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Query: EC:6.5.1.2 (DNA ligase)
 2,749 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Toluene treated cells have been used to study the processes of DNA synthesis and DNA degradation in ultra-violet irradiated Escherichia coli K12. Synthesis and degradation are both shown to occur extensively if polynucleotide ligase is inhibited, and to occur to a much lesser extent if ligase activity is optimal. Extensive UV-induced DNA synthesis in toluene-treated cells requires ATP for the initial incision step, and DNA polymerase I. Extensive degradation also depends on the early ATP-dependent incision step, and the subsequent degradation shows a partial requirement for ATP. Curtailment of degradation by ligase requires DNA polymerase activity, but is not dependent upon DNA polymerase I. Apparently this process can be carried out with equal facility by either DNA polymerase II or polymerase III. These observations suggest that extensive DNA polymerase I-dependent repair synthesis and extensive DNA degradation are facets of two divergent pathways of excision repair, both of which depend upon the early uvrABC determined ATP-dependent incision step.
Mol Gen Genet 1977 Nov 29
PMID:DNA synthesis and degradation in UV-irradiated toluene treated cells of E. coli K12: the role of polynucleotide ligase. 34 Sep 17

ColE1amp plasmids carrying the entire bio gene cluster were constructed in vitro using ColE1amp as the cloning vehicle and a lambda transducing phage, lambdaatt2, as the source of bio DNA. Restriction endonuclease EcoRI digests of ColE1amp and lambdaatt2 DNA were joined by polynucleotide ligase and plasmids bearing the entire bio gene cluster were selected, after transformation, in bio deletion strains of E. coli. Recombinant DNA molecules contained one ColE1amp fragment (7.4 X 10(6) daltons) and one lambdaatt2 DNA fragment (5.4 X 10(6) daltons). Clones carrying ColE1 amp-bio plasmids produce elevated levels of biotin and biotin synthetase activity.
Mol Gen Genet 1978 Nov 09
PMID:Isolation and characterization of a ColE1 plasmid containing the entire bio gene cluster of Escherichia coli K12. 36 79

The cell cycle mutant, cdc9, in the yeast Saccharomyces cerevisiae is defective in DNA ligase be deficient in the repair of DNA damaged by methyl methane sulphonate. On the other hand survival of cdc9 after irradiation by gamma-rays is little different from that of the wild-type, even after a period of stress at the restrictive temperature. The mutant cdc9 is not allelic with any known rad or mms mutants.
Mol Gen Genet 1979 Feb 16
PMID:The DNA repair capability of cdc9, the Saccharomyces cerevisiae mutant defective in DNA ligase. 37 19

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.
Mol Gen Genet 1979 Mar 20
PMID:Genetic evidence for the nature, and excision repair, of DNA lesions resulting from incorporation of 5-bromouracil. 37 26

Plasmids carrying various portions of colicin E1 plasmid (ColE1) DNA have been isolated in an attempt to determine the regions of ColE1 DNA which are required for maintenance of the plasmid in bacteria. To construct the plasmids, the DNA of a ColE1 derivative that contains a gene which controls ampicillin resistance was cleaved by the restriction endonuclease HaeII. The digestion products were joined by T4 DNA ligase and then used to transform bacteria to ampicillin resistance. The plasmid derivatives obtained in this way were always composed of certain HaeII segments. These contain approximately 10% of the ColE1 genome and include the origin of replication of ColE1. We presume that the region of ColE1 which is common to all these derivatives is required for maintenance of the plasmid. After a description of these results, the nucleotide sequence of this region is presented, and possible roles of the region in plasmid replication and maintenance are discussed.
Mol Gen Genet 1979 Oct 03
PMID:Nucleotide sequence of the region required for maintenance of colicin E1 plasmid. 39 52

A composite plasmid (pAT2010) has been constructed in vitro from RSF2124 and Bacillus subtilis IFO3022 plasmid (pAT1060) by covalent joining of the two DNA molecules by means of Escherichia coli DNA ligase through the cohesive ends generated by restriction endonuclease RI (EcoRI) cleavage. The composite plasmid was selected by transformation of E. coliC600r-m- with the ligated mixture after enrichment for composite plasmid by preparative agarose gel electrophoresis, and plating of the transformants on a medium containing ampicillin and colicin E1. Treatment of the composite plasmid with EcoRI yielded two fragments corresponding to the linear forms of the parental plasmids. The composite plasmids replicated as biologically functionally units in E. coli, and expressed genetic information carried by RSF2124. In the presence of chloramphenicol, the composite plasmids continued to replicate and the copy number gradually increased. Such nature of replication in the presence of chloramphenicol is characteristic to RSF2124 derived from colicin E1 factor, and so it is suggested that the replicator of RSF2124 is functional in the composite plasmid. The composite plasmid was found to synthesize mRNA of B. subtilis plasmid in cell-free extracts of E. Coli, by hybridization of the mRNA to the original plasmid DNA of pAT1060.
Mol Gen Genet 1977 Nov 29
PMID:Molecular cloning and in vitro transcription of Bacillus subtilis plasmid in Escherichia coli. 41 72

Strand breaks accumulated in the DNA of a temperature-sensitive DNA ligase mutant of Escherichia coli growing at the restrictive temperature, as detected by zone sedimentation through alkaline sucrose density gradients. The rate of strand breakage was increased by concomitant thymine starvation. Rifampicin and chloramphenicol inhibited the accumulation of strand breaks in the DNA. There was a correlation between the accumulation of strand breaks in the DNA and lethality, suggesting that such breaks are the basis for lethality at the restrictive temperature.
J Gen Microbiol 1976 Jun
PMID:Properties of a DNA ligase mutant of Escherichia coli: introduction of strand breaks in DNA. 78 Nov 80

We have examined DNA strand breakage, DNA degradation, and the rate of DNA synthesis in lig and lig-recB strains of Escherichia coli K12 incubated in the presence and absence of 3 mug/ml chloramphenicol. Substantial DNA strand breakage and DNA degradation is observed in the lig strain upon growth at 40 degrees C; however, such strand breakage and DNA degradation is not observed in th lig-recB strainl Incubation of the lig strain at 40 degrees C in the presence of 3 mug/ml chloramphenicol reduces the amount of DNA strand breakage and DNA degradation to the level observed in the lig-recB strain. Together, these results demonstrate that exonuclease V (the recBC gene product) is responsible for the increased DNA degradation associated with DNA ligase deficiency.
Mol Gen Genet 1976 Aug 10
PMID:Effect of chloramphenicol and the recB gene product on DNA metabolism in Escherichia coli K12 strains defective in DNA ligase. 78 29

Escherichia coli B/r (suo) was infected, at 30 degrees C, with T4Dam+, T4DamB24-amN82 (I-, 44-, DNA-negative phenotype), and T4DamN134amBL292 (33-, 55-, maturation-defective phenotype). A genetic ('transformation') assay was used to monitor transcription of genes 30 (polynucleotide ligase), 42 (deoxycytidylate hydroxymethylase), 43 (DNA polymerase), rIIA, rIIB, and e (endolysin). The principal results are: (I) All of the genes studied were transcribed exlusively from the so-called l-strand of phage DNA. (2) DNA synthesis and the maturation-defective proteins were required to turn-off transcription of genes 42, rIIA, tIIB, and 43. Experiments performed with chloramphenicol suggested that all phage-specific proteins required to turn-off transcription of these genes were not present until 6 to 8 min post infection (p.i.). (3) During a normal developmental programme, gene 30 was transcribed throughout the eclipse. DNA-negative and maturation-defective conditions had no obvious effect on transcription of this gene. (4) During a normal lytic event, two discrete waves of gene e transcription were observed. The late wave was dependent upon DNA-synthesis and presence of functional maturation-defective proteins. The early wave was unaffected by DNA-negative or maturation-defective conditions. Experiments with chloramphenicol indicated that, if any virus-specific proteins are involved with regulation of early e transcription, such proteins are present by 3 min p.i. The data are interpreted to mean that early gene transcription is regulated by a minimum of two mechanisms. One of these mechanisms is fully operational by the 3rd min and, among the genes studied, controlled early e transcription. A second mechanism becomes operational between 6 and 8 min p.i. and controls transcription of genes 42, 43, rIIA, and rIIB.
J Gen Virol 1976 Jun
PMID:Transcriptional control of T4 coliphage-specific genes 30, 42, 43, rIIA, rIIB, and e. 94 27

A soluble extract prepared from T7-infected E. coli is able to initiate DNA synthesis on an exogenous T7 DNA template. We have developed a fractionation procedure to resolve and identify the proteins required for T7 DNA synthesis. By this method we have purified the following T7 replication-related proteins (each greater than 50% pure as judged by sodium dodecyl sulfate gel electrophoresis): T7 DNA-binding protein (27,000 daltons), T7 RNA polymerase (105,000 daltons), T7 DNA polymerase (gene 5-protein, 85,000 daltons, plus host-factor), T7 DNA ligase (40,000 daltons), and T7 DNA-priming protein (65,000 daltons). The T7 DNA-priming protein, synthesized between 7.5 and 15 min following infection, was not detectable if the infecting phage carried an amber mutation in gene 4. Using an in vitro complementation assay which specifically measures the stimulation of DNA synthesis in an extract prepared from T7 gene 4-mutant infected cells, we have purified the DNA-priming protein about 2,000-fold. The purified priming protein preparations are essentially free of endonuclease, exonuclease, DNA ligase and DNA polymerase activity, but they do contain measurable DNA-dependent RNA synthetic acitvity. The enzyme is rapidly inactivated by heating to 46 degrees C and by treatment with N-ethylmalemide. In the presence of T7 DNA-binding protein and all four ribonucleoside triphosphates, the DNA-priming protein enables T7 DNA polymerase to initiate DNA synthesis on intact duplex T7 DNA. Closer studies of its enzymatic function as well as of the possible roles of the other proteins in the T7 replication system will be presented in the accompanying paper.
Mol Gen Genet 1975 Dec 01
PMID:Studies on bacteriophage T7 DNA synthesis in vitro. I. Resolution of the T7 replication system into its components. 110 17


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