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

---

Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An activity that binds preferentially to depurinated DNA and inserts purines into those sites was partially purified from Drosophila melanogaster embryos. The protein has a sedimentation coefficient of 4.9 S and is devoid of AP (apurinic/apyrimidinic) endonuclease activity. Upon incorporation of purines into apurinic DNA, the number of alkali-labile sites decreases, thus establishing the conversion of depurinated sites into normal nucleotides. The activity requires K+, and is totally inhibited by caffeine or EDTA. Guanine is specifically incorporated into partially depurinated poly(dG-dC) and adenine is specifically incorporated into poly(dA-dT), thus demonstrating the apparent template specificity of the enzyme.
...
PMID:Characterization of a depurinated-DNA purine-base-insertion activity from Drosophila. 241 89

We have purified 3-methyladenine DNA glycosylase I from Escherichia coli to apparent physical homogeneity. The enzyme preparation produced a single band of Mr 22,500 upon sodium dodecyl sulphate/polyacrylamide gel electrophoresis in good agreement with the molecular weight deduced from the nucleotide sequence of the tag gene (Steinum, A.-L. and Seeberg, E. (1986) Nucl. Acids Res. 14, 3763-3772). HPLC confirmed that the only detectable alkylation product released from (3H)dimethyl sulphate treated DNA was 3-methyladenine. The DNA glycosylase activity showed a broad pH optimum between 6 and 8.5, and no activity below pH 5 and above pH 10. MgSO4, CaCl2 and MnCl2 stimulated enzyme activity, whereas ZnSO4 and FeCl3 inhibited the enzyme at 2 mM concentration. The enzyme was stimulated by caffeine, adenine and 3-methylguanine, and inhibited by p-hydroxymercuribenzoate, N-ethylmaleimide and 3-methyladenine. The enzyme showed no detectable endonuclease activity on native, depurinated or alkylated plasmid DNA. However, apurinic sites were introduced in alkylated DNA as judged from the strand breaks formed by mixtures of the tag enzyme and the bacteriophage T4 denV enzyme which has apurinic/apyrimidinic endonuclease activity. It was calculated that wild-type E. coli contains approximately 200 molecules per cell of 3-methyladenine DNA glycosylase I.
...
PMID:Purification and characterization of 3-methyladenine DNA glycosylase I from Escherichia coli. 355 Jul 3

An endonuclease that incises lightly ultraviolet-irradiated supercoiled plasmid DNA was identified in cell-free extracts of Deinococcus radiodurans R1 wild-type. The endonuclease was absent from strains mutant in the uvsC, uvsD or uvsE genes identifying it as 'UV endonuclease beta' responsible for the initial incision step of one excision-repair pathway for the removal of pyrimidine dimers from D. radiodurans DNA in vivo. The enzyme was purified free from contaminating nuclease activities and was partially characterised. The enzyme has an apparent molecular weight of 36 000, is ATP-independent, caffeine-insensitive and is inactivated by N-ethylmaleimide. It also has a novel requirement for manganese ions distinguishing it from all other known DNA-repair enzymes.
...
PMID:Identification and initial characterisation of a pyrimidine dimer UV endonuclease (UV endonuclease beta) from Deinococcus radiodurans; a DNA-repair enzyme that requires manganese ions. 383 72

Extracts of DNA polymerase I defective Escherichia coli infected with phage T4 contain an exonuclease activity that removes thymine dimers from UV-irradiated DNA previously nicked with T4 UV endonuclease. This activity is not expressed if cells are infected in the presence of chloramphenicol. The enzyme has a requirement for divalent cation and is not affected by caffeine, but excision is inhibited in the presence of proflavine. The enzyme is present in all phage T4 mutants thus far examined, including 25 UV-sensitive mutants isolated during the course of the experiments, all of which are defective in the v gene. A similar activity can be detected in cells infected with phages T2, T3, and T6, but not in cells infected with phage T7.
...
PMID:Excision of thymine dimers in vitro by extracts of bacteriophage-infected Escherichia coli. 459 98

We have studied repair of ultraviolet light (UV)-induced damage in a strain of Bloom's syndrome cells which we have shown to be defective in host cell reactivation of UV-irradiated herpes simplex virus. Excision repair was monitored by following loss of sensitivity of DNA in permeabilized cells to digestion by the Micrococcus luteus UV endonuclease preparation. The Bloom's syndrome fibroblasts apparently removed endonuclease-sensitive sites from the DNA slightly less efficiently than did normal strains. After 24 hr, 38% of the sites remained in the Bloom's syndrome cells in comparison with 16% in normal fibroblasts. DNA newly synthesized in UV-irradiated Bloom's syndrome cells sedimented less far into alkaline sucrose gradients than did DNA from similarly treated normal cells. In other respects, including the effect of caffeine exposure, DNA synthesis in Bloom's syndrome cells was indistinguishable from that in normal cells. We were therefore able to detect only minor defects in the repair of UV-induced damage in Bloom's syndrome fibroblasts. This is consistent with the normal survival exhibited by these cells. The defect in excision repair may, however, be sufficient to allow the cellular repair capacity to become saturated at high infecting multiplicities of UV-irradiated herpes simplex virus.
...
PMID:Excision of ultraviolet damage and the effect of irradiation on DNA synthesis in a strain of Bloom's syndrome fibroblasts. 625 83

An endodeoxyribonuclease from HeLa cells acting on apurinic/apyrimidinic (AP) sites has been purified to apparent homogeneity as judged by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The presence of Triton X-100 was necessary throughout the purification for stabilization and stimulation of activity. The endonuclease has an apparent native molecular weight of 32,000 determined by molecular sieving and an apparent subunit molecular weight of 41,000 as judged by its electrophoretic mobility in SDS-polyacrylamide gels. The activity has an absolute requirement for Mg2+ or Mn2+ and a broad pH optimum between 6.7 and 9.0 with maximal activity near pH 7.5. The enzyme has no detectable exonuclease activity, nor any endonuclease activity on untreated duplex or single-stranded DNA. It is inhibited by adenine, hypoxanthine, adenosine, AMP, ADP-ribose, and NAD+, but it is unaffected by caffeine, the pyrimidine bases, ADP, ATP, or NADH. The use of a variety of damaged DNA substrates provided no indication that the enzyme acts on other than AP sites. The enzyme appears to cleave AP DNA so as to leave deoxyribose-5-phosphate at the 5' terminus and a 3'-OH at the 3' terminus; it also removes deoxyribose-5-phosphate from AP DNA which has deoxyribose at the 3' terminus. Specific antibody has been produced in rabbits which interacts only with a 41,000-dalton protein present in the purified enzyme (presumably the enzyme itself), as well as with partially purified AP endonuclease fractions from human placenta and fibroblasts.
...
PMID:Purification and characterization of an apurinic/apyrimidinic endonuclease from HeLa cells. 625 65

CHO cells were treated in G1 stage of the cell cycle with chromosome-breaking agents that act in an S-dependent manner. The cells were challenged in G2 stage, before fixation, with various inhibitors of DNA synthesis or repair. Short-wave UV, mitomycin C, decarbomyl mitomycin and 4-nitroquinoline oxide (4NQO) were used as chromosome-breaking agents. The inhibitors of DNA repair or synthesis used were hydroxyurea, aphidicolin and caffeine. Permeabilization of cells followed by a treatment with Neurospora endonuclease (a treatment to convert DNA single-strand breaks into double-strand breaks) did not have any influence on the frequencies of chromatid aberrations induced by the chemicals used, whereas with the inhibitors the extent of potentiation varied depending on the mutagen and the inhibitor used.
...
PMID:Formation of chromatid-type aberrations in G2 stage of the cell cycle. 687 59

A DNA-binding protein was partially purified from extracts of HeLa cells by high-speed centrifugation and chromatography on DEAE-cellulose, phosphocellulose and ultraviolet light-irradiated DNA-cellulose columns. It eluted from the phosphocellulose column with 0.375 M potassium phosphate and from the ultraviolet light-irradiated DNA-cellulose column between 0.5 M and 1 M NaCl. The protein binds preferentially to supercoiled PM2 DNA treated with ultraviolet light or N-acetoxy-N-acetyl-2-aminofluorene, as compared to native supercoiled PM2 DNA. The binding is non-cooperative. Nicked or linear forms of PM2 DNA (damaged or untreated) are not efficient substrates, indicating a requirement of DNA supercoiling for DNA binding. The sedimentation coefficient of the protein estimated by glycerol gradient centrifugation is 2.0-2.5 S, corresponding to a molecular weight of about 20000-25000 if the protein is spherical. The binding to DNA irradiated with ultraviolet light or treated with acetoxyacetylaminofluorene is optimal at around 100-200 mM NaCl and is relatively independent of temperature and pH. MgCl2 and MnCl2 at concentrations between 1 and 5 mM do not markedly affect the binding, but it is inhibited by sucrose, ATP and caffeine. The biological significance of the DNA-binding protein remains to be determined. It does not possess significant glycosylase, endonuclease or exonuclease activities. The dissociation equilibrium constant for the binding reaction of the protein to the ultraviolet light or acetoxyacetylaminofluorene-induced binding sites on DNA is estimated to be 4.10(-11) M. There are at least 1.10(5) DNA-binding protein molecules/HeLa cell.
...
PMID:DNA-binding protein from HeLa cells that binds preferentially to supercoiled DNA damaged by ultraviolet light or N-acetoxy-N-acetyl-2-aminofluorene. 689 60

Apoptosis has been measured in cells of the human TK6 lymphoblastoid cell line by recording the release of endonuclease-digested DNA from affected cells using flow cytometry. In asynchronously dividing cells, DNA degradation characteristic of apoptosis was first seen 12 h after irradiation as a defined DNA fluorescent peak of sub-G1-phase content, reaching a maximum of 30-50% of the population by 24-72 h. Treating cells with 2 mM caffeine either before or up to 3 h after irradiation eliminated the degradation of DNA entirely. In addition, the percentage of cells in which apoptosis could be detected microscopically decreased from 62.4 +/- 0.95% to 16.7 +/- 1.5% 72 h after caffeine treatment. Delaying caffeine treatment for 12 h after irradiation reduced DNA degradation by approximately 50% compared to cells receiving radiation alone. DNA degradation induced by serum deprivation was unaffected by caffeine treatment. These data support the contention that irradiation of TK6 cells produces a long-lived cellular signal which triggers apoptosis. Apoptosis produced by serum deprivation does not operate through the same pathway.
...
PMID:Effect of caffeine on radiation-induced apoptosis in TK6 cells. 783 55

Despite a wide interindividual variation of cytochrome P-450 1A2 (CYP1A2) activity, genetic polymorphism of CYP1A2 has not been reported. By amplification of exons of CYP1A2 by polymerase chain reaction in eight Chinese subjects, the polymerase chain reaction products were directly sequenced. One subject showed heterozygous C2866-->G (Phe21-->Leu) polymorphism. DNA from 157 Chinese subjects (104 polychlorinated biphenyl-exposed subjects and 53 control subjects) was screened for polymorphism by single-strand conformation polymorphism method and MboII endonuclease digestion. Only 1 of 157 samples showed another heterozygous C2866-->G mutation. The subject was previously exposed to polychlorinated biphenyl and showed a value of 3.5% in the caffeine breath test. The value is not significantly higher than the mean value of polychlorinated biphenyl-exposed subjects (3.12 +/- 0.29%, mean +/- S.E.M.). The incidence of the point mutation in these Chinese subjects is less than 1%. The prevalence of the F21L mutation in other ethnic groups and its effect on the metabolic activity of CYP1A2 remain to be further evaluated.
...
PMID:Detection of a novel cytochrome P-450 1A2 polymorphism (F21L) in Chinese. 988 16


<< Previous 1 2 3 Next >>

---