• Title/Summary/Keyword: DNA polymerase beta

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Association of Two Polymorphisms of DNA Polymerase Beta in Exon-9 and Exon-11 with Ovarian Carcinoma in India

  • Khanra, Kalyani;Panda, Kakali;Bhattacharya, Chandan;Mitra, A.K.;Sarkar, Ranu;Bhattacharyya, Nandan
    • Asian Pacific Journal of Cancer Prevention
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    • v.13 no.4
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    • pp.1321-1324
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    • 2012
  • Background: DNA polymerase beta ($pol{\beta}$) is a key enzyme in the base excision repair pathway. It is 39kDa protein, with two subunits, one large subunit of 31 kDa having catalytic activity between exon V to exon XIV, and an 8 kDa smaller subunit having single strand DNA binding activity. Exons V to VII have double strand DNA binding activity, whereas exons VIII to XI account for the nucleotidyl transferase activity and exons XII to XIV the dNTP selection activity. Aim: To examine the association between $pol{\beta}$ polymorphisms and the risk of ovarian cancer, the present case control study was performed using 152 cancer samples and non-metastatic normal samples from the same patients. In this study, mutational analysis of $pol{\beta}$ genomic DNA was undertaken using primers from exons IX to XIV - the portion having catalytic activity. Results: We detected alteration in DNA polymerase beta by SSCP. Two specific heterozygous point mutations of $pol{\beta}$ were identified in Exon 9:486, A->C (polymorphism 1; 11.18%) and in Exon 11:676, A->C (polymorphism 2; 9.86%). The correlation study involving polymorphism 1 and 4 types of tissue showed a significant correlation between mucinous type with a Pearson correlation value of 4.03 (p=0.04). The association among polymorphism 2 with serous type and stage IV together have shown Pearson ${\chi}^2$ value of 3.28 with likelihood ratio of 4.4 (p=0.07) with OR =2.08 (0.3-14.55). This indicates that there is a tendency of correlation among polymorphism 2, serous type and stage IV, indicating a risk factor for ovarian cancer. Conclusion: Hence, the results indicate that there is a tendency for $pol{\beta}$ polymorphisms being a risk factor for ovarian carcinogenesis in India.

HeLa Cells Containing a Truncated Form of DNA Polymerase Beta are More Sensitized to Alkylating Agents than to Agents Inducing Oxidative Stress

  • Khanra, Kalyani;Chakraborty, Anindita;Bhattacharyya, Nandan
    • Asian Pacific Journal of Cancer Prevention
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    • v.16 no.18
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    • pp.8177-8186
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    • 2016
  • The present study was aimed at determining the effects of alkylating and oxidative stress inducing agents on a newly identified variant of DNA polymerase beta ($pol{\beta}{\Delta}_{208-304}$) specific for ovarian cancer. $Pol{\beta}{\Delta}_{208-304}$ has a deletion of exons 11-13 which lie in the catalytic part of enzyme. We compared the effect of these chemicals on HeLa cells and HeLa cells stably transfected with this variant cloned into in pcDNAI/neo vector by MTT, colony forming and apoptosis assays. $Pol{\beta}{\Delta}_{208-304}$ cells exhibited greater sensitivity to an alkylating agent and less sensitivity towards $H_2O_2$ and UV when compared with HeLa cells alone. It has been shown that cell death in $Pol{\beta}{\Delta}_{208-304}$ transfected HeLa cells is mediated by the caspase 9 cascade. Exon 11 has nucleotidyl selection activity, while exons 12 and 13 have dNTP selection activity. Hence deletion of this part may affect polymerizing activity although single strand binding and double strand binding activity may remain same. The lack of this part may adversely affect catalytic activity of DNA polymerase beta so that the variant may act as a dominant negative mutant. This would represent clinical significance if translated into a clinical setting because resistance to radiation or chemotherapy during the relapse of the disease could be potentially overcome by this approach.

Hypersensitivity of Somatic Mutations and Mitotic Recombinations Induced by Mutagens in Transgenic Drosophila bearing Rat DNA Polymerase $\beta$ (Rat의 DNA Polymerase$\beta$ cDNA가 도입된 Transgenic Drosophila의 체세포 돌연변이 유발에 관한 연구)

  • 최영현;유미애;이원호
    • Environmental Mutagens and Carcinogens
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    • v.15 no.2
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    • pp.100-105
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    • 1995
  • The effects of DNA polymerase $\beta$ on the somatic chromosome mutations and mitotic recombinations were investigated using the transgenic Drosophila beating chimetic gene consisting of a promoter region of Drosophila actin 5C gene and rat DNA polymerase $\beta$. For detecting the somatic chromosome mutations and mitotic recombinations, the heterozygous (mwh/+) strains possessing or lacking transgene poi 13 were used. The spontaneous frequency of small mwh spots, due to deletion or nondisjunction etc., in the non-transgenic w strain and the transgenic p[pol $\beta$]-130 strain was 0.351 and 0.606, respectively. The spontaneous frequency (0.063) of large mwh spots, arises mostly from somatic recombination between the centromere and the locus mwh, in the transgenic p[pol $\beta$]-130 strain was about three times higher than that (0.021) of the non-transgenic w strain. The mutant clone frequencies of small and large mwh spots induced by N-methyl-N'-nitro-N-nitrosoguanidine and ethyl methanesulfonate in the transformant p[pol $\beta$]-130 were higher than those in the host strain w. The present results suggest that rat DNA polymerase $\beta$ participate at least in the somatic chromosome mutations and mitotic recombination processes.

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Exon 8-9 Mutations of DNA Polymerase β in Ovarian Carcinoma Patients from Haldia, India

  • Khanra, Kalyani;Panda, Kakali;Mitra, A.K.;Sarkar, Ranu;Bhattacharya, Chandan;Bhattacharyya, Nandan
    • Asian Pacific Journal of Cancer Prevention
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    • v.13 no.8
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    • pp.4183-4186
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    • 2012
  • Background: Ovarian cancer is the number one killer among all the gynecological cancers. We undertook association study to identify potential alterations in the genomic DNA of a DNA repair gene, DNA polymerase beta ($pol{\beta}$), involved in base excision repair (BER), in ovarian carcinomas of patients from Haldia, India. Mutations, splice variants have been reported earlier in different tumors other than ovarian tumors. Aim: In this study we explored the possibility of association of any mutation of $pol{\beta}$ (Exon 8) with prognosis in 152 ovarian cancer samples. Results: Alteration in the exon 8 region (Exon 8:468, $A{\rightarrow}C$; 15.1%) was noted among fifty seven polymorphism positive samples. Alteration in the intervening sequence 8 (IVS8, -25, $A{\rightarrow}C$; 3.9%) was also noted. All alterations are heterozygous in nature. Conclusions: We found no significant association among the samples from serous type, stage IV, and the $pol{\beta}$ mutations ($P{\leq}0.01$). Only a slight tendency of association was evident between IVS8, -25, A to C; and stage III. Further analysis with a larger number of samples is needed.

Association of a Newly Identified Variant of DNA Polymerase Beta (polβΔ63-123, 208-304) with the Risk Factor of Ovarian Carcinoma in India

  • Khanra, Kalyani;Bhattacharya, Chandan;Bhattacharyya, Nandan
    • Asian Pacific Journal of Cancer Prevention
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    • v.13 no.5
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    • pp.1999-2002
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    • 2012
  • Background: DNA polymerase is a single-copy gene that is considered to be part of the DNA repair machinery in mammalian cells. The encoded enzyme is a key to the base excision repair (BER) pathway. It is evident that pol beta has mutations in various cancer samples, but little is known about ovarian cancer. Aim: Identification of any variant form of $pol{\beta}$ cDNA in ovarian carcinoma and determination of association between the polymorphism and ovarian cancer risk in Indian patients. We used 152 samples to isolate and perform RT-PCR and sequencing. Results: A variant of polymerase beta (deletion of exon 4-6 and 11-13, comprising of amino acid 63-123, and 208-304) is detected in heterozygous condition. The product size of this variant is 532 bp while wild type pol beta is 1 kb. Our study of association between the variant and the endometrioid type shows that it is a statistically significant factor for ovarian cancer [OR=31.9 (4.12-246.25) with p<0.001]. The association between variant and stage IV patients further indicated risk (${\chi}^2$ value of 29.7, and OR value 6.77 with 95% CI values 3.3-13.86). The correlation study also confirms the association data (Pearson correlation values for variant/stage IV and variant/endometrioid of 0.44 and 0.39). Conclusion: Individuals from this part of India with this type of variant may be at risk of stage IV, endometrioid type ovarian carcinoma.

Environmental Toxic Agents on Genetic Material and Cellular Ativity V. The Roles of DNA Polymerases on Mutagen-Induced DNA Repair Synthesis in Relation to Cell Cycle in Chinese Hamster Ovary Cells (환경성 유해요인이 유전물질과 세포활성에 미치는 영향 V. CHO세포에서 세포주기에 따라 돌연변이원에 의해 유발된 DNA회복합성에 미치는 DNA중합효소의 역할)

  • 엄경일;김춘광;신은주;문용석;이천복
    • Environmental Mutagens and Carcinogens
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    • v.9 no.1
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    • pp.23-32
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    • 1989
  • Chinese hamster ovary (CHO)-K1 cells echibited a differential sensitivity in the process of DNA repair synthesis induced by ethyl methanesulfonate (EMS) or bleomycin (BLM) in relation to cell cycle. Two assays were employed in this study: alkaline elution and unscheduled DNA synthesis. The post-treat-ment with aphidicolin (APC), an inhibitor of DNA polymerase alpha, inhibited DNA repair synthesis induced by EMS in G2 phase, while APC did not show any effect on BLM-induced DNA repair synthesis in all phases. On the other hands, the 2', 3'-dideoxythymidine (ddTTP), an inhibitor of DNA polymerase beta, inhibited DNA repair synthesis induced by EMS or BLM in both of G1 and G2 phases. These results suggested that the involvement of DNA polymerase alpha and beta in DNA repair was dependent on cell stage or used chemical agent.

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Enviromental Toxic Agents on Genetic Material and Cellular Activity III. DNA Polymerase Inhibitors on Repair of Mutagen-Induced DNA Damage in Mammalian Cells (환경성 유해요인이 유전물질과 세포활성에 미치는 영향 III. 포유동물세포에서 돌연변이원에 의한 DNA 상해의 회복에 미치는 DNA 중합효소저해제의 영향)

  • 엄경일;선우양일;이천복;신은주
    • 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.

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