Role of Bacillus subtilis Error Prevention Oxidized Guanine System in Counteracting Hexavalent Chromium-Promoted Oxidative DNA Damage

ABSTRACTChromium pollution is potentially detrimental to bacterial soil communities, compromising carbon and nitrogen cycles that are essential for life on earth. It has been proposed that intracellular reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] may cause bacterial death by a mechanism that involves reactive oxygen species (ROS)-induced DNA damage; the molecular basis of the phenomenon was investigated in this work. Here, we report thatBacillus subtiliscells lacking a functional error prevention oxidized guanine (GO) system were significantly more sensitive to Cr(VI) treatment than cells of the wild-type (WT) strain, suggesting that oxidative damage to DNA is involved in the deleterious effects of the oxyanion. In agreement with this suggestion, Cr(VI) dramatically increased the ROS concentration and induced mutagenesis in a GO-deficientB. subtilisstrain. Alkaline gel electrophoresis (AGE) analysis of chromosomal DNA of WT and ΔGO mutant strains subjected to Cr(VI) treatment revealed that the DNA of the ΔGO strain was more susceptible to DNA glycosylase Fpg attack, suggesting that chromium genotoxicity is associated with 7,8-dihydro-8-oxodeoxyguanosine (8-oxo-G) lesions. In support of this notion, specific monoclonal antibodies detected the accumulation of 8-oxo-G lesions in the chromosomes ofB. subtiliscells subjected to Cr(VI) treatment. We conclude that Cr(VI) promotes mutagenesis and cell death inB. subtilisby a mechanism that involves radical oxygen attack of DNA, generating 8-oxo-G, and that such effects are counteracted by the prevention and repair GO system.

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Defects in the Error Prevention Oxidized Guanine System Potentiate Stationary-Phase Mutagenesis in Bacillus subtilis

Journal of Bacteriology ◽

10.1128/jb.01210-08 ◽

2008 ◽

Vol 191 (2) ◽

pp. 506-513 ◽

Cited By ~ 26

Author(s):

Luz E. Vidales ◽

Lluvia C. Cárdenas ◽

Eduardo Robleto ◽

Ronald E. Yasbin ◽

Mario Pedraza-Reyes

Keyword(s):

Oxidative Stress ◽

Bacillus Subtilis ◽

Stationary Phase ◽

Repair System ◽

Induced Mutations ◽

General Role ◽

Error Prevention ◽

Repair Mechanisms ◽

Induced Mutagenesis ◽

Oxidized Guanine

ABSTRACT Previous studies showed that a Bacillus subtilis strain deficient in mismatch repair (MMR; encoded by the mutSL operon) promoted the production of stationary-phase-induced mutations. However, overexpression of the mutSL operon did not completely suppress this process, suggesting that additional DNA repair mechanisms are involved in the generation of stationary-phase-associated mutants in this bacterium. In agreement with this hypothesis, the results presented in this work revealed that starved B. subtilis cells lacking a functional error prevention GO (8-oxo-G) system (composed of YtkD, MutM, and YfhQ) had a dramatic propensity to increase the number of stationary-phase-induced revertants. These results strongly suggest that the occurrence of mutations is exacerbated by reactive oxygen species in nondividing cells of B. subtilis having an inactive GO system. Interestingly, overexpression of the MMR system significantly diminished the accumulation of mutations in cells deficient in the GO repair system during stationary phase. These results suggest that the MMR system plays a general role in correcting base mispairing induced by oxidative stress during stationary phase. Thus, the absence or depression of both the MMR and GO systems contributes to the production of stationary-phase mutants in B. subtilis. In conclusion, our results support the idea that oxidative stress is a mechanism that generates genetic diversity in starved cells of B. subtilis, promoting stationary-phase-induced mutagenesis in this soil microorganism.

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Apurinic endonuclease-1 preserves neural genome integrity to maintain homeostasis and thermoregulation and prevent brain tumors

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1809682115 ◽

2018 ◽

Vol 115 (52) ◽

pp. E12285-E12294 ◽

Cited By ~ 6

Author(s):

Lavinia C. Dumitrache ◽

Mikio Shimada ◽

Susanna M. Downing ◽

Young Don Kwak ◽

Yang Li ◽

...

Keyword(s):

Dna Damage ◽

Nervous System ◽

Brain Tumors ◽

Oxidative Dna Damage ◽

Early Death ◽

Etiologic Agent ◽

Dna Lesions ◽

Oxidative Modification ◽

Early Gene ◽

Content Type

Frequent oxidative modification of the neural genome is a by-product of the high oxygen consumption of the nervous system. Rapid correction of oxidative DNA lesions is essential, as genome stability is a paramount determinant of neural homeostasis. Apurinic/apyrimidinic endonuclease 1 (APE1; also known as “APEX1” or “REF1”) is a key enzyme for the repair of oxidative DNA damage, although the specific role(s) for this enzyme in the development and maintenance of the nervous system is largely unknown. Here, using conditional inactivation of murine Ape1, we identify critical roles for this protein in the brain selectively after birth, coinciding with tissue oxygenation shifting from a placental supply to respiration. While mice lacking APE1 throughout neurogenesis were viable with little discernible phenotype at birth, rapid and pronounced brain-wide degenerative changes associated with DNA damage were observed immediately after birth leading to early death. Unexpectedly, Ape1Nes-cre mice appeared hypothermic with persistent shivering associated with the loss of thermoregulatory serotonergic neurons. We found that APE1 is critical for the selective regulation of Fos1-induced hippocampal immediate early gene expression. Finally, loss of APE1 in combination with p53 inactivation resulted in a profound susceptibility to brain tumors, including medulloblastoma and glioblastoma, implicating oxidative DNA lesions as an etiologic agent in these diseases. Our study reveals APE1 as a major suppressor of deleterious oxidative DNA damage and uncovers specific and broad pathogenic consequences of respiratory oxygenation in the postnatal nervous system.

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Transcriptional Regulation and Mechanism of SigN (ZpdN), a pBS32-Encoded Sigma Factor in Bacillus subtilis

mBio ◽

10.1128/mbio.01899-19 ◽

2019 ◽

Vol 10 (5) ◽

Cited By ~ 4

Author(s):

Aisha T. Burton ◽

Aaron DeLoughery ◽

Gene-Wei Li ◽

Daniel B. Kearns

Keyword(s):

Dna Damage ◽

Bacillus Subtilis ◽

Sigma Factor ◽

Consensus Sequence ◽

Sigma Factors ◽

Sequencing Analysis ◽

Dependent Manner ◽

Content Type ◽

Alternative Sigma Factors ◽

Bona Fide

ABSTRACT Laboratory strains of Bacillus subtilis encode many alternative sigma factors, each dedicated to expressing a unique regulon such as those involved in stress resistance, sporulation, and motility. The ancestral strain of B. subtilis also encodes an additional sigma factor homolog, ZpdN, not found in lab strains due to being encoded on the large, low-copy-number plasmid pBS32, which was lost during domestication. DNA damage triggers pBS32 hyperreplication and cell death in a manner that depends on ZpdN, but how ZpdN mediates these effects is unknown. Here, we show that ZpdN is a bona fide sigma factor that can direct RNA polymerase to transcribe ZpdN-dependent genes, and we rename ZpdN SigN accordingly. Rend-seq (end-enriched transcriptome sequencing) analysis was used to determine the SigN regulon on pBS32, and the 5′ ends of transcripts were used to predict the SigN consensus sequence. Finally, we characterize the regulation of SigN itself and show that it is transcribed by at least three promoters: PsigN1, a strong SigA-dependent LexA-repressed promoter; PsigN2, a weak SigA-dependent constitutive promoter; and PsigN3, a SigN-dependent promoter. Thus, in response to DNA damage SigN is derepressed and then experiences positive feedback. How cells die in a pBS32-dependent manner remains unknown, but we predict that death is the product of expressing one or more genes in the SigN regulon. IMPORTANCE Sigma factors are utilized by bacteria to control and regulate gene expression. Some sigma factors are activated during times of stress to ensure the survival of the bacterium. Here, we report the presence of a sigma factor that is encoded on a plasmid that leads to cellular death after DNA damage.

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Genome-Wide Analysis of Phosphorylated PhoP Binding to Chromosomal DNA Reveals Several Novel Features of the PhoPR-Mediated Phosphate Limitation Response in Bacillus subtilis

Journal of Bacteriology ◽

10.1128/jb.02570-14 ◽

2015 ◽

Vol 197 (8) ◽

pp. 1492-1506 ◽

Cited By ~ 14

Author(s):

Letal I. Salzberg ◽

Eric Botella ◽

Karsten Hokamp ◽

Haike Antelmann ◽

Sandra Maaß ◽

...

Keyword(s):

Cell Wall ◽

Bacillus Subtilis ◽

Response Regulator ◽

Teichoic Acid ◽

Phosphate Limitation ◽

Chromosomal Dna ◽

Cell Wall Metabolism ◽

Wall Teichoic Acid ◽

Content Type ◽

Two Component

ABSTRACTThe PhoPR two-component signal transduction system controls one of three responses activated byBacillus subtilisto adapt to phosphate-limiting conditions (PHO response). The response involves the production of enzymes and transporters that scavenge for phosphate in the environment and assimilate it into the cell. However, inB. subtilisand some otherFirmicutesbacteria, cell wall metabolism is also part of the PHO response due to the high phosphate content of the teichoic acids attached either to peptidoglycan (wall teichoic acid) or to the cytoplasmic membrane (lipoteichoic acid). Prompted by our observation that the phosphorylated WalR (WalR∼P) response regulator binds to more chromosomal loci than are revealed by transcriptome analysis, we established the PhoP∼P bindome in phosphate-limited cells. Here, we show that PhoP∼P binds to the chromosome at 25 loci: 12 are within the promoters of previously identified PhoPR regulon genes, while 13 are newly identified. We extend the role of PhoPR in cell wall metabolism showing that PhoP∼P binds to the promoters of four cell wall-associated operons (ggaAB,yqgS,wapA, anddacA), although none show PhoPR-dependent expression under the conditions of this study. We also show that positive autoregulation ofphoPRexpression and full induction of the PHO response upon phosphate limitation require PhoP∼P binding to the 3′ end of thephoPRoperon.IMPORTANCEThe PhoPR two-component system controls one of three responses mounted byB. subtilisto adapt to phosphate limitation (PHO response). Here, establishment of the phosphorylated PhoP (PhoP∼P) bindome enhances our understanding of the PHO response in two important ways. First, PhoPR plays a more extensive role in adaptation to phosphate-limiting conditions than was deduced from transcriptome analyses. Among 13 newly identified binding sites, 4 are cell wall associated (ggaAB,yqgS,wapA, anddacA), revealing that PhoPR has an extended involvement in cell wall metabolism. Second, amplification of the PHO response must occur by a novel mechanism since positive autoregulation ofphoPRexpression requires PhoP∼P binding to the 3′ end of the operon.

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Comparative Roles of the Two Helicobacter pylori Thioredoxins in Preventing Macromolecule Damage

Infection and Immunity ◽

10.1128/iai.00232-15 ◽

2015 ◽

Vol 83 (7) ◽

pp. 2935-2943 ◽

Cited By ~ 11

Author(s):

Lisa G. Kuhns ◽

Ge Wang ◽

Robert J. Maier

Keyword(s):

Dna Damage ◽

Helicobacter Pylori ◽

Oxidative Dna Damage ◽

Lipid Peroxides ◽

Transcript Abundance ◽

Protein Carbonylation ◽

Content Type ◽

Thioredoxin System ◽

Wide Range ◽

H Pylori

Thioredoxins are highly conserved throughout a wide range of organisms, and they are essential for the isurvival of oxygen-sensitive cells. The gastric pathogenHelicobacter pyloriuses the thioredoxin system to maintain its thiol/disulfide balance. There are two thioredoxins present inH. pylori, Trx1 and Trx2 (herein referred to as TrxA and TrxC). TrxA has been shown to be important as an electron donor for some antioxidant enzymes, but the function of TrxC remains unknown (L. M. Baker, A. Raudonikiene, P. S. Hoffman, and L. B. Poole, J Bacteriol 183:1961–1973, 2001; P. Alamuri and R. J. Maier, J Bacteriol 188:5839–5850, 2006). We demonstrate that both TrxA and TrxC are important in protectingH. pylorifrom oxidative stress. Individual ΔtrxAand ΔtrxCdeletion mutant strains each show a greater abundance of lipid peroxides and suffer more DNA damage and more protein carbonylation than the parent. Both deletion mutants were much more sensitive to O2-mediated viability loss than the parent. Unexpectedly, the oxidative DNA damage and protein carbonylation was more severe in the ΔtrxCmutant than in the ΔtrxAmutant; it had 20-fold- and 4-fold-more carbonylated protein content than the wild type and the ΔtrxAstrain, respectively, after 4 h of atmospheric O2stress.trxtranscript abundance was altered by the deletion of the heterologoustrxgene. The ΔtrxCmutant lacked mouse colonization ability, while the ability to colonize mouse stomachs was significantly reduced in the ΔtrxAmutant.

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Increased Chromosomal and Oxidative DNA Damage in Patients with Multinodular Goiter and Their Association with Cancer

International Journal of Endocrinology ◽

10.1155/2017/2907281 ◽

2017 ◽

Vol 2017 ◽

pp. 1-7 ◽

Cited By ~ 8

Author(s):

Hamiyet Donmez-Altuntas ◽

Fahri Bayram ◽

Nazmiye Bitgen ◽

Sibel Ata ◽

Zuhal Hamurcu ◽

...

Keyword(s):

Dna Damage ◽

Thyroid Cancer ◽

Multinodular Goiter ◽

Oxidative Dna Damage ◽

Thyroid Nodules ◽

Clinical Problem ◽

Peripheral Blood Lymphocytes ◽

Chromosomal Dna ◽

Increased Risk ◽

Cancer Types

Thyroid nodules are a common clinical problem worldwide. Although thyroid cancer accounts for a small percentage of thyroid nodules, the majority are benign. 8-Hydroxy-2′-deoxyguanosine (8-OHdG) levels are a marker of oxidative stress and play a key role in the initiation and development of a range of diseases and cancer types. This study evaluates cytokinesis-block micronucleus cytome (CBMN-cyt) assay parameters and plasma 8-OHdG levels and their association with thyroid nodule size and thyroid hormones in patients with multinodular goiter. The study included 32 patients with multinodular goiter and 18 age- and sex-matched healthy controls. CBMN-cyt assay parameters in peripheral blood lymphocytes of patients with multinodular goiter and controls were evaluated, and plasma 8-OHdG levels were measured. The micronucleus (MN) frequency (chromosomal DNA damage), apoptotic and necrotic cells (cytotoxicity), and plasma 8-OHdG levels (oxidative DNA damage) were significantly higher among patients with multinodular goiter. Our study is the first report of increased chromosomal and oxidative DNA damage in patients with multinodular goiter, which may predict an increased risk of thyroid cancer in these patients. MN frequency and plasma 8-OHdG levels may be markers of the carcinogenic potential of multinodular goiters and could be used for early detection of different cancer types, including thyroid cancer.

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The Therapeutic Role of Glutathione in Oxidative Stress and Oxidative DNA Damage Caused by Hexavalent Chromium

Biological Trace Element Research ◽

10.1007/s12011-016-0733-0 ◽

2016 ◽

Vol 174 (2) ◽

pp. 387-391 ◽

Cited By ~ 18

Author(s):

Asim Kart ◽

Evren Koc ◽

Kezban Yildiz Dalginli ◽

Canan Gulmez ◽

Mustafa Sertcelik ◽

...

Keyword(s):

Oxidative Stress ◽

Dna Damage ◽

Hexavalent Chromium ◽

Oxidative Dna Damage ◽

Therapeutic Role

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Therapeutic effects of statins on chromosomal DNA damage of dyslipidemic patients

Experimental Biology and Medicine ◽

10.1177/1535370219871895 ◽

2019 ◽

Vol 244 (13) ◽

pp. 1089-1095 ◽

Cited By ~ 1

Author(s):

Hamiyet Donmez-Altuntas ◽

Fahri Bayram ◽

Ayse N Coskun-Demirkalp ◽

Osman Baspınar ◽

Derya Kocer ◽

...

Keyword(s):

Dna Damage ◽

Statin Therapy ◽

Oxidative Dna Damage ◽

Nuclear Division ◽

Statin Treatment ◽

Therapeutic Effects ◽

Chromosomal Dna ◽

Control Subjects ◽

Before And After ◽

Nuclear Division Index

Statins are a group of cholesterol lowering drugs and frequently used in the therapy of dyslipidemia. Our knowledge of the impact of statin therapy on DNA damage is as yet rudimentary. In this study, we aimed to assess the possible (1) genotoxic, cytostatic, and cytotoxic effects of statins in peripheral blood lymphocytes by using the cytokinesis-block micronucleus cytome (CBMN-cyt) assay, and (2) oxidative DNA damage by measuring plasma 8-hydroxy-2′-deoxyguanosine (8-OHdG) levels in response to statin therapy. Thirty patients with dyslipidemia who had no chronic diseases and did not use any medicines that interfere lipid values and twenty control subjects were included in the study. Statin therapy was initiated at risk-stratified doses. Blood samples were taken before and after treatment with statins and from control subjects, and CBMN-cyt assay parameters and 8-OHdG levels were evaluated. The chromosomal DNA damage (micronuclei and nucleoplasmic bridges [NPBs]), cytostasis (nuclear division index [NDI]), and cytotoxicity (apoptotic and necrotic cell frequencies) were decreased in patients with dyslipidemia after statin treatment. No significant differences were found for 8-OHdG levels between patients with dyslipidemia before or after statin therapy. The total cholesterol and low-density lipoprotein-cholesterol levels showed positive correlations with NPB frequency in patients with dyslipidemia prior to statin treatment. The present study is the first to evaluate CBMN-cyt assay biomarkers and 8-OHdG levels in patients with dyslipidemia before and after treatment with statins. The observed reductions of chromosomal DNA damage and NDI values with statin treatment could represent an important and under-appreciated pleiotropic effect of these agents. Impact statement In literature, it is possible to find some in vitro cytokinesis-block micronucleus (CBMN) assay studies about human lymphocytes and statins. But, there are no data on CBMN-cytome (CBMN-cyt) assay parameters related to statin therapy in patients with dyslipidemia. The present study is the first to evaluate CBMN-cyt assay biomarkers and 8-OHdG levels in patients with dyslipidemia before treatment and after treatment with statins (5–10 mg/day rosuvastatin or 10–20 mg/day atorvastatin). In this study we show that statin therapy decreased chromosomal DNA damage (micronuclei and nucleoplasmic bridges) and nuclear division index (NDI) values in patients with dyslipidemia by possible molecular reasons independent of oxidative DNA damage. In addition, the decrease of chromosomal DNA damage and NDI values with statin treatment could be indicated by the association between statin use and reduced risk of cancer.

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Role of Mfd and GreA in Bacillus subtilis Base Excision Repair-Dependent Stationary-Phase Mutagenesis

Journal of Bacteriology ◽

10.1128/jb.00807-19 ◽

2020 ◽

Vol 202 (9) ◽

Author(s):

Hilda C. Leyva-Sánchez ◽

Norberto Villegas-Negrete ◽

Karen Abundiz-Yañez ◽

Ronald E. Yasbin ◽

Eduardo A. Robleto ◽

...

Keyword(s):

Bacillus Subtilis ◽

Stationary Phase ◽

Excision Repair ◽

Dna Lesions ◽

Ap Endonuclease ◽

Content Type ◽

Error Prone Repair ◽

Base Excision ◽

Oxidized Guanine

ABSTRACT We report that the absence of an oxidized guanine (GO) system or the apurinic/apyrimidinic (AP) endonucleases Nfo, ExoA, and Nth promoted stress-associated mutagenesis (SAM) in Bacillus subtilis YB955 (hisC952 metB5 leuC427). Moreover, MutY-promoted SAM was Mfd dependent, suggesting that transcriptional transactions over nonbulky DNA lesions promoted error-prone repair. Here, we inquired whether Mfd and GreA, which control transcription-coupled repair and transcription fidelity, influence the mutagenic events occurring in nutritionally stressed B. subtilis YB955 cells deficient in the GO or AP endonuclease repair proteins. To this end, mfd and greA were disabled in genetic backgrounds defective in the GO and AP endonuclease repair proteins, and the strains were tested for growth-associated and stress-associated mutagenesis. The results revealed that disruption of mfd or greA abrogated the production of stress-associated amino acid revertants in the GO and nfo exoA nth strains, respectively. These results suggest that in nutritionally stressed B. subtilis cells, spontaneous nonbulky DNA lesions are processed in an error-prone manner with the participation of Mfd and GreA. In support of this notion, stationary-phase ΔytkD ΔmutM ΔmutY (referred to here as ΔGO) and Δnfo ΔexoA Δnth (referred to here as ΔAP) cells accumulated 8-oxoguanine (8-OxoG) lesions, which increased significantly following Mfd disruption. In contrast, during exponential growth, disruption of mfd or greA increased the production of His+, Met+, or Leu+ prototrophs in both DNA repair-deficient strains. Thus, in addition to unveiling a role for GreA in mutagenesis, our results suggest that Mfd and GreA promote or prevent mutagenic events driven by spontaneous genetic lesions during the life cycle of B. subtilis. IMPORTANCE In this paper, we report that spontaneous genetic lesions of an oxidative nature in growing and nutritionally stressed B. subtilis strain YB955 (hisC952 metB5 leuC427) cells drive Mfd- and GreA-dependent repair transactions. However, whereas Mfd and GreA elicit faithful repair events during growth to maintain genome fidelity, under starving conditions, both factors promote error-prone repair to produce genetic diversity, allowing B. subtilis to escape from growth-limiting conditions.

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