• Korean Journal of Environmental Biology
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• v.29 no.1
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• pp.68-73
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• 2011

The single cell gel electrophoresis (SCGE) assay is a microelectrophoretic technique for assessments of DNA damage at the level of the individual eukaryotic cell. The SCGE assay, due to its simplicity, sensitivity and need of a few cells, has advantages compared to other genomic damage assays such as sister chromatid exchange, chromosomal aberration and micronucleus test. In this study, investigated were the levels of DNA damage and the repair kinetics in the coelomocytes of Eisenia fetida treated with HgCl2 and ionizing radiation by means of the SCGE assay. For detecting DNA damage and repair in coelomocytes, earthworms (E. fetida) were irradiated with six doses of ${\gamma}$-rays (0, 2.5, 5, 10, 20 and 50 Gy) and in vivo exposed to mercuric chloride at 0, 80 and 160 mg $kg^{-1}$ for 48 hours. Then the Olive tail moments were measured during 0~12 hours after irradiation and 0~72 hours after Hg treatment. The results showed that the more the oxidative stress was induced by mercury and radiation, the longer the repair time was required. Also, the results suggest that the SCGE assay may be used as an important tool for comparison of the sensitivity of different species to oxidative stresses.

• BMB Reports
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• v.57 no.2
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• pp.98-103
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• 2024

The mammalian sirtuin family (SIRT1-SIRT7) has shown diverse biological roles in the regulation and maintenance of genome stability under genotoxic stress. SIRT7, one of the least studied sirtuin, has been demonstrated to be a key factor for DNA damage response (DDR). However, conflicting results have proposed that Sirt7 is an oncogenic factor to promote transformation in cancer cells. To address this inconsistency, we investigated properties of SIRT7 in hepatocellular carcinoma (HCC) regulation under DNA damage and found that loss of hepatic Sirt7 accelerated HCC progression. Specifically, the number, size, and volume of hepatic tumor colonies in diethylnitrosamine (DEN) injected Sirt7-deficient liver were markedly enhanced. Further, levels of HCC progression markers and pro-inflammatory cytokines were significantly elevated in the absence of hepatic Sirt7, unlike those in the control. In chromatin, SIRT7 was stabilized and colocalized to damage site by inhibiting the induction of γH2AX under DNA damage. Together, our findings suggest that SIRT7 is a crucial factor for DNA damage repair and that hepatic loss-of-Sirt7 can promote genomic instability and accelerate HCC development, unlike early studies describing that Sirt7 is an oncogenic factor.

• BMB Reports
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• v.32 no.6
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• pp.554-560
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• 1999

TTD1BI cells are non-hypersensitive to UV irradiation and perform normal genome repair of pyrimidine dimers but fail to excise 6-4 photoproducts and, concomitantly, are unable to restore RNA synthesis levels following UV irradiation. This pointed to a detect in gene-specific repair and this study was undertaken to examine repair of 6-4 photoproducts at the gene-level. The results indicated a defect in gene-specific repair of 6-4 photoproducts in active genes, although strand-specificity of 6-4 photoproduct removal was essentially similar to that of normal cells. These findings indicate that the near normal UV resistance of TTD1BI cells may be due to the inability of these cells to remove DNA lesions preferentially, as well as to the cells opting out of the cell cycle to repair damage before resuming replication.

• YAKHAK HOEJI
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• v.36 no.5
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• pp.449-454
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• 1992

The effect of radioprotective ginseng protein fraction on DNA repair capacity was determined by measuring the amount of $^{3}H-thymidine$ incorporated into DNA in the process of repair synthesis for UV damaged DNA. CHO-Kl cells were prepared whose semiconservative replication was inhibited by trimethylpsoralen plus near-UV(PUVA) treatment. When the cells were exposed to UV light alone, the DNA repair capacity was increased at first and then decreased as UV dose increased. However, when the ginseng fraction was treated to the cells, the DNA repair capacity was kept increasing regardless of UV dose increment. When the concentration of protein contained in the added fraction was increased gradually, the repair capacity was also increased almost linearly showing dose-response relationship of the effect. These results suggest that the enhancement of DNA repair capacity of the cell can be one of the mechanisms of radioprotection by the ginseng fraction.

• Biomedical Science Letters
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• v.22 no.1
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• pp.18-23
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• 2016

Ultraviolet (UV) irradiation induces cellular damage. A variety of cellular responses for repairing cellular damage including DNA damage occur after UV irradiation. During the repair processes, expression and activation of various molecules are regulated depending on the types of cellular damage. Parkin is an E3 ligase and act as a tumor suppressor. Recently, it has been reported that Parkin is involved in the DNA repair process. In the current study, we investigated whether UVB irradiation influences expression of Parkin. Parkin expression transiently decreased after UVB irradiation both at the mRNA and protein levels, but returned to normal levels thereafter. Taken together with cell viability data, Parkin expression is down-regulated during UVB-induced suppression of cell growth and is increased again in accordance with recovery of UVB-induced cell growth inhibition. However, Parkin overexpression or knockdown did not influence UVB-induced cell growth inhibition and recovery. We propose that Parkin could be a useful molecular marker for evaluating conditions of cells after UVB irradiation.

• Biomolecules & Therapeutics
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• v.17 no.2
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• pp.113-124
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• 2009

Aging is a multifaceted biological process that affects all organs and organ systems of the body. This review provides an up-to-date analysis of this highly exciting, rapidly changing field of science. The aging process is largely under genetic control but is highly responsive to diverse environmental influences. The genes that control aging are those that are involved with cell maintenance, cell damage and repair. The environmental factors that accelerate aging are those that influence either damage of cellular macromolecules, or interfere with their repair. Prominent among these are chronic inflammation, chronic infection, some metallic chemicals, ultraviolet light, and others that heighten oxidative stress. Other environment factors slow the aging process. Included among these agents are resveratrol and vitamin D. In addition, dietary restriction and exercise have been found to extend human lifespan. The various mechanisms whereby all these agents exert their influence on aging include epigenetic modification, chromatin maintenance, protection of telomeres, and anti-oxidant defense, among others. The complex process of aging remains under continued, intense investigation.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.8
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• pp.3301-3306
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• 2015

Nucleolin (C23) is an important anti-apoptotic protein that is ubiquitously expressed in exponentially growing eukaryotic cells. In order to understand the impact of C23 in radiation therapy, we attempted to investigate the relationship of C23 expression with the radiosensitivity of human non-small cell lung cancer (NSCLC) cells. We investigated the role of C23 in activating the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), which is a critical protein for DNA double-strand breaks (DSBs) repair. As a result, we found that the expression of C23 was negatively correlated with the radiosensitivity of NSCLC cell lines. In vitro clonogenic survival assays revealed that C23 knockdown increased the radiosensitivity of a human lung adenocarcinoma cell line, potentially through the promotion of radiation-induced apoptosis and adjusting the cell cycle to a more radiosensitive stage. Immunofluorescence data revealed an increasing quantity of ${gamma}$-H2AX foci and decreasing radiation-induced DNA damage repair following knockdown of C23. To further clarify the mechanism of C23 in DNA DSBs repair, we detected the expression of DNA-PKcs and C23 proteins in NSCLC cell lines. C23 might participate in DNA DSBs repair for the reason that the expression of DNA-PKcs decreased at 30, 60, 120 and 360 minutes after irradiation in C23 knockdown cells. Especially, the activity of DNA-PKcs phosphorylation sites at the S2056 and T2609 was significantly suppressed. Therefore we concluded that C23 knockdown can inhibit DNA-PKcs phosphorylation activity at the S2056 and T2609 sites, thus reducing the radiation damage repair and increasing the radiosensitivity of NSCLC cells. Taken together, the inhibition of C23 expression was shown to increase the radiosensitivity of NSCLC cells, as implied by the relevance to the notably decreased DNA-PKcs phosphorylation activity at the S2056 and T2609 clusters. Further research on targeted C23 treatment may promote effectiveness of radiotherapy and provide new targets for NSCLC patients.

• Molecules and Cells
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• v.26 no.1
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• pp.5-11
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• 2008

Stalled DNA replication forks activate specific DNA repair mechanism called post-replication repair (PRR) pathways that simply bypass DNA damage. The bypassing of DNA damage by PRR prevents prolonged stalling of DNA replication that could result in double strand breaks (DSBs). Proliferating cell nuclear antigen (PCNA) functions to initiate and choose different bypassing pathways of PRR. In yeast, DNA replication forks stalled by DNA damage induces monoubiquitination of PCNA at K164, which is catalyzed by Rad6/Rad18 complex. PCNA monoubiquitination triggers the replacement of replicative polymerase with special translesion synthesis (TLS) polymerases that are able to replicate past DNA lesions. The PCNA interaction motif and/or the ubiquitin binding motif in most TLS polymerases seem to be important for the regulation of TLS. The TLS pathway is usually error-prone because TLS polymerases have low fidelity and no proofreading activity. PCNA can also be further polyubiquitinated by Ubc13/ Mms2/Rad5 complex, which adds an ubiquitin chain onto monoubiquitinated K164 of PCNA. PCNA polyubiquitination directs a different PRR pathway known as error-free damage avoidance, which uses the newly synthesized sister chromatid as a template to bypass DNA damage presumably through template switching mechanism. Mammalian homologues of all of the yeast PRR proteins have been identified, thus PRR is well conserved throughout evolution. Mutations of some PRR genes are associated with a higher risk for cancers in mice and human patients, strongly supporting the importance of PRR as a tumor suppressor pathway.

• Journal of Applied Biological Chemistry
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• v.56 no.1
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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.

• Bioinformatics and Biosystems
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• v.2 no.1
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• pp.12-16
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• 2007

DNA repair means a collection of processes that a cell identifies and corrects damage to genome sequence. The DNA repair processes are important because a genome would not be able to maintain its essential cellular functions without the processes. In this research, we make some gene regulatory networks of DNA repair in S. cerevisiae to know how each gene interacts with others. Two approaches are adapted to make the networks; Bayesian Network and ARACNE. After construction of gene regulatory networks based on the two approaches, the two networks are compared to each other to predict which genes have important roles in the DNA repair processes by finding conserved interactions and looking for hubs. In addition, each interaction between genes in the networks is validated with interaction information in S. cerevisiae genome database to support the meaning of predicted interactions in the networks.