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)

A DNA fragment carrying an immunoglobulin gene coding for both variable (V) and constant (C) regions of a mouse lambda light chain was enriched about 15-fold from a total endonuclease EcoRI digest of a plasmacytoma (HOPC 2020) DNA by preparative agarose gel electrophoresis. The DNA fraction was used for cloning of a lambda chain gene in the phage lambdagtWES vector. After screening [Benton, W. D. & Davis, R. W. (1977) Science 196, 180-182] of about 70,000 plaques, each arising from an independent transfection event, we isolated one clone (Ig 303) that contained both a Vlambda and a Clambda DNA sequence. Electron microscopy of R-loops formed between the cloned DNA and purified lambda chain mRNA (HOPC 2020) revealed that the Vlambda and Clambda DNA sequences are separated by a 1250-base DNA fragment.
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PMID:Variable and constant parts of the immunoglobulin light chain gene of a mouse myeloma cell are 1250 nontranslated bases apart. 41 23

The activity of damage-dependent endonuclease in mouse plasmacytoma cells (line MPC-11) has been studied using damaged phi X 174 RFI DNA as substrate. The DNA was treated with ultraviolet light, acid, or osmium tetroxide to introduce different types of lesions. Ultraviolet light-damaged DNA was cleaved at approx. 1.1 sites per 35 thymine-containing dimers by the extract, which indicates no specificity towards this type of lesion. The acid-treated DNA, which contains apurinic sites, was enzymatically broken in every alkalilabile site and this strongly suggests the presence of an apurinic-specific endonuclease activity in the nuclear extract. The activity which acts on ultraviolet-irradiated DNA and that which acts on acid-treated DNA have different specificities as shown by their salt requirements and the extent to which they are stimulated by magnesium. While the ultraviolet-endonuclease activity was very little affected by reducing the KCl concentration, the apurinic-specific activity was almost completely abolished. Osmium tetroxide renders the DNA an excellent substrate for endonucleolytic activity in the mouse cell extract. The response to KCl and MgCl2 of the osmium tetroxide-specific endonuclease activity is qualitatively similar to that of the endonuclease activity, which acts on ultraviolet-irradiated DNA. Treatment of DNA with osmium tetroxide is known to produce 5,6-dihydroxydihydrothymine which is a minor photoproduct in DNA after irradiation, suggesting that the ultraviolet-specific endonuclease activity acts upon this lesion.
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PMID:Endonuclease activities from a permanently established mouse cell line that act upon DNA damaged by ultraviolet light, acid and osmium tetroxide. 69 23

This report describes an unexpected difference in the efficiency of removal of UV-induced DNA damage in the c-myc locus in splenic B lymphoblasts from two inbred strains of mice. In cells from plasmacytoma-resistant DBA/2N mice, 35% of UV-induced damage in the regulatory and 5' flank of c-myc is removed by 12 h. However, in cells from plasmacytoma-susceptible BALB/cAn mice, damage is not removed from this region. In the protein-encoding region and 3' flank of c-myc as well as in two dihydrofolate reductase gene fragments, UV damage is repaired with similar efficiency in B lymphoblasts from both strains of mice. Furthermore, in the protein-encoding portion and 3' flank of c-myc, damage is selectively removed from only the transcribed strand. No repair is detected in the nontranscribed strand. In contrast, DNA repair in the 5' flank of c-myc is not strand specific; in DNA from DBA/2N cells, UV damage is rapidly removed from both the transcribed and nontranscribed strands. In BALB/cAn cells no repair was detected in either strand in the 5'flank, consistent with the results with double-stranded, nick-translated probes to this region of c-myc. In addition to the repair studies, we have detected post-UV-damage formation: in most of the genes studied, we find that additional T4 endonuclease-sensitive sites are formed in the DNA 2 h after irradiation. Our findings provide new insights into the details of gene-specific and strand-specific DNA repair and suggest that there may be close links between DNA repair and B-cell neoplastic development.
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PMID:DNA repair in the c-myc proto-oncogene locus: possible involvement in susceptibility or resistance to plasmacytoma induction in BALB/c mice. 171 24

Mitochondrial forms of uracil DNA glycosylase and UV endonuclease have been purified and characterized from the mouse plasmacytoma cell line, MPC-11. As in other cell types, the mitochondrial uracil DNA glycosylase has properties very similar to those of the nuclear enzyme, although in this case the mitochondrial activity was also distinguishable by extreme sensitivity to dilution. Three mitochondrial UV endonuclease activities are also similar to nuclear enzymes; however, the relative amounts of these enzyme activities in the mitochondria is significantly different from that in the nucleus. In particular, mitochondria contain a much higher proportion of an activity analogous to UV endonuclease III. Nuclear UV endonuclease III activity is absent from XP group D fibroblasts and XP group D lymphoblasts have reduced, but detectable levels of the mitochondrial form of this enzyme. This residual activity differs in its properties from the normal mitochondrial form of UV endonuclease III, however. The presence of these enzyme activities which function in base excision repair suggests that such DNA repair occurs in mitochondria. Alternatively, these enzymes might act to mark damaged mitochondrial genomes for subsequent degradation.
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PMID:Mammalian mitochondrial endonuclease activities specific for ultraviolet-irradiated DNA. 231 45

We have developed a strategy by which the nature of phosphodiester bond breaks produced by various DNA-repair endonucleases and also other nucleases, can be characterized. A purified apurinic/apyrimidinic (AP) specific endonuclease from a permanently established mouse plasmacytoma cell-line (MPC-11) has been examined with respect to the exact incision site generated at the baseless site. By the aid of enzymatic treatment with calf intestinal phosphatase, the 3'-phosphatase activity of T4-polynucleotide kinase, chemical modification with piperidine in addition to the Maxam-Gilbert sequencing procedure, followed by separation on a DNA-sequencing gel, the nature of the cleaved phosphodiester bond, both 3' and 5' to the cleavage site, has been established. The AP-specific endonuclease investigated was classified as a class II AP-endonuclease according to the four possible classes of AP-endonuclease with respect to the termini produced. By use of this technique each single damaged and cleaved site can be investigated separately.
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PMID:Analysis of cleavage products of DNA repair enzymes and other nucleases. Characterization of an apurinic/apyrimidinic specific endonuclease from mouse plasmacytoma cells. 245 3

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

Three endonucleases from murine plasmacytoma cells that specifically nick DNA which was heavily irradiated with ultraviolet (UV) light were resolved by Sephacryl S-200 column chromatography. Two of these, UV endonucleases I and II, were purified extensively. UV endonuclease I appears to be a monomeric protein with a molecular mass of 43 kDa; UV endonuclease II has an S value of 2.9 S, with a corresponding molecular mass estimated at 28 kDa. Both enzymes act as a class I AP endonuclease, cleaving phosphodiester bonds via a beta-elimination mechanism, so as to form an unsaturated deoxyribose at the 3' terminus. Both have thymine glycol DNA glycosylase activity and their substrate specificities generally appear to be overlapping but not identical. UV endonuclease I acts on both supercoiled and relaxed DNAs, whereas II acts only on supercoiled DNA. Both enzymes are active in EDTA, but have different optima for salt, pH, and Triton X-100. Each enzyme is also present in cultured diploid human fibroblasts.
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PMID:Purification and characterization of UV endonucleases I and II from murine plasmacytoma cells. 246 92

An apurinic/apyrimidinic (AP) specific endonuclease from mouse plasmacytoma cells (line MPC-11), was observed to cleave apurinic sites in oligonucleotides 9, 11, 12, 39 and 40 nucleotides in length. However, the enzyme failed to cleave AP-sites in two oligonucleotides 7 nucleotides in length. The maximum rates of digestion observed on these short single-stranded DNA (ssDNA) fragments were approximately 1/30 of the rates observed on double-stranded DNA (dsDNA). In studies using the Maxam-Gilbert DNA sequencing analysis, apurinic sites in purine-rich regions were preferentially cleaved in dsDNA but not in ssDNA, indicating that the enzyme has a sequence preference on dsDNA. These results suggest that some sites on DNA might be more efficiently repaired than others.
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PMID:Action of a mammalian AP-endonuclease on DNAs of defined sequences. 246 39

The properties of a DNA-repair endonuclease isolated from mouse plasmacytoma cells have been further studied. It acted on ultraviolet-light-irradiated supercoiled DNA, and the requirement for a supercoiled substrate was absolute at ultraviolet light doses below 1.5 kJ m-2. At higher doses relaxed DNA could also serve as a substrate, but the activity on this DNA was due mostly to hydrolysis of ultraviolet-light-induced apurinic/apyrimidinic (AP) sites by the AP-endonuclease activity associated with the enzyme. The latter enzyme activity did not require a supercoiled form of the DNA. The enzyme also introduced nicks in unirradiated d(A-T)n. The nicked ultraviolet-light-irradiated DNA served as a substrate for DNA polymerase I, showing that the nicks contained free 3'-OH ends. Treatment of the nicked ultraviolet-light-irradiated DNA with bacterial alkaline phosphatase followed by T4 polynucleotide kinase, resulted in the phosphorylation of the 5' ends of the nicks, indicating that the nicks possessed a 5'-phosphate group; 5'- and 3'-mononucleotide analyses of the labelled DNA suggested that the enzyme introduced breaks primarily between G and T residues. The enzyme did not act on any specific region on the supercoiled DNA molecule; it produced random nicks in ultraviolet-light-modified phi X 174 replicative form I DNA. Antibodies raised against ultraviolet-light-irradiated DNA inhibited the activity. DNA adducts such as N-acetoxy-2-acetylaminofluorene and psoralen were not recognized by the enzyme. It is suggested that the enzyme has a specificity directed toward helical distortions.
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PMID:Properties of a DNA repair endonuclease from mouse plasmacytoma cells. 258 76

An endonuclease specific for apurinic sites in double stranded DNA has been purified 373-fold from the nuclei of mouse plasmacytoma cells (line MPC-11). The enzyme is free of any detectable amounts of aspecific nucleases. The enzyme does not act on methylated or OsO4-treated DNA. However, high doses of UV-light and gamma-rays render the DNA slightly susceptible to endonucleolytic attack, which is believed to be due to depurination of depyrimidination caused by the treatment. The molecular weight of the enzyme is determined to be 28,000 and its apparent Km of the purified enzyme is calculated to be 2.7 nM apurinic sites. The activity is not absolutely dependent upon the presence of Mg2+ in the assay mixture although metal chelating agents such as sodium citrate and EDTA abolish the activity completely. The nuclease was stimulated by moderate concentrations of potassium chloride optimizing at 50 mM, and higher concentrations inhibiting the activity. The pH optimun for the reaction was 9.5.
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PMID:Purification and characterization of an endonuclease specific for apurinic sites in DNA from a permanently established mouse plasmacytoma cell line. 625 41


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