• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1996.04a
• /
• pp.183-183
• /
• 1996

Bacteriophage T4 endonuclease V initiates the repair of ultraviolet (UV)-induced pyrimidine dimer photoproducts in duplex DNA. The mechanism of DNA strand cleavage involves four sequential stens: linear diffusion along dsDNA, pyrimidine dimer-specific binding,l pyrimidine dimer-DNA glycosylase activity, and Af lyase activity. Although crystal structure is known for this enzyme, solution structure has not been yet known. In order to elucidate the solution structure of this enzyme NMR spectroscopy was used. As a basis for the NMR peak assignment of the protein, HSQC spectrum was obtained on the uniformly $\^$15/N-labeled T4 endonuclease V. Each amide peak of the spectrum were classified according to amino acid spin systems by interpreting the spectrum of $\^$15/N amino acid-specific labeled T4 endonuclease V. The assignment was mainly obtained from three-dimensional NMR spectra such as 3D NOESY-HMQC, 3D TOCSY-HMQC. These experiments were carried out will uniformly $\^$15/N-labeled sample. In order to assign tile resonance of backbon atom, triple-resonance theree-dimensional NMR experiments were also performed using double labeled($\^$15/N$\^$13/C) sample. 3D HNCA, HN(CO)CA, HNCO, HN(CA)HA spectra were recorded for this purpose. The results of assignments were used to interpret the interaction of this enzyme with DNA. HSQC spectrum was obtained for T4 endonuclease V with specific $\^$15/N-labeled amino acids that have been known for important residue in catalysis. By comparing the spectrum of enzyme*DNA complex with that of the enzyme, we could confirm the important role of some residues of Thr, Arg, Tyr in activity. The results of assignments were also used to predict the secondary structure by chemical shift index (CSI).

• Asian Pacific Journal of Cancer Prevention
• /
• v.17 no.10
• /
• pp.4599-4608
• /
• 2016

Background: The x-ray repair cross-complementing group 3 (XRCC3) encodes a protein involved in the homologous recombination repair (HRR) pathway for double-strand DNA repair. Associations of the XRCC3 Thr241Met polymorphism with various cancers have been widely reported. However, published data on links between XRCC3 Thr241Met and gastrointestinal (GI) cancer risk are inconsistent. Objective and Methods: A meta-analysis was conducted to characterize the relationship between XRCC3 Thr241Met polymorphisms and GI cancer risk. Pooled odds ratios (ORs) and 95.0% confidence intervals were assessed using random- or fixed- effect models for 28.0 relevant articles with 30.0 studies containing 7,649.0 cases and 11,123.0 controls. Results: The results of the overall meta-analysis suggested a borderline association between the XRCC3 Thr241Met polymorphism and GI cancer susceptibility (T vs. C: OR=1.18, 9 % CI=1.0-1.4, POR=0.04; TT vs. CT+CC: OR=1.3, 95 % CI=1.0-1.6, POR=0.04). After removing studies not conforming to Hardy-Weinberg equilibrium (HWE), however, this association disappeared (T vs. C: OR=1.00, 95 % CI=0.9-1.1, POR=0.96; TT vs. CT+CC: OR=0.9, 95 % CI=0.8-1.1, POR=0.72). When stratified by ethnicity, source of controls or cancer type, although some associations between XRCC3 Thr241Met polymorphism and GI cancer susceptibility were detected, these associations no longer existed after removing studies not conforming to HWE. Conclusion: Our meta-analysis suggests that the XRCC3 Thr241Met polymorphism is not associated with risk of GI cancer based on current evidence.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.24
• /
• pp.10985-10989
• /
• 2015

Background: The capability for DNA double-strand breaks (DSBs) repair is crucial for inherent radiosensitivity of tumor and normal cells. We have investigated the clinicopathologic significance of DNA repair gene expression in nasopharyngeal (NP) carcinoma. Materials and Methods: A total of 65 NP cancer patients who received radiotherapy were included. The immunopositivity to Ku 70, DNA-PKcs, MRN, RAD50, XRCC4, and LIG4 were examined in all tumor tissues. Results: The patients comprised 42 males and 23 females, with a median age of 56 years (range, 18-84). The expression levels of RAD50 (0,+1,+2,+3) were 27.7%, 32.3%, 21.5%, and 18.5%. LIG4 (${\pm}$) were 43.1% and 56.9% respectively. The 5-year OS rate of patients with LIG4 (${\pm}$) were 90% and 67.9%, respectively (p=0.035). The 5-year TTP rate of patients with LIG4 (${\pm}$) were 75.9%, 55.5%, respectively (P=0.039). Conclusions: Our results suggest the possibility of predicting the radiosensitivity of NP cancer by performing immunohistochemical analysis of LIG4.

• Asian Pacific Journal of Cancer Prevention
• /
• v.16 no.1
• /
• pp.175-179
• /
• 2015

Rad51, a key factor in the homologous recombination pathway for the DNA double-strand break repair, plays a vital role in genesis of non-small-cell lung cancer (NSCLC). In recent years, more and more studies indicate that high expression of Rad51 is of great relevance to resistance of NSCLC to chemotherapeutic agents and ionizing radiation. However, the underlying molecular mechanisms are poorly understood. In this study, we investigated the role of single Rad51 on cell viability in vitro. Our results show that depletion of endogenous Rad51 is sufficient to inhibit the growth of the A549 lung cancer cell line, by accumulating cells in G1 phase and inducing cell death. We conclude that independent Rad51 expression is critical to the survival of A549 cells and can be an independent prognostic factor in NSCLC patients.

• Toxicological Research
• /
• v.24 no.3
• /
• pp.175-182
• /
• 2008

DNA-dependent protein kinase(DNA-PK) is involved in joining DNA double-strand breaks induced by ionizing radiation or V(D)J recombination and is activated by DNA ends and composed of a DNA binding subunit, Ku, and a catalytic subunit, DNA-PKcs. It has been suggested that DNA-PK might be $2^{nd}$ upstream kinase for protein kinase B(PKB). In this report, we showed that Ser473 phosphorylation in the hydrophobic-motif of PKB is blocked in DNA-PK knockout mouse embryonic fibroblast cells(MEFs) following insulin stimulation, while there is no effect on Ser473 phosphorylation in DNA-PK wild type MEF cells. The observation is further confirmed in human glioblastoma cells expressing a mutant form of DNA-PK(M059J) and a wild-type of DNA-PK(M059K), indicating that DNA-PK is indeed important for PKB activation. Furthermore, the treatment of cells with doxorubicin, DNA-damage inducing agent, leads to PKB phosphorylation on Ser473 in control MEF cells while there is no response in DNA-PK knockout MEF cells. Together, these results proposed that DNA-PK has a potential role in insulin signaling as well as DNA-repair signaling pathway.

• Asian Pacific Journal of Cancer Prevention
• /
• v.13 no.7
• /
• pp.3431-3436
• /
• 2012

Objective: X-ray cross-complementing group 4 (XRCC4) is a major repair gene for DNA double-strand breaks (DSB) in the non-homologous end-joining (NHEJ) pathway. Several potentially functional polymorphisms of the XRCC4 gene have been implicated in breast cancer risk, but individually published studies showed inconclusive results. The aim of this meta-analysis was to investigate the association between XRCC4 polymorphisms and the risk of breast cancer. Methods: The MEDLINE, EMBASE, Web of science and CBM databases were searched for all relevant articles published up to June 20, 2012. Potential associations were assessed with comparisons of the total mutation rate (TMR), complete mutation rate (CMR) and partial mutation rate (PMR) in cases and controls. Statistical analyses were performed using RevMan 5.1.6 and STATA 12.0 software. Results: Five studies were included with a total of 5,165 breast cancer cases and 4,839 healthy controls. Meta-analysis results showed that mutations of rs2075686 (C>T) and rs6869366 (G>T) in the XRCC4 gene were associated with increased risk of breast cancer, while rs2075685 (G>T) and rs10057194 (A>G) might decrease the risk of breast cancer. However, rs1805377 (A>G), rs1056503 (G>T), rs28360317 (ins>del) and rs3734091 (A>G) polymorphisms of XRCC4 gene did not appear to have an influence on breast cancer susceptibility. Conclusion: Results from the current meta-analysis suggest that the rs2075685 (G>T) and rs6869366 (G>T) polymorphisms of the XRCC4 gene might increase the risk of breast cancer, whereas rs2075685 (G>T) and rs10057194 (A>G) might be protective factors.

• Asian Pacific Journal of Cancer Prevention
• /
• v.13 no.7
• /
• pp.3417-3422
• /
• 2012

Objective: Non-homologous end joining (NHEJ) is one of the pathways of repair of DNA double-strand breaks. A number of genes involved in NHEJ have been implicated as breast cancer susceptibility genes such as LIG4. However, some studies have generated conflicting results. The aim of this Human Genome Epidemiology (HuGE) review and meta-analysis was to investigate association between LIG4 gene polymorphisms in the NHEJ pathway and breast cancer risk. Methods: Studies focusing on the relationship between LIG4 gene polymorphisms and susceptibility to breast cancer were selected from the Pubmed, Cochrane library, Embase, Web of Science, Springerlink, CNKI and CBM databases. Data were extracted by two independent reviewers and the meta-analysis was performed with Review Manager Version 5.1.6 and STATA Version 12.0 software, calculating odds ratios (ORs) with 95% confidence intervals (95%CIs). Results: According to the inclusion criteria, we final included seven studies with a total of 10,321 breast cancer cases and 10,160 healthy controls in the meta-analysis. The results showed no association between LIG4 gene polymorphisms (rs1805386 T>C, rs1805389 C>T, rs1805388 C>T and rs2232641 A>G) and breast cancer risk, suggesting that the mutant situation of these SNPs neither increased nor decreased the risk for breast cancer. In the subgroup analysis by Hardy-Weinberg equilibrium (HWE) and ethnicity, we also found no associations between the variants of LIG4 gene and breast cancer risk among HWE, non-HWE, Caucasians, Asians and Africans. Conclusion: This meta-analysis suggests that there is a lack of any association between LIG4 gene polymorphisms and the risk of breast cancer.

• Radiation Oncology Journal
• /
• v.22 no.3
• /
• pp.208-216
• /
• 2004

Purpose: DNA-dependent protein kinase (DNA-PK) is a serine/threonine kinase consisting of a 470 kDa catalytic subunit (DNA-PKcs) and a heterodimeric regulatory complex, called Ku, which is composed of 70 kDa(Ku 70) and 86 kDa (Ku 80) proteins. The DNA-PK has been shown to play a pivotal role in rejoining DNA double-strand-breaks (dsb) in mammalian cells. The purpose of this study is to examine the relationship between the level of Ku expression and radiation sensitivity. Methods and Materials: Nine head and neck, cancer cell lines showed various intrinsic radiation sensitivities. Among the nine, AMC-HN-3 cell was the most sensitive for X-ray irradiation and AMC-HN-9 cell was the most resistance. The most sensitive and resistant cell lines were selected and the test sensitivity of radiation and expression of Ku were measured. Radiation sensitivity was obtained by colony forming assay and Ku protein expression using Western blot analysis. Results: Ku80 increased expression by radiation, wheres Ku70 did not. Overexpression of Ku80 protein increased radiation resistance in AMC-HN9 cell line. There was a correlation between Ku8O expression and radiation resistance. Ku80 was shown to play an important role in radiation damage response. Conclusion: Induction of Ku80 expression had an important role in DNA damage repair by radiation. Ku80 expression may be an effective predictive assay of radiosensitivity on head and neck cancer.

• Asian Pacific Journal of Cancer Prevention
• /
• v.13 no.2
• /
• pp.683-687
• /
• 2012

Ku70 plays an important role in DNA double-strand break repair. Studies revealing conflicting results on the role of the Ku70-1310C/G promoter polymorphism on cancer risk led us to perform a meta-analysis to investigate this relationship. Ten case-control studies with 2566 cases and 3058 controls were identified. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of associations. The overall results suggested no association between the Ku70-1310C/G promoter polymorphism and total cancer risk. However, on stratified analysis, significantly increased risks were observed among the Asian population (GG vs. CC: OR=1.50, 95%CI=1.10-2.06; GG vs. CC/CG: OR=1.47, 95%CI=1.07-2.01) and population-based case-control studies (GG vs. CC: OR=1.57, 95%CI=1.12-2.22; CG vs. CC: OR=1.35, 95%CI=1.11-1.64; CG/GG vs. CC: OR=1.37, 95%CI=1.14-1.65). Additionally, variant genotypes were associated with a significantly increased breast cancer risk (GG vs. CC: OR=1.80, 95%CI=1.26-2.56; GG vs. CC/CG: OR=1.40, 95%CI=1.01-1.95).

• Asian Pacific Journal of Cancer Prevention
• /
• v.13 no.3
• /
• pp.851-856
• /
• 2012

Objective: NBS1 plays a key role in the repair of DNA double-strand break (DSB). We conducted this study to investigate the effect of two critical polymorphisms (rs1805794 and rs13312840) in NBS1 on treatment response and prognosis of advanced non-small cell lung cancer (NSCLC) patients with platinum-based chemotherapy. Methods: Using TaqMan methods, we genotyped the two polymorphisms in 147 NSCLC patients. Odds ratios (ORs) and their 95% confidential intervals (CIs) were calculated as a measure of difference in the response rate of platinum-based chemotherapy using logistic regression analysis. The Kaplan-Meier and log-rank tests were used to assess the differences in progression-free survival (PFS) and overall survival (OS). Cox proportional hazards model was applied to assess the hazard ratios (HRs) for PFS and OS. Results: Neither of the two polymorphisms was significantly associated with treatment response of platinum-based chemotherapy. However, patients carrying the rs1805794 CC variant genotype had a significantly improved PFS compared to those with GG genotype (16.0 vs. 8.0 months, P = 0.040). Multivariable cox regression analysis further showed that rs1805974 was a significantly favorable prognostic factor for PFS [CC/CG vs. GG: Adjusted HR = 0.62, 95% CI: 0.39-0.99; CC vs. CG/GG: Adjusted HR = 0.56, 95% CI: 0.32-0.97). Similarly, rs13312840 with a small sample size also showed a significant association with PFS (CC vs. CT/TT: Adjusted HR = 25.62, 95% CI: 1.53-428.39). Conclusions: Our findings suggest that NBS1 polymorphisms may be genetic biomarkers for NSCLC prognosis especially PFS with platinum-based chemotherapy in the Chinese population.