scholarly journals Mutational Specificity of the Ferrous Ion in a supF Gene of Endonuclease III/VIII Deficient Escherichia coli.

1997 ◽  
Vol 38 (3) ◽  
pp. 165-171 ◽  
Author(s):  
HIDEO SHIMAMURA ◽  
SUSUMU AKASAKA ◽  
KIHEI KUBO ◽  
YUSUKE SAITO ◽  
SATOSHI NAKAJIMA ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Ferrous Ion ◽  
Endonuclease Iii ◽  
Mutational Specificity ◽  
Supf Gene

scholarly journals A Novel Role for Escherichia coliEndonuclease VIII in Prevention of Spontaneous G→T Transversions

1999 ◽  
Vol 181 (20) ◽  
pp. 6396-6402 ◽  
Author(s):  
Jeffrey O. Blaisdell ◽  
Zafer Hatahet ◽  
Susan S. Wallace
Keyword(s):  
Escherichia Coli ◽  
Mutation Frequency ◽  
Spontaneous Mutation ◽  
Dna Glycosylase ◽  
Dna Glycosylases ◽  
Substrate Specificities ◽  
Endonuclease Iii ◽  
Mutational Specificity ◽  
Spontaneous Mutation Frequency

ABSTRACT In the bacterium Escherichia coli, oxidized pyrimidines are removed by two DNA glycosylases, endonuclease III and endonuclease VIII (endo VIII), encoded by the nth and neigenes, respectively. Double mutants lacking both of these activities exhibit a high spontaneous mutation frequency, and here we show that all of the mutations observed in the double mutants were G:C→A:T transitions; no thymine mutations were found. These findings are in agreement with the preponderance of C→T transitions in the oxidative and spontaneous mutational databases. The major oxidized purine lesion in DNA, 7,8-dihydro-8-oxoguanine (8-oxoG), is processed by two DNA glycosylases, formamidopyrimidine DNA glycosylase (Fpg), which removes 8-oxoG opposite C, and MutY DNA glycosylase, which removes misincorporated A opposite 8-oxoG. The high spontaneous mutation frequency previously observed in fpg mutY double mutants was significantly enhanced by the addition of the neimutation, suggesting an overlap in the substrate specificities between endo VIII and Fpg/MutY. When the mutational specificity was examined, all of the mutations observed were G:C→T:A transversions, indicating that in the absence of Fpg and MutY, endo VIII serves as a backup activity to remove 8-oxoG. This was confirmed by showing that, indeed, endo VIII can recognize 8-oxoG in vitro.

scholarly journals The Saccharomyces cerevisiae Homologues of Endonuclease III from Escherichia coli, Ntg1 and Ntg2, Are Both Required for Efficient Repair of Spontaneous and Induced Oxidative DNA Damage in Yeast

1999 ◽  
Vol 19 (5) ◽  
pp. 3779-3787 ◽  
Author(s):  
Ingrun Alseth ◽  
Lars Eide ◽  
Manuela Pirovano ◽  
Torbjørn Rognes ◽  
Erling Seeberg ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Saccharomyces Cerevisiae ◽  
Dna Damage ◽  
Oxidative Dna Damage ◽  
High Efficiency ◽  
Intracellular Localization ◽  
Genome Project ◽  
Yeast Genome ◽  
Enzyme Analysis ◽  
Endonuclease Iii

ABSTRACT Endonuclease III from Escherichia coli is the prototype of a ubiquitous DNA repair enzyme essential for the removal of oxidized pyrimidine base damage. The yeast genome project has revealed the presence of two genes in Saccharomyces cerevisiae,NTG1 and NTG2, encoding proteins with similarity to endonuclease III. Both contain the highly conserved helix-hairpin-helix motif, whereas only one (Ntg2) harbors the characteristic iron-sulfur cluster of the endonuclease III family. We have characterized these gene functions by mutant and enzyme analysis as well as by gene expression and intracellular localization studies. Targeted gene disruption of NTG1 and NTG2produced mutants with greatly increased spontaneous and hydrogen peroxide-induced mutation frequency relative to the wild type, and the mutation response was further increased in the double mutant. Both enzymes were found to remove thymine glycol and 2,6-diamino-4-hydroxy-5-N-methylformamidopyrimidine (faPy) residues from DNA with high efficiency. However, on UV-irradiated DNA, saturating concentrations of Ntg2 removed only half of the cytosine photoproducts released by Ntg1. Conversely, 5-hydroxycytosine was removed efficiently only by Ntg2. The enzymes appear to have different reaction modes, as judged from much higher affinity of Ntg2 for damaged DNA and more efficient borhydride trapping of Ntg1 to abasic sites in DNA despite limited DNA binding. Northern blot and promoter fusion analysis showed that NTG1 is inducible by cell exposure to DNA-damaging agents, whereas NTG2 is constitutively expressed. Ntg2 appears to be a nuclear enzyme, whereas Ntg1 was sorted both to the nucleus and to the mitochondria. We conclude that functions of both NTG1 and NTG2 are important for removal of oxidative DNA damage in yeast.

scholarly journals Multiprobe RNase Protection Assay Analysis of mRNA Levels for the Escherichia coli Oxidative DNA Glycosylase Genes under Conditions of Oxidative Stress

2000 ◽  
Vol 182 (19) ◽  
pp. 5416-5424 ◽  
Author(s):  
Christine M. Gifford ◽  
Jeffrey O. Blaisdell ◽  
Susan S. Wallace
Keyword(s):  
Escherichia Coli ◽  
Base Excision Repair ◽  
Excision Repair ◽  
Dna Glycosylase ◽  
Mrna Levels ◽  
Aerobic Growth ◽  
Rnase Protection ◽  
Transcript Levels ◽  
Endonuclease Iii ◽  
Base Excision

ABSTRACT Escherichia coli formamidopyrimidine DNA glycosylase (Fpg), MutY DNA glycosylase, endonuclease VIII, and endonuclease III are oxidative base excision repair DNA glycosylases that remove oxidized bases from DNA, or an incorrect base paired with an oxidized base in the case of MutY. Since genes encoding other base excision repair proteins have been shown to be part of adaptive responses inE. coli, we wanted to determine whether the oxidative DNA glycosylase genes are induced in response to conditions that cause the type of damage their encoded proteins remove. The genesfpg, mutY, nei, and nthencode Fpg, MutY, endonuclease VIII, and endonuclease III, respectively. Multiprobe RNase protection assays were used to examine the transcript levels of these genes under conditions that induce the SoxRS, OxyR, and SOS regulons after a shift from anaerobic to aerobic growth and at different stages along the growth curve. Transcript levels for all four genes decreased as cells progressed from log-phase growth to stationary phase and increased after cells were shifted from anaerobic to aerobic growth. None of the genes were induced by hydrogen peroxide, paraquat, X rays, or conditions that induce the SOS response.

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