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:3.1.21.1 (DNase)
7,655 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bovine pancreatic deoxyribonuclease requires divalent metal cations for hydrolysis of DNA. The effects of calcium and magnesium, alone and combined, on the rate and kinetics of the reaction were examined. Divalent metal salts of DNA were used as substrates. The ratio of either Ca-2+ or Mg-2+ to DNA-P in these salts was 1:2. The Mg-2+ salt of DNA was found to have sufficient Mg-2+ for optimal DNAase activity. Addition of MgCl-2 to a large excess of Mg-2+ over DNA-P had no effect on the rate. Km for the hydrolysis of Mg-2+-DNA was 1.76 mM. Km for the hydrolysis of Ca-2+-DNA was too low to measure by our methods of assay, indicating a high affinity of enzyme for substrate. The rate of hydrolysis of Ca-2+-DNA, however, is slow compared to that of Mg-2+-DNA. By mixing the Ca-2+ and Mg-2+ salts of DNA, a synergistic effect on the activity of DNAase was observed. On the basis of kinetic studies the synergistic effect is attributed to an increased affinity of DNAase for DNA (Km equals 0.34 mM for the mixed Ca-2+, Mg-2+ salt of DNA). A 2-fold increase in DNAase activity was observed when DNAase was incubated in CaCl-2 before assay. This 2-fold stimulation was not related to the synergistic effect. DNAase I is inactive against the sodium salt of DNA. In experiments with mixed Na+ and Mg-2+ salts of DNA, Na+-DNA was found to be a competitive inhibitor of the action of DNAase against Mg-2+-DNA.
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PMID:Some effects of calcium and magnesium ions on the activity of bovine pancreatic deoxyribonuclease A. 109 74

The 3'-termini of procaryotic and eucaryotic DNA fragments obtained by shearing, sonication and irradiation have been analyzed. Analysis of the 3'-ends of DNA fragments was done by 32-P-labeling with terminal transferase, hydrolysis of products by spleen DNAase and spleen exonuclease and separation of labeled 3'-terminal nucleotides on polyethyleneimine plates. In the case of sonication the deviation from DNA base composition of 3'-terminal nucleotides is very close to random for Escherichia coli and Haemophilius influenzae DNA, whereas for calf thymus, mouse and yeast mitochondrial DNAs a significant increase in dA and decrease in dC was observed. Shearing at high salt released random 3'-termini in E. coli DNA and 3'-termini with 4 to 6% deviation from base composition in calf thymus DNA. In the case of gamma-irradiation no real differences have been found between E. coli and calf thymus DNA and 3'-terminal nucleotide composition is very close to random. Mechanical breakage of eucaryotic DNA seems to release 3'-termini having a composition which differs slightly but significantly from the average base composition of the DNA.
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PMID:Analysis of the breaking sites in the physical degradation of DNA. 109 47

In rats treated with DOCA plus high salt or with high salt alone, hypertensive rats with renal vascular lesions showed an incomplete suppression of KRA. Cathepsin activity of rat kidney was higher under high salt loading than in the control. Beta-glucuronidase activity was greatest in rats with renal vascular lesions and smallest in rats fed on normal chow. RNase and DNase activities were greater in rats with renal vascular lesions than in rats without renal vascular lesions under high salt loading. 2) In rats of both sexes SHR showed greater KRA and cathepsin activities than WK rat under high salt loading. In female rats DNase, RNase and beta-GPase activities were greater in SHR than in WK rat under high salt loading. 3) KRA was higher in SHRSP aged 10 months than in SHRSR, though KRA of SHR was smaller than KRA of WK rat. Cathepsin activity was greater in SHRSP than in SHRSR. DNase and beta-NAGA activities were greater in SHR than in WK rat. 4) In 7 weeks of age SHRSR showed more PRC than SHRSP. At the age of 10 months SHRSP showed higher PRC than WK rat. The roles renin and lysosomal enzymes in hypertensive renal vascular lesions were discussed to some extent.
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PMID:Hypertensive vascular lesions and renin or lysosomal enzymes in rats. 115 86

Rapidly labeled polydispersed nuclear RNA is part of a ribonucleoprotein (RNP) network which in turn is tightly bound to the nuclear membrane. The membranous attachment, therefore, established a connection between chromatin and cytoplasm. The ultrastructure of the RNP network comprises fibrils and granules similar to those observed in intact nuclei. When bound to the nuclear membrane it has the composition of 63% protein, 14% RNA, 0.4% DNA, and 22.6% lipids. The proportion of lipids diminishes to 2.2% when nuclear membrane is not present. Chromatin, nucleoli, and ribosomes are minor contaminants since histones and ribosomal proteins are not detectable in polyacrylamide gel electrophoresis. Nuclear disruption at high pressure in a French pressure cell causes fragmentation of the RNP network into a series of polydispersed RNP particles. Fragmentation can be prevented by using mild pressure, or by disrupting nuclei with high salt buffer and digesting the dispersed chromatin with deoxyribonuclease. A RNP network, almost free of membrane, is also obtained if the nucleus is deprived of its envelope by treatment with Triton X-100. Since no polydispersed RNP particles are found following dissolution of the nuclear membrane, it is assumed that the particles are components of the RNP network whose fragmentation occurs as a consequence of two processes: (a) activation of nuclear nucleases and (b) shearing forces.
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PMID:Isolation of a nuclear ribonucleoprotein network that contains heterogeneous RNA and is bound to the nuclear envelope. 117 5

Under specific binding conditions RNA polymerase forms complexes at several sites of the replicative form DNA of bacteriophage fd. One of these complexes becomes stable to both high salt and low temperature after incubation with GTP. None of the complexes is stabilized by ATP. The stabilization by GTP results from the synthesis of an oligo(G) chain, which is bound in the complex. Size and pyrimidine fingerprints of the DNA segment protected by the enzyme against digestion with DNase are not changed upon initiation of oligo(G) synthesis. This result indicates that binding site and initiation site are identical parts of a promoter region.
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PMID:Stabilization of promoter complexes with a single ribonucleoside triphosphate. 117 37

A DNA polymerase from Ustilago maydis has been purified to apparent homogeneity. The native enzyme possesses a subunit structure consisting of 50000 and 55000-dalton monomers. The apparent sedimentation coefficient of the polymerase activity in the absence of salt is 8.4 S (Mr=180000-200000), that in its presence (0.6 M NaCl or 0.12 M KCl) being 6.3 S (Mr=80000-100000). Low concentrations of EDTA also converted the 8.4-S to a 6.3-S form, whereas magnesium ions catalysed the reverse association. The enzyme has an absolute requirement for both a DNA or RNA template and a DNA primer. For homopolymer templates the primer requirement was satisified by a short complementary oligodeoxynucleotide, but oligoribonucleotides were extremely inefficient primers. With the template-primer poly(dA) X (dT)12, the enzyme added an average of 50 dTMP nucleotides on to each primer molecule, whereas with poly(rA) X (dT)12, this figure was 300. The enzyme also possesses an associated deoxyribonuclease activity. No other DNA polymerase activity was detected in cell-free extracts of U. maydis.
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PMID:A DNA polymerase from Ustilago maydis. 1. Purification and properties of the polymerase activity. 124 75

The polymerase and deoxyribonuclease activities of the purified Ustilago maydis DNA polymerase coeluted from a hydroxyapatite column, cosedimented in sucrose gradients in both the absence and presence of salt, possessed similar thermolabilities and reaction requirements. These observations suggest that both activities are associated with the same enzyme and that the deoxyribonuclease activity is not a contaminant. The initial rate of degradation of native 3'-end-group-labelled DNA was similar to that of a heat-denatured substrate, but the final extent was greater for the former. The enzyme exhibits a high specificity for degradation of DNA in a 3' leads to 5' direction. The degradation of a DNA template was inhibited by the presence of the deoxyribonucleoside triphosphates necessary for simultaneous DNA synthesis, but not that of the newly synthesised DNA. About 50%, 29% and 13% of the purine, cytosine and thymine deoxyribonucleotide residues incorporated by the enzyme into DNA respectively, were subsequently excised when monitored by the resulting conversion of the triphosphate substrates to free monophosphate. The majority of the purine deoxyribonucleoside monophosphates appear after the synthetic phase of the reaction has ceased. In many respects, therefore, the deoxyribonuclease activity of the U. maydis DNA polymerase is similar to the bacteriophage T4-induced enzyme.
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PMID:A DNA polymerase from Ustilago maydis. 2. Properties of the associated deoxyribonuclease activity. 124 76

DNA in spores of Bacillus and Clostridium species is associated with small, acid-soluble proteins (SASP) of the alpha/beta type; the presence of these proteins is a major factor in causing spore resistance to UV light, alpha/beta-type SASP did not bind to single-stranded DNA, single- or double-stranded RNA, or DNA-RNA hybrids in vitro. However, these proteins bound a variety of double-stranded DNAs and conferred protection against DNase cleavage. The binding of alpha/beta-type SASP to DNA saturated at a protein/DNA ratio (wt/wt) of 4:1 to 5:1, which is approximately 1 SASP per 4 bp. alpha/beta-type SASP-DNA interaction did not require divalent cations, was independent of pH between 6 and 8, and, for some SASP-DNA pairs, was relatively insensitive to salt up to 0.3 M. The relative affinity of alpha/beta-type SASP for different DNAs was poly(dG).poly(dC) greater than poly(dG-dC).poly(dG-dC) greater than plasmid pUC19 greater than poly(dA-dT).poly(dA-dT), with poly(dA).poly(dT) giving no detectable binding. This order in alpha/beta-type SASP-DNA affinities parallels the facility with which the DNAs adopt an A-like conformation, the conformation in alpha/beta-type SASP-DNA complexes. An oligo(dG).oligo(dC) of 12 bp was bound by alpha/beta-type SASP. While a 26-bp oligo(dG).oligo(dC) bound more tightly than the 12-mer, there was no significant increase in affinity for alpha/beta-type SASP with further increase in size of oligo(dG).oligo(dC). In contrast, binding of alpha/beta-type SASP to oligo(dA-dT).oligo(dA-dT) was minimal up to at least a 70-mer, and binding to poly(dA-dT).poly(dA-dT) was very cooperative. In addition to blocking DNase digestion, binding of alpha/beta-type SASP to DNA blocked (i) cleavage of the DNA backbone by hydroxyl radicals and orthophenanthroline-Cu2+, (ii) DNA cleavage by restriction enzymes, in particular those with specificity for GC-rich sequences; and (iii) in vitro transcription of some but not all genes. However, methylation of dG residues by dimethyl sulfate was not affected by alpha/beta-type SASP binding.
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PMID:Interaction between DNA and alpha/beta-type small, acid-soluble spore proteins: a new class of DNA-binding protein. 131 1

We have investigated the ability of dehydroepiandrosterone (DHEA) to alter the production of interleukin-2 (IL-2) and to bind to a specific binding complex in antiCD3 epsilon activated T cells. Binding activity correlated with the presence of a specific DHEA binding complex in the cytosol and nuclei of DHEA-responsive T-cell hybridomas, as well as in CD4+ and CD8+ cells isolated from peripheral lymph nodes of normal mice. Scatchard analysis determined that intact lymphocytes and cytosolic fractions contained high affinity binding for [3H]DHEA (approx. 2.6 nM) with 1000-7000 binding sites existing per cell. Five of the T-cell hybridomas tested both responded to DHEA treatment with increased production of IL-2 and also contained specific high affinity [3H]DHEA binding. Four additional T-cell hybridomas were found to contain no specific [3H]DHEA binding and were also unresponsive to DHEA influences on IL-2 production. Sucrose density gradients demonstrated a 3-4s [3H]DHEA binding complex in high salt and a 7-8s binding complex in low salt. Specific binding was inhibited by preincubation of the cytosol fractions with either trypsin or chymotrypsin, or by heating to 60 degrees C for 1 h (less than 15% of control). [3H]DHEA binding was unaffected by preincubation of the cytosol fractions with ribonuclease, deoxyribonuclease, or phospholipase A. The DHEA-protein complexes bound to DNA-cellulose with the amount of binding being slightly increased by preincubation at 25 degrees C as compared to 4 degrees C. As expected, [3H]DHEA binding was inhibited by the addition of unlabeled DHEA, but was also modestly inhibited by dihydrotestosterone and cortisol. Binding of DHEA was unaffected by progesterone, dexamethasone, estradiol, androsterone, DHEAS, and beta-etiocholanolone at all concentrations tested. DHEA was incapable of inhibiting the binding of [3H]DHT to the androgen receptor or [3H]dexamethasone to the glucocorticoid receptor. Collectively, these findings suggest that murine T cells contain a specific DHEA receptor. We believe that DHEA is a steroid hormone that is directly involved in the regulation of IL-2 production by both normal and some T-cell hybridomas.
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PMID:The presence of a dehydroepiandrosterone-specific receptor binding complex in murine T cells. 135 1

Exposure of mammalian cells to a variety of agents leads to the activation of pre-existing proteins and the induction of specific genes. We have recently described the appearance of a specific DNA-binding protein in nuclei from cells exposed to ionizing radiation (Singh, S. P., and Lavin, M. F. (1990) Mol. Cell. Biol. 10, 5279-5285). This protein is present in the cytoplasm of unperturbed cells and is apparently translocated to the nucleus in response to radiation damage. We describe here the purification and characterization of this specific DNA-binding protein. Purification involved the use of affinity chromatography employing a multimeric form of the DNA-binding motif conjugated to cyanogen bromide-activated Sepharose. Three DNA-binding species were recognized by UV-cross-linking and South-Western analysis. The major species or that with the highest affinity was approximately 70 kDa in size. DNase-1 footprint analysis revealed a single binding site in the kappa immunoglobulin gene enhancer and in a putative control sequence upstream from the c-myc gene. At salt concentrations as high as 1 M, up to 40% of the DNA-binding activity was maintained and the Kd was calculated to be 1.205 x 10(-6) M-1. Binding activity was found to be modulated by phosphorylation. Removal of phosphate groups from the protein resulted in a major loss of binding activity. It is not clear at this stage whether the factor(s) described here plays a role in transcription control or a more general DNA-processing role in response to radiation damage.
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PMID:Purification and characterization of a DNA-binding protein activated by ionizing radiation. 158 18


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