• Animal cells and systems
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• v.9 no.2
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• pp.79-85
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• 2005

Oxidized abasic residues arise as a major class of DNA damage by a variety of agents involving free radical attack and oxidation of deoxyribose sugar components. 2-deoxyribonolactone (dL) is a C1'-oxidized abasic lesion implicated in DNA strand scission, mutagenesis, and covalent DNA-protein cross-link (DPC). We show here that mammalian cell-free extract give rise to stable DPC formation that is specifically mediated by dL residue. When a duplex DNA containing dL at the site-specific position was incubated with cell-free extracts of Po ${\beta}-proficient$ and -deficient mouse embryonic fibroblast cells, the formation of major dL-mediated DPC was dependent on the presence of DNA polymerase (Pol) ${\beta}$. Formation of dL-specific DPC was also observed with histones and FEN1 nuclease, although the reactivity in forming dL-mediated DPC was significantly higher with Pol ${\beta}$ than with histones or FEN1. DNA repair assay with a defined DPC revealed that the dL lesion once cross-linked with Pol ${\beta}$ was resistant to nucleotide excision repair activity of cell-free extract. Analysis of nucleotide excision repair utilizing a model DNA substrate containing a (6-4) photoproduct suggested that excision process for DPC was inhibited because of DNA single-strand incision at 5' of the lesion. Consequently DPC mediated by dL lesion may not be readily repaired by DNA excision repair pathway but instead function as unusual DNA damage causing a prolonged DNA strand break and trapping of the major base excision repair enzyme.

• 대한약리학회:학술대회논문집
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• 2006.11a
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• pp.69.2-69.2
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• 2006

• BMB Reports
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• v.33 no.3
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• pp.268-275
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• 2000

In contrast to the pyrimidine (6-4)pyrimidone photoproduct [(6-4) adduct], its Dewar valence isomer (Dewar product) is low mutagenic and produces a broad range of mutations with a 42 % replicating error frequency. In order to determine the origin of the mutagenic property of the Dewar product, we used experimental NMR restraints and molecular dynamics to determine the solution structure of a Dewar·lesion DNA decamer duplex, which contains a mismatched base pair between the 3'-T residue and an opposed G residue. The 3'-T of the Dewar lesion forms stable hydrogen bonds with the opposite G residue. The helical bending and unwinding angles of the DW/GA duplex, however, are much higher than those of the DW/AA duplex. The stable hydrogen bonding of the G 15 residue does not increase the thermal stability of the overall helix. It also does not restore the distorted backbone conformation of the DNA helix that is caused by the forming of a Dewar lesion. These structural features implicate that no thermal stability, or conformational benefits of G over A opposite the 3'-T of the Dewar lesion, facilitate the preferential incorporation of an A. This is in accordance with the A rule during translesion replication and leads to the low frequent $3'-T{\rightarrow}C$ mutation at this site.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.7
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• pp.3455-3460
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• 2012

Objectives: To report the prevalence of atypical squamous cells of undetermined significance and atypical squamous cells-cannot exclude high squamous intraepithelial lesions and to determine the possible association of Pap test results with high-risk human papillomavirus and high squamous intraepithelial lesions in women from Duhok, Iraq. Design: A prospective, observational study was conducted between January 2005 and December 2011. Overall, 596 women with a cervicovaginal Pap test showing atypical squamous cells of undetermined significance and 93 atypical squamous cells-cannot exclude high squamous intraepithelial lesion for whom pathologic follow-up was available were studied. Follow-up consisted of repeat cytology, colposcopy and histology. High risk human papillomavirus DNA testing was performed on exfoliated cervical cells from 106 women, using conventional PCR after at least 36 months from the initial Pap smear. Results: Significantly high proportions of both atypical squamous cells of undetermined significance (87.9%) and atypical squamous cells-cannot exclude high squamous intraepithelial lesion (62.4%) demonstrated no significant lesion on subsequent follow up. Low squamous intraepithelial lesions were observed in 1.7% of cases of atypical squamous cells of undetermined significance and in 5.4% of atypical squamous cells-cannot exclude high squamous intraepithelial lesion. High squamous intraepithelial lesion was demonstrated in 0.8% and 16.1% respectively. In the latter there was also one case of invasive carcinoma. High-risk HPV DNA was demonstrated in 40% of atypical squamous cells of undetermined significance and 57.1% of atypical squamous cells-cannot exclude high squamous intraepithelial lesions. Conclusions: Since both atypical squamous cells of undetermined significance and atypical squamous cells-cannot exclude high squamous intraepithelial lesion identify patients who are at an increased risk for the development of high squamous intraepithelial lesions and a considerable percentage harbor high risk-HPV, both should be retained as diagnostic categories and patients warrant a diligent follow up and testing for high risk-HPV DNA. Colposcopic evaluation and biopsy, when indicated, are a must.

• Journal of Photoscience
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• v.9 no.2
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• pp.448-450
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• 2002

DNA samples extracted from Japanese cypress leaf tissues contain isopropyl alcohol-precipitable, high molecular weight compounds, which interfere ELISA for cyclobutane pyrimidine dimers (CPD). Removal of the compounds is achieved by DEAE ion-exchange column chromatography and improves the ELISA responses of the DNA. When extracting DNA repeatedly from the same leaf tissues, the DNA samples show CPD responses which increase with the order in sequential extraction, and hence for a reliable detennination of DNA lesion a thorough extraction of DNA is required. Clearing these two problems it was demonstrated that CPD level was slightly higher in the leaves of trees growing under full sunlight than in those growing under UBV -cut sunlight.

• YAKHAK HOEJI
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• v.54 no.1
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• pp.62-66
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• 2010

Benzopyrene is known to be one of the most powerful carcinogens which can build intercalated motif between base pairs in damaged DNA. The dimension of benzopyrene itself is much bigger than any of the DNA bases and thus the question whether the lesion of some base pair by insertion of benzopyrene can happen with or without a dramatic distortion of the helical structure is a highly interesting theme. In this work we used a molecular mechanics simulation using AMBER program package to go into the conformational characteristics. The condition of the insertion process of the benzopyrene motif from minor groove of the starting structure between the base pairs in the internal area of double helix was investigated using the molecular dynamics simulation at elevated temperature.

• Biomedical Science Letters
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• v.15 no.1
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• pp.1-8
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• 2009

Human genomic DNA is continuously attacked by oxygen radicals originated from cellular metabolic processes and numerous environmental carcinogens. 2-deoxyribonolactone (dL) is a major type of oxidized abasic (AP) lesion implicated in DNA strand scission, mutagenesis, and formation of covalent DNA-protein crosslink (DPC) with DNA polymerase (Pol) ${\beta}$. We show here that human DNA polymerase (Pol)${\iota}$ and mitochondrial $Pol{\gamma}$ give rise to stable DNA-protein crosslink (DPC) formation that is specifically mediated by dL lesion. $Pol{\gamma}$ mediates DPC formation at the incised dL residue by its 5'-deoxyribose-5-phosphate (dRP) lyase activity, while $Pol{\gamma}$ cross links with dL thorough its intrinsic dRP lyase and AP lyase activities. Reactivity in forming dL-mediated DPC was significantly higher with $Pol{\gamma}$ than with $Pol{\iota}$. DPC formation by $Pol{\gamma}$, however, can be reduced by an accessory factor of $Pol{\gamma}$ holoenzyme that may attenuate deleterious effects of crosslink adducts on mitochondrial DNA. Comparative kinetic analysis of DPC formation showed that the rate of DPC formation with either $Pol{\iota}$ or $Pol{\gamma}$ was lower than that with $Pol{\beta}$. These results revealed that the activity of catalytic lyase in DNA polymerases determine the efficiency of DPC formation with dL damages. Irreversible crosslink formation of such DNA polymerases by dL lesions may result in a prolonged strand scission and a suicide of DNA repair proteins, both of which could pose a threat to the genetic and structural integrity of DNA.

• Journal of the Korean Magnetic Resonance Society
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• v.3 no.1
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• pp.60-70
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• 1999

The pyrimidine(6-4) pyrimidone photoproduct [(6-4) adduct] is one of the major photoproducts induced by UV irradiation of DNA and occurs at TpT sites. The (6-4) adduct is highly mutagenic and specific during translesion replication. The marked preference for insertion of A opposite the 5'-T and G opposite the 3--T of the (6-4) adducts leads to a predominantly 3'-T\longrightarrowC transition with 85% replicating error rate. In order to obtain insight into the origin of 3'-T\longrightarrowC transition induced by the (6-4) adduct, we have performed one - and two-dimensional NMR experiment. The 3'-Tof the (6-4) lesion forms the stable hydrogen bonding to the imino proton of an opposed G, which stabilizes the overall helix and diminishes the highly distorted conformation caused by the (6-4) lesion in the (6-4)/AA duplex. We proposed that the greater insertion of a G over an A opposite the 3'-T of the (6-4) lesion These results may account for the greater preference for the insertion of a G over a A opposite the 3'-T of the (6-4) lesion. Thus this insertion leads to the highly specific 3'-T\longrightarrowC multation at the (6-4) lesion site.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.4
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• pp.1519-1523
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• 2015

Infection of the uterine cervix by human papilloma viruses (HPV) may be associated with cervical pre-cancer and invasive cervical carcinoma if left untreated. With advance in molecular techniques, it has become easier to detect the resence of HPV DNA long before the appearance of any lesion. This study concerned cervical scrape samples of 310 married non-pregnant women attending a gynecology outpatient department for both Pap and PCR testing to detect HPV DNA. Nested PCR using primers for L1 consensus gene with My9/My11 and GP6+/GP5+followed by multiplex PCR were carried out to detect HPV 16 and HPV18. Result: HPV prevalence was 11.9% out of which 3.67% cases of negative for intra-epithelial lesion or malignancy (NILM) and in 71.1% (27/38) of atypical cervical smears were HPV positive. There was increasing trend of high-risk-HPV positivity (HR HPV 16 and 18), from 20% in benign cytology (NILM) to 42.9 % in LSIL, 71.41% in HSIL and 100% in SCC. There was highly significant association of HPV infection with cervical lesion ($x^2=144.0$, p<0.01) and also with type specific HPV prevalence ($x^2=7.761^*$, p<0.05).

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.24
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• pp.10809-10812
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• 2015

Background: Human papillomavirus (HPV) DNA testing is an effective method to screen for precancerous changes in the cervix. Samples from self-collection rather than Pap smear can potentially be used to test for HPV as they are more acceptable and preferred for use in certain settings. The objective of this study was to compare HPV DNA testing from self-collected vaginal swabs and physician-collected cervical swabs. Materials and Methods: A total of 101 self-collected vaginal and physician-collected cervical swabs of known cytology from Thai women were tested by electrochemical DNA chip assay. The specimens were divided into 4 groups: 29 with normal cytology, 14 with atypical squamous cells of undetermined significance (ASCUS), 48 with low-grade squamous intraepithelial lesion (LSIL), and 10 with high-grade squamous intraepithelial lesion (HSIL). Results: Positive detection rates of HPV from self-collected swabs were similar to those from physician-collected swabs. Among specimens with abnormal cytology, HPV was found in 50% of self-collected swabs and 47.2% of physician-collected swabs. In specimens with normal cytology, 17.2% of self-collected swabs and 24.1% of physician-collected swabs were positive for HPV. Concordance was relatively high between results from self-collected and physician-collected samples. The most common HPV genotype detected was HPV 51. Conclusions: HPV DNA testing using self-collected swabs is a feasible alternative to encourage and increase screening for cervical cancer in a population who might otherwise avoid this important preventive examination due to embarrassment, discomfort, and anxiety.