Introduction:DNA polymerases are crucial for maintaining genome stability and influencing tumorigenesis.However,the clinical implications of DNA polymerases in tumorigenesis and their potential as anti-cancer therapy ...Introduction:DNA polymerases are crucial for maintaining genome stability and influencing tumorigenesis.However,the clinical implications of DNA polymerases in tumorigenesis and their potential as anti-cancer therapy targets are not well understood.Methods:We conducted a systematic analysis using TCGA Pan-Cancer Atlas data and Gene Set Cancer Analysis results to examine the expression profiles of 15 DNA polymerases(POLYs)and their clinical correlations.We also evaluated the prognostic value of POLYs by analyzing their expression levels in relation to overall survival time(OS)using Kaplan-Meier survival curves.Additionally,we investigated the correlations between POLY expression and immune cells,DNA damage repair(DDR)pathways,and ubiquitination.Drug sensitivity analysis was performed to assess the relationship between POLY expression and drug response.Results:Our analysis revealed that 14 out of 15 POLYs exhibited significantly distinct expression patterns between tumor and normal samples across most cancer types,except for DNA nucleotidylexotransferase(DNTT).Specifically,POLD1 and POLE showed elevated expression in almost all cancers,while POLQ exhibited high expression levels in all cancer types.Some POLYs showed heightened expression in specific cancer subtypes,while others exhibited low expression.Kaplan-Meier survival curves demonstrated significant prognostic value of POLYs in multiple cancers,including PAAD,KIRC,and ACC.Cox analysis further validated these findings.Alteration patterns of POLYs varied significantly among different cancer types and were associated with poorer survival outcomes.Significant correlations were observed between the expression of POLY members and immune cells,DDR pathways,and ubiquitination.Drug sensitivity analysis indicated an inverse relationship between POLY expression and drug response.Conclusion:Our comprehensive study highlights the significant role of POLYs in cancer development and identifies them as promising prognostic and immunological biomarkers for various cancer types.Additionally,targeting POLYs therapeutically holds promise for tumor immunotherapy.展开更多
Objective To explore the toxicological mechanism of hydroquinone in human bronchial epithelial cells and to investigate whether DNA polymerase beta is involved in protecting cells from damage caused by hydroquinone. M...Objective To explore the toxicological mechanism of hydroquinone in human bronchial epithelial cells and to investigate whether DNA polymerase beta is involved in protecting cells from damage caused by hydroquinone. Methods DNA polymerase beta knock-down cell line was established via RNA interference as an experimental group. Normal human bronchial epithelial cells and cells transfected with the empty vector of pEGFP-C1 were used as controls. Cells were treated with different concentrations of hydroquinone (ranged from 10 μmol/L to 120 μmol/L) for 4 hours. MTT assay and Comet assay [single-cell gel electrophoresis (SCGE)] were performed respectively to detect the toxicity of hydroquinone. Results assay showed that DNA polymerase beta knock-down cells treated with different concentrations of hydroquinone had a lower absorbance value at 490 nm than the control cells in a dose-dependant manner. Comet assay revealed that different concentrations of hydroquinone caused more severe DNA damage in DNA polymerase beta knock-down cell line than in control cells and there was no significant difference in the two control groups. Conclusions Hydroquinone has significant toxicity to human bronchial epithelial cells and causes DNA damage. DNA polymerase beta knock-down cell line appears more sensitive to hydroquinone than the control cells. The results suggest that DNA polymerase beta is involved in protecting cells from damage caused by hydroquinone.展开更多
在他们描述脱氧核糖核酸双螺旋,沃森和克里克的结构写了什么可以是在科学文学的最大的保守的陈述之一的精液的出版,也就是那“这没疏忽特定的配对我们立即要求了为遗传物质建议可能的拷贝机制。“半个世纪以后,我们更充分欣赏它是与...在他们描述脱氧核糖核酸双螺旋,沃森和克里克的结构写了什么可以是在科学文学的最大的保守的陈述之一的精液的出版,也就是那“这没疏忽特定的配对我们立即要求了为遗传物质建议可能的拷贝机制。“半个世纪以后,我们更充分欣赏它是与精确性复制 60 亿核苷酸的巨大的挑战需要稳定地在许多代上维持人的染色体的。这挑战也许比大 50 年以前被认识到,因为随后的研究表明了染色体能被在脱氧核糖核酸而且由现在质问到复制的正常脱氧核糖核酸的各种各样的顺序主题产生潜在地细胞毒素、诱变的损害的一个大数字和变化的环境压力使动摇不仅。向染色体稳定性的许多决定因素的更好的理解,这章考察 undamaged 和损坏脱氧核糖核酸与被拷贝的忠实,与真核细胞的 B 家庭和 Y 家庭 DNA 的一个焦点,并且考虑这忠实怎么被完成。展开更多
Library construction is a common method used to screen target genes in molecular biology.Most library constructions are not suitable for a small DNA library(<100 base pair(bp))and low RNA library output.To maximize...Library construction is a common method used to screen target genes in molecular biology.Most library constructions are not suitable for a small DNA library(<100 base pair(bp))and low RNA library output.To maximize the library’s complexity,error-prone polymerase chain reaction(PCR)was used to increase the base mutation rate.After introducing the DNA fragments into the competent cell,the library complexity could reach 109.Library mutation rate increased exponentially with the dilution and amplification of error-prone PCR.The error-prone PCR conditions were optimized including deoxyribonucleotide triphosphate(dNTP)concentration,Mn^(2+)concentration,Mg^(2+)concentration,PCR cycle number,and primer length.Then,a RNA library with high complexity can be obtained by in vitro transcription to meet most molecular biological screening requirements,and can also be used for mRNA vaccine screening.展开更多
AIM: To observe the variation of DNA polymerase β (polβ)in esophageal carcinoma.METHODS: Thirty specimens containing adjacent normal epithelial tissues were collected from patients in Linzhou region (a high risk are...AIM: To observe the variation of DNA polymerase β (polβ)in esophageal carcinoma.METHODS: Thirty specimens containing adjacent normal epithelial tissues were collected from patients in Linzhou region (a high risk area for esophageal squamous carcinoma) and 25 specimens were from a non-high risk area. Total RNA was extracted from the samples and reverse transcription polymerase chain reaction (RT-PCR) was performed. PCR products were cloned and sequenced to investigate the polβ gene with DNASIS and OMIGA. Statistical significance was evaluated using the x2 test.RESULTS: High-incidence area group: polβ gene variation was detected in 13 of 30 esophageal carcinoma tissue specimens, and only one variation was found in 30corresponding adjacent normal tissue specimens. Non high-incidence area group: polβ gene variation was detected in 5 of 25 esophageal carcinoma tissue specimens,and no variation was found in 25 corresponding adjacent normal tissue specimens. The incidence of polβ gene variation observed in the high-incidence area group was significantly higher than in the non-high incidence area group. Two mutation hot spots (454-466 and 648-670 nt)and a 58 bp deletion (177-234 nt) were found.CONCLUSION: Variations of polβ perform different functions between the high-incidence areas and the other areas, and may play a more important role in the high-incidence areas.展开更多
AIM: To look for a rapid low-cost technique for the detection of HBV variants.METHODS: Two patients who underwent orthotopic liver transplantation (OLT) for HBV infection were treated with lamivudine (100 mg daily) an...AIM: To look for a rapid low-cost technique for the detection of HBV variants.METHODS: Two patients who underwent orthotopic liver transplantation (OLT) for HBV infection were treated with lamivudine (100 mg daily) and HBV infection recurred in the grafted livers. The patients were monitored intensively for liver enzymes, hepatitis B surface antigen (HBsAg) and HBV DNA in serum. Liver biopsy was performed regularly. HBV DNA in a conserved polymerase domain (the YMDD locus) was amplified from serum of each patient by PCR and sequenced. HBV genotypes were analyzed by restriction fragment length polymorphism (RFLP) of the PCR products generated from a fragment of the polymerase gene.RESULTS: YMDD wild-type HBV was detected in one patient by PCR-RFLP and DNA sequencing 19 mo after OLT, and YIDD mutant-type HBV in the other patient, 16 mo after OLT.CONCLUSION: PCR-RFLP assay is an accurate and simple method for genotyping lamivudine-resistant HBV variants.展开更多
The large fragment of E.coli DNA polymerase I is imaged by scanning tunneling microscope. The specimen is deposited on highly oriented pyrolytic graphite surface, and then covered with pure paraffin oil in order to ma...The large fragment of E.coli DNA polymerase I is imaged by scanning tunneling microscope. The specimen is deposited on highly oriented pyrolytic graphite surface, and then covered with pure paraffin oil in order to maintain hydration of the molecules. Images of the enzyme reveal an ellipsoid shape of 5.5-6.0nm wide and 7.0 -7.5 nm long. The conformation of the enzyme is in agreement with the model derived from X- ray crystallography studies.展开更多
The sensitivity of PCR was determined for detection of HBV DNA in paraffin-embed-ded liver tissue with different methods for sample preparation.Of 8 cases of HBeAg-positiveHBV infection,HBV DNA was detected in 6 by ex...The sensitivity of PCR was determined for detection of HBV DNA in paraffin-embed-ded liver tissue with different methods for sample preparation.Of 8 cases of HBeAg-positiveHBV infection,HBV DNA was detected in 6 by extracting DNA from both frozen and dewaxedsamples,but in none by direct reaction.Of 12 cases subjected to Southern blot hybridization,HBV DNA was detected in 7 by this technique,in 10 by PCR with both methods of DNA extrac-tion and in 3 by direct PCR.The results showed that PCR was sensitive and was comparablewith blot hybridization in detecting intrahepatic HBV DNA.In comparison between differentmethods of sample preparation,the viral detection rate from the dewaxed samples was near thatfrom the frozen ones,while by the direct reaction HBV DNA could be detected only in a fewsamples with high level of infection.展开更多
To investigate the effects of γ rays on DNA polymerase β properties and its DNA repair functions before or after γ rays exposure, DNA polymerase βactivity, gene expression and mRNA levels in SMMC-LTNM hepatomas ho...To investigate the effects of γ rays on DNA polymerase β properties and its DNA repair functions before or after γ rays exposure, DNA polymerase βactivity, gene expression and mRNA levels in SMMC-LTNM hepatomas horn on nude mice or the samples of the liver cancer tissues from 15 patients were measured with 3H-TTP incorporation test, immunocytochemistry and cytoplasmic dot hybridization analysis, respectively.Irradiation was carried out with 60Co-γ rays at ice bath. It was found that DNA polymerase β activity, gene expression and the amount of mRNA were much higher in hepatoma cells than those in normal hepatocytes (P<0.01). In vitro studies, the enzyme activity both in hepatoma and normal liver cells appeared unchanged within 40 Gy γ-ray exposure. Following whole-body exposure of the nude mice bearing SMMC-LTNM with 2 Gy or 4 Gy of γ rays, DNA polymerase β activity in hepatoma increased temorarily at 48 hours postirradiation, and its gene expression seemed more active.The euzyme mRNA increased to 1.76-fold of the control group. 72 hours after exposure, all of these changes returned to normal levels. DNA polymerase βparticipated in DNA repair synthesis and this effect was different between hepatoma and hepatocytes because there were some biologic differences of the enzyme between hepatoma cells and normal liver cells. These data suggested that DNA polymeraseβactivity, its gene expression and mRNA level in hepatomas could increased temporarily after γ rays exposure, which may facilitate the cells to repair DNA damages from radiation.展开更多
The roles of DNA polymerase β in the repair synthesis of γ-rays irradiated DNA from calf thymus .SMMC-LTNM hepatoma and nude mouse hepatocytes were evaluated, using NEM or d2TTP as selective inhibitors to DNA polyme...The roles of DNA polymerase β in the repair synthesis of γ-rays irradiated DNA from calf thymus .SMMC-LTNM hepatoma and nude mouse hepatocytes were evaluated, using NEM or d2TTP as selective inhibitors to DNA polymerase a or β . It was observed that the rate of [3H]-TTP incorporating into calf thymus DNA damaged by 10 Gy γ-ray was much higher( P<0.01 ) than that of the non-irradiated one. when there was some amount of recombinant rat DNA polymerase β in the reaction mixture. We also found that the [3H]-TTP incorporation rate reflecting the DNA repair synthesis increased gradually as γ-rays absorbed doserose to 20 Gy for hepatocyte nuclei or to 5 Gy for hepatoma nuclei. and then decreased slowly as the absorbeddose rose higher. These results suggest that DNA polyrnerase β could participate in DNA repair synthesis inboth normal and neoplastic nuclei irradiated by γ-rays and its roles in DNA repair may be related to cell typesand absorbed dose.展开更多
Objective: To detect the effect of extract of Camellia Sinensis (ECS) and extract of Camellia Ptilophylla Chang (ECPC) on DNA polymerase (Pol) of Ehrlich ascites tumor cells Methods: Referring to the method of K ...Objective: To detect the effect of extract of Camellia Sinensis (ECS) and extract of Camellia Ptilophylla Chang (ECPC) on DNA polymerase (Pol) of Ehrlich ascites tumor cells Methods: Referring to the method of K Ono, Pol was extracted from Ehrlich ascites tumor cells in mice Pol α, β, and γ were separated by phosphocellulose column chromatography and were identified The effect of ECPC and ECS on Pol was studied Results: ECPC and ECS were shown to inhibit the activity of Pol α, β, and γ IC 50 values of ECS on Pol α , β, and γ were 10 2μg/ml, 9 9μg/ml and 28 9μg/ml respectively IC 50 values of ECPC on Pol α, Pol β and Pol γ were 5 6μg/ml, 15μg/ml and 14 7μg/ml respectively The modes of inhibition of ECPC on Pol α, Pol β and Pol γ were noncompetitive with respect to template DNA The Ki values of ECPC on Pol α , β, and γ were 2 68±0 12μg/ml, 2 24±0 12μg/ml , 2 56±0 18μg/ml Conclusion: ECPC and ECS were shown to have inhibitory effect on DNA polymerase of tumor cells The mode of inhibition of ECPC on Pol α, Pol β and Pol γ were noncompetitive with respect to template DNA展开更多
Human Cytomegalovirus (HCMV) DNA polymerase gene was overexpressed in insect cells using the baculovirus transfer system. A6. 2 kb HCMV Rsr Ⅱ-EcoRI DNA fragment with intact HCMV pci gene coding sequence was engineere...Human Cytomegalovirus (HCMV) DNA polymerase gene was overexpressed in insect cells using the baculovirus transfer system. A6. 2 kb HCMV Rsr Ⅱ-EcoRI DNA fragment with intact HCMV pci gene coding sequence was engineered into NheI site of vector pBlueBac under the control of polyhedrin promoter of Autographa californica nuclear polyhedrosis virus (AcNPV). Recombinant AcNPV carried HCMV pci gene was generated by cotransfection of Spodoptera frugiperta cell (SF21) with AcNPV DNA and baculovirus transfer vector with HCMV pci gene. In fection of SF21 cell with recombinant virus lead to the expression of 140 kD peptide of HCMV specific DNA polymerase at the level approximately 2 mg per 108 cells. The polypeptide was purified from the infected SF21 cells by a series of column chromatography to homogeneity. The purified enzyme had a molecular weight of 140 kD and reacted with antiserum specific for HCMV DNA polymerase. It exhibited both 3'-5'and 5'-3' exonuclease activities.This enzyme is also sensitive to phosphono acetate.展开更多
基金supported by the project of funds by the Consultation of Provincial Department and University for S&T Innovation granted by Hebei Provincial Department of Science and Technology and Hebei Medical University(2020TXZH04).
文摘Introduction:DNA polymerases are crucial for maintaining genome stability and influencing tumorigenesis.However,the clinical implications of DNA polymerases in tumorigenesis and their potential as anti-cancer therapy targets are not well understood.Methods:We conducted a systematic analysis using TCGA Pan-Cancer Atlas data and Gene Set Cancer Analysis results to examine the expression profiles of 15 DNA polymerases(POLYs)and their clinical correlations.We also evaluated the prognostic value of POLYs by analyzing their expression levels in relation to overall survival time(OS)using Kaplan-Meier survival curves.Additionally,we investigated the correlations between POLY expression and immune cells,DNA damage repair(DDR)pathways,and ubiquitination.Drug sensitivity analysis was performed to assess the relationship between POLY expression and drug response.Results:Our analysis revealed that 14 out of 15 POLYs exhibited significantly distinct expression patterns between tumor and normal samples across most cancer types,except for DNA nucleotidylexotransferase(DNTT).Specifically,POLD1 and POLE showed elevated expression in almost all cancers,while POLQ exhibited high expression levels in all cancer types.Some POLYs showed heightened expression in specific cancer subtypes,while others exhibited low expression.Kaplan-Meier survival curves demonstrated significant prognostic value of POLYs in multiple cancers,including PAAD,KIRC,and ACC.Cox analysis further validated these findings.Alteration patterns of POLYs varied significantly among different cancer types and were associated with poorer survival outcomes.Significant correlations were observed between the expression of POLY members and immune cells,DDR pathways,and ubiquitination.Drug sensitivity analysis indicated an inverse relationship between POLY expression and drug response.Conclusion:Our comprehensive study highlights the significant role of POLYs in cancer development and identifies them as promising prognostic and immunological biomarkers for various cancer types.Additionally,targeting POLYs therapeutically holds promise for tumor immunotherapy.
基金This work was supported by a grant from the Major State Basic Research Development Program of China (No. 2002CB512904, 2002CB512903).
文摘Objective To explore the toxicological mechanism of hydroquinone in human bronchial epithelial cells and to investigate whether DNA polymerase beta is involved in protecting cells from damage caused by hydroquinone. Methods DNA polymerase beta knock-down cell line was established via RNA interference as an experimental group. Normal human bronchial epithelial cells and cells transfected with the empty vector of pEGFP-C1 were used as controls. Cells were treated with different concentrations of hydroquinone (ranged from 10 μmol/L to 120 μmol/L) for 4 hours. MTT assay and Comet assay [single-cell gel electrophoresis (SCGE)] were performed respectively to detect the toxicity of hydroquinone. Results assay showed that DNA polymerase beta knock-down cells treated with different concentrations of hydroquinone had a lower absorbance value at 490 nm than the control cells in a dose-dependant manner. Comet assay revealed that different concentrations of hydroquinone caused more severe DNA damage in DNA polymerase beta knock-down cell line than in control cells and there was no significant difference in the two control groups. Conclusions Hydroquinone has significant toxicity to human bronchial epithelial cells and causes DNA damage. DNA polymerase beta knock-down cell line appears more sensitive to hydroquinone than the control cells. The results suggest that DNA polymerase beta is involved in protecting cells from damage caused by hydroquinone.
文摘在他们描述脱氧核糖核酸双螺旋,沃森和克里克的结构写了什么可以是在科学文学的最大的保守的陈述之一的精液的出版,也就是那“这没疏忽特定的配对我们立即要求了为遗传物质建议可能的拷贝机制。“半个世纪以后,我们更充分欣赏它是与精确性复制 60 亿核苷酸的巨大的挑战需要稳定地在许多代上维持人的染色体的。这挑战也许比大 50 年以前被认识到,因为随后的研究表明了染色体能被在脱氧核糖核酸而且由现在质问到复制的正常脱氧核糖核酸的各种各样的顺序主题产生潜在地细胞毒素、诱变的损害的一个大数字和变化的环境压力使动摇不仅。向染色体稳定性的许多决定因素的更好的理解,这章考察 undamaged 和损坏脱氧核糖核酸与被拷贝的忠实,与真核细胞的 B 家庭和 Y 家庭 DNA 的一个焦点,并且考虑这忠实怎么被完成。
基金Shanghai Science and Technology Commission’s“Belt and Road Initiative”International Cooperation Project,China(No.19410741800)。
文摘Library construction is a common method used to screen target genes in molecular biology.Most library constructions are not suitable for a small DNA library(<100 base pair(bp))and low RNA library output.To maximize the library’s complexity,error-prone polymerase chain reaction(PCR)was used to increase the base mutation rate.After introducing the DNA fragments into the competent cell,the library complexity could reach 109.Library mutation rate increased exponentially with the dilution and amplification of error-prone PCR.The error-prone PCR conditions were optimized including deoxyribonucleotide triphosphate(dNTP)concentration,Mn^(2+)concentration,Mg^(2+)concentration,PCR cycle number,and primer length.Then,a RNA library with high complexity can be obtained by in vitro transcription to meet most molecular biological screening requirements,and can also be used for mRNA vaccine screening.
基金Supported by the National Natural Science Foundation of China,No. 39870287
文摘AIM: To observe the variation of DNA polymerase β (polβ)in esophageal carcinoma.METHODS: Thirty specimens containing adjacent normal epithelial tissues were collected from patients in Linzhou region (a high risk area for esophageal squamous carcinoma) and 25 specimens were from a non-high risk area. Total RNA was extracted from the samples and reverse transcription polymerase chain reaction (RT-PCR) was performed. PCR products were cloned and sequenced to investigate the polβ gene with DNASIS and OMIGA. Statistical significance was evaluated using the x2 test.RESULTS: High-incidence area group: polβ gene variation was detected in 13 of 30 esophageal carcinoma tissue specimens, and only one variation was found in 30corresponding adjacent normal tissue specimens. Non high-incidence area group: polβ gene variation was detected in 5 of 25 esophageal carcinoma tissue specimens,and no variation was found in 25 corresponding adjacent normal tissue specimens. The incidence of polβ gene variation observed in the high-incidence area group was significantly higher than in the non-high incidence area group. Two mutation hot spots (454-466 and 648-670 nt)and a 58 bp deletion (177-234 nt) were found.CONCLUSION: Variations of polβ perform different functions between the high-incidence areas and the other areas, and may play a more important role in the high-incidence areas.
基金Supported by the National Natural Science Foundation of China, No. 30170363 the Major Science and Technology Program of Ministry of Education, No. 01003 the Major State Basic Research Development Program of China, No. 2002CB513100 the National Key Technology Research and Development Program of China during the 10~(th) Five-Year Plan Period, No. 2001BA703B05
文摘AIM: To look for a rapid low-cost technique for the detection of HBV variants.METHODS: Two patients who underwent orthotopic liver transplantation (OLT) for HBV infection were treated with lamivudine (100 mg daily) and HBV infection recurred in the grafted livers. The patients were monitored intensively for liver enzymes, hepatitis B surface antigen (HBsAg) and HBV DNA in serum. Liver biopsy was performed regularly. HBV DNA in a conserved polymerase domain (the YMDD locus) was amplified from serum of each patient by PCR and sequenced. HBV genotypes were analyzed by restriction fragment length polymorphism (RFLP) of the PCR products generated from a fragment of the polymerase gene.RESULTS: YMDD wild-type HBV was detected in one patient by PCR-RFLP and DNA sequencing 19 mo after OLT, and YIDD mutant-type HBV in the other patient, 16 mo after OLT.CONCLUSION: PCR-RFLP assay is an accurate and simple method for genotyping lamivudine-resistant HBV variants.
文摘The large fragment of E.coli DNA polymerase I is imaged by scanning tunneling microscope. The specimen is deposited on highly oriented pyrolytic graphite surface, and then covered with pure paraffin oil in order to maintain hydration of the molecules. Images of the enzyme reveal an ellipsoid shape of 5.5-6.0nm wide and 7.0 -7.5 nm long. The conformation of the enzyme is in agreement with the model derived from X- ray crystallography studies.
文摘The sensitivity of PCR was determined for detection of HBV DNA in paraffin-embed-ded liver tissue with different methods for sample preparation.Of 8 cases of HBeAg-positiveHBV infection,HBV DNA was detected in 6 by extracting DNA from both frozen and dewaxedsamples,but in none by direct reaction.Of 12 cases subjected to Southern blot hybridization,HBV DNA was detected in 7 by this technique,in 10 by PCR with both methods of DNA extrac-tion and in 3 by direct PCR.The results showed that PCR was sensitive and was comparablewith blot hybridization in detecting intrahepatic HBV DNA.In comparison between differentmethods of sample preparation,the viral detection rate from the dewaxed samples was near thatfrom the frozen ones,while by the direct reaction HBV DNA could be detected only in a fewsamples with high level of infection.
文摘To investigate the effects of γ rays on DNA polymerase β properties and its DNA repair functions before or after γ rays exposure, DNA polymerase βactivity, gene expression and mRNA levels in SMMC-LTNM hepatomas horn on nude mice or the samples of the liver cancer tissues from 15 patients were measured with 3H-TTP incorporation test, immunocytochemistry and cytoplasmic dot hybridization analysis, respectively.Irradiation was carried out with 60Co-γ rays at ice bath. It was found that DNA polymerase β activity, gene expression and the amount of mRNA were much higher in hepatoma cells than those in normal hepatocytes (P<0.01). In vitro studies, the enzyme activity both in hepatoma and normal liver cells appeared unchanged within 40 Gy γ-ray exposure. Following whole-body exposure of the nude mice bearing SMMC-LTNM with 2 Gy or 4 Gy of γ rays, DNA polymerase β activity in hepatoma increased temorarily at 48 hours postirradiation, and its gene expression seemed more active.The euzyme mRNA increased to 1.76-fold of the control group. 72 hours after exposure, all of these changes returned to normal levels. DNA polymerase βparticipated in DNA repair synthesis and this effect was different between hepatoma and hepatocytes because there were some biologic differences of the enzyme between hepatoma cells and normal liver cells. These data suggested that DNA polymeraseβactivity, its gene expression and mRNA level in hepatomas could increased temporarily after γ rays exposure, which may facilitate the cells to repair DNA damages from radiation.
文摘The roles of DNA polymerase β in the repair synthesis of γ-rays irradiated DNA from calf thymus .SMMC-LTNM hepatoma and nude mouse hepatocytes were evaluated, using NEM or d2TTP as selective inhibitors to DNA polymerase a or β . It was observed that the rate of [3H]-TTP incorporating into calf thymus DNA damaged by 10 Gy γ-ray was much higher( P<0.01 ) than that of the non-irradiated one. when there was some amount of recombinant rat DNA polymerase β in the reaction mixture. We also found that the [3H]-TTP incorporation rate reflecting the DNA repair synthesis increased gradually as γ-rays absorbed doserose to 20 Gy for hepatocyte nuclei or to 5 Gy for hepatoma nuclei. and then decreased slowly as the absorbeddose rose higher. These results suggest that DNA polyrnerase β could participate in DNA repair synthesis inboth normal and neoplastic nuclei irradiated by γ-rays and its roles in DNA repair may be related to cell typesand absorbed dose.
文摘Objective: To detect the effect of extract of Camellia Sinensis (ECS) and extract of Camellia Ptilophylla Chang (ECPC) on DNA polymerase (Pol) of Ehrlich ascites tumor cells Methods: Referring to the method of K Ono, Pol was extracted from Ehrlich ascites tumor cells in mice Pol α, β, and γ were separated by phosphocellulose column chromatography and were identified The effect of ECPC and ECS on Pol was studied Results: ECPC and ECS were shown to inhibit the activity of Pol α, β, and γ IC 50 values of ECS on Pol α , β, and γ were 10 2μg/ml, 9 9μg/ml and 28 9μg/ml respectively IC 50 values of ECPC on Pol α, Pol β and Pol γ were 5 6μg/ml, 15μg/ml and 14 7μg/ml respectively The modes of inhibition of ECPC on Pol α, Pol β and Pol γ were noncompetitive with respect to template DNA The Ki values of ECPC on Pol α , β, and γ were 2 68±0 12μg/ml, 2 24±0 12μg/ml , 2 56±0 18μg/ml Conclusion: ECPC and ECS were shown to have inhibitory effect on DNA polymerase of tumor cells The mode of inhibition of ECPC on Pol α, Pol β and Pol γ were noncompetitive with respect to template DNA
文摘Human Cytomegalovirus (HCMV) DNA polymerase gene was overexpressed in insect cells using the baculovirus transfer system. A6. 2 kb HCMV Rsr Ⅱ-EcoRI DNA fragment with intact HCMV pci gene coding sequence was engineered into NheI site of vector pBlueBac under the control of polyhedrin promoter of Autographa californica nuclear polyhedrosis virus (AcNPV). Recombinant AcNPV carried HCMV pci gene was generated by cotransfection of Spodoptera frugiperta cell (SF21) with AcNPV DNA and baculovirus transfer vector with HCMV pci gene. In fection of SF21 cell with recombinant virus lead to the expression of 140 kD peptide of HCMV specific DNA polymerase at the level approximately 2 mg per 108 cells. The polypeptide was purified from the infected SF21 cells by a series of column chromatography to homogeneity. The purified enzyme had a molecular weight of 140 kD and reacted with antiserum specific for HCMV DNA polymerase. It exhibited both 3'-5'and 5'-3' exonuclease activities.This enzyme is also sensitive to phosphono acetate.