• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.316-316
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• 1994

자외선 등에 의한 DNA 합성억제의 회복과정에서의 기작을 규명하기 위하여 자외선에 의하여 억제되었던 DNA 합성이 새로운 replication origin을 사용하는 지를 DNA 복제가 일어나는 장소로 알려진 nuclear matrix와 연관지어서 살펴 보았다. 자외선 조사후 새로 합성된 DNA 분자들의 크기는 시간이 경과하여도 대조군의 DNA 분자들의 크기보다 작았으나 그 성장 양상은 차이가 얼었고, 자외선이 조사된 세포에서 parental DNA의 부가적인 결합이 DNA 합성률의 회복에 필요함을 알 수 있었다. 또한 자외선 상해의 회복과정에서 생기는 알카리 민감성 부위는 RNA linker에 의해 생겨남을 알 수 있었다. 이상의 결과들을 종합하여 보면, 자외선에 의해 pyrimidine dimer가 생기면 첫째로 절제회복에 의해 제거되어지지만, 남아 있는 pyrimidine dimel에 의해서 DNA 복제억제는 여전히 억제되어 있다. DNA 복제억제의 회복은 새로운 복제원점이 활성화되어 nuclear matrix에 결합하여 새로운 DNA 합성이 시작됨으로써 이루어진다. 이때 RNA linker는 복제진행시 DNA 상의 gap으로 생긴 tyopological strain을 제거하는데 이용되어진다.

• Environmental Mutagens and Carcinogens
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• v.9 no.2
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• pp.63-72
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• 1989

본 연구는 N-methyl-N'-nitro-N-nitrosoguanidine(MNNG) 를 처리한 CHO-K1세포에서 DNA 복제억제와 그 회복과정의 분자론적 기작을 규명할 목적으로 방사선 이중표지에 의한 DNA합성율의 측정, 알카리 자당농도구배 초원심분리법에 의한 DNA 분자량과 후복제 회복율을 측정하여 다음과 같은 결과를 얻었다. DNA 합성율은 2nM 이하의 낮은 농도의 MNNG 처리군에서는 급격히 감소하였으나, 5nM 이상의 농도에서는 그 감소양상이 둔화되었다. 억제되었던 DNA 합성율은 시간경과에 따라 회복되어 처리 후 4시간 째에는 대조군 수준 또는 그 이상으로 회복되었다. MNNG 처리 후 DNA 분자 크기의 분포와 새로 합성된 DNA 분자의 생장양상을 알카리 자당농도구배 초원심분리법으로 조사한 결과 MNNG 처리 후 시간 경과에 따라 새로합성된 DNA 분자들의 크기분포는 1*107 달톤 이하의 DNA 분자들의 합성양이 특이하게 증가하였다가 감소함을 보였다.

• The Korean Journal of Zoology
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• v.20 no.1
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• pp.41-48
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• 1977

Dose response of DNA repair synthesis induced by bleomycin was dose-dependent in lower doses, and maximum rate of it at 5 $\\mu$g/ml represents about 15% of total cells analyzed. At higher doses DNA-repair synthesis was reduced and the rate of it remained unchanged even prolonged treatment. Pretreatment with BUdR or IUdR was found to enhance DNA repair synthesis and also to interfere with semiconservative DNA synthesis at higher doses. Time dependence study showed that DNA repair synthesis occurred as long as for 24 hours after removal of bleomycin. These results seem to suggest that bleomycin is not to be an effective chemical in inducing excision repair and that damages induced in DNA by this drug might include not only strand breaks but other types of DNA damage.

• Environmental Mutagens and Carcinogens
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• v.9 no.1
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• pp.33-46
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• 1989

본 연구는 알킬화제를 처리한 CHO-K1 세포에서 DNA 복제억제와 그 회복과정의 분자론적 기작을 규명할 목적으로 방사선 이중 표지에 의한 DNA 합성율의 측정, 알칼리 자당 농도구배 초원심분리법에 의한 DNA 분자량과 후복제 회복율을 측정하여 다음과 같은 결과를 얻었다. (1) 1mM methyl methanesulfonate (MMS)와 1nM N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) 이하의 낮은 농도의 처리군에서는 DNA 합성율이 급격히 감소하였으나, 2 mM MMS, 2mM MNNG이상의 농도에서는 그 감소양상이 둔화되었다, (2) DNA 합성율은 알킬화제의 처리 직후 감소하였다가 시간경과에 따라 회복되어 처리후 4시간 째에는 대조군 수준 또는 그 이상으로 회복되었다.

• Journal of Radiation Protection and Research
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• v.20 no.2
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• pp.71-78
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• 1995

To develop methods to reduce radiation risk and apply such knowledge to improvement of radiation protection, the effects of cobaltous chloride known as bioantimutagen on the function of E. coli RecA protein involved in the repair of DNA damage were examined. The results demonstrated two distinct effects of cobaltous chloride on the RecA protein function necessary for the strand exchange reaction. Cobaltous chloride enhanced the ability of RecA protein to displace SSB protein from single-stranded DNA and the duplex DNA-dependent ATPase activity. RecA protein was preferentially bound with UV-irradiated supercoiled DNA as compared with nonirradiated DNA The binding of RecA protein to UV-irradiated supercoiled DNA was enhanced in a dose-dependent manner. It is likely that studies on the factors affecting repair efficiency and the DNA repair proteins may provide information on the repair of ionizing radiation-induced DNA damage and the mechanism for DNA radioprotection.

• The Korean Journal of Zoology
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• v.20 no.2
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• pp.93-99
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• 1977

Dose response forDNA repair synthesis induced by various concentrations of MMC (0.05 $\\sim$ 0.5 $\\mu$g/ml) in HeLa $S_3$ cells was not dose-dependent and the amounts of it were relatively lower, representing $7\\sim9%$ of total DNA synthesizing cells in $0.1\\sim0.5 \\mug/ml$ concentrations. Time dependence study showed that MMC-induced DNA repair synthesis occurred as long as for 24 hours with similar incidences in all time courses. Pretreatment with BUdR was found to have a sensitization effect on MMC-induced DNA repair synthesis, but that with IUdR was not. Combined treatment with BUdR of IUdR and MMC suppressed remarkably the semiconservative DNA synthesis especially at later time course. These results seem to suggest that damages induced in DNA by MMC might be repaired by both fast and slow excision processes.

• Environmental Mutagens and Carcinogens
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• v.8 no.1
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• pp.1-12
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• 1988

The effects of aphidicolin (APC), an inhibitor of DNA polymerase alpha, or 2', 3'-dideoxythymidine 5'-triphosphate (ddTTP), an inhibitor of DNA polymerase beta, on the repair of DNA damage induced by ethyl methanesulfonate (EMS) or bleomycin (BLM) were investigated in Chinese hamster ovary (CHO)-K1 cells. Three assays were employed in this study: unscheduled DNA synthesis, alkaline elution and alkaline sucrose gradient sedimentation. It was shown that APC or ddTTP inhibited DNA induced by EMS, and thus, the post-treatment with APC or ddTTP following EMS treatment was resulted in the more amount of unscheduled DNA synthesis, and the more accumulation of DNA single-stand breaks than the cells post-incubated without APC or ddTTP. While, in the BLM induced DNA repair, only ddTTP inhibited DNA repair induced by BLM. And thus, the groups post-incubated with or without APC after BLM treatment had the same value in the amount of unscheduled DNA synthesis and of DNA single-strand breaks, while post-treatment with ddTTP was resulted in the increased amount of unscheduled DNA synthesis and the increased DNA sin -strand breaks than the group without ddTTP. These results suggested that both of DNA polymerase $\alpha$ and $\beta$ participated in the repair of DNA damage induced by EMS, but in BLM-induced DNA repair, polymerase $\beta$ participated.ipated.

• The Korean Journal of Zoology
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• v.26 no.1
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• pp.19-28
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• 1983

Alkaline elution profiles showed that the frequency of DNA single strand breaks associated with DNA-protein crosslinks in cells treated with both an inducing dose of MMC $(MMC_1)$ and a challenge dose of MMC $(MMC_2)$ was slightly less than that in cells treated with MMC alone. The amount of unscheduled DNA synthesisi in cells treated with both $MMC_1$ and $MMC_2$ was greater than that in cells treated with MMC alone. This enhancement of exicision repair detected by UDS autoradiography and alkaline elution, was not observed, when cells were incubated with cyclohexmide between the two treatments of $MMC_1$ and $MMC_2$. These results suggest that MMC-damaged DNA from Chinses hamster cells is repaired by excision repair mechanisms that require de novo protein synthesis for enhancement, and that an inducible repair mechanism may exist in CHO cells.

• The Korean Journal of Zoology
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• v.26 no.3
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• pp.171-179
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• 1983

Amounts of DNA single strand breaks and unscheduled DNA synthesis in CHO cells exposed to MMS were increased in the presence of 3-aminobenzamide, a potent inhibitor of poly (ADP-ribose) polymerase. However, those in cells irradiated with UV-light were decreased. These results suggest that poly (ADP-ribose) polymerase acts negatively on the MMS-induced base excision repair but positively on the UV-induced nucleotide excision repair. In the combined treatment with MMS and UV-light in the presence of this inhibitor, amounts of strand breaks were just the same as those in the absence of the inhibitor. But those of unscheduled DNA synthesis were increased up to the amount induced by UV-light alone. These results may suggest that poly (ADP-ribose) polymerase affects the incision step of excision repair induced by MMS and UV-light independently, and that it may potentiate the complete cleaving of UV-induced pyrimidine dimers possibly by the repair enzymes which might have been partially inactivated by MMS.

• Environmental Analysis Health and Toxicology
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• v.18 no.4
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• pp.287-294
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• 2003

출아형 효모 Saccharomyces cerevisiae RAD3 유전자는 절제회복 및 세포의 생존에 필수적이며, DNA dependent ATPase와 DNA-RNA helicase활성을 가지고 있는 것으로 알려져 있다. 본 연구는 분열형 효모 Schizosaccharomyces pombe에서 절제회복과 세포의 생존에 필수적인 출아형 효모 RADS유전자와 유사한 유전자를 S. pombe genomic DNA library에서 분리하여 그 특성을 연구하였다. 분리한 RADS 유사유전자를 HRD3 유전자라 명명하였다. 발현 vector pET3a를 이용하여 분리한 HRD3 유전자를 과 발현하였을 때 HRD3단백질은 숙주단백질의 합성 억제 또는 분해 촉진을 유발하여 숙주세포인 대장균에 독성 효과를 나타냄이 관찰되었다. HRD3유전자와 lacZ유전자를 융합시킨 여러 가지 재조합 vector를 만들어 이들 융합단백질을 분리하였다. 이 결과 HRD3단백질의 카르복실 말단 부위가 DNA회복기능과 대장균에서의 독성효과를 나타내는 중요한 부위로 생각된다.