Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.22.1 (DNase II)
 429 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

The composition of rat testis chromatin proteins in fractions produced by limited DNase II digestion followed by differential precipitation with MgCl2 has been studied. Over 50% of the acid-soluble proteins in the soluble chromatin fraction appeared to be quite similar to proteins which are associated with ribonucleoprotein (RNP) particles in HeLa cells. Although the ratios of the testis RNP protein components differed from those of HeLa RNP particles, the three major polypeptides were most similar to the HeLa components designated A2, B2, and C1. The soluble chromatin fraction was also enriched in the high mobility group proteins HMG1 and HMG2.
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PMID:Release of ribonucleoprotein during digestion of rat testis chromatin with deoxyribonuclease II (3.1.4.6). 647 94

The positions and relative frequencies of the primary cleavages made by micrococcal nuclease on the DNA of nucleosome core particles have been found by fractionating the double-stranded products of digestion and examining their single-stranded compositions. This approach overcomes the problems caused by secondary events such as the exonucleolytic and pseudo-double-stranded actions of the nuclease and, combined with the use of high resolution gel electrophoresis, enables the cutting site positions to be determined with a higher precision than has been achieved hitherto. The micrococcal nuclease primary cleavage sites lie close (on average, within 0.5 nucleotide) to those previously determined by Lutter (1981) for the nucleases DNase I and DNase II. These similarities show that the accessible regions are the same for all three nucleases, the cleavage sites being dictated by the structure of the nucleosome core. The differences in the final products of the digestion are explained in terms of secondary cleavage events of micrococcal nuclease. While the strongly protected regions of the nucleosome core DNA are common to all three nucleases, there are differences in the relative degrees of cutting at the more exposed sites characteristic of the particular enzyme. In particular, micrococcal nuclease shows a marked polarity in the 3'-5' direction in the cutting rates as plotted along a single strand of the nucleosomal DNA. This is explained in terms of the three-dimensional structure of the nucleosome where, in any accessible region of the double helix, the innermost strand is shielded by the outermost strand on the one side and the histone core on the other. The final part of the paper is concerned with the preference of micrococcal nuclease to cleave at (A,T) sequences in chromatin.
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PMID:Location of the primary sites of micrococcal nuclease cleavage on the nucleosome core. 663 65

The investigations reported in this paper were designed to analyze the patterns of DNA-purine methylation in hepatic chromatin following in vivo exposure to the carcinogenic alkylating agents dimethylnitrosamine (DMN) or methylnitrosourea (MNU). Male Sprague-Dawley rats were exposed to [14C]DMN (8 mumoles, 1.0 microCi per mumole per 100 g) or [3H]MNU (15 mumoles, 10 microCi per mumole per 100 g) via gastric intubation. Hepatic chromatin was fractionated into portions having characteristics of template-active euchromatin (S2) and template-repressed heterochromatin (P2) by digestion with DNase II followed by MgCl2 precipitation. Specific DNA purines were identified at 24 hr post-intubation using an isocratic high pressure liquid chromatographic system. A qualitatively similar pattern of 7-methylguanine, O6-methylguanine, 1-methyladenine and 3-methyladenine alkylation was observed in DNA from total chromatin versus heterochromatin at 24 hr following exposure to either carcinogen. These assessments were made at times following carcinogen exposure which produced maximal quantitative differences in alkylation of euchromatin versus heterochromatin DNA. Similar patterns of DNA purine alkylation were observed in total chromatin and heterochromatin. These observations suggest that, once the reactive species is generated and access to chromatin DNA occurs, a similar pattern of DNA-purine alkylation is produced in different regions of the genome.
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PMID:DNA-purine methylation in hepatic chromatin following exposure to dimethylnitrosamine or methylnitrosourea. 670 74

Oral administration of lantana leaf powder to guinea pigs caused an increase in the hepatic postmitochondrial fraction:homogenate ratios of activities of lysosomal enzymes--acid phosphatase, cathepsin B and DNase II. Enzyme activities of glucokinase, aldolase, lactate dehydrogenase and glucose-6-phosphate dehydrogenase were elevated whereas activity of glutathione-S-transferase decreased. Alterations in the activities of lysosomal and cytosol enzymes appear to constitute an important biochemical lesion in the pathogenesis of guinea pig liver in lantana toxicity.
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PMID:Effect of lantana toxicity on lysosomal and cytosol enzymes in guinea pig liver. 683 12

Nuclease digestion patterns have been used to discriminate between possible orientations of nucleosomes in the higher order structure of chromatin. Computer simulations were done assuming 3 basically different orientations of nucleosomes which include all proposed models for the '30 nm fibre'. It is found that only alternating exposure of consecutive nucleosomes can explain the DNase I and DNase II digestion patterns.
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PMID:Nuclease digestion patterns as a criterion for nucleosome orientation in the higher order structure of chromatin. 686 26

Chromatin from myeloma cells RPC5 and ABPC22, and from spleen and liver cells of immunized rats and mice, and mice bearing tumours, was fractionated into three part: 0.35 M NaCl-soluble, 2 M NaCl-soluble and residual. The residual fraction from myeloma cells differed from that of immunized spleen cells, described previously as containing unique sequences (5), in that it has higher protein and DNA levels, lower DNase II sensitivity and lower template activity.
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PMID:Differences in salt solubility, DNase II sensitivity and template activity of chromatin from antibody synthesizing spleen cells and myeloma cells RPC 5 and ABPC 22. 689 Jun 25

The initial binding of N-fluorenylacetamide (2-FAA) and its N-hydroxy metabolite N-hydroxyl-N-2-fluorenylacetamide (N-OH-2-FAA) within the hepatic genome and the effect of ingestion of a 2-FAA-containing (0.05% wt/wt) diet on this binding were examined in the male noninbred Sprague-Dawley rat. Ingestion of 2-FAA for 2 weeks reduced the amount of newly bound carcinogen up to 80%. The extent of this decrease was significantly greater in rats treated with a single injection of 2-FAA when compared to one of N-OH-2-FAA. The distribution of carcinogen within the genome was measured after fractionation of chromatin by DNase II digestion followed by selective MgCl2 precipitation. Two hours after a single injection of N-OH-2-FAA, the amount of carcinogen bound per milligram DNA in the presumed template-active chromatin fraction was 16 times that bound to DNA of the presumed template-repressed chromatin fraction. The amount bound to DNA in the nuclease-resistant chromatin was equal to that observed in the DNA of the presumed template-active fraction. Most (85%) of the total bound carcinogen was located on less than 25% of the total DNA. Evaluation of the amount of carcinogen bound to the N-2 or C-8 positions of guanine demonstrated a significant inverse correlation between the amount bound to a DNA fragment and the percent of that binding occurring at the N-2 position. DNA of the repressed chromatin fraction had the largest N-2/C-8 ratio when compared to the ratios seen in both the expressed chromatin and the nuclease-resistant chromatin DNA. Pretreatment of rats with 2-FAA when compared to one of N-OH-2-FAA. The distribution of carcinogen within the genome was measured after fractionation of 66:667-672.
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PMID:Factors influencing the binding of N-2-fluorenylacetamide to specific regions of the hepatic genome in vivo in rats. 693 14

We report spectroscopic, hydrodynamic, and biochemical studies on the complex of ethidium bromide with 140 base pair nucleosomal core particles. Fluorescence titration indicates a greater intrinsic affinity of ethidium for nucleosomes than for DNA, and fluorescence depolarization measurements imply increased immobilization of ethidium bound to nucleosomes, but with more extensive dye-dye energy transfer compared to DNA-bound dye. Ethidium intercalated into DNA in nucleosomes has a limiting reduced linear dichroism of -0.45 at 320 nm and -0.25 at 530 nm. Both the energy transfer and dichroism results are consistent with clustering of the nucleosome-bound dye molecules. Electric dichroism measurements and ultracentrifugation studies reveal that structural distortion of the nucleosome accompanies ethidium binding, occurring in the range of r (ethidium residues per base pair) values from 0.02 to 0.06. The distortion transition is characterized by an increase in the negative limiting reduced dichroism from 0.29 to 0.45 at 265 nm, an increase in the field-induced viscosity-limited rotational orientation time from 0.8 to 3 mus, and a decrease in sedimentation coefficient from 10.5 to 8.2 S. The complex was modeled hydrodynamically as a cylinder of 335-A length and 67-A diameter, containing 1.4 superhelical turns of DNA. Dimethylsuberimidate cross-linked nucleosomes, or native nucleosomes in the presence of Mg2+, bind ethidium weakly and are not distorted. The periodicity of cutting sites produced by DNase II digestion of nucleosomes remains constant as ethidium is added, but the bandwidth increases. A thermodynamic model is proposed to interpret the binding isotherm, based on enhancement of drug binding affinity due to release of superhelical stress in the nucleosome-ethidium complex.
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PMID:Unfolding of nucleosomes by ethidium binding. 735 52

The degree of 5-methylcytosine formation in DNA sequences differing in reassociation rate and susceptibility to DNase II digestion has been investigated in human chronic myelogenic leukemia and acute leukemia leukocytes, human PHA-stimulated lymphocytes and murine L5178Y lymphoblasts cultured in various phases of growth. The results indicate that in all forms of cells studied by us the general pattern of intragenomic 5-methylcytosine distribution is similar, with two preferentially methylated regions: the sequences fast reassociating and rendered Mg++-soluble after DNase II digestion of nuclei. The most variable fraction as regards the level of methylation seemed to be DNA of Mg++-soluble fraction of DNase II digest, which in acute leukemia leukocytes, PHA-stimulated lymphocytes and exponentially growing L5178Y cells revealed about twice greater relative proportion of methylated cytosines than in leukocytes of chronic myelogenic leukemia and L5178Y cells maintained at saturation density.
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PMID:Intragenomic distribution of 5-methylcytosine in various forms of human and murine leukemic cells. 739 57


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