• Archives of Pharmacal Research
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• 제29권3호
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• pp.213-217
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• 2006

The present study was undertaken to test the hypothesis that dietary antioxidants protect DNA damage induced by peroxynitrite, a potent physiological inorganic toxin. The present study showed that dietary antioxidants such as (-)-epigallocatechin gallate, quercerin, rutin, resveratrol, and ursolic acid inhibit single strand breaks in supercoiled plasmid DNA induced by 3-morpholinosydnomine N-ethylcarbamide (SIN-1), a generator of peroxynitrite through the reaction between nitric oxide and superoxide anion. The formation of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) in calf thymus DNA by SIN-1 was also inhibited by dietary antioxidants. When U937 cells were incubated with 1 mM SIN-1 bolus, a significant increase of 8-OH-dG level was observed. However, oxidative DNA damage was significantly lower in the cells pre-treated with dietary antioxidants when cells were exposed to SIN-1.

• 한국임상수의학회지
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• 제21권3호
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• pp.253-258
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• 2004

DNA double-strand break (DSB) is a serious treat for the cells including mutations, chromosome rearrangements, and even cell death if not repaired or misrepaired. Ku heterodimer regulatory DNA binding subunits (Ku70/Ku80) bound to double strand DNA breaks are able to interact with 470-kDa DNA-dependent protein kinase catalytic subunit (DNA-PKcs), and the interaction is essential for DNA-dependent protein kinase (DNA-PK) activity. The Ku80 mutants were designed to bind Ku70 but not DNA end binding activity and the peptides were treated in breast cancer cells for co-therapy strategy to see whether the targeted inhibition of DNA-dependent protein kinase (DNA-PK) activity sensitized breast cancer cells to ionizing irradiation or chemotherapy drug to develop a treatment of breast tumors by targeting proteins involved in damage-signaling pathway and/or DNA repair. We designed domains of Ku80 mutants, 26 residues of amino acids (HN-26) as a control peptide or 38 (HNI-38) residues of amino acids which contain domains of the membrane-translocation hydrophobic signal sequence and the nuclear localization sequence, but HNI-38 has additional twelve residues of peptide inhibitor region. We observed that the synthesized peptide (HNI-38) prevented DNA-PKcs from binding to Ku70/Ku80, resulting in inactivation of DNA-PK complex activity in breast cancer cells (MDA-465 and MDA-468). Consequently, the peptide treated cells exhibited poor to no DNA repair, and became highly sensitive to irradiation or chemotherapy drugs. The growth of breast cancer cells was also inhibited. These results demonstrate the possibility of synthetic peptide to apply breast cancer therapy to induce apoptosis of cancer cells.

• 대한수의학회지
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• 제38권3호
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• pp.606-613
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• 1998

Cadmium is one of the well-known environmental toxicants and induces cancer in rodents and human, but its carcinogenic mechanism has not been well demonstrated until now. Genotoxic effects of cadmium in Salmonella typhimurium TA98, TA100 and TA1535/pSK1002 or in WB-F344 rat liver epithelial cells were investigated to elucidate the tumor initiating effects of cadmium. TA98, TA100 and TA1535/pSK1002 tester strains were used to detect frameshift mutation, base-pair mutation and SOS repair response, respectively, in Salmonella mutation test. Reverse mutations from histidine to $histidin^+$ of Salmonella typhimurium TA98 and TA100 by $CdCl_2$ were not significantly different from control up to the maximum doses ($100{\mu}M$ and $200{\mu}M$ in TA98 and TA100, respectively) at which non-cytotoxicity was observed. DNA SOS repair responses(${\beta}$-galactosidase activity) generally did not show significant increases compared to control in both of the conditions with or without metabolic activation in Salmonella typhimurium TA1535/pSK1002 by $CdCl_2$. But the activities of ${\beta}$-galactosidase by $400{\mu}M$ of $CdCl_2$ in metabolic activation condition and by 130 and $400{\mu}M$ of $CdCl_2$ in non-metabolic activation condition were more decreased than those of control. DNA single strand breaks for 4hrs were observed only in WB-F344 rat liver epithelial cells treated with $200{\mu}M$ of $CdCl_2$. As a conclusion, $CdCl_2$ did not induce gene mutation in microbials but induce DNA single strand breaks in rat liver epithelial cells.

• BMB Reports
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• 제52권10호
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• pp.607-612
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• 2019

During meiosis, programmed double-strand breaks (DSBs) are repaired via recombination pathways that are required for faithful chromosomal segregation and genetic diversity. In meiotic progression, the non-homologous end joining (NHEJ) pathway is suppressed and instead meiotic recombination initiated by nucleolytic resection of DSB ends is the major pathway employed. This requires diverse recombinase proteins and regulatory factors involved in the formation of crossovers (COs) and non-crossovers (NCOs). In mitosis, spontaneous DSBs occurring at the G1 phase are predominantly repaired via NHEJ, mediating the joining of DNA ends. The Ku complex binds to these DSB ends, inhibiting additional DSB resection and mediating end joining with Dnl4, Lif1, and Nej1, which join the Ku complex and DSB ends. Here, we report the role of the Ku complex in DSB repair using a physical analysis of recombination in Saccharomyces cerevisiae during meiosis. We found that the Ku complex is not essential for meiotic progression, DSB formation, joint molecule formation, or CO/NCO formation during normal meiosis. Surprisingly, in the absence of the Ku complex and functional Mre11-Rad50-Xrs2 (MRX) complex, a large portion of meiotic DSBs was repaired via the recombination pathway to form COs and NCOs. Our data suggested that Ku complex prevents meiotic recombination in the elimination of MRX activity.

• Journal of Applied Biological Chemistry
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• 제56권1호
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• pp.37-42
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• 2013

In eukaryotes, most of the genome are transcribed, however only a small proportion of total transcripts encodes for protein, thus resulting in many of noncoding RNAs. In order to recover DNA damage including DNA double-strand breaks (DSBs) eukaryotes have evolved complex mechanisms and these are processed through coordinated mechanisms of protein sensors, transducers, and effectors including RNAs. During recent years, small RNAs have been increasingly studied and gradually considered as key regulators in various aspects of biology. Upon DNA damage, small RNAs including diRNAs (DSB induced RNA) are generated in both plant and human cell lines. Inhibition of their biogenesis has severe influence on DSB repair system.

• The Korean Journal of Physiology and Pharmacology
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• 제13권5호
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• pp.343-348
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• 2009

53BP1 is an important genome stability regulator, which protects cells against double-strand breaks. Following DNA damage, 53BP1 is rapidly recruited to sites of DNA breakage, along with other DNA damage response proteins, including ${\gamma}$-H2AX, MDC1, and BRCA1. The recruitment of 53BP1 requires a tandem Tudor fold which associates with methylated histones H3 and H4. It has already been determined that the majority of DNA damage response proteins are phosphorylated by ATM and/or ATR after DNA damage, and then recruited to the break sites. 53BP1 is also phosphorylated at several sites, like other proteins after DNA damage, but this phosphorylation is not critically relevant to recruitment or repair processes. In this study, we evaluated the functions of phosphor-53BP1 and the role of the BRCT domain of 53BP1 in DNA repair. From our data, we were able to detect differences in the phosphorylation patterns in Ser25 and Ser1778 of 53BP1 after neocarzinostatin-induced DNA damage. Furthermore, the foci formation patterns in both phosphorylation sites of 53BP1 also evidenced sizeable differences following DNA damage. From our results, we concluded that each phosphoryaltion site of 53BP1 performs different roles, and Ser1778 is more important than Ser25 in the process of DNA repair.

• Journal of Radiation Protection and Research
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• 제24권2호
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• pp.93-99
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• 1999

Alkaline single cell gel electrophoresis (SCGE) assay는 일명 혜성분석이라고 부르며 in vivo 와 in vitro 에서 많은 화학적, 생물학적인 인자에 의한 DNA 손상을 감지하는데 유용한 기법으로 각각의 세포에서 DNA 단일 가닥 절단과 알칼리에 약한 장소를 평가하는 새로운 방법으로 인정되고 있다. 단세포 겔 전기영동법 (SCGE)을 사용하여 복숭아씨 추출물이 방사선에 의하여 사람 림프구 DNA에 나타나는 손상을 보호하는 지 여부를 평가하였다. 복숭아씨 추출물로 10 분간 전처리한 림프구를 0, 0.1, 0.3, 0.5, 1.0, 2.0 Gy 의 방사선으로 조사하였고 방사선만을 조사한 림프구 실험군과 비교평가하였다. 혜성분석에서 DNA 가닥 절단에 대한 표식인 tail moment의 증가는 감마선에 대해서 뚜렷한 선량-반응 관계를 나타내었으며 각각의 농도별로 복숭아씨 추출물이 처리된 림프구의 DNA 손상은 현저히 감소하였다. 단세포 겔 전기영동법을 통한 평가결과 복숭아씨 추출물은 방사선에 의한 림프구 DNA 손상에 대한 탁월한 방어효과를 나타내었다.

• Environmental Analysis Health and Toxicology
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• 제23권1호
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• pp.33-39
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• 2008

The genotoxicity of mercury compounds have been investigated with a variety of genetic endpoints in prokaryotic and eukaryotic cells. The mercury ions are positively charged and easily form complexes with DNA by binding with negatively charged centers to cause mutagenesis. Further, the mercury ions can react with sulfhydryl (-SH) groups of proteins associated with DNA replication and alter genetic information. Another mechanism by which mercury damages DNA molecule is via its probable involvement of reactive oxygen species (ROS) and induces DNA strand breaks. In order to investigate whether the ROS production was induced by mercury, we performed ROS assay. As the result, the ROS production was significantly increased when it grows dose-dependently and time-dependently. We compared mercury alone-treated group and mercury co-treated with Vitamin C or glutathione group. As the result, the ROS production induced by mercury was decreased by Vitamin C and glutathione. Co-treated with Vitamin C and glutathione group was the most effective to lowering ROS production induced by mercury.

• Environmental Engineering Research
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• 제15권1호
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• pp.23-27
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• 2010

Genotoxic- and ecotoxic assessments of silver nanoparticles (AgNPs) were conducted on the freshwater crustacean Daphnia magna. AgNPs may have genotoxic effects on D. magna, given that the DNA strand breaks increased when exposed to this nanoparticle. Increased mortality was concomitantly observed with DNA damage in the AgNPs-exposed D. magna, which suggests AgNPs-induced DNA damage might provoke higher-level consequences. The results of the comparative toxicities of AgNPs and Ag ions suggest that AgNPs are slightly more toxic than Ag ions. Overall, these results suggest that AgNPs may be genotoxic toward D. magna, which may contribute to the knowledge relating to the aquatic toxicity of AgNPs on aquatic ecosystems, for which little data are available.

• BMB Reports
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• 제52권8호
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• pp.475-481
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• 2019

The evolution of genome editing technology based on CRISPR (clustered regularly interspaced short palindromic repeats) system has led to a paradigm shift in biological research. CRISPR/Cas9-guide RNA complexes enable rapid and efficient genome editing in mammalian cells. This system induces double-stranded DNA breaks (DSBs) at target sites and most DNA breakages induce mutations as small insertions or deletions (indels) by non-homologous end joining (NHEJ) repair pathway. However, for more precise correction as knock-in or replacement of DNA base pairs, using the homology-directed repair (HDR) pathway is essential. Until now, many trials have greatly enhanced knock-in or substitution efficiency by increasing HDR efficiency, or newly developed methods such as Base Editors (BEs). However, accuracy remains unsatisfactory. In this review, we summarize studies to overcome the limitations of HDR using the CRISPR system and discuss future direction.