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| 2. |
- Bajinskis, Ainars, et al.
(författare)
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The indirect effect of radiation reduces the repair fidelity of NHEJ as verified in repair deficient CHO cell lines exposed to different radiation qualities and potassium bromate
- 2012
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Ingår i: Mutation research. - : Elsevier. - 0027-5107 .- 1873-135X. ; 731, s. 125-132
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Tidskriftsartikel (refereegranskat)abstract
- The complexity of DNA lesions induced by ionizing radiation is mainly dependent on radiation quality, where the indirect action of radiation may contribute to different extent depending on the type of radiation under study. The effect of indirect action of radiation can be investigated by using agents that induce oxidative DNA damage or by applying free radical scavengers. The aim of this study was to investigate the role of the indirect effect of radiation for the repair fidelity of non-homologous end-joining (NHEJ), homologous recombination repair (HRR) and base excision repair (BER) when DNA damage of different complexity was induced by gamma radiation, alpha particles or from base damages (8-oxo-dG) induced by potassium bromate (KBrO3).CHO cells lines deficient in XRCC3 (HRR) irs1SF, XRCC7 (NHEJ) V3-3 and XRCC1 (BER) EM9 were irradiated in the absence or presence of the free radical scavenger dimethyl sulphoxide (DMSO). The endpoints investigated included rate of cell proliferation by the DRAG assay, clonogenic cell survival and the level of primary DNA damage by the comet assay.The results revealed that the indirect effect of low-LET radiation significantly reduced the repair fidelity of both NHEJ and HRR pathways. For high-LET radiation the indirect effect of radiation also significantly reduced the repair fidelity for the repair deficient cell lines. The results suggest further that the repair fidelity of the error prone NHEJ repair pathway is more impaired by the indirect effect of high-LET radiation relative to the other repair pathways studied. The response to bromate observed for the two DSB repair deficient cell lines strongly support earlier studies that bromate induces complex DNA damages. The significantly reduced repair fidelity of irs1SF and V3-3 suggests that NHEJ as well as HRR are needed for the repair, and that complex DSBs are formed after bromate exposure.
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- de Verdier, Petra J., et al.
(författare)
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Genotypes, haplotypes and diplotypes of three XPC polymorphisms in urinary-bladder cancer patients
- 2010
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Ingår i: Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis. - : Elsevier BV. - 1879-2871 .- 0027-5107. ; 694:1-2, s. 39-44
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Tidskriftsartikel (refereegranskat)abstract
- Purpose The XPC gene is involved in DNA damage recognition in the nucleotide excision repair pathway (NER) We investigated the additive effects of single nucleotide polymorphisms (SNPs) in bladder-cancer patients and population controls for three XPC polymorphisms A499V (C>T) K939Q (A>C) and poly AT (PAT -/+) Experimental Design 311 bladder-cancer patients from a population-based cohort and 337 population controls were genotyped using the PCR-restriction fragment length polymorphism (RFLP) technique Results We found complete linkage between the K939Q (A>C) and PAT (-/+) polymorphisms and therefore only the K939Q (A>C) polymorphism was included in analyses The over all estimated odds ratio was 1 7 (95% CI 1 3-2 4) for A499V (C>T) and 1 4 (95% CI 1 0-2 0) for K939Q (A>C) The associated odds ratio Increase with the variant allele homozygotes was six-fold for the A499V (C>T) and three-fold for the K939Q (A>C) polymorphism (OR=5 7 95% CI 3 4-9 5 and OR=2 6 95% CI 1 3-5 6 respectively) The variant allele haplotype of the two polymorphisms (T499C939) was associated with a nearly four fold increased odds ratio compared to the common allele haplotype (C(499)A(939)) (OR=3 6 95% Cl 1 9-6 9) Combined genotype analysis showed an Increased disease association with increasing number of variant alleles (p<0 0001) with a dominant effect of the A499V polymorphism In addition we observed association of the disease with increasing number of variant alleles for the A499V polymorphism and an early age at diagnosis (p=0 004) Conclusions Our results suggest an association between the XPC genotypes of the A499V K939Q and PAT polymorphisms and urinary-bladder cancer We propose a poly-allelic effect of these polymorphisms where the cumulative effect on disease becomes higher than the individual allelic effects (C) 2010 Elsevier B V All rights reserved
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| 5. |
- Engström, Karin, et al.
(författare)
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Low 8-oxo-7,8-dihydro-2'-deoxyguanosine levels and influence of genetic background in an Andean population exposed to high levels of arsenic.
- 2010
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Ingår i: Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis. - : Elsevier BV. - 1879-2871 .- 0027-5107. ; 683:1-2, s. 98-105
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Arsenic (As) causes oxidative stress through generation of reactive oxygen species. 8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a sensitive marker of oxidative DNA damage, has been associated with As exposure in some studies, but not in others, possibly due to population-specific genetic factors. OBJECTIVES: To evaluate the association between As and 8-oxodG in urine in a population with a low urinary monomethylated As (%MMA) and high dimethylated As (%DMA), as well as the genetic impact on (a) 8-oxodG concentrations and (b) the association between As and 8-oxodG. MATERIALS AND METHODS: Women (N=108) in the Argentinean Andes were interviewed and urine was analyzed for arsenic metabolites (ICPMS) and 8-oxodG (LC-MS/MS). Twenty-seven polymorphisms in genes related to oxidative stress and one in As(+III)methyltransferase (AS3MT) were studied. RESULTS: Median concentration of 8-oxodG was 4.7nmol/L (adjusted for specific weight; range 1.6-13, corresponding to 1.7mug/g creatinine, range 0.57-4.8) and of total urinary As metabolites (U-As) 290mug/L (range 94-720; 380mug/g creatinine, range 140-1100). Concentrations of 8-oxodG were positively associated with %MMA (strongest association, p=0.013), and weakly associated with U-As (positively) and %DMA (negatively). These associations were strengthened when taking ethnicity into account, possibly reflecting genetic differences in As metabolism and genes regulating oxidative stress and DNA maintenance. A genetic influence on 8-oxodG concentrations was seen for polymorphisms in apurinic/apyrimidinic endonuclease 1 (APEX1), DNA-methyltransferases 1 and 3b (DNMT1, DNMT3B), thioredoxin reductase 1 (TXNRD1) and 2 (TXNRD2) and glutaredoxin (GLRX). CONCLUSION: Despite high As exposure, the concentrations of 8-oxodG in this population were low compared with other As-exposed populations studied. The strongest association was found for %MMA, stressing that some inconsistencies between As and 8-oxodG partly depend on population variations in As metabolism. We found evidence of genetic impact on 8-oxodG concentrations.
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| 7. |
- Fotouhi, Asal, et al.
(författare)
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Analysis of mutant frequencies and mutation spectra in hMTH1 knockdown TK6 cells exposed to UV radiation
- 2013
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Ingår i: Mutation research. - : Elsevier BV. - 0027-5107 .- 1873-135X. ; 751, s. 8-14
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Tidskriftsartikel (refereegranskat)abstract
- Ultraviolet radiation is a highly mutagenic agent that damages the DNA by the formation of mutagenic photoproducts at dipyrimidine sites and by oxidative DNA damages via reactive oxygen species (ROS). ROS can also give rise to mutations via oxidation of dNTPs in the nucleotide pool, e.g. 8-oxo-dGTP and 2-OH-dATP and subsequent incorporation during DNA replication. Here we show that expression of human MutT homolog 1 (hMTH1) which sanitizes the nucleotide pool by dephosphorylating oxidized dNTPs, protects against mutagenesis induced by long wave UVA light and by UVB light but not by short wave UVC light. Mutational spectra analyses of UVA-induced mutations at the endogenous Thymidine kinase gene in human lymphoblastoid cells revealed that hMTH1 mainly protects cells from transitions at GC and AT base pairs.
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| 8. |
- Fotouhi, Asal, et al.
(författare)
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Reduction of 8-oxodGTP in the nucleotide pool by hMTH1 leads to reduction in mutations in the human lymphoblastoid cell line TK6 exposed to UVA
- 2011
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Ingår i: Mutation research. - : Elsevier BV. - 0027-5107 .- 1873-135X. ; 715:1-2, s. 13-18
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Tidskriftsartikel (refereegranskat)abstract
- UVA has been suggested to play an important role in UV-induced mutagenesis. The mechanisms by which UVA induces mutations are still a matter of debate. Our aim was to investigate the protective capacity of hMTH1, a nucleotide pool sanitization enzyme with 8-oxodGTPase activity. Human B lymphoblastoid cells were stably transfected with shRNA directed against hMTH1. Clonogenic survival, mutations, intracellular and extracellular levels of 8-oxodG (8-oxo-7, 8-dihydro-2'-deoxyguanosine) and dG in the nucleotide pool of UVA-irradiated transfected and non-transfected cells were investigated. Mutations were determined in the thymidine kinase locus. Intracellular 8-oxodG and dG were measured using a modified ELISA and HPLC, respectively, after extraction of the nucleotide pool and conversion of nucleotides to their corresponding nucleosides. 8-oxodG in the medium was measured using ELISA. UVA-induced mutations were significantly higher while the survival was slightly lower in transfected compared to non-transfected cells. The increased mutation rate in transfected cells at increased exposure correlated with enhanced levels of 8-oxodG in the nucleotide pool, and a somewhat reduced level of 8-oxodG in the medium. The results indicate that the nucleotide pool is a significant target for UVA-induced mutations and implicates that hMTH1 plays an important role in protecting cells from UVA-induced oxidative stress.
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| 10. |
- Gustafsson, Ann-Sofie, et al.
(författare)
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Suppression of DNA-dependent protein kinase sensitize cells to radiation without affecting DSB repair
- 2014
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Ingår i: Mutation research. - : Elsevier BV. - 0027-5107 .- 1873-135X. ; 769, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Efficient and correct repair of DNA double-strand break (DSB) is critical for cell survival. Defects in the DNA repair may lead to cell death, genomic instability and development of cancer. The catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) is an essential component of the non-homologous end joining (NHEJ) which is the major DSB repair pathway in mammalian cells. In the present study, by using siRNA against DNA-PKcs in four human cell lines, we examined how low levels of DNA-PKcs affected cellular response to ionizing radiation. Decrease of DNA-PKcs levels by 80-95%, induced by siRNA treatment, lead to extreme radiosensitivity, similar to that seen in cells completely lacking DNA-PKcs and low levels of DNA-PKcs promoted cell accumulation in G2/M phase after irradiation and blocked progression of mitosis. Surprisingly, low levels of DNA-PKcs did not affect the repair capacity and the removal of 53BP1 or gamma-H2AX foci and rejoining of DSB appeared normal. This was in strong contrast to cells completely lacking DNA-PKcs and cells treated with the DNA-PKcs inhibitor NU7441, in which DSB repair were severely compromised. This suggests that there are different mechanisms by which loss of DNA-PKcs functions can sensitize cells to ionizing radiation. Further, foci of phosphorylated DNA-PKcs (T2609 and S2056) co-localized with DSB and this was independent of the amount of DNA-PKcs but foci of DNA-PKcs was only seen in siRNA-treated cells. Our study emphasizes on the critical role of DNA-PKcs for maintaining survival after radiation exposure which is uncoupled from its essential function in DSB repair. This could have implications for the development of therapeutic strategies aiming to radiosensitize tumors by affecting the DNA-PKcs function.
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