scholarly journals Gene-Targeted Mice Lacking the Trex1 (DNase III) 3′→5′ DNA Exonuclease Develop Inflammatory Myocarditis

2004 ◽  
Vol 24 (15) ◽  
pp. 6719-6727 ◽  
Author(s):  
Masashi Morita ◽  
Gordon Stamp ◽  
Peter Robins ◽  
Anna Dulic ◽  
Ian Rosewell ◽  
...  
Keyword(s):  
Nuclear Dna ◽  
Excision Repair ◽  
Spontaneous Mutation ◽  
Repair System ◽  
Dna Base Excision Repair ◽  
Dna Base ◽  
Base Excision ◽  
Base Excision Repair System

ABSTRACT TREX1, originally designated DNase III, was isolated as a major nuclear DNA-specific 3′→5′ exonuclease that is widely distributed in both proliferating and nonproliferating mammalian tissues. The cognate cDNA shows homology to the editing subunit of the Escherichia coli replicative DNA polymerase III holoenzyme and encodes an exonuclease which was able to serve a DNA-editing function in vitro, promoting rejoining of a 3′ mismatched residue in a reconstituted DNA base excision repair system. Here we report the generation of gene-targeted Trex1−/− mice. The null mice are viable and do not show the increase in spontaneous mutation frequency or cancer incidence that would be predicted if Trex1 served an obligatory role of editing mismatched 3′ termini generated during DNA repair or DNA replication in vivo. Unexpectedly, Trex1−/− mice exhibit a dramatically reduced survival and develop inflammatory myocarditis leading to progressive, often dilated, cardiomyopathy and circulatory failure.

The Influence of Hepatitis C Virus Therapy on the DNA Base Excision Repair System of Peripheral Blood Mononuclear Cells

2017 ◽  
Vol 36 (7) ◽  
pp. 535-540 ◽  
Author(s):  
Piotr Czarny ◽  
Anna Merecz-Sadowska ◽  
Kinga Majchrzak ◽  
Maciej Jabłkowski ◽  
Janusz Szemraj ◽  
...  
Keyword(s):  
Base Excision Repair ◽  
Mononuclear Cells ◽  
Excision Repair ◽  
Repair System ◽  
Peripheral Blood Mononuclear ◽  
Dna Base Excision Repair ◽  
Dna Base ◽  
Blood Mononuclear Cells ◽  
Base Excision ◽  
Base Excision Repair System

scholarly journals Antagonism of Ultraviolet-Light Mutagenesis by the Methyl-Directed Mismatch-Repair System of Escherichia coli

Genetics ◽  
2000 ◽  
Vol 154 (2) ◽  
pp. 503-512 ◽  
Author(s):  
Hongbo Liu ◽  
Stephen R Hewitt ◽  
John B Hays
Keyword(s):  
Escherichia Coli ◽  
Mismatch Repair ◽  
Excision Repair ◽  
Spontaneous Mutation ◽  
Repair System ◽  
Uv Mutagenesis ◽  
Repair Protein ◽  
Mismatch Repair System

Abstract Previous studies have demonstrated that the Escherichia coli MutHLS mismatch-repair system can process UV-irradiated DNA in vivo and that the human MSH2·MSH6 mismatch-repair protein binds more strongly in vitro to photoproduct/base mismatches than to “matched” photoproducts in DNA. We tested the hypothesis that mismatch repair directed against incorrect bases opposite photoproducts might reduce UV mutagenesis, using two alleles at E. coli lacZ codon 461, which revert, respectively, via CCC → CTC and CTT → CTC transitions. F′ lacZ targets were mated from mut+ donors into mutH, mutL, or mutS recipients, once cells were at substantial densities, to minimize spontaneous mutation prior to irradiation. In umu+ mut+ recipients, a range of UV fluences induced lac+ revertant frequencies of 4–25 × 10−8; these frequencies were consistently 2-fold higher in mutH, mutL, or mutS recipients. Since this effect on mutation frequency was unaltered by an Mfd− defect, it appears not to involve transcription-coupled excision repair. In mut+ umuC122::Tn5 bacteria, UV mutagenesis (at 60 J/m2) was very low, but mutH or mutL or mutS mutations increased reversion of both lacZ alleles roughly 25-fold, to 5–10 × 10−8. Thus, at UV doses too low to induce SOS functions, such as Umu2′D, most incorrect bases opposite occasional photoproducts may be removed by mismatch repair, whereas in heavily irradiated (SOS-induced) cells, mismatch repair may only correct some photoproduct/base mismatches, so UV mutagenesis remains substantial.

scholarly journals Role of DNA polymerase β oxidized nucleotide insertion in DNA ligation failure

2017 ◽  
Vol 58 (5) ◽  
pp. 603-607 ◽  
Author(s):  
Melike Çağlayan ◽  
Samuel H Wilson
Keyword(s):  
Dna Polymerase ◽  
Genome Stability ◽  
Excision Repair ◽  
Cancer Therapeutics ◽  
Repair System ◽  
Dna Polymerase Β ◽  
Dna Base Excision Repair ◽  
Dna Base ◽  
Nucleotide Insertion ◽  
Base Excision

Abstract Production of reactive oxygen and nitrogen species (ROS), such as hydrogen peroxide, superoxide and hydroxyl radicals, has been linked to cancer, and these oxidative molecules can damage DNA. Base excision repair (BER), a major repair system maintaining genome stability over a lifespan, has an important role in repairing oxidatively induced DNA damage. Failure of BER leads to toxic consequences in ROS-exposed cells, and ultimately can contribute to the pathobiology of disease. In our previous report, we demonstrated that oxidized nucleotide insertion by DNA polymerase β (pol β) impairs BER due to ligation failure and leads to formation of a cytotoxic repair intermediate. Biochemical and cytotoxic effects of ligation failure could mediate genome stability and influence cancer therapeutics. In this review, we discuss the importance of coordination between pol β and DNA ligase I during BER, and how this could be a fundamental mechanism underlying human diseases such as cancer and neurodegeneration. A summary of this work was presented in a symposium at the International Congress of Radiation Research 2015 in Kyoto, Japan.

DNA base excision repair potentiates the protective effect of Salmonella Pathogenicity Island 2 within macrophages

Microbiology ◽  
2005 ◽  
Vol 151 (2) ◽  
pp. 557-567 ◽  
Author(s):  
Akamol E. Suvarnapunya ◽  
Murry A. Stein
Keyword(s):  
Base Excision Repair ◽  
Excision Repair ◽  
Pathogenicity Island ◽  
Discrete Systems ◽  
Dna Lesions ◽  
Repair System ◽  
Dna Base Excision Repair ◽  
Base Excision ◽  
Base Excision Repair System ◽  
Reactive Oxidants

Reactive oxidants are a primary weapon of the macrophage antibacterial arsenal. The ability of virulent Salmonella to repair oxidative DNA lesions via the base-excision repair system (BER) enables its survival and replication within the macrophage, but is not required for extracellular growth. Salmonella also inhibits the targeting of oxidant generators to the Salmonella-containing vacuole (SCV) via Salmonella Pathogenicity Island 2 (SPI2). Accordingly, the relative contributions of these two discrete systems to Salmonella resistance to both oxidative mutagenesis and lethality within RAW 264.7 macrophages were investigated. A mutant unable to initiate BER was constructed by deleting all three BER bifunctional glycosylases (Δfpg/nth/nei), and was significantly impaired for early intramacrophage survival. Mutations in various SPI2 effector (sifA and sseEFG) and structural (ssaV) genes were then analysed in the BER mutant background. Loss of SPI2 function alone appeared to increase macrophage-induced mutation. Statistical analyses of the reduced intramacrophage survival of SPI2 mutants and the corresponding SPI2/BER mutants indicated a synergistic interaction between BER and SPI2, suggesting that SPI2 promotes intramacrophage survival by protecting Salmonella DNA from exposure to macrophage oxidants. Furthermore, this protection may involve the SseF and SseG effectors. In contrast, the SifA effector did not seem to play a major role in oxidant protection. It is speculated that Salmonella initially stalls oxidative killing by preserving its genomic integrity through the function of BER, until it can upregulate SPI2 to limit its exposure to macrophage oxidants.

scholarly journals Participation of RecJ in the base excision repair pathway of Deinococcus radiodurans

2020 ◽  
Vol 48 (17) ◽  
pp. 9859-9871
Author(s):  
Kaiying Cheng ◽  
Ying Xu ◽  
Xuanyi Chen ◽  
Huizhi Lu ◽  
Yuan He ◽  
...  
Keyword(s):  
Base Excision Repair ◽  
Deinococcus Radiodurans ◽  
Excision Repair ◽  
Spontaneous Mutation ◽  
Nuclease Activity ◽  
Binding Pocket ◽  
Spontaneous Mutation Rate ◽  
Base Excision

Abstract RecJ reportedly participates in the base excision repair (BER) pathway, but structural and functional data are scarce. Herein, the Deinococcus radiodurans RecJ (drRecJ) deletion strain exhibited extreme sensitivity to hydrogen peroxide and methyl-methanesulphonate, as well as a high spontaneous mutation rate and an accumulation of unrepaired abasic sites in vivo, indicating the involvement of drRecJ in the BER pathway. The binding affinity and nuclease activity preference of drRecJ toward DNA substrates containing a 5′-P-dSpacer group, a 5′-deoxyribose-phosphate (dRP) mimic, were established. A 1.9 Å structure of drRecJ in complex with 5′-P-dSpacer-modified single-stranded DNA (ssDNA) revealed a 5′-monophosphate binding pocket and occupancy of 5′-dRP in the drRecJ nuclease core. The mechanism for RecJ 5′-dRP catalysis was explored using structural and biochemical data, and the results implied that drRecJ is not a canonical 5′-dRP lyase. Furthermore, in vitro reconstitution assays indicated that drRecJ tends to participate in the long-patch BER pathway rather than the short-patch BER pathway.

scholarly journals Repair of APOBEC3G-mutated retroviral DNA in vivo is facilitated by the host enzyme uracil DNA glycosylase 2

2021 ◽  
Author(s):  
Karen Salas Briceno ◽  
Susan R. Ross
Keyword(s):  
Base Excision Repair ◽  
Excision Repair ◽  
Critical Role ◽  
Dna Glycosylase ◽  
Repair System ◽  
Viral Dna ◽  
Uracil Dna Glycosylase ◽  
Base Excision

Apolipoprotein B mRNA Editing Enzyme Catalytic Subunit 3 (APOBEC3) proteins are critical for the control of infection by retroviruses. These proteins deaminate cytidines in negative strand DNA during reverse transcription, leading to G to A changes in coding strands. Uracil DNA glycosylase (UNG) is a host enzyme that excises uracils in genomic DNA, which the base excision repair machinery then repairs. Whether UNG removes uracils found in retroviral DNA after APOBEC3-mediated mutation is not clear, and whether this occurs in vivo has not been demonstrated. To determine if UNG plays a role in the repair of retroviral DNA, we used APOBEC3G (A3G) transgenic mice which we showed previously had extensive deamination of murine leukemia virus (MLV) proviruses. The A3G transgene was crossed onto an UNG and mouse APOBEC3 knockout background (UNG-/-APO-/-) and the mice were infected with MLV. We found that virus infection levels were decreased in A3G UNG-/-APO-/- compared to A3G APO-/- mice. Deep sequencing of the proviruses showed that there were significantly higher levels of G-to-A mutations in proviral DNA from A3G transgenic UNG-/-APO-/- than A3G transgenic APO-/- mice, suggesting that UNG plays a role in the repair of uracil-containing proviruses. In in vitro studies, we found that cytoplasmic viral DNA deaminated by APOBEC3G was uracilated. In the absence of UNG, the uracil-containing proviruses integrated at higher levels into the genome than did those made in the presence of UNG. Thus, UNG also functions in the nucleus prior to integration by nicking uracil-containing viral DNA, thereby blocking integration. These data show that UNG plays a critical role in the repair of the damage inflicted by APOBEC3 deamination of reverse-transcribed DNA. Importance While APOBEC3-mediated mutation of retroviruses is well-established, what role the host base excision repair enzymes play in correcting these mutations is not clear. This question is especially difficult to address in vivo . Here, we use a transgenic mouse developed by our lab that expresses human APOBEC3G and also lacks the endogenous uracil DNA glycosylase ( Ung ) gene, and show that UNG removes uracils introduced by this cytidine deaminase in MLV reverse transcripts, thereby reducing G-to-A mutations in proviruses. Furthermore, our data suggest that UNG removes uracils at two stages in infection – in unintegrated nuclear viral reverse transcribed DNA, resulting in its degradation and second, in integrated proviruses, resulting in their repair. These data suggest that retroviruses damaged by host cytidine deaminases take advantage of the host DNA repair system to overcome this damage.

scholarly journals Repair of APOBEC3G-mutated retroviral DNA in vivo is facilitated by the host enzyme uracil DNA glycosylase 2

2021 ◽  
Author(s):  
Karen Salas Briceno ◽  
Susan R. Ross
Keyword(s):  
Base Excision Repair ◽  
Excision Repair ◽  
Critical Role ◽  
Dna Glycosylase ◽  
Repair System ◽  
Viral Dna ◽  
Uracil Dna Glycosylase ◽  
Base Excision

AbstractApolipoprotein B mRNA Editing Enzyme Catalytic Subunit 3 (APOBEC3) proteins are critical for the control of infection by retroviruses. These proteins deaminate cytidines in negative strand DNA during reverse transcription, leading to G to A changes in coding strands. Uracil DNA glycosylase (UNG) is a host enzyme that excises uracils in genomic DNA, which the base excision repair machinery then repairs. Whether UNG removes uracils found in retroviral DNA after APOBEC3-mediated mutation is not clear, and whether this occurs in vivo has not been demonstrated. To determine if UNG plays a role in the repair of retroviral DNA, we used APOBEC3G (A3G) transgenic mice which we showed previously had extensive deamination of murine leukemia virus (MLV) proviruses. The A3G transgene was crossed onto an UNG and mouse APOBEC3 knockout background (UNG-/-APO-/-) and the mice were infected with MLV. We found that virus infection levels were decreased in A3G UNG-/-APO-/- compared to A3G APO-/- mice. Deep sequencing of the proviruses showed that there were significantly higher levels of G-to-A mutations in proviral DNA from A3G transgenic UNG-/-APO-/- than A3G transgenic APO-/- mice, suggesting that UNG plays a role in the repair of uracil-containing proviruses. In in vitro studies, we found that cytoplasmic viral DNA deaminated by APOBEC3G was uracilated. In the absence of UNG, the uracil-containing proviruses integrated at higher levels into the genome than did those made in the presence of UNG. Thus, UNG also functions in the nucleus prior to integration by nicking uracil-containing viral DNA, thereby blocking integration. These data show that UNG plays a critical role in the repair of the damage inflicted by APOBEC3 deamination of reverse-transcribed DNA.ImportanceWhile APOBEC3-mediated mutation of retroviruses is well-established, what role the host base excision repair enzymes play in correcting these mutations is not clear. This question is especially difficult to address in vivo. Here, we use a transgenic mouse developed by our lab that expresses human APOBEC3G and also lacks the endogenous uracil DNA glycosylase (Ung) gene, and show that UNG removes uracils introduced by this cytidine deaminase in MLV reverse transcripts, thereby reducing G-to-A mutations in proviruses. Furthermore, our data suggest that UNG removes uracils at two stages in infection – in unintegrated nuclear viral reverse transcribed DNA, resulting in its degradation and second, in integrated proviruses, resulting in their repair. These data suggest that retroviruses damaged by host cytidine deaminases take advantage of the host DNA repair system to overcome this damage.

scholarly journals Toxicological Comparison of Mancozeb and Zoxamide Fungicides at Environmentally Relevant Concentrations by an In Vitro Approach

2021 ◽  
Vol 18 (16) ◽  
pp. 8591
Author(s):  
Gabriele Lori ◽  
Roberta Tassinari ◽  
Laura Narciso ◽  
Ion Udroiu ◽  
Antonella Sgura ◽  
...  
Keyword(s):  
Comet Assay ◽  
Cell Lines ◽  
Excision Repair ◽  
Micronucleus Test ◽  
Repair System ◽  
Control Programs ◽  
Nucleotide Excision ◽  
Base Excision ◽  
Base Excision Repair System

Mancozeb (MZ) and zoxamide (ZOX) are fungicides commonly used in pest control programs to protect vineyards. Their toxic and genotoxic potential were investigated in vitro on HepG2 and A549 cell lines at environmentally relevant concentrations. Cytotoxicity, apoptosis, necrosis and intracellular reactive oxygen species (ROS), comet assay and a micronucleus test with CREST immunofluorescence were used. The expression of a panel of genes involved in apoptosis/necrosis (BAX/BCL2), oxidative stress (NRF2), drug metabolism (CYP1A1) and DNA repair (ERCC1/OGG1) was evaluated by real-time PCR. Both fungicides were cytotoxic at the highest tested concentrations (295.7 and 463.4 µM, respectively); MZ induced necrosis, ZOX did not increase apoptosis but modulated BAX and BCL2 expression, suggesting a different mechanism. Both compounds did not increase ROS, but the induction of CYP1A1 and NRF2 expression supported a pro-oxidant mechanism. The comet assay evidenced MZ genotoxicity, whereas no DNA damage due to ZOX treatment was observed. Positive micronuclei were increased in both cell lines treated with MZ and ZOX, supporting their aneugenic potential. ERCC1 and OGG1 were differently modulated, indicating the efficient activation of the nucleotide excision repair system by both fungicides and the inhibition of the base excision repair system by MZ. Overall, MZ confirmed its toxicity and new ZOX-relevant effects were highlighted.

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