YtkD and MutT Protect Vegetative Cells but Not Spores of Bacillus subtilis from Oxidative Stress

ABSTRACT ytkD and mutT of Bacillus subtilis encode potential 8-oxo-dGTPases that can prevent the mutagenic effects of 8-oxo-dGTP. Loss of YtkD but not of MutT increased the spontaneous mutation frequency of growing cells. However, cells lacking both YtkD and MutT had a higher spontaneous mutation frequency than cells lacking YtkD. Loss of either YtkD or MutT sensitized growing cells to hydrogen peroxide (H2O2) and t-butylhydroperoxide (t-BHP), and the lack of both proteins sensitized growing cells to these agents even more. In contrast, B. subtilis spores lacking YtkD and MutT were not sensitized to H2O2, t-BHP, or heat. These results suggest (i) that YtkD and MutT play an antimutator role and protect growing cells of B. subtilis against oxidizing agents, and (ii) that neither YtkD nor MutT protects spores against potential DNA damage induced by oxidative stress or heat.

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Role of the Nfo and ExoA Apurinic/Apyrimidinic Endonucleases in Repair of DNA Damage during Outgrowth of Bacillus subtilis Spores

Journal of Bacteriology ◽

10.1128/jb.01625-07 ◽

2008 ◽

Vol 190 (6) ◽

pp. 2031-2038 ◽

Cited By ~ 27

Author(s):

Juan R. Ibarra ◽

Alma D. Orozco ◽

Juan A. Rojas ◽

Karina López ◽

Peter Setlow ◽

...

Keyword(s):

Oxidative Stress ◽

Dna Damage ◽

Bacillus Subtilis ◽

Spore Germination ◽

Mutation Frequency ◽

Oxidative Dna Damage ◽

Excision Repair ◽

Spontaneous Mutation ◽

Dna Lesions ◽

Spore Outgrowth

ABSTRACT Germination and outgrowth are critical steps for returning Bacillus subtilis spores to life. However, oxidative stress due to full hydration of the spore core during germination and activation of metabolism in spore outgrowth may generate oxidative DNA damage that in many species is processed by apurinic/apyrimidinic (AP) endonucleases. B. subtilis spores possess two AP endonucleases, Nfo and ExoA; the outgrowth of spores lacking both of these enzymes was slowed, and the spores had an elevated mutation frequency, suggesting that these enzymes repair DNA lesions induced by oxidative stress during spore germination and outgrowth. Addition of H2O2 also slowed the outgrowth of nfo exoA spores and increased the mutation frequency, and nfo and exoA mutations slowed the outgrowth of spores deficient in either RecA, nucleotide excision repair (NER), or the DNA-protective α/β-type small acid-soluble spore proteins (SASP). These results suggest that α/β-type SASP protect DNA of germinating spores against damage that can be repaired by Nfo and ExoA, which is generated either spontaneously or promoted by addition of H2O2. The contribution of RecA and Nfo/ExoA was similar to but greater than that of NER in repair of DNA damage generated during spore germination and outgrowth. However, nfo and exoA mutations increased the spontaneous mutation frequencies of outgrown spores lacking uvrA or recA to about the same extent, suggesting that DNA lesions generated during spore germination and outgrowth are processed by Nfo/ExoA in combination with NER and/or RecA. These results suggest that Nfo/ExoA, RecA, the NER system, and α/β-type SASP all contribute to the repair of and/or protection against oxidative damage of DNA in germinating and outgrowing spores.

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Oxidative-Stress Resistance Mutants of Helicobacter pylori

Journal of Bacteriology ◽

10.1128/jb.184.12.3186-3193.2002 ◽

2002 ◽

Vol 184 (12) ◽

pp. 3186-3193 ◽

Cited By ~ 79

Author(s):

Adriana A. Olczak ◽

Jonathan W. Olson ◽

Robert J. Maier

Keyword(s):

Oxidative Stress ◽

Stress Resistance ◽

Double Mutant ◽

Mutation Frequency ◽

Spontaneous Mutation ◽

Type I ◽

Wild Type ◽

Oxidative Stress Resistance ◽

Spontaneous Mutation Frequency ◽

Resistance Mutants

ABSTRACT Within a large family of peroxidases, one member that catalyzes the reduction of organic peroxides to alcohols is known as alkyl hydroperoxide reductase, or AhpC. Gene disruption mutations in the gene encoding AhpC of Helicobacter pylori (ahpC) were generated by screening transformants under low-oxygen conditions. Two classes of mutants were obtained. Both types lack AhpC protein, but the major class (type I) isolated was found to synthesize increased levels (five times more than the wild type) of another proposed antioxidant protein, an iron-binding, neutrophil-activating protein (NapA). The other class of mutants, the minor class (type II), produced wild-type levels of NapA. The two types of AhpC mutants differed in their frequencies of spontaneous mutation to rifampin resistance and in their sensitivities to oxidative-stress chemicals, with the type I mutants exhibiting less sensitivity to organic hydroperoxides as well as having a lower mutation frequency. The napA promoter regions of the two types of AhpC mutants were identical, and primer extension analysis revealed their transcription start site to be the same as for the wild type. Gene disruption mutations were obtained in napA alone, and a double mutant strain (ahpC napA) was also created. All four of the oxidative-stress resistance mutants could be distinguished from the wild type in oxygen sensitivity or in some other oxidative-stress resistance phenotype (i.e., in sensitivity to stress-related chemicals and spontaneous mutation frequency). For example, growth of the NapA mutant was more sensitive to oxygen than that of the wild-type strain and both of the AhpC-type mutants were highly sensitive to paraquat and to cumene hydroperoxide. Of the four types of mutants, the double mutant was the most sensitive to growth inhibition by oxygen and by organic peroxides and it had the highest spontaneous mutation frequency. Notably, two-dimensional gel electrophoresis combined with protein sequence analysis identified another possible oxidative-stress resistance protein (HP0630) that was up-regulated in the double mutant. However, the transcription start site of the HP0630 gene was the same for the double mutant as for the wild type. It appears that H. pylori can readily modulate the expression of other resistance factors as a compensatory response to loss of a major oxidative-stress resistance component.

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Antioxidative Effect of Rhus javanica Linne Extract Against Hydrogen Peroxide or Menadione Induced Oxidative Stress and DNA Damage in HepG2Cells

Preventive Nutrition and Food Science ◽

10.3746/jfn.2004.9.2.150 ◽

2004 ◽

Vol 9 (2) ◽

pp. 150-155 ◽

Cited By ~ 2

Author(s):

Chi-Sung Chun ◽

Ji-Hyun Kim ◽

Hyun-Ae Lim ◽

Ho-Yong Sohn ◽

Kun-Ho Son ◽

...

Keyword(s):

Oxidative Stress ◽

Hydrogen Peroxide ◽

Dna Damage ◽

Antioxidative Effect

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Escherichia coli MutM Suppresses Illegitimate Recombination Induced by Oxidative Stress

Genetics ◽

10.1093/genetics/151.2.439 ◽

1999 ◽

Vol 151 (2) ◽

pp. 439-446 ◽

Cited By ~ 2

Author(s):

Masaaki Onda ◽

Katsuhiro Hanada ◽

Hirokazu Kawachi ◽

Hideo Ikeda

Keyword(s):

Oxidative Stress ◽

Escherichia Coli ◽

Hydrogen Peroxide ◽

Dna Damage ◽

Double Strand Breaks ◽

Illegitimate Recombination ◽

Recombination Analysis ◽

Wild Type ◽

Strand Breaks ◽

In The Wild

Abstract DNA damage by oxidative stress is one of the causes of mutagenesis. However, whether or not DNA damage induces illegitimate recombination has not been determined. To study the effect of oxidative stress on illegitimate recombination, we examined the frequency of λbio transducing phage in the presence of hydrogen peroxide and found that this reagent enhances illegitimate recombination. To clarify the types of illegitimate recombination, we examined the effect of mutations in mutM and related genes on the process. The frequency of λbio transducing phage was 5- to 12-fold higher in the mutM mutant than in the wild type, while the frequency in the mutY and mutT mutants was comparable to that of the wild type. Because 7,8-dihydro-8-oxoguanine (8-oxoG) and formamido pyrimidine (Fapy) lesions can be removed from DNA by MutM protein, these lesions are thought to induce illegitimate recombination. Analysis of recombination junctions showed that the recombination at Hotspot I accounts for 22 or 4% of total λbio transducing phages in the wild type or in the mutM mutant, respectively. The preferential increase of recombination at nonhotspot sites with hydrogen peroxide in the mutM mutant was discussed on the basis of a new model, in which 8-oxoG and/or Fapy residues may introduce double-strand breaks into DNA.

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SPONTANEOUS UNSTABLE UNC-22 IV MUTATIONS IN C. ELEGANS VAR. BERGERAC

Genetics ◽

10.1093/genetics/108.4.859 ◽

1984 ◽

Vol 108 (4) ◽

pp. 859-877

Author(s):

D G Moerman ◽

R H Waterston

Keyword(s):

Mutation Frequency ◽

Spontaneous Mutation ◽

Phenotypic Effect ◽

C Elegans ◽

High Mutation Frequency ◽

Mutator Activity ◽

Discrete Site ◽

Unstable Mutations ◽

Spontaneous Mutation Frequency ◽

Forward Mutation

ABSTRACT This paper describes a mutator system in the nematode Caenorhabditis elegans var. Bergerac for the gene unc-22. Of nine C. elegans and two C. briggsae strains tested only the Bergerac BO strain yielded mutant animals at a high frequency and the unc-22 IV gene is a preferred mutational target. The forward spontaneous mutation frequency at the unc-22 locus in Bergerac BO is about 1 × 10-4, and most of these spontaneous unc-22 mutations revert at frequencies between 2 × 10-3 and 2 × 10-4. Both the forward mutation frequency and the reversion frequency are sensitive to genetic background. Spontaneous unc-22 mutations derived in a Bergerac background and placed in a primarily Bristol background revert at frequencies of <10-6. When reintroduced into a Bergerac/Bristol hybrid background the mutations once again become unstable. The mutator activity could not be localized to a discrete site in the Bergerac genome. Nor did mutator activity require the Bergerac unc-22 gene as a target since the Bristol unc-22 homolog placed in a Bergerac background also showed high mutation frequency. Intragenic mapping of two spontaneous unc-22 alleles, st136 and st137, place both mutations in the central region of the known unc-22 map. However, these mutations probably recombine with one another, suggesting that the unstable mutations can occur in more than one site in unc-22. Examination of the phenotypic effect of these mutations on muscle structure indicates that they are less severe in their effect than a known amber allele. We suggest that this mutator system is polygenic and dispersed over the nematode genome and could represent activity of the transposable element Tc1.

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Determination of the spontaneous mutation frequency per cell per generation in human diploid fibroblasts cultured at different temperatures

Mutation Research/Environmental Mutagenesis and Related Subjects ◽

10.1016/0165-1161(83)90153-x ◽

1983 ◽

Vol 113 (3-4) ◽

pp. 306

Author(s):

J.W.I.M. Simons

Keyword(s):

Mutation Frequency ◽

Spontaneous Mutation ◽

Diploid Fibroblasts ◽

Human Diploid Fibroblasts ◽

Different Temperatures ◽

Spontaneous Mutation Frequency

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Nuclear mutations in Saccharomyces cerevisiae which increase the spontaneous mutation frequency in mitochondrial DNA

MGG Molecular & General Genetics ◽

10.1007/bf00267066 ◽

1979 ◽

Vol 170 (3) ◽

pp. 327-331 ◽

Cited By ~ 24

Author(s):

Leland H. Johnson

Keyword(s):

Saccharomyces Cerevisiae ◽

Mitochondrial Dna ◽

Mutation Frequency ◽

Spontaneous Mutation ◽

Nuclear Mutations ◽

Spontaneous Mutation Frequency

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Stable down-regulation of human polynucleotide kinase enhances spontaneous mutation frequency and sensitizes cells to genotoxic agents

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.0400099101 ◽

2004 ◽

Vol 101 (18) ◽

pp. 6905-6910 ◽

Cited By ~ 104

Author(s):

A. Rasouli-Nia ◽

F. Karimi-Busheri ◽

M. Weinfeld

Keyword(s):

Mutation Frequency ◽

Spontaneous Mutation ◽

Down Regulation ◽

Polynucleotide Kinase ◽

Genotoxic Agents ◽

Spontaneous Mutation Frequency

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Sml1 Inhibits the DNA Repair Activity of Rev1 in Saccharomyces cerevisiae during Oxidative Stress

Applied and Environmental Microbiology ◽

10.1128/aem.02838-19 ◽

2020 ◽

Vol 86 (7) ◽

Author(s):

Rui Yao ◽

Pei Zhou ◽

Chengjin Wu ◽

Liming Liu ◽

Jing Wu

Keyword(s):

Oxidative Stress ◽

Saccharomyces Cerevisiae ◽

Dna Damage ◽

Survival Rate ◽

Type Strain ◽

Mutation Frequency ◽

Wild Type Strain ◽

Yeast Cells ◽

Wild Type ◽

Content Type

ABSTRACT In Saccharomyces cerevisiae, Y family DNA polymerase Rev1 is involved in the repair of DNA damage by translesion DNA synthesis (TLS). In the current study, to elucidate the role of Rev1 in oxidative stress-induced DNA damage in S. cerevisiae, REV1 was deleted and overexpressed; transcriptome analysis of these mutants along with the wild-type strain was performed to screen potential genes that could be associated with REV1 during response to DNA damage. When the yeast cells were treated with 2 mM H2O2, the deletion of REV1 resulted in a 1.5- and 2.8-fold decrease in the survival rate and mutation frequency, respectively, whereas overexpression of REV1 increased the survival rate and mutation frequency by 1.1- and 2.9-fold, respectively, compared to the survival rate and mutation frequency of the wild-type strain. Transcriptome and phenotypic analyses identified that Sml1 aggravated oxidative stress in the yeast cells by inhibiting the activity of Rev1. This inhibition was due to the physical interaction between the BRCA1 C terminus (BRCT) domain of Rev1 and amino acid residues 36 to 70 of Sml1; the cell survival rate and mutation frequency increased by 1.8- and 3.1-fold, respectively, when this interaction was blocked. We also found that Sml1 inhibited Rev1 phosphorylation under oxidative stress and that deletion of SML1 increased the phosphorylation of Rev1 by 46%, whereas overexpression of SML1 reduced phosphorylation of Rev1. Overall, these findings demonstrate that Sml1 could be a novel regulator that mediates Rev1 dephosphorylation to inhibit its activity during oxidative stress. IMPORTANCE Rev1 was critical for cell growth in S. cerevisiae, and the deletion of REV1 caused a severe growth defect in cells exposed to oxidative stress (2 mM H2O2). Furthermore, we found that Sml1 physically interacted with Rev1 and inhibited Rev1 phosphorylation, thereby inhibiting Rev1 DNA antioxidant activity. These findings indicate that Sml1 could be a novel regulator for Rev1 in response to DNA damage by oxidative stress.

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