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)

1. Alkaline ribonuclease (pH optimum 7.6) was isolated from rye (Secale cereale L) germ cytosol and partially purified; the preparation was devoid of other nucleolytic activities. 2. The enzyme is a typical endonuclease hydrolysing all phosphodiester bonds in RNA, yielding ultimately purine and pyrimidine nucleoside 2',3'-cyclic phosphates and the corresponding 3'-phosphates. Upon extensive digestion of synthetic polyribonucleotides, pyrimidine, but not purine, nucleoside 3'-phosphates are formed. The enzyme does not hydrolyse synthetic purine cyclic nucleotides. 3. The enzyme does not depolymerize double-stranded complexes of poly(A) and poly(U). 4. Susceptibility to photooxidation and inhibition by 2-hydroxy-5-nitrobenzyl bromide and N-bromosuccinimide implies the involvement of tryptophan residue in the active centre of the enzyme.
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PMID:Alkaline ribonuclease from rye germ cytosol. 0 57

The circular DNA of hepatitis B Dane particles, which serves as the primer/template for an endogenous DNA polymerase, was analyzed by electrophoresis before and after a polymerase reaction and after digestion by restriction endonuclease or single-strand-specific endonuclease S1. The unreacted molecules extracted from the particles were electrophoretically heterogeneous, and treatment with S1 nuclease produced double-stranded linear DNA ranging in length from 1,700 to 2,800 base pairs (bp). After an endogenous DNA polymerase reaction, two discrete species of DNA molecules were found: a circular form and a linear form 3,200 bp long. The reaction resulted in a population of molecules with an elongated and more homogeneous double-stranded region. These results suggest that the circular molecules in Dane particles have single-stranded regions of varying lengths that are made double stranded during the DNA polymerase reaction. The endogenous DNA polymerase was found to initiate apparently at random in a region spanning more than a third of the molecule. Analysis of restriction endonuclease cleavage fragments of the fully elongated DNA revealed that although the molecules were of a uniform length, they were somewhat heterogeneous in sequence. The sum of the sizes of the 10 major endonuclease Hae III-generated fragments, detected by ethidium bromide, was 3,880 bp. Two additional fragments (B and G) detected by autoradiography after an endogenous DNA polymerase reaction with (32)P-labeled deoxynucleoside triphosphates made the total 4,910 bp.
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PMID:Structure of hepatitis B Dane particle DNA and nature of the endogenous DNA polymerase reaction. 6 27

Ether-permeabilized (nucleotide-permeable) Escherichia coli cells respond to alkylating and arylalkylating carcinogens with DNA excision repair, as assessed by their stimulation of DNA repair synthesis. In the present work, we have investigated whether DNA repair synthesis in ether-treated E. coli cells can serve as a general indicator to monitor the DNA-binding of carcinogens, mutagens and antitumor agents. Therefore, a standard assay was developed and comparative analyses were performed on 11 ultimate carcinogens, 10 proximate carcinogens, 2 tumor promoters, 6 mutagens, and 12 antitumor agents. All ultimate carcinogens (alkylating, acylating, arylalkylating agents) and mutagens (e.g., hydrogeen peroxide, acridine derivatives) caused DNA excision repair in wild type cells as measured by [3H] dTMP incorporation and simultaneously inhibited replicative DNA synthesis to various extents. Control experiments with the mutant cells uvrA and uvrB were performed to determine whether the pyrimidine-dimer-specific UV-endonuclease was involved in the removal of DNA damage. This was found to be true for the ultimate carcinogens (Ac)2 ONFln, mitomycin C, and for very reactive alkylating carcinogens. None of the ultimate carcinogens induced repair polymerization in mutant cells lacking the 5'-3' exonucleolytic activity of DNA polymerase I. Proximate carcinogens, such as Me2NNO, 4-nitroquinoline-1-oxide and aflatoxins, did not induce excision repair in the standard assay, probably because of the inability of E. coli to perform the activation steps necessary for covalent DNA-binding. However, Me2NNO, when pretreated with Udenfriend's hydroxylating mixture, gave rise to a low level of repair polymerization in ether-treated cells. Intercalating mutagens, such as quinacrine and ethidum bromide, inhibited replicative DNA synthesis. However, they were not found to be repair-inducers. THE TUMOR PROMOters TPA and phorbol-12,13-didecanoate did not cause excision repair, even when applied at high concentrations, nor did they inhibit repair synthesis stimulated by MeNOUr or (Ac)2 ONFln. The antitumor agents may be classified into two groups on the basis of the influence they exert on DNA synthesis: members of the first group (involving BCNU and bleomycin) stimulate repair polymerization and, in addition, inhibit DNA replication. These compounds are known to bind covalently to DNA. The second group of drugs (including adriamycin and cis-Pt(II)diammine complexes) inhibits DNA replication without stimulating repair synthesis. The predominant DNA-interaction of these compounds is known to be a non-covalent (i.e., intercalative, electrostatic) binding. Our experiments show that the ether-permeabilized E. coli cell can be successfully used to test ultimate carcinogens, mutagens and antitumor agents for repair-inducing and replication-inhibiting activity. The standard test might be extended to pre- and proximate carcinogens, provided these can be suitably activated.
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PMID:The nucleotide-permeable Escherichia coli cell, a sensitive DNA repair indicator for carcinogens, mutagens, and antitumor agents binding covalently to DNA. 15 98

The cleavage of DNA by restriction endonucleases can be limited by the addition of ethidium bromide. When closed circular DNA is used as a substrate, DNA with one-site cleavages of one or both strands can be made by adding appropriate amounts of dye. The singly cleaved DNA is a complete set of full-length permuted linear molecules. Fractionation of the products of a digestion of the permuted linears with a single-hitting restriction endonuclease by gel electrophoresis yields a series of bands that can be used to determine relative molecular weights of the DNA fragments in the gel without the introduction of standards. It is possible to determine the relative molecular weight of a fragment to within +/-2.5%. These molecular weights immediately allow the determination of the HindIII and Hpa I maps of simian virus 40. The HindIII map of bacteriophage PM2 was determined by this method with one ambiguity that was resolved by using traditional techniques.
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PMID:Mapping of closed circular DNAs by cleavage with restriction endonucleases and calibration by agarose gel electrophoresis. 19 36

Endonuclease activities of cytoplasmic extracts of BSC-1 (E1) and BHK-21-cl 13 (E2) cells were assayed with SV-40 as a substrate and analysed by velocity sedimentation in alkaline and neutral sucrose gradients. Endonucleases were found to require Mg2+ ions for their activity. E1 endonuclease generated linear 6 S DNA fragments, pointing to non-random double-strand cleavage of DNA ; the action of E2 endonuclease resulted in double-strand DNA cleavage to fragments heterogeneous in size. Both endonucleases were inhibited by ATP. The inhibitory effect of actinomycin D (AD) was proportional to the AD/DNA molar ratio. AD+ATP association as well as the presence of ethidium bromide altered the cleavage pattern of E1 towards the predominance of single-strand breaks.
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PMID:Alteration of the cytoplasmic endonuclease cleavage pattern of SV-40 deoxyribonucleic acid in the presence of ATP, actinomycin D and ethidium bromide. 19 89

The positions of the several sea urchin histone genes on the eukaryotic fragments of the chimeric plasmids pSp2 and pSp17 have been mapped relative to the Eco RI and Hind III restriction endonuclease sites on the plasmids. Two principal mapping methods using the electron microscope have been used: (a) the R-loop procedure and a new modification thereof to map the genes on duplex DNA; (b) the gene 32-ethidium bromide technique to visualize RNA-DNA hybrids on single strands of DNA. It is known that there are two histone genes, H3 and H2A, on pSp17. There are two Eco RI sites at the two junctions of the procaryotic segment with the eucaryotic segment on the plasmid. We show, by an electron microscope method, that for H2A, with a length of 0.52 kilobases (kb), one end of the gene is situated 0.02 to 0.03 kb from one RI site, and that there is a Hind III site within this gene at about 0.13 kb from the end phe other RI site of this plasmid. The H4 gene lies between H2B and H1. The ms the incubation temperature is raised up to a temperature just below that at which strand dissociation of the duplex DNA occurs.
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PMID:Positions of sea urchin (Strongylocentrotus purpuratus) histone genes relative to restriction endonuclease sites on the chimeric plasmids pSp2 and pSp17. 32 Oct 20

Replicating DNA molecules of the mini R6-5 plasmid, pKTO71, were purified by equilibrium centrifugation in two successive ethidium bromide-caesium chloride gradients, converted to linear forms by cleavage with either HindIII or BglII restriction endonuclease, and examined in the electron microscope. Determination of the replication fork positions in 65 replicating molecules demonstrated that replication is initiated at a unique location on the plasmid and that it proceeds uni-directionally from this site. The direction of replication is such that the origin-proximal BglII cleavage site is replicated late or, in the case of the parent R6-5 plasmid, is such that the R-determinant region of the molecule is replicated early. The origin of replication, located by these experiments at R6-5 coordinate 98.6 kb, is clearly distinct from that of the R6-5 incompatibility determinant which has been shown to be located on an adjacent PstI-generated DNA fragment whose termini have R6-5 coordinates 96.8 and 97.9 kb. This result indicates that the incompatibility function is not an origin DNA sequence.
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PMID:Plasmid replication functions. III. Origin and direction of replication of a "mini" plasmid derived from R6-5. 37 38

A quick and convenient assay for depurination and AP endonuclease activities has been developed. (The term 'AP endonuclease' refers to a nuclease that acts on apurinic and probably apyrimidinic sites on DNA.) It is based on the observation that different topological forms of DNA, such as open circular DNA and covalently closed circular DNA, bind different amounts of the fluorescent intercalator ethidium bromide, and can therefore be distinguished by their fluorescence. This assay has been used to measure AP endonuclease activity in 22 repair-deficient mutants of Saccharomyces cerevisiae. All 22 had normal or nearly normal AP endonuclease activity. The AP endonuclease activity was partially characterized.
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PMID:A novel assay for endonucleases acting at apurinic sites and its use in measuring AP endonuclease activity in repair-deficient mutants of Saccharomyces cerevisiae. 38 41

Equilibrium density gradient centrifugation in CsCl confirms that DNA synthesized after vaccinia virus infection of HeLa cells is homogeneous in buoyant density and thus in base composition and is similar in this respect to bulk HeLa cell DNA. In contrast, rate sedimentation in alkaline sucrose gradients distinguishes two main classes of virus-induced DNA, neither of which can be equated with cell DNA synthesized in the same cultures prior to infection. The slower sedimenting class of virus-induced DNA co-sediments with DNA from purified virus particles: the second class sediments faster than pre-labelled cell DNA. Heterogeneity of virus-induced DNA does not result from fragmentation of radioactively labelled DNA, virus-mediated breakdown of cell DNA or association with either proteins or polyamines. Both slow and fast sedimenting classes of virus-induced DNA contain sequences complementary to all restriction endonuclease Hind III-specific fragments of the virus genome. The multiple species of DNA synthesized after infection are distinguished further by the effect of ethidium bromide. At a concentration which prevents the formation of infectious progeny virus, this compound inhibits selectively the de novo synthesis of that class of virus-induced DNA which sediments faster in alkaline sucrose gradients.
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PMID:De novo synthesis of two classes of DNA induced by vaccinia virus infection of HeLa cells. 75 58

A chimeric plasmid has been constructed in vitro from colicin E1 factor (Col E1), nontransmissible R-factor RSF-1010, and Drosophila melanogaster DNAs by the sequential action of Escherichia coli endonuclease RI(Eco RI) and T4 phage DNA ligase. The chimeric plasmid was assembled in two stages--first, a composite plasmid consisting of Col E1 and RSF 1010 was constructed, followed by partial digestion of the composite with Eco RI (in order to open one of the susceptible cleavage sites) and ligation with an Eco RI-digested D. melanogaster DNA preparation. The chimeric plasmid was selected and amplified in vivo by sequential transformation of E. COLI C with the ligated mixture, selection of transformants in medium containing streptomycin plus colicin E1, followed by amplification in the presence of chloramphenicol and purification of the extracted plasmid by dye-buoyant density gradient centrifugation in ethidium bromide-CsCl solution. Treatment of the chimeric plasmid with Eco RI yields three fragments with mobilities corresponding to the linear forms of the constituents--COL E1, mol wt 4.2 times 106, RSF 1010, mol wt 5.5 times 106 and D. melanogaster DNA, mol wt 4.0 times 106. The buoyant densities of the three constituents are respectively 1.706, 1.719, and 1.697 g/cm3, while the buoyant density of the composite factor is 1.712 and that of the chimeric plasmid is 1.705. Serratia marscesens endonuclease R (Sma) which introduces a single cut in Col E1, but not in RSF 1010, converts the chimeric plasmid to a single linear molecule (mol wt 13.7 times 106) and sequential digestion with both Sma and Hin III yields two distinct fragments, mol wt 3.7 and 10.0 times 10.6, respectively; this implies that the two sites are unique and occur at distinctly different positions. Sequential digestion with both Hin III and Eco RI reveals that the Hin III cut is in the D. melanogaster segment; neither Col E1 nor RSF 1010 contain sites susceptible to digestion with Hin III. In the presence of chloramphenicol, the chimeric plasmid continues toreplicate for 9 hr while bacterial chromosomal DNA replicates at a much slower rate. As in the case of the composite plasmid, continued synthesis is the presence of chloramphenicol suggests that the replicator of Col E1 is functional in the chimeric plasmid as well. Examination of the chimeric plasmid by partial denaturation mapping permits identification of its constituents, each of which presents a characteristic profile. The D. melanogaster segment reveals a wealth of detail at the molecular level pertaining to the distribution of AT-rich regions.
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PMID:Construction and characterization of a chimeric plasmid composed of DNA Pfrom Escherichia coli and Drosophila melanogaster. 80 34


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