contrast, a clear difference was shown in the circulating CD34+ cells, in that only Mg(2+)-dependent, Ca(2+)-independent endonuclease activity was detected. Consistent with these findings is the emergence of the Ca2+/Mg(2+)-dependent and acidic endonuclease concomitantly with the disappearance of the Mg(2+)-dependent endonuclease when CD34+ cells were induced to differentiate in vitro toward granulocytes. Leukemic cell lines of all lineages also had Mg(2+)-dependent nuclease activity. Our results suggest an association of the Mg(2+)-dependent endonuclease with hematopoietic progenitor cells and that the relative activities of the nuclear nuclease in human myeloid cells change substantially during granulocytic differentiation.
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PMID:Types of nuclear endonuclease activity capable of inducing internucleosomal DNA fragmentation are completely different between human CD34+ cells and their granulocytic descendants. 754 3

Activation of a triplet of nuclear proteins (NP42-50) was observed in human Jurkat T cell line following treatment with an antibody to CD95 (Fas/Apo-1), a cell surface molecule involved in apoptotic cell death. The nuclease activity, corresponding to a triplet of proteins observed at approximately 42, 45, and 50 kDa in size, was extractable, heat-stable, and detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis containing deoxyribonucleic acids (SDS-PAGE-DNA) assay. The NP42-50 activity requires the presence of Mg2+/Ca2+ and is insensitive to inactivation by heating at 80 degrees C for 5 min. Zinc effectively inhibited the enzymatic activity of NP42-50 on SDS-PAGE-DNA and also protected Jurkat cells from the CD95-mediated apoptosis in cell cultures. The nuclease activation, however, was not a unique pathway for the CD95-mediated cell death. The apoptosis induced by arabinofuranosyl cytosine, a chemotherapeutic agent, also activated the NP42-50 nuclease activity in Jurkat cells, suggesting that a similar cascade of subsequent events in apoptosis may occur in most instances although many different signals can initiate apoptotic cell death in various cell types. The nuclease identified by this study appears to be distinguishable from DNase I or DNase II by its molecular characteristics and its enzymatic requirements. The NP42-50, with respect to the nuclease activity closely associated with apoptotic cell death, may serve as a candidate for the endonuclease(s) involved in the cleavage of DNA into fragments during apoptosis.
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PMID:A triplet of nuclease proteins (NP42-50) is activated in human Jurkat cells undergoing apoptosis. 755 79

Apoptosis is a pathway of cell death characterized by internucleosomal digestion of genomic DNA. Such DNA digestion can be induced by both physiological stimuli and cytotoxic treatment with many anticancer agents. This digestion has generally been considered to be mediated by a Ca2+/Mg(2+)-dependent endonuclease that is activated by increases in intracellular Ca2+. However, we suggest that an alternate endonuclease, DNase II, may be a more likely candidate. In these studies, apoptosis was induced in human HL-60 cells by a 30-min incubation with the topoisomerase II inhibitor etoposide. DNA digestion characteristic of apoptosis began within 3 h of removal of etoposide. Morphological indication of apoptosis was observed concurrently. Only about 20% of the cells underwent apoptosis at this time; these appeared to be cells in S phase at the time of etoposide treatment. The remainder of the cells progressed to the G2 phase and arrested there for at least 48 h. Intracellular Ca2+ and pH were measured in individual cells by flow cytometry. No changes in intracellular Ca2+ were observed, but an acidification of up to 1 pH unit occurred in about 15% of the cells and correlated with the time course of appearance of DNA digestion. Cells were sorted on the basis of intracellular pH and only the acidic cells showed the morphology and DNA digestion characteristic of apoptosis. These results demonstrate the involvement of DNase II in apoptotic DNA digestion and suggest mechanisms of pH homeostasis as regulators of apoptosis.
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PMID:Etoposide-induced apoptosis in human HL-60 cells is associated with intracellular acidification. 838 92

Cell death occurs by apoptosis during programmed deletion of cells and following exposure to cytotoxic agents. Central to the mechanism of apoptosis is internucleosomal DNA digestion by an endogenous endonuclease which is thought to mediate cell death. An axiom of apoptosis is that the endonuclease involved is a Ca2+/Mg(2+)-dependent endonuclease. During purification of endonucleases from Chinese hamster ovary cells, we found little Ca2+/Mg(2+)-dependent endonuclease activity, but large amounts of an endonuclease active below pH 7. This acidic endonuclease was activated in intact cells by reducing intracellular pH values below 7 with a proton ionophore. This activity generated internucleosomal digestion of DNA characteristic of apoptosis. Nuclear extracts contained a cation-independent endonuclease with identical pH-dependent activity. We have compared the acidic endonuclease to bovine deoxyribonuclease II (DNase II) and have found them nearly identical by all tests, including sensitivity to various inhibitors, purification by the same chromatographic steps, and recognition by antibody raised against the bovine enzyme. Addition of either the acidic endonuclease or bovine DNase II to isolated nuclei induced internucleosomal DNA digestion up through pH 6.5. These data demonstrate that DNase II can mediate internucleosomal DNA digestion characteristic of apoptosis following intracellular acidification. Furthermore, these data question the premise that the Ca2+/Mg(2+)-dependent endonuclease is the only endonuclease involved in apoptosis.
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PMID:Identification of deoxyribonuclease II as an endonuclease involved in apoptosis. 842 78


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