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)

gamma-Endonuclease Y, an enzyme that hydrolyses phosphodiester bonds at alkalistable lesions in gamma-irradiated (N2, tris buffer) DNA, has been partially purified from Micrococcus luteus. The enzyme has a molecular weight of about 19 000, induces single-strand breaks with 3'OH-5'PO4 termini and contains endonuclease activity towards DNA treated with 7-bromomethylbenz(a)anthracene. gamma-Endonuclease Y induces breaks in OsO4-treated poly(dA-dT) and apparently is specific towards gamma-ray-induced base lesions of the t' type. The complete excision repair of gamma-endonuclease Y substrate sites has been performed in vitro by gamma-endonuclease Y, DNA polymerase and ligase.
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PMID:Excision repair of gamma-ray-induced alkali-stable DNA lesions with the help of gamma-endonuclease from Micrococcus luteus. 31 80

Deoxyribonucleic acid (DNA) from bacteriophage T7 has been used to monitor the capacity of gently lysed extracts of Escherichia coli to perform repair resynthesis after ultraviolet (UV) irradiation. Purified DNA damaged by up to 100 J of UV radiation per m2 was treated with an endonuclease from Micrococcus luteus that introduces single-strand breaks in irradiated DNA. This DNA was then used as a substrate to study repair resynthesis by extracts of E. coli. It was found that incubation with the extract and exogenous nucleoside triphosphates under suitable assay conditions resulted in removal of all pyrimidine dimers and restoration of the substrate DNA to its original molecular weight. Repair resynthesis, detected as nonconservative, UV-stimulated DNA synthesis, was directly proportional tothe number of pyrimidine dimers introduced by radiation. The repair mode described here appears to require DNA polymerase I since it does no occur at the restrictive temperature in polA12 mutants, which contain a thermolabile polymerase. The addition of purified DNA polymerase I to extracts made from a polA mutant restores the ability to complete repair at the restrictive temperature.
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PMID:Deoxyribonucleic acid repair in vitro by extracts of Escherichia coli. 32 26

cDNA, synthesized from rabbit globin mRNA, was used in a self-priming reaction, with avian myeloblastosis virus DNA polymerase, for the synthesis of double-stranded DNA. Globin DNA ranging from about 400 to 650 base pairs was elongated with dG tails using deoxypolynucleotide transferase and was annealed to linear Escherichia coli plasmic pCR1, elongated with dC tails. Preparation of the plasmid DNA involved an enzymatic reconstruction of one EcoRI-specific site on each side of the molecule. After transformation of E. coli cells to kanamycin resistance with the hybrid molecules, bacterial clones harboring recombinant plasmids were studied for the presence of globin-specific DNA. Plasmids containing either alpha or beta rabbit globin gene sequences were obtained. There was a 4-fold excess of recombinant plasmids containing beta-globin sequences over those with alpha-globin DNA. The longest beta-globin sequences found in plasmids were about 550 to 600 pairs long, and correspond therefore to the entire beta-globin structural gene and to some of the untranslated regions. The alpha-globin sequences were 400 to 450 base pairs long. Treatment of clone pCR1betarG 19 with EcoRI endonuclease released two DNA fragments (410 and 210 base pairs) resulting from cleavage at two reconstructed external EcoRI sites and at one internal EcoRI site within the rabbit globin gene. The same treatment of pCR1alpharG 11 released one fragment. In most other recombinant plasmids studied however, no fragment was released by EcoRI digestion.
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PMID:Cloning and amplification of rabbit alpha- and beta-globin gene sequences into Escherichia coli plasmids. 32 53

Py pyrimidine dimers Py correndonucleases I and II from Micrococcus luteus act exclusively on thymine-thymine, cytosine-cytosine, and thymine-cytosine cyclobutyl dimers in DNA, catalyzing incision 5' to the damage and generating 3'-hydroxyl and 5'-phosphoryl termini. Both enzymes initiate excision of pyrimidine dimers in vitro by correxonucleases and DNA polymerase I. The respective incised DNAs, however, differ in their ability to act as substrate for phage T4 polynucleotide ligase or bacterial alkaline phosphatase, suggesting that each endonuclease is specific for a conformationally unique site. The possibility that their respective action generates termini which represent different degrees of single strandedness is suggested by the unequal protection by Escherichia coli binding protein from the hydrolytic action of exonuclease VII.
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PMID:Micrococcus luteus correndonucleases. II. Mechanism of action of two endonucleases specific for DNA containing pyrimidine dimers. 33 May 26

When DNA from bacteriophage T7 is irradiated with UV light, the efficiency with which this DNA can be packaged in vitro to form viable phage particles is reduced. A comparison between irradiated DNA packaged in vitro and irradiated intact phage particles shows almost identical survival as a function of UV dose when Escherichia coli wild type or polA or uvrA mutants are used as the host. Although uvrA mutants perform less host cell reactivation, the polA strains are identical with wild type in their ability to support the growth of irradiated T7 phage or irradiated T7 DNA packaged in vitro into complete phage. An examination of in vitro repair performed by extracts of T7-infected E.coli suggests that T7 DNA polymerase may substitute for E. coli DNA polymerase I in the resynthesis step of excision repair. Also tested was the ability of a similar in vitro repair system that used extracts from uninfected cells to restore biological activity of irradiated DNA. When T7 DNA damaged by UV irradiation was treated with an endonuclease from Micrococcus luteus that is specific for pyrimidine dimers and then was incubated with an extract of uninfected E. coli capable of removing pyrimidine dimers and restoring the DNA of its original (whole genome size) molecular weight, this DNA showed a higher packaging efficiency than untreated DNA, thus demonstrating that the in vitro repair system partially restored the biological activity of UV-damaged DNA.
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PMID:In vitro packaging of UV radiation-damaged DNA from bacteriophage T7. 33 Aug 77

A plaque-forming lambdapolA phage was isolated from a population of transducing phage made in vitro from Escherichia coli DNA and a phage vector digested with restriction endonuclease HindIII. Amber mutations, in genes whose products are necessary for late protein synthesis (Q) and cell lysis (S), were crossed into the lambdapolA phage. Infection of either polA+ or polA- bacteria with this phage, under conditions permitting DNA replication but preventing phage production and lysis, elevated the levels of DNA polymerase I to between 75- and 100-fold that detected in a wild-type strain. The kinetics of enzyme production suggest that the polA gene is transcribed from its own promoter rather than from any of the well-characterized phage promoters. The fragment of E. coli DNA within the lambdapolA phage comprises approximately 5000 base pairs, sufficient to accommodate the polA gene and one, or two, coding sequences for smaller proteins.
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PMID:Isolation and characterization of a lambdapolA transducing phage. 34 Nov 64

The main endonuclease for apurinic sites of Escherichia coli (endonuclease VI) has no action on normal strands, either in double-stranded or single-stranded DNA, or on alkylated sites. The enzyme has an optimum pH at 8.5, is inhibited by EDTA and needs Mg2+ for its activity; it has a half-life of 7 min at 40 degrees C. A purified preparation of endonuclease VI, free of endonuclease II activity, contained exonuclease III; the two activities (endonuclease VI and exonuclease III) copurified and were inactivated with the same half-lives at 40 degrees C. Endonuclease VI cuts the DNA strands on the 5' side of the apurinic sites giving a 3'-OH and a 5'-phosphate, and exonuclease III, working afterwards, leaves the apurinic site in the DNA molecule; this apurinic site can subsequently be removed by DNA polymerase I. The details of the excision of apurinic sites in vitro from DNA by endonuclease VI/exonuclease III, DNA polymerase I and ligase, are described; it is suggested that exonuclease III works as an antiligase to facilitate the DNA repair.
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PMID:Properties of the main endonuclease specific for apurinic sites of Escherichia coli (endonuclease VI). Mechanism of apurinic site excision from DNA. 34 34

Details are presented of the in vitro synthesis of double-stranded DNA complementary to purified Xenopus globin messenger RNA, using a combination of reverse transcriptase, fragment 'A' of E. coli DNA polymerase 1 and S1 endonuclease. After selection of duplex DNA molecules approaching the length of Xenopus globin messenger RNA by sedimentation of the DNA through neutral sucrose gradients, the 3'-OH termini of the synthetic globin gene sequences were extended with short tracts of oligo dGMP using terminal transferase. This material was integrated into oligo dCMP-extended linear pCR1 plasmid DNA and amplified by transfection of E. coli. Plasmids carrying globin sequences were identified by hybridization of 32P-labelled globin mRNA to total cellular DNA in situ, by hybridization of purified plasmids to globin cDNA in solution, by analysis of recombinant DNA on polyacrylamide and agarose gels, and by heteroduplex mapping. The results show that extensive DNA copies of Xenopus globin mRNA have been integrated into recombinant plasmids.
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PMID:Recombinant plasmids containing Xenopus laevis globin structural genes derived from complementary DNA. 34 4

A new type of Escherichia coli mutant which shows increased sensitivity to methyl methane sulfonate but not to UV light or to gamma rays was isolated after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. The mutant is unable to reactivate phage lambdavir or double-stranded phiX174 DNA (replicative form) that had been treated with methyl methane sulfonate. The mutant is sensitive to other alkylating agents, such as ethyl methane sulfonate, mitomycin C, and N-methyl-N'-nitro-N-nitrosoguanidine, as well. It grows normally and exhibits almost normal recombination proficiency. The mutant possesses normal levels of DNA polymerase I, exonuclease I, exonuclease V, endonuclease specific for methyl methane sulfonate-treated DNA, and 3-methyladenine-DNA glycosidase activities. The genetic locus responsible has been named alk and is located near his on the chromosome.
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PMID:Escherichia coli gene that controls sensitivity to alkylating agents. 35 28

Escherichia coli mutants defective in DNA uracil N-glycosidase (ung-) or endonuclease VI active against apurinic/apyrimidinic sites in DNA (xthA-) exhibit enhanced sensitivity towards 5-bromodeoxyuridine relative to the wild type strain, pointing to involvement of these enzymes in repair of bromouracil-induced lesions in DNA. Mutants defective in DNA polymerase I, either in polymerizing activity (polAl-) or (5' leads to 3')-exonuclease activity (polA107-) exhibit unusually high sensitivity (including marked lethality) in the presence of 5-bromodeoxyuridine. The results indicate that DNA polymerase I, and its associated (5'--3')-exonuclease activity, are involved in repair of bromouracil-induced lesions and are not readily replaced, if at all, by DNA polymerases II and III. Thermosensitive mutant in DNA ligase gene (lig ts7) shows high sensitivity towards 5-bromodeoxyuridine at 42 degrees C indicating the role of the enzyme in repair of bromouracil-induced lesions in DNA. Involvement of DNA uracil N-glycosidase, and endonuclease active against apurinic/apyrimidinic sites in recognition and repair of 5-bromouracil-induced damage permits of some inferences regarding the nature of this damage (lesions), in particular dehalogenation of incorporated bromouracil to uracil residues.
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PMID:Genetic evidence for the nature, and excision repair, of DNA lesions resulting from incorporation of 5-bromouracil. 37 26


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