Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.1 (phosphodiesterase)
 18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endonuclease I, exonuclease I, and exonuclease II-deoxyribonucleic acid (DNA) polymerase I activities are not vital functions in Escherichia coli, although the latter two enzymes have been indirectly shown to be involved in DNA repair processes. Acridines such as acridine orange and proflavine interfere with repair in vivo, and we find that such compounds inhibit the in vitro activity of exonuclease I and DNA polymerase I but stimulate endonuclease I activity and hydrolysis of p-nitrophenyl thymidine-5'-phosphate by exonuclease II. Another acridine, 10-methylacridinium chloride, binds strongly to DNA but is relatively inert both in vivo and in vitro. These experiments suggest that acridines affect enzyme activity by interacting with the enzyme directly as well as with DNA. Resulting conformational changes in the DNA-dependent enzymes might explain why similar acridines which form similar DNA complexes have such a wide range of physiological effects. Differential sensitivity of exonuclease I and DNA polymerase I to acridine inhibition relative to other DNA-dependent enzymes may contribute to the acridine sensitivity of DNA repair.
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PMID:Effect of deoxyribonucleic acid ligands on deoxyribonucleases and deoxyribonucleic acid polymerase I of Escherichia coli K-12. 456 96

Mutations in sbcB inactivate exonuclease I and suppress the UV-sensitive, mitomycin-sensitive, recombination-deficient phenotypes associated with recB and recC mutations. Mapping experiments have located sbcB about 0.4 minutes from the his operon at 38.0 on the standard map of E. coli. This places sbcB between supD and his. A four-point cross shows that sbcB lies between P2 attH and his. P2 eduction deleting the his operon beginning with P2 attH also deletes sbcB and produces the expected exonuclease I deficiency and suppression of recB(-). The occurrence of chemical-mutagen-induced and spontaneous mutations indirectly suppressing recB(-) and recC(-) is examined. Three lines of strains produce only sbcA mutations while only sbcB mutations occur in a fourth line. Explanations for this behavior are proposed in light of the ability of the first three lines to express sbcB mutations which they inherit by transduction.
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PMID:Genetic analysis of mutations indirectly suppressing recB and recC mutations. 456 84

Partially replicated T4 DNA molecules (PRM) whose parental or progeny DNA was labeled with bromodeoxyuridine BUdR was analyzed by gradual shearing followed by CsCl banding of the sheared product. Analysis of PRM containing 18-mum replicated DNA showed that each replicated region was 3- to 6-mum long, indicating three to 6 replicative sites per molecule. Analysis of PRM containing 9-mum replicated DNA similarly indicated two to three replicated regions per molecule. DNA from the replicated regions of PRM containing 10-mum replicated DNA ("donor") was hybridized to DNA from mature phage ("recipient"), and the resulting hybrid was subjected to digestion with exonuclease I. The extent of protection of the recipient and more efficient self-annealing of progeny fragments from PRM indicated that the replicated regions represented 8 to 10 nonrandom locations of the genome. Possible significance of multiple sites for initiation of DNA replication is discussed.
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PMID:Multiple and specific initiation of T4 DNA replication. 457 21

The time course of the appearance of intracellular viral DNA has been studied in mouse L cells infected with the single-stranded DNA virus MVM (minute virus of mice) by using a selective extraction procedure. Approximately half of this DNA elutes from hydroxyapatite as single-stranded DNA. It is sensitive to Escherichia coli exonuclease I and shows a sedimentation profile similar to DNA from the virus, suggesting that it is progeny viral DNA. The remainder of the selectively extracted DNA elutes from hydroxyapatite in the position of double-stranded DNA and is resistant to exonuclease I. Most of this DNA has a sedimentation coefficient of 14 to 16S, indicating that its molecular weight is twice that of the viral DNA. Denaturation renders the majority of the double-stranded DNA sensitive to exonuclease I, but a significant fraction renatures spontaneously in a monomolecular fashion, indicating that it has a cross-linked or hairpin structure. Chromatography of the double-stranded DNA on benzoylated diethylaminoethyl cellulose resolves two components, one with duplex structure and one which contains single-stranded regions. A short pulse label late in infection predominantly labels the latter class of DNA, suggesting that it contains replicating intermediates. The possible roles of these various forms of DNA in the replication of the viral genome are discussed.
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PMID:Replication of the parvovirus MVM. II. Isolation and characterization of intermediates in the replication of the viral deoxyribonucleic acid. 458 79

The indirect suppression of recB(-) and recB(-)recC(-) mutations by the sbcB(-) allele is caused by the loss of a nuclease active on denatured DNA. Results from enzyme purifications and studies with a specific antiserum demonstrate that the activity present in sbcB(+) strains, and lost in sbcB(-) strains, is exonuclease I. It is likely that sbcB is the structural gene for exonuclease I. The loss of exonuclease I activity restores the recombination proficiency of Escherichia coli cells that has been lost by mutations in the recB and/or recC genes. This indicates that in the absence of the recB-recC-determined enzyme, exonuclease I prevents recombination. Hypothetical pathways illustrating this conclusion are presented.
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PMID:Genetic recombination in Escherichia coli: the role of exonuclease I. 492 75

More than 50% of the [(3)H]thymidine incorporated during short pulses into the DNA of Escherichia coli 15T(-) can be extracted by alkali as high molecular weight DNA. Density gradient centrifugation and digestion with exonuclease I suggest that these large pieces of DNA are composed of newly synthesized DNA attached to pre-existing material at the 3' end of the molecule.
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PMID:DNA replication in Escherichia coli: location of recently incorporated thymidine within molecules of high molecular weight DNA. 494 76

1. DNA polymerase activity is present in both nuclear and supernatant fractions prepared from rapidly dividing L929 mouse cells. 2. Nuclear preparations are 2-5 times more active with added native DNA as template and the supernatant fractions show an equivalent preference for heat-denatured DNA. 3. Isolated nuclei can carry on limited DNA synthesis in the absence of added template but are stimulated five- to ten-fold by addition of 50mug of native DNA per assay. 4. DNA polymerase activity can be released from intact nuclei by ultrasonic treatment or by extraction with 1.5m-potassium chloride. 5. The activities in nuclear and supernatant fractions, with their preferred templates, respond similarly to changes in pH and Mg(2+) and K(+) concentrations. 6. Maximal enzyme activity is approached with 40mug of DNA per assay and activation of the DNA template by treatment with deoxyribonuclease does not decrease the amount of DNA required to reach saturation. 7. The nuclear enzyme, incubated with native DNA, is markedly inhibited by the addition of heat-denatured DNA to the assay. In contrast, the supernatant DNA polymerase activity on denatured templates is not affected by the presence of native DNA. 8. The nuclear enzyme exhibits high activity in the absence of one or more deoxyribonucleoside triphosphates but this is much diminished after partial purification of the enzyme by precipitation at pH5 and fractionation on Sephadex G-200 columns. 9. The (3)H-labelled DNA products formed by Sephadex-purified nuclear and supernatant fractions, with their preferred templates, were found to be resistant to treatment with exonuclease I. Alkali-denaturation of the (3)H-labelled DNA products rendered them susceptible to attack by exonuclease I. 10. Analysis of the products on alkaline sucrose density gradients suggests that the newly synthesized material may not be covalently bound to the original DNA template. 11. By using their preferred templates the specific activity of supernatant fractions varies markedly with the position of the cells in the cell-cycle, but the specific activity of nuclear fractions varies only slightly.
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PMID:Characteristics of deoxyribonucleic acid polymerase activity in nuclear and supernatant fractions of cultured mouse cells. 553 Nov 81

The recovery of phage P1 mediated transductants varies with the marker selected in a manner which cannot be fully accounted for by dosage differences in the donor gene population. This variation in transduction frequency is due primarily to recombinational discrimination in the recipient cell. We show here that increasing the intracellular level of recA protein, which might be expected to increase the contribution of recF mediated events to recombinant formation, decreases this discrimination slightly, and that replacing recBC mediated recombination by a recF dependent process, augmented by an additional, as yet uncharacterized mutation, dramatically reduces recombinational discrimination. We conclude that although recBC mediated transductional recombination is selective, recombination which relies on recF need not be so. We also show that UV-damaged DNA can be successfully recombined in the absence of the recB product (even in sbcB+ cells) and that eliminating exonuclease I (the sbcB product) facilitates the recombination of heavily irradiated DNA.
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PMID:Reduction of marker discrimination in transductional recombination. 609 Aug 69

The role of inducible cell functions in repair and mutagenesis after bleomycin-induced DNA damages was studied in Escherichia coli. Influence on these processes of some rec genes as well as sbcB, the structural gene for exonuclease I, was investigated. The data obtained suggest that this enzyme plays a negative role in the repair of DNA damaged by bleomycin. The hypersensitivity of recA mutant to bleomycin and recAlexA-dependence of bleomycin-induced mutagenesis do not suggest any principal differences between UV-induced pyrimidine dimers and apyrimidinic sites in the case of post-replication repair.
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PMID:[Repair of bleomycin-induced damage to Escherichia coli DNA. II. Participation of inducible processes]. 616 59

The recombination proficiency of three recipient strains of Escherichia coli K12 carrying different plasmids was investigated by conjugal mating with Hfr Cavalli. Some plasmids (e.g. R1drd 19, R6K) caused a marked reduction in the yield of recombinants formed in crosses with Hfr but did not reduce the ability of host strains to accept plasmid F104. The effect of plasmids on recombination was host-dependent. In Hfr crosses with AB1157 (R1-19) used as a recipient the linkage between selected and unselected proximal markers of the donor was sharply decreased. Plasmid R1-19 also decreased the yield of recombinants formed by recF, recL, and recB recC sbcA mutants, showed no effect on the recombination proficiency of recB recC sbcB mutant, and increased the recombination proficiency of recB, recB recC sbcB recF, and recB recC sbcB recL mutants. An ATP-dependent exonuclease activity was found in all tested recB recC mutants carrying plasmid R1-19, while this plasmid did not affect the activity of exonuclease I in strain AB1157 and its rec- derivatives. The same plasmid was also found to protect different rec- derivatives of the strain AB1157 against the lethal action of UV light. We suppose that a new ATP-dependent exonuclease determined by R1-19 plays a role in both repair and recombination of the host through the substitution of or competition with the exoV coded for by the genes recB and recC.
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PMID:Plasmid control of recombination of E. coli K12. 625 17


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