Glycosylase Research Articles

Role of DNA methylation in sepsis-associated encephalopathy in mice

Objective To evaluate the role of DNA methylation in sepsis-associated encephalopathy in mice. Methods A total of 144 clean-grade healthy male C57BL/6 mice, aged 6-8 weeks, weighing 20-25 g, were divided into 4 groups (n=36 each) using a random number table method: sham operation group (group Sham), sepsis group (group Sepsis), sham operation plus S-adenosyl methionine (SAM) group (group Sham+ SAM) and sepsis plus SAM group (group Sepsis+ SAM). Sepsis was produced by cecum ligation and puncture (CLP). In Sham+ SAM and Sepsis+ SAM groups, DNA methylated methyl donor SAM 100 mg/kg was intraperitoneally injected at 1 h before operation and 12 h after operation, while the equal volume of normal saline was given instead in Sham and Sepsis groups.The cognitive function was assessed using Y-maze and contextual fear conditioning test at 1, 3 and 7 days after CLP.Mice were sacrificed at 1, 3 and 7 days after CLP, and the hippocampal tissues were taken for determination of genome-wide DNA methylation (by colorimetric assay) and expression of DNA methyltransferase enzymes (DNMT1, DNMT3a, and DNMT3b), ten-eleven translocation (TET) enzymes (TET1, TET2 and TET3) and thymine-DNA glycosylase (TDG) mRNA (by fluorescent quantitative real-time). Results Compared with group Sham, the time of staying at the novel arm was significantly shortened, the percentage of time spent freezing and the total number of entries into each arm were reduced, genome-wide DNA methylation in hippocampal tissues was decreased at 1, 3 and 7 days after CLP, the expression of DNMT1, DNMT3a, TET1, TET2, TET3 and TDG was up-regulated, and the expression of DNMT3b was down-regulated in group Sepsis (P<0.05). Compared with group Sepsis, the time of staying at the novel arm was significantly prolonged, the percentage of time spent freezing and the total number of entries into each arm were increased, the expression of DNMT1, DNMT3a, TET1, TET2, TET3 and TDG mRNA was down-regulated, and the expression of DNMT3b was up-regulated in group Sepsis+ SAM(P<0.05). Conclusion DNA methylation is involved in the development of sepsis-associated encephalopathy in mice. Key words: DNA methylation; Sepsis-associated encephalopathy

Base excision repair and targeted therapy strategies

Base excision repair (BER) is an important pathway for DNA oxidative damage repair, and mutations in this pathway cause gene instability and increase cancer risk. A large number of studies have shown that abnormal expression of key proteins in the BER pathway in a variety of tumors, such as DNA glycosylase, apurinic/apyrimidinic endonuclease 1, DNA polymerase and so on. Single nucleotide polymorphisms of these proteins affect the repair activity of tumor cells, and are expected to be important indicators for the diagnosis, treatment and evaluation of prognosis. Key words: DNA repair; Polymorphism; Genomic instability; Base excision repair

Research progress of relationship among DNA oxidative damage, its repair enzymes and neoplasms

DNA oxidative damage can lead to dysfunctions and diseases. There are many pathways to repair DNA oxidative damage and base excision repair (BER) is the most important one. 8-oxoguanine nucleotide triphosphatase, also known as MutT homologue (MTH)1, and 8-oxoguanine DNA glycosylase (OGG)1 are major repair enzymes, which are closely related with tumorigenesis and growth of tumor cells. This review is about the relationship among tumorigenesis, growth of tumor cells, therapy of neoplasms and DNA oxidative damage and the repair enzymes. Key words: DNA oxidative damage; DNA repair; Neoplasms; Therapy; 8-OxodGTPase; 8-Oxoguanine DNA glycosylase 1, zebrafish

N-methylpurine-DNA glycosylase (MPG; APNG; AAG)

N-methylpurine-DNA glycosylase (MPG; APNG; AAG)

Relationship between hOGG1 and XPD gene polymorphism and genetic susceptibility of gastric cancer

Objective To investigate the relationship between hOGG1 and XPD gene polymorphism and genetic susceptibility of gastric cancer.Methods This study was carried out in Dongying Shengli Petroleum Administration Bureau Hospital.Under the narrow band imaging(NBI) mode,the blood samples of a total of 98 gastric cancers and 80 controls without cancers were collected.Genetic polymorphisms of DNA repair genes were identified by polymerase chain reaction restriction fragment length polymorphism(PCR-RFLP),then its relationship with cancers was analyzed.Results Carrying 326Cys allele with the wine increased the risk of gastric cancer; Lys 751Gln genotype increased the susceptibility of the gastric cancers (OR =1.486,0.73 ～ 3.025).Conclusion Lys751 Gln genotype increases the risk of gastric cancer. Key words: DNA glycosylases; Xeroderma pigmentosum group D protein; Genetic pleiotropy; Stomach neoplasms; Genetic predisposition to disease

Human 8-oxoguanine DNA glycosylase and lung cancer

Dysfunction of the human 8-oxoguanine DNA glycosylase (hOGG1) is closely related to development of lung neoplasms and other cancers.Polymorphisms in hOGG1 gene may alter glycosylase activity,thereby affect its repair capacity to the damaged DNA,contributing to carcinogenesis.Joint effects of hOGG1 and other DNA repair gene SNPs have showed complex gene-gene interactions may significantly contribute to people's lung cancer susceptibility.HOGG1 plays an important role in maintaining mitochondrial respiration thus affects tumor cell growth. Key words: Lung neoplasms; DNA, mitochondrial; hOGG1

Effect of leptin on the oxidative damage in human retinal pigment epithelial cells

Objective To investigate the effects of leptin on the oxidative damage in human retinal pigment epithelial (RPE) cells.Methods Human RPE cells (ARPE-19) were cultured in vitro,and randomly divided into control group and insulin resistance group.RPE cells were treated with 0,10,100 ng/mL leptin for 24,48,72 hours respectively.Then the levels of reactive oxygen species (ROS) expression in RPE cells were detected by 2',7'-dichlorofluorescin-diacetate (DCFH-DA),and the levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG) expression in RPE cells were observed by immunocytochemistry (ICC),and the levels of human 8-oxoguanine DNA glycosylase 1 (hOGG1) expression in lysate were measured by Western blot.Results After 24,48,72 hours,the level of ROS (Control group:F=37.136,37.178,49.634; P＜0.05.Insulin resistance group:F=9.822,28.881,71.150;P＜0.05),8-OHdG (Control group:F =88.643,390.920,1039.276; P ＜ 0.05.Insulin resistance group:F =273.311,299.155,82.237;P＜0.05) and hOGGl (Control group:F=470.062,1073.113,295.456;P＜0.05.Insulin resistance group:F =240.032,592.389,527.760 ; P＜0.05) expression increased significantly with the increase of leptin concentration in control group and insulin resistance group.Under the same leptin concentration,the level of 8-OHdG has a trend that it was higher in the insulin resistance group than the control group.After 24 hours,the difference of hOGGl expression between control group and insulin resistance group was not significant (F=23.392,P＞0.05).After 72 hours,the level of hOGGl expression was significantly higher in the insulin resistance group than the control group (F=129.394,P＜0.05).The level of hOGGl expression was significantly higher at 48 hours than that at 24 hours and 72 hours (P＜ 0.05).Conclusion Leptin could induce the oxidative damage of RPE cells in normal and insulin resistance status.With the increase of leptin concentration and time extended,the degree of oxidative damage and its repair were both increased.The degree of oxidative repair increased with the increase of leptin concentration,but decreased with time extended. Key words: Retinal pigment epithelium/injuries; Leptin/poisoning; Reactive oxygen species/poisoning

Effect of dexmedetomidine on expression of OGG1 mRNA in rat hippocampal neurons subjected to oxygenglucose deprivation/reoxygenation and restoration

Objective To evaluate the effect of dexmedetomidine on the expression of 8-Oxoguanine DNA glycosylase 1 (OGG1) mRNA in rat hippocampal neurons subjected to oxygen-glucose deprivation/reoxygenation and restoration (OGD/R).Methods Hippocampal neurons isolated from pathogen-free neonatal Sprague-Dawley rats born within 3 days,were cultured primarily and seeded in 96-well plates (100 μl/well) or 6-well plates (2 ml/well) at the density of 1 × 106 cells/ml.The cells were randomly divided into 5 groups (n=30 each):control group (group C),group OGD/R,and different concentrations of dexmedetomidine groups (DEX1-3 groups).The cells were cultured in normal culture medium in group C and the cells were subjected to OGD/R in the other groups.In DEX1-3 groups,dexmedetomidine with the final concentrations of 0.1,1.0 and 10.0μmol/L were added,respetively,at 2h before OGD.At 24h of restoration,hippocampal neurons were stained with haematoxylin and eosin (H.E) for examination of pathological changes,the cell survival rate was detected by MTT method,the activity of superoxide dismutase (SOD) and content of malondialdehyde (MDA) were detected by colorimetric method,and the expression of OGG1 mRNA was detected by RT-PCR.Results The pathological changes of neurons were obvious in group OGD/R,and the pathological changes of neurons were significantly mitigated in DEX1,DEX2 and DEX3 groups.Compared with group C,the cell survival rate and SOD activity were significantly decreased,MDA content was increased,and the expression of OGG1 mRNA was down-regulated in OGD/R,DEX1,DEX2 and DEX3 groups (P ＜ 0.05).Compared with group OGD/R,the cell survival rate and SOD activity were significantly increased,MDA content was decreased,and the expression of OGG1 mRNA was up-regulated in DEX1,DEX2 and DEX3 groups (P ＜ 0.05).There was no significant difference in the indices mentioned above between DEX1,DEX2 and DEX3 groups (P ＞ 0.05).Conclusion Dexmedetomidine may protect hippocampal neurons against oxidative stress injury by up-regulating the expression of OGG1 mRNA in rat hippocampal neurons subjected to OGD/R. Key words: Dexmedetomidine ; DNA Glycosylases ; Hippocampus ; Neurons ; Reperfusion injury

Relationship between the functional single nucleotide polymorphism rs1052133 in the 8-oxoguanine DNA glycosylase 1 (OGG1) gene and vitiligo in a Chinese Han population

Objective To estimate the relationship of the functional single nucleotide polymorphism (SNP) rs1052133 in the 8-oxoguanine DNA glycosylase 1 (OGG1) gene with vitiligo in a Chinese Han population.Methods Blood samples were collected from 800 patients with vitiligo and 800 healthy human controls,and subjected to genomic DNA extraction.PCR-restriction fragment length polymorphism (PCR-RFLP) analysis was performed to analyze the genotype of the SNP rs1052133 in the OGG1 gene.The relationship between the SNP and the risk of vitiligo was evaluated by chi-square test and unconditional logistic regression analysis.Enzyme linked immunosorbent assay (ELISA) was carried out to assess the serum level of 8-hydroxydeoxyguanosine (8-OHdG) in 83 patients with vitiligo and 83 healthy human controls,then,t test was used to compare the serum 8-OHdG level between the patients and controls.Results The frequency of CC,CG and GG genotype of the SNP rs1052133 was 16.8％,54.0％ and 29.2％ respectively in the patients,21.4％,52.8％ and 25.8％respectively in the controls (x2 =6.26,P ＜ 0.05).Increased frequency of G allele of the SNP rs1052133 was observed in the patients with vitiligo compared with the controls (56.2％ vs.52.2％,x2 =5.16,P ＜ 0.05).A statistically increased risk of vitiligo was associated with the CG (x2 =3.98,P ＜ 0.05,adjusted odds ratio 1.31,95％ confidence interval:1.01-1.70) and GG (x2 =6.01,P ＜ 0.05,adjusted odds ratio 1.45,95％ confidence interval:1.08-1.94) genotype of SNP rs1052133 compared with the CC genotype,which was more evident among the patients with the following characteristics:female,nonsegmental vitiligo,active vitiligo,long clinical course (＞ 12 months),a family history of vitiligo,and no accompanied autoimmune diseases.In addition,the patients with the CG or GG genotype of SNP rs1052133 had a higher serum 8-OHdG level than those with the CC genotype ((838.23 ± 294.11) μg/L vs.(593.84 ± 190.14) μg/L,t =3.63,P ＜ 0.01).Conclusions The SNP rs1052133 in the OGG1 gene may be responsible for the development of vitiligo in Chinese Han populations,which is likely to be associated with defects in DNA repair. Key words: Vitiligo; Polymorphism, single nucleotide; OGG1 gene; 8-OHdG

N-Methylpurine-DNA glycosylase (MPG; APNG)

N-Methylpurine-DNA glycosylase (MPG; APNG)

Reduction of H2O2 and DDP sensitivity of ESCC cells by high-level expression of DNA repair enzyme hOGG1

Objective To explore the effect of high-level expression of DNA repair enzyme human 8-oxoguanine DNA glycosylase (hOGG1) on H2O2 and cisplatin (DDP) sensitivity of esophageal squamous cell carcinoma (ESCC) EC9706 cells. Methods Recombinant adenovirus pAd-CMV5-DEST-hOGG1 was transferred into EC 9706 cells to establish the EC9706 cell model with high-level expression of hOGG1 protein. EC9706 cells infected with the recombinant adenovirus (EC9706-hOGG1) or adenovirus vector (EC9706-LACZ), or non-transfected EC9706 cells (EC9706) were acted by H2O2 and DDP, respectively. The survival rate of the three kinds of cells was compared by using methyl thiazol tetrazolium (MTT) and trypan blue experiments. The comparison of the oxidative damage of the three kinds of ceils was performed by using 8-oxoG immunohistochemistry. The apoptosis index were assayed by the TUNEL staining and flow cytometry (FCM). Results The higher survival rate and the lower 8-oxoG oxidative damage and the lower apoptosis index of the EC9706 cells with high-lever high hOGGlexpression were than ones of the two control groups;Detected by FCM,after 1000 μmol/L H2O2 inducing apoptosis 1.5 hour, cell apoptosis rate of EC9706-hOGG1 ( 5.50％ ) was downregulated markedly than EC9706-LACZ ( 12. 54％ ) and EC9706 cells (13.48％). After three groups treat with 10 mg/L DDP 1.5 h,the apoptois rate in groups EC9706-hOGG1 ,EC9706-LACZ and EC9706 was 3.95％, 11.59％ and 11.48％. There was significant difference between group EC9706-hOGG1 and other control groups. Conclusion The high-level expression of hOGG1 protein of EC 9706 cells may reduce H2O2 and cisplatin sensitivity to EC 9706 cells. Key words: Esophageal squamous cell carcinoma; hOGG1 ; H2O2 ; Cisplatin

Role of heterogeneous nuclear ribonucleoprotein A2/B1 protein in the pathogenesis of non-small cell lung cancer

To study the expression of heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) in non-small cell lung cancer (NSCLC), and the interaction between hnRNP A2/B1 protein and mRNA of DNA repair enzymes O(6)-methylguanine DNA-methyltransferase (MGMT), 8-oxoguanine DNA glycosylase (OGG1), redox factor 1(Ref-1), DNA-dependent protein kinase (including DNA-PKcs and ku). The expression and distribution of hnRNP A2/B1 were detected by immunohistochemistry and Western blot on 50 NSCLC samples from patients who underwent resection in Zhongshan Hospital. The hnRNP A2/B1 mRNA expression was tested by real-time PCR. Co-immunoprecipitation (co-IP) combined RT-PCR was used to investigate whether hnRNP A2/B1 could be bound with the mRNA of the above mentioned 5 DNA repair enzymes in human lung cancer cell line (HTB-182). Then immunohistochemistry and real-time PCR were used to detect the expression of MGMT in the same group of patients. HnRNP A2/B1 protein and mRNA expressions were increased in the NSCLC tissues than that in the corresponding normal lung tissues. HnRNP A2/B1 was expressed predominantly in the nuclei of tumor cells. The positive rate and immunohistochemistry score of hnRNP A2/B1 in tumor tissue were significantly higher than that in normal tissue (P < 0.01). In stage III-IV NSCLC, hnRNP A2/B1 expression was higher than that in stage I-II. There was no significant differences of hnRNP A2/B1 expression among patients of different age, sex, histological type, and smoking history. The results of co-IP combined RT-PCR suggested that hnRNP A2/B1 is bound with MGMT mRNA, and MGMT expression is decreased in tumor tissue of NSCLC. The results of this study show that hnRNP A2/B1 protein and mRNA are highly expressed in NSCLC, and hnRNP A2/B1 is bound with MGMT mRNA, which indicate that it might be one of the mechanisms of hnRNP A2/B1 participating in the pathogenesis of NSCLC.

Effect of adenoviral N-methylpurine DNA glycosylase overexpression on chemosensitivity of human osteosarcoma cells

The overexpression of N-methylpurine DNA glycosylase (MPG) may imbalance the DNA base excision repair (BER) to sensitize tumor cells to current DNA damage chemotherapy. In an effort to improve the efficacy of cancer chemotherapy, we have constructed adenoviral vector of MPG, to study its ability to sensitize human osteosarcoma cell HOS to DNA damage agents. The adenoviral infection and MPG expression, as well as enzyme activity were determined by flow cytometry, Western blot, and HEX labeled oligonucleotide-based assay respectively. The cell survival/proliferation was measured using MTS, SRB, and [(3)H] thymidine incorporation assay. Apoptosis cell death was assayed by flow cytometry after treatment using phycoerythin (PE)-conjugated Annexin V and 7-amino-actinomycin (7-AAD). A 10 MOI of recombinant nonreplicating adenovirus was found to infect more than 90% of HOS cells within 24 hours by EGFP fluorescence, in which the MPG overexpression and MPG enzyme activity were also detected. The MPG overexpression HOS cells were significantly more sensitive to the DNA damage agents, including MMS, MNNG, and TMZ, with changes in the IC50 of 6.0, 4.5, and 2.5 fold respectively. These data establish transient MPG overexpression as a potential therapeutic approach for increasing HOS cellular sensitivity to DNA damage agent chemotherapy.

Identification of hepatitis B virus integration sites in hepatocellular carcinoma tissues from patients with chronic hepatitis B

Hepatitis B virus (HBV) integration into the host genome is frequently detected in HBV positive hepatocellular carcinoma (HCC) in China. The aim of this study is to carry out a large-scale screening for the HBV integrations sites in HCC samples from Chinese patients. Cellular DNA was extracted from 40 HBV-related HCC by proteinase K digestion/phenol extraction method. One primer specific to HBV sequence and another primer directed to human Alu repeat were used to amplify the virus/cellular DNA junction. To avoid undesirable amplifications between Alu sequences, primers were constructed with dUTPs and destroyed by uracil DNA glycosylase treatment after 15 initial cycles of amplification. Only desirable fragments were then further amplified with specific primers to the known region and to a tag sequence introduced in the Alu-Specific primer. The PCR product was purified and subject to direct sequencing by ABI 3700 Auto sequencer. NCBI (national center for biotechnology information) BLAST and MapViewer search were used for identification of HBV location on human genomes. In 40 HBsAg positive HCC samples, 34 (85%) were showed to have at least one copy of HBV fragment in host genome, indicating HBV-Alu-PCR is a rapid way for identification of new cellular DNA sequences adjacent to HBV. Analysis from the 68 isolated viral-cellular junctions, X gene was found to be interrupted at any length, not specifically at DR1 and DR2 regions. Three-prime-deleted X gene was observed in 65 (96%) cases. HBV preferred to integrate into the intron and the up-stream regulatory region of the cellular genes. In no case HBV inserted into the exon. Our results also demonstrated that the cellular genes targeted by HBV are usually key regulators of cell proliferation and cell death. Three genes, myeloid/lymphoid or mixed-lineage leukemia 4, G protein alpha transducing activity polypeptide 1 and fibronectin, were found to be recurrently targeted by HBV. HBV-Alu-PCR is a powerful tool for the study of HBV integration sites. Truncated X is a major form existed in the HBV integrants. HBV integration is not distributed evenly throughout the host genome and viral insertional mutagenesis may play an important role in the development of HCC.

Inhibition of DNA repair glycosylases by base analogs and tryptophan pyrolysate, Trp-P-1.

DNA base analogs, 2,4,5,6-substituted pyrimidines and 2,6-substituted purines were tested as potential inhibitors of E. coli Fpg protein (formamidopyrimidine -DNA glycosylase). Three of the seventeen compounds tested revealed inhibitory properties. 2-Thioxanthine was the most efficient, inhibiting 50% of 2,6-diamino-4-hydroxy-5N-methyl-formamidopyrimidine (Fapy-7MeG) excision activity at 17.1 microM concentration. The measured K(i) was 4.44 +/- 0.15 microM. Inhibition was observed only when the Fpg protein was first challenged to its substrate followed by the addition of the base analog, suggesting uncompetitive (catalytic) inhibition. For two other compounds, 2-thio- or 2-oxo-4,5,6-substituted pyrimidines, IC(50) was only 343.3 +/- 58.6 and 350 +/- 24.4 microM, respectively. No change of the Fpg glycosylase activity was detected in the presence of Fapy-7MeG, up to 5 microM. We also investigated the effect of DNA structure modified by tryptophan pyrolysate (Trp-P-1) on the activity of base excision repair enzymes: Escherichia coli and human DNA glycosylases of oxidized (Fpg, Nth) and alkylated bases (TagA, AlkA, and ANPG), and for bacterial AP endonuclease (Xth protein). Trp-P-1, which changes the secondary DNA structure into non-B, non-Z most efficiently inhibited excision of alkylated bases by the AlkA glycosylase (IC(50) = 1 microM). The ANPG, TagA, and Fpg proteins were also inhibited although to a lesser extent (IC(50) = 76.5 microM, 96 microM, and 187.5 microM, respectively). Trp-P-1 also inhibited incision of DNA at abasic sites by the beta-lyase activity of the Fpg and Nth proteins, and to a lesser extent by the Xth AP endonuclease. Thus, DNA conformation is critical for excision of damaged bases and incision of abasic sites by DNA repair enzymes.

Mismatch dependent uracil/thymine-DNA glycosylases excise exocyclic hydroxyethano and hydroxypropano cytosine adducts.

Exocyclic adducts of DNA bases, such as etheno- and hydroxyalkano- ones, are generated by a variety of bifunctional agents, including endogenously formed products of lipid peroxidation. In this work we selectively modified cytosines in the 5'-d(TTT TTT CTT TTT CTT TTT CTT TTT T)-3' oligonucleotide using: chloroacetaldehyde to obtain 3,N(4)-alpha-hydroxyethano- (HEC) and 3,N(4)-etheno- (epsilonC), acrolein to obtain 3,N(4)-alpha-hydroxypropano- (HPC) and crotonaldehyde to obtain 3,N(4)-alpha-hydroxy-gamma-methylpropano- (mHPC) adducts of cytosine. The studied adducts are alkali-labile which results in oligonucleotide strain breaks at the sites of modification upon strong base treatment. The oligonucleotides carrying adducted cytosines were studied as substrates of Escherichia coli Mug, human TDG and fission yeast Thp1p glycosylases. All the adducts studied are excised by bacterial Mug although with various efficiency: epsilonC >HEC >HPC >mHPC. The yeast enzyme excises efficiently epsilonC>HEC>HPC, whereas the human enzyme excises only epsilonC. The pH-dependence curves of excision of eC, HEC and HPC by Mug are bell shaped and the most efficient excision of adducts occurs within the pH range of 8.6-9.6. The observed increase of excision of HEC and HPC above pH 7.2 can be explained by deprotonation of these adducts, which are high pK(a) compounds and exist in a protonated form at neutrality. On the other hand, since epsilonC is in a neutral form in the pH range studied, we postulate an involvement of an additional catalytic factor. We hypothesize that the enzyme structure undergoes a pH-induced rearrangement allowing the participation of Lys68 of Mug in catalysis via a hydrogen bond interaction of its epsilon-amino group with N(4) of the cytosine exocyclic adducts.

A DNA Glycosylase from Pyrobaculum aerophilum with an 8-Oxoguanine Binding Mode and a Noncanonical Helix-Hairpin-Helix Structure

Studies of DNA base excision repair (BER) pathways in the hyperthermophilic crenarchaeon Pyrobaculum aerophilum identified an 8-oxoguanine-DNA glycosylase, Pa-AGOG (archaeal GO glycosylase), with distinct functional characteristics. Here, we describe its crystal structure and that of its complex with 8-oxoguanosine at 1.0 and 1.7 A resolution, respectively. Characteristic structural features are identified that confirm Pa-AGOG to be the founding member of a functional class within the helix-hairpin-helix (HhH) superfamily of DNA repair enzymes. Its hairpin structure differs substantially from that of other proteins containing an HhH motif, and we predict that it interacts with the DNA backbone in a distinct manner. Furthermore, the mode of 8-oxoguanine recognition, which involves several hydrogen-bonding and pi-stacking interactions, is unlike that observed in human OGG1, the prototypic 8-oxoguanine HhH-type DNA glycosylase. Despite these differences, the predicted kinked conformation of bound DNA and the catalytic mechanism are likely to resemble those of human OGG1.

Characterization of specialized mtDNA glycosylases.

Characterization of specialized mtDNA glycosylases.

Increased incorporation of 5-fluorodeoxyuridine into DNA of human T-lymphoblastic cell lines.

Various human leukemoblastoid cell lines in logarithmic growth were incubated for 16 hr with 0.5 microM [3H]fluorodeoxyuridine (FdUrd) and the incorporation of [3H]FdUrd into DNA was measured. T-acute lymphoblastic leukemia (T-ALL) cell lines incorporated 2.4-7.0 times more [3H]FdUrd into newly synthesized DNA than cell lines from B-lymphoid, pre B-ALL, null cell ALL and acute myeloid leukemia cells. T-ALL cells incorporated 1.93-3.15 pmol of [3H]FdUrd nucleotides into DNA per 10(7) cells. The amount of [3H]FdUrd incorporated into DNA was inversely correlated with the activity level of uracil DNA glycosylase of the cells. On the other hand, no correlation was observed between the incorporation and the level of deoxyuridine triphosphate diphosphohydrolase of each cell line. However, the amount of FdUrd incorporated into DNA could not be correlated with the antiproliferative activity of FdUrd against these cell lines.