Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of several enzymes of the DNA metabolism of Escherichia coli on the biological activity of native and single-stranded T7 DNA was studied by transfection of lysozyme-EDTA spheroplasts prepared from various E. coli mutants. It is shown that the presence of the recBC DNase in the recipient cells decreases the infectivity of native and denatured DNA by about 100- and 10-fold, respectively. Lack of exonuclease I did not stimulate transfection by single-stranded DNA. Separated light (l) and heavy (r) strands of T7 DNA are fully infective, with a linear dependence on DNA concentrations, whereas heat-denatured DNA shows a two-hit kinetics. Single-stranded DNA was observed to depend on a functional DNA polymerase III for infectivity in polAB cells, whereas transfection with native T7 DNA was independent of the host DNA polymerases. The results are discussed with respect to the mode of T7 DNA replication.
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PMID:In vivo effects of recBC DNase, exonuclease I, and DNA polymerases of Escherichia coli on the infectivity of native and single-stranded DNA of bacteriophage T7. 32 5

A homopolymer system has been developed to examine the digestion strategies of DNA exonucleases. Escherichia coli exonuclease I and lambda-exonuclease, are processive enzymes. However, T7 exonuclease, spleen exonuclease, E. coli exonuclease III, the 3' leads to 5'-exonuclease of T4 DNA polymerase, and both the 3' leads to 5' and the 5' leads to 3' activity of E. coli DNA polymerase I dissociate frequently from the substrate during the course of digestion. Regions of duplex DNA are a dissociation signal for exonuclease I.
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PMID:Processivity of DNA exonucleases. 33 8

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

The rate of formation of high-molecular-weight daughter DNA in the conditionally lethal double mutant polA12 uvrE502, incubated at nonpermissive temperature, was slower than that in the single polA12 mutant. There exist at least two pathways determining viability of Escherichia coli cells: one of them is dependent on polA+ and recB+ genes, while another is polA+ and recB+ genes, while another is polA recB independent but requires the uvrE+ gene and can be blocked by exonuclease I. The RecF but not the RecBC pathway of genetic recombination was found to be absolutely dependent on the polymerizing activity of DNA polymerase I. The involvement of DNA polymerase I in genetic recombination in the recB- C- sbsB strain and viability in the uvrE- or recB- strains suggest the existence of the common steps required for the accomplishing of the RecF pathway of recombination and for viability of E. coli.
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PMID:The role of DNA polymerase I in genetic recombination and viability of Escherichia coli. 110 51

Isolation and general properties of 3'-5' exonucleases I and II (EC 3.1.4.26), which are specific to single-stranded DNA, are described. Such enzymes, being components of replication complexes, could correct replication errors. Homogeneous exonucleases I and II consist of a single subunit with molecular mass of 50 and 40 kDa, respectively. These enzymes are located preferentially in the nuclear membrane and chromatin. They form complexes with nuclear DNA polymerases and some other proteins and are not observed practically in a free state. Molecular masses of the complexes amount from 70 to 1.500 kDa. The complexes dissociate as a result of solution hydrophobization and can be reconstituted after the decrease of hydrophobization. The heavy membrane complex form of 3'----5' exonuclease I manifests enzymatic activities of DNA polymerase alpha (EC 2.7.7.7), non-specific nucleoside triphosphatase (EC 3.1.3.2), nucleotidase (EC 3.1.3.31) and faint activity of endonuclease (EC 3.1.4.5). Complexes under study do not display activity of thymidine kinase (EC 2.7.1.21), marker protein of replitase, neither in G0 nor in S-period.
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PMID:[Homogeneous 3'----5'-exonucleases and their multienzyme complexes from the rat liver]. 234 19

DNA mismatch correction is a strand-specific process involving recognition of noncomplementary Watson-Crick nucleotide pairs and participation of widely separated DNA sites. The Escherichia coli methyl-directed reaction has been reconstituted in a purified system consisting of MutH, MutL, and MutS proteins, DNA helicase II, single-strand DNA binding protein, DNA polymerase III holoenzyme, exonuclease I, DNA ligase, along with ATP (adenosine triphosphate), and the four deoxynucleoside triphosphates. This set of proteins can process seven of the eight base-base mismatches in a strand-specific reaction that is directed by the state of methylation of a single d(GATC) sequence located 1 kilobase from the mispair.
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PMID:DNA mismatch correction in a defined system. 266 76

DNA polymerase activity can be unmasked in avian myeloblastosis virus (AMV) by treatment with the nonionic detergent Nonidet P-40. Two products are formed: (1) RNA.DNA hybrid molecules and (2) duplex DNA molecules. The kinetics of dTTP incorporation into DNA are biphasic: an initial rapid reaction for 4 min at 37 degrees C with a minimal polymerization rate of 10-20 nucleotides per see, and a second reaction at about half the initial rate. Viral RNA.DNA complexes are detected as early as 30 sec after the initiation of DNA synthesis; DNA free of template is formed subsequently. Most of the free AMV DNA forms an RNA.DNA hybrid when annealed with viral RNA. Over half of the free AMV DNA product is inferred to be double-stranded, since it is retained on hydroxyapatite columns after elution with 0.12 M phosphate buffer, and is resistant to Escherichia coli exonuclease I. Adenovirus or calfthymus DNA added to unmasked AMV stimulates DNA synthesis 4-16 times if there is no treatment with RNase, and 40-130 fold if RNase treatment precedes the enzyme assay. It is possible that two polymerases are present, or that a single enzyme forms both the RNA.DNA hybrid and the double-stranded product.
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PMID:Mechanism of carcinogenesis by RNA tumor viruses. 3. Formation of RNA, DNA complex and duplex DNA molecules by the DNA polymerase (s) of avian myeloblastosis virus. 432 24

The effects of Escherichia coli exonuclease I, exonuclease III, and deoxyribonucleic acid (DNA) polymerase on the biological activity of mature DNA from temperate Bacillus bacteriophage phi105 were investigated. Intact DNA loses infectivity rapidly upon exposure to exonuclease III. Although there is an overall decrease in marker rescue from exonuclease III-digested DNA, digestion preferentially affects markers at the end of the genetic map. This is taken to indicate a nonpermuted gene sequence in mature DNA. Incubation of mature DNA in the presence of exonuclease I or DNA polymerase has no effect on its biological activity. The possible structure of the ends of mature phi105 DNA is discussed. The rate of digestion of mature phi105 DNA by exonuclease III is only about 1/20 the rate of lambda DNA. Results of digestion of various DNA substrates by exonuclease III indicate that the enzyme distinguishes between different DNA terminal structures.
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PMID:Structure and biological activity of deoxyribonucleic acid from Bacillus bacteriophage phi 105: effects of Escherichia coli exonucleases. 432 11

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

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


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