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Wu FW, Wang LB, Li BF, Yan XL, Zi JR, Peng J, Cai X, Bao XY, Yang YM. [Prevalence of human soil-borne nematode infections in Yunnan Province: a cross-sectional study in 2015]. Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi 2021; 33:513-517. [PMID: 34791851 DOI: 10.16250/j.32.1374.2021112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
OBJECTIVE To investigate the current prevalence of human soil-borne nematode infections in Yunnan province, so as to provide the scientific evidence for formulating the soil-borne nematodiasis control strategy in the province. METHODS In 2015, a total of 20 survey sites were sampled in 10 counties (cities) of Yunnan Province using the stratified cluster random sampling method. Stool samples were collected from all local permanent residents at ages of one year and older in each survey site, and the soil-borne nematode eggs were identified using the modified Kato-Katz technique and the egg number was counted. In addition, the hookworm species was identified using the filter-paperculture method, and Enterobius vermicularis eggs were detected using the cellophane tape method in children at ages of 3 to 6 years. RESULTS A total of 5 067 residents received stool examinations, and 950 residents were detected with soil-borne nematode infections, with an overall prevalence rate of 18.75%. The prevalence of Ascaris lumbricoides, Trichuris trichura and hookworm was 7.52%, 8.47% and 9.02%, respectively. Among 446 children detected using the cellophane tape method, 5 children were detected with E. vermicularis infections. Among the 160 residents with hookworm infections, there were 139 residents with Necator americanus infections (86.88%), 16 with A. duodenale infections (10.00%) and 5 with mixed infections (3.12%). Mild A. lumbricoides (67.98%, 259/381), T. trichura (88.58%, 380/429) and hookworm infections (94.53%, 432/457) were predominant. Among the four ecological zones, the highest prevalence of human soilborne nematode infections was found in the East Tibet-South Sichuan Ecological Zone (31.79%), and among the 10 survey counties (cities), the greatest prevalence was seen in Gongshan Derung and Nu Autonomous County (50.13%), while the lowest prevalence was found in Ninglang Yi Autonomous County (0.40%). The prevalence of human soil-borne nematode infections was 5.67% (43/759), 26.67% (610/2 287) and 14.70% (297/2 021) in high-, moderate- and low-economic-level regions, respectively. There were no significant differences in the prevalence of human soil-borne nematode infections in terms of ecological regions, survey counties (cities) or economic development levels (χ2 = 342.20, 814.60 and 201.34, all P < 0.05). There was no significantdifference in the prevalence of human soil-borne nematode infections between male (18.21%, 441/2 422) and female residents (19.24%, 509/2 645) (χ2 = 0.89, P > 0.05), and soil-borne nematode infections were detected in residents at all age groups, with the greatest prevalence found in residents at ages of 1 to 9 years (25.88%). In addition, the highest prevalence of soil-borne nematode infections was seen in residents with the Dulong Ethnic Minority (82.09%), in preschool children (25.06%) and in illiterate residents (24.80%), and there was no age-, ethnicity-, occupation- or education level-specific prevalence of soil-borne nematode infections detected (χ2 = 46.50, 1 016.96, 36.33 and 52.43, all P < 0.05). CONCLUSIONS The prevalence of human soil-borne nematode infections remains high in Yunnan Province. The management of soil-borne nematodiasis requires to be reinforced among low-age children, farmers, old people and residents with low educations levels or ethnic groups.
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Affiliation(s)
- F W Wu
- Yunnan Institute of Parasitic Diseases, Pu'er 665000, China
| | | | - B F Li
- Yunnan Institute of Parasitic Diseases, Pu'er 665000, China
| | - X L Yan
- Yunnan Institute of Parasitic Diseases, Pu'er 665000, China
| | - J R Zi
- Yunnan Institute of Parasitic Diseases, Pu'er 665000, China
| | - J Peng
- Yunnan Institute of Parasitic Diseases, Pu'er 665000, China
| | - X Cai
- Yunnan Institute of Parasitic Diseases, Pu'er 665000, China
| | - X Y Bao
- Yunnan Institute of Parasitic Diseases, Pu'er 665000, China
| | - Y M Yang
- Yunnan Institute of Parasitic Diseases, Pu'er 665000, China
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Liu KQ, Wei H, Lin D, Wang Y, Zhou CL, Liu BC, Li XL, Zhao Y, Li HJ, Wang CW, Li QH, Li BF, Gong YT, Liu XY, Gong YC, Mi JX, Wang J. [Clinical significance of minimal residual disease in patients with Ph-negative precursor B-acute lymphoblastic leukemia]. Zhonghua Xue Ye Xue Za Zhi 2019; 39:724-728. [PMID: 30369181 PMCID: PMC7342254 DOI: 10.3760/cma.j.issn.0253-2727.2018.09.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
目的 探讨微小残留病(MRD)水平在Ph染色体阴性的急性B淋巴细胞白血病(Ph− B-ALL)中的预后意义。 方法 采用多色流式细胞术对2010年9月至2017年11月初诊的193例Ph− B-ALL患者在治疗后1、3、6个月进行骨髓MRD监测,并对不同MRD水平患者的预后进行比较。 结果 中位随访22(1~92)个月,所有193例患者共行497次MRD检测。1个月时MRD水平<0.1%和≥0.1%患者的3年预期无复发生存(RFS)率分别为74.5%和29.9%,3年预期总生存(OS)率分别为67.5%和30.3%;3个月时MRD水平阴性和阳性患者的3年预期RFS率分别为75.6%和29.7%,3年预期OS率分别为71.6%和27.8%;6个月时MRD水平阴性或阳性患者的3年预期RFS率分别为74.6%和11.6%,3年预期OS率分别为74.0%和15.7%,差异均有统计学意义(P值均<0.001)。3个监测点全部达到MRD阴性标准的患者与至少1次未达到MRD阴性标准的患者比较,3年预期RFS、OS率差异均有统计学意义(80.5%对30.5%,77.1%对29.4%,P值均<0.001)。多因素分析结果显示,3个月时的MRD水平是Ph− B-ALL患者独立的预后因素之一。 结论 治疗后MRD监测对Ph− B-ALL的预后判断有重要意义。
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Affiliation(s)
- K Q Liu
- Institute of Hematology and Blood Diseases Hospital, CAMS & PUMC, Tianjin 300020, China
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Hu YT, Li BF, Zhang PJ, Wu D, Li YY, Li ZW, Shen L, Dong B, Gao J, Zhu X. Dbx2 exhibits a tumor-promoting function in hepatocellular carcinoma cell lines via regulating Shh-Gli1 signaling. World J Gastroenterol 2019; 25:923-940. [PMID: 30833799 PMCID: PMC6397724 DOI: 10.3748/wjg.v25.i8.923] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 12/25/2018] [Accepted: 12/28/2018] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide. HCC patients suffer from a high mortality-to-incidence ratio and low cure rate since we still have no specific and effective treatment. Although tremendous advances have been made in the investigation of HCC, the specific mechanisms of the progression of this disease are still only partially established. Hence, more research is needed to elucidate the underlying potential mechanisms to develop effective strategies for HCC.
AIM To determine the role of developing brain homeobox 2 (Dbx2) gene in promoting the development of HCC.
METHODS Dbx2 expression in clinical specimens and HCC cell lines was detected by Western blot (WB) and immunohistochemistry. Gain and loss of Dbx2 function assays were performed in vitro and in vivo. Cell viability assays were used to investigate cell growth, flow cytometry was employed to assess cell cycle and apoptosis, and trans-well assays were conducted to evaluate cell migration, invasion, and metastasis. The expression of key molecules in the sonic hedgehog (Shh) signaling was determined by WB.
RESULTS Compared to matched adjacent non-tumorous tissues, Dbx2 was overexpressed in 5 HCC cell lines and 76 surgically resected HCC tissues. Dbx2 overexpression was correlated with large tumor size. Both gain and loss of function assays indicated that Dbx2 promoted HCC cell proliferation by facilitating the transition from G1 to S phase, attenuating apoptosis and promoted HCC proliferation, migration, and invasion in vitro and in vivo. Mechanistically, Dbx2 modulated Shh signaling by enhancing FTCH1 and GLi1 expression in HCC cells that overexpressed Dbx2, which was reversed in HCC cells with Dbx2 knockdown.
CONCLUSION Our results indicate that Dbx2 is significantly upregulated in HCC tissues and plays significant roles in proliferation and metastasis of HCC cells by activating the Shh pathway.
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Affiliation(s)
- Yan-Ting Hu
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Gastrointestinal Oncology, Peking University Cancer Hospital and Institute, Beijing 100142, China
| | - Bei-Fang Li
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Gastrointestinal Oncology, Peking University Cancer Hospital and Institute, Beijing 100142, China
| | - Peng-Jun Zhang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Interventional Therapy, Peking University Cancer Hospital and Institute, Beijing 100142, China
| | - Di Wu
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Interventional Therapy, Peking University Cancer Hospital and Institute, Beijing 100142, China
| | - Yan-Yan Li
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Gastrointestinal Oncology, Peking University Cancer Hospital and Institute, Beijing 100142, China
| | | | - Lin Shen
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Gastrointestinal Oncology, Peking University Cancer Hospital and Institute, Beijing 100142, China
| | - Bin Dong
- Key laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Pathology, Peking University Cancer Hospital and Institute, Beijing 100142, China
| | - Jing Gao
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Gastrointestinal Oncology, Peking University Cancer Hospital and Institute, Beijing 100142, China
| | - Xu Zhu
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Interventional Therapy, Peking University Cancer Hospital and Institute, Beijing 100142, China
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Xia LP, Li BF, Shen H, Lu J. Interleukin-27 and interleukin-23 in patients with systemic lupus erythematosus: possible role in lupus nephritis. Scand J Rheumatol 2015; 44:200-5. [PMID: 25562331 DOI: 10.3109/03009742.2014.962080] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVES To analyse the concentration of interleukin (IL)-27 and IL-23 in serum and urine of patients with systemic lupus erythematosus (SLE) compared with healthy controls (HC). METHOD An enzyme-linked immunosorbent assay (ELISA) was used to analyse the serum and urine concentration of IL-27 and IL-23 from 50 patients with lupus nephritis (LN), 55 patients without LN, and 30 HC. The correlations between the levels of IL-27, IL-23, and disease activity, clinical parameters in SLE patients were analysed. RESULTS The levels of IL-27 and IL-23 increased significantly in the serum and urine of SLE patients with and without LN compared with HC. Moreover, urine levels of IL-27 and IL-23 were correlated with the renal SLE Disease Activity Index (rSLEDAI) score and 24-h urinary protein levels. After 6 months of immunosuppressive treatment, urine IL-27 expression rose significantly in SLE patients with LN. CONCLUSIONS IL-27 and IL-23 may be involved in the pathogenesis of LN.
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Affiliation(s)
- L P Xia
- Departments of Rheumatology, 1st Affiliated Hospital of China Medical University , Shenyang , PR China
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Nong DB, Li BF, Yin BS, Yu DK, Zhou X, Zhu H. [The design and application of ML-2 ECG lead converter/selector]. Zhongguo Ying Yong Sheng Li Xue Za Zhi 2001; 17:402-403. [PMID: 21207713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
AIM Because no ECG lead cable and lead selector is equipped, SYD-4228 Physiology Experiment System can not be used to record and observe ECG. This paper introduces an ECG lead converter/selector designed and implemented by us. METHODS With resistor network and lead input cable, an ECG lead converter/selector was produced. RESULTS As an independent and assistant part of SYD-4228 system, this ECG lead converter/selector can be used to record ECG waveform in animal experiment. CONCLUSION Capable of matching both SYD-4228 system and other ECG recording systems, this ECG lead converter/selector can record ECG waveforms with different lead systems simultaneously. Real-time observation and comparison of waveforms recorded by different lead systems can be available.
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Affiliation(s)
- D B Nong
- Research Center of Cardioelectricity, The First Military Medical University, Guangzhou 510515, China
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Teo AK, Oh HK, Ali RB, Li BF. The modified human DNA repair enzyme O(6)-methylguanine-DNA methyltransferase is a negative regulator of estrogen receptor-mediated transcription upon alkylation DNA damage. Mol Cell Biol 2001; 21:7105-14. [PMID: 11564893 PMCID: PMC99886 DOI: 10.1128/mcb.21.20.7105-7114.2001] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Cell proliferation requires precise control to prevent mutations from replication of (unrepaired) damaged DNA in cells exposed spontaneously to mutagens. Here we show that the modified human DNA repair enzyme O(6)-methylguanine-DNA methyltransferase (R-MGMT), formed from the suicidal repair of the mutagenic O(6)-alkylguanine (6RG) lesions by MGMT in the cells exposed to alkylating carcinogens, functions in such control by preventing the estrogen receptor (ER) from transcription activation that mediates cell proliferation. This function is in contrast to the phosphotriester repair domain of bacterial ADA protein, which acts merely as a transcription activator for its own synthesis upon repair of phosphotriester lesions. First, MGMT, which is constitutively present at active transcription sites, coprecipitates with the transcription integrator CREB-binding protein CBP/p300 but not R-MGMT. Second, R-MGMT, which adopts an altered conformation, utilizes its exposed VLWKLLKVV peptide domain (codons 98 to 106) to bind ER. This binding blocks ER from association with the LXXLL motif of its coactivator, steroid receptor coactivator-1, and thus represses ER effectively from carrying out transcription that regulates cell growth. Thus, through a change in conformation upon repair of the 6RG lesion, MGMT switches from a DNA repair factor to a transcription regulator (R-MGMT), enabling the cell to sense as well as respond to mutagens. These results have implications in chemotherapy and provide insights into the mechanisms for linking transcription suppression with transcription-coupled DNA repair.
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Affiliation(s)
- A K Teo
- Chemical Carcinogenesis Laboratory, Institute of Molecular and Cell Biology, National University of Singapore, Singapore 117609, Republic of Singapore
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Ali RB, Teo AK, Oh HK, Chuang LS, Ayi TC, Li BF. Implication of localization of human DNA repair enzyme O6-methylguanine-DNA methyltransferase at active transcription sites in transcription-repair coupling of the mutagenic O6-methylguanine lesion. Mol Cell Biol 1998; 18:1660-9. [PMID: 9488483 PMCID: PMC108881 DOI: 10.1128/mcb.18.3.1660] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
DNA lesions that halt RNA polymerase during transcription are preferentially repaired by the nucleotide excision repair pathway. This transcription-coupled repair is initiated by the arrested RNA polymerase at the DNA lesion. However, the mutagenic O6-methylguanine (6MG) lesion which is bypassed by RNA polymerase is also preferentially repaired at the transcriptionally active DNA. We report here a plausible explanation for this observation: the human 6MG repair enzyme O6-methylguanine-DNA methyltransferase (MGMT) is present as speckles concentrated at active transcription sites (as revealed by polyclonal antibodies specific for its N and C termini). Upon treatment of cells with low dosages of N-methylnitrosourea, which produces 6MG lesions in the DNA, these speckles rapidly disappear, accompanied by the formation of active-site methylated MGMT (the repair product of 6MG by MGMT). The ability of MGMT to target itself to active transcription sites, thus providing an effective means of repairing 6MG lesions, possibly at transcriptionally active DNA, indicates its crucial role in human cancer and chemotherapy by alkylating agents.
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Affiliation(s)
- R B Ali
- Chemical Carcinogenesis Laboratory, Institute of Molecular and Cell Biology, National University of Singapore, Republic of Singapore
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Li BF. Ethical practice in the management of impaired neonates--a Chinese viewpoint. Med Law 1998; 17:553-562. [PMID: 10396916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In recent years, the issue of whether medical care should be given to impaired neonates has given rise to widely divergent views among practitioners of medicine, law and ethics. The general public also holds wide-ranging opinions on this subject. The divergence centres on whether medical care should be given to seriously impaired neonates, on whom should make decisions in these matters, and who should perform acts of euthanasia, in accordance with the current climate of opinion in China. This opinion has been focused both on ethical principles and on relevant precepts relevant to the "value of life." The author presents his opinions and explanations on the rights of impaired neonates, the rights and duties of parents and medical staff, and his views on the application of beneficence relative to this subject.
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Affiliation(s)
- B F Li
- Dept. of Medical Ethics, Beijing Medical University, People's Republic of China
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Ko SC, Chen GS, Li BF, Yu HS. Cutaneous sarcoidosis. Report of two cases and literature review. Kaohsiung J Med Sci 1997; 13:690-4. [PMID: 9425869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Sarcoidosis is a multi-system granulomatous disorder of unknown cause that presents more frequently in young adults with bilateral hilar adenopathy, pulmonary infiltrates, and skin or eye lesions. The multisystem clinical manifestations of this disease are a diagnostic challenge to all physicians. Although the clinical and pathological characteristics of sarcoidosis are well described, the decision to treat and the optimal therapy are less well defined. We report two patients of systemic sarcoidosis with cutaneous manifestations of the disease. Gallium whole body scintigraphy was performed and showed increased activity over the bilateral pulmonary hilar region (lambda sign), lacrimal and parotid glands (panda sign).
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Affiliation(s)
- S C Ko
- Department of Dermatology, Kaohsiung Medical College, Taiwan, Republic of China
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Abstract
DNA-(cytosine-5) methyltransferase (MCMT) methylates newly replicated mammalian DNA, but the factors regulating this activity are unknown. Here, MCMT is shown to bind proliferating cell nuclear antigen (PCNA), an auxiliary factor for DNA replication and repair. Binding of PCNA requires amino acids 163 to 174 of MCMT, occurs in intact cells at foci of newly replicated DNA, and does not alter MCMT activity. A peptide derived from the cell cycle regulator p21(WAF1) can disrupt the MCMT-PCNA interaction, which suggests that p21(WAF1) may regulate methylation by blocking access of MCMT to PCNA. MCMT and p21(WAF1) may be linked in a regulatory pathway, because the extents of their expression are inversely related in both SV40-transformed and nontransformed cells.
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Affiliation(s)
- L S Chuang
- Chemical Carcinogenesis Laboratory, Institute of Molecular and Cell Biology, National University of Singapore, Kent Ridge Crescent, Singapore 119260, Republic of Singapore
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Abstract
Epidemiologic studies have implicated the involvement of environmental factors in the etiology of esophageal cancer (EC). Our previous data have indicated that EC patients and their blood relatives show genomic instability and are deficient in repair of DNA damage induced by N-nitroso-compounds and related genotoxic agents. Thus, exposure to high levels of N-alkylnitrosamines, which are known animal carcinogens and which induce alkyl adducts in DNA, may be causally linked to EC. Among the alkyl adducts, O6-alkylguanine was shown to be the critical one related to carcinogenic lesions; its repair varies widely in a tissue-specific fashion. O6-methylguanine-DNA methyltransferase (MGMT) is responsible for its repair. Hence, inactivating mutations in this protein would impair the efficiency of the repair process. To screen for possible mutations in the MGMT polypeptide in EC patients, we analyzed a highly conserved region of the MGMT gene in 40 EC tissues and lymphocytes of 6 high-risk EC family members from high EC areas of Northern China by polymerase chain reaction single-strand conformation polymorphism and by direct sequencing of PCR products. Ten base substitutions (point mutations) within 8 codons of 7 EC samples were identified. However, no germline mutation was found in the high EC families studied so far. Concurrent study in 30 pairs of fresh EC tissues and their adjacent normal mucosa by Southern blot and Western blot analyses showed deletion of the MGMT gene in 2 samples. Thus, the high frequency of mutations (7/40) and deletions (2/30) of the MGMT gene may be partially responsible for the overall high mutation rate observed in EC tissues.
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Affiliation(s)
- L Wang
- Department of Cell Biology, Cancer Institute, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing
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Chang YC, Wu TY, Li BF, Gao LH, Liu CI, Wu CL. Purification and biochemical characterization of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate-sensitive L-glutamate receptors of pig brain. Biochem J 1996; 319 ( Pt 1):49-57. [PMID: 8870648 PMCID: PMC1217734 DOI: 10.1042/bj3190049] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Two preparations of glutamate receptors were purified from the synaptic junctions of pig brain by a combination of detergent solubilization, anion-exchange chromatography, wheat-germ agglutinin affinity chromatography and sedimentation through sucrose gradients. These preparations were enriched in specific L-[3H]glutamate binding activity (> 5000 pmol of glutamate binding sites/mg of protein), and the rank order of ligand affinity for binding to these preparations was: quisqualate > 6-cyano-7- nitroquinoxaline-2,3-dione > alpha-amino-3-hydroxy-5-methyl-4- isoxazolepropionic acid (AMPA) > L-glutamate > kainate > > N-methyl-D-aspartate approximately L-2-amino-4-phosphonobutyrate. SDS/PAGE analysis revealed that more than 80% of the protein in either of these preparations appeared as a single protein band of 106 kDa. Two-dimensional gel electrophoresis further revealed that these 106 kDa proteins consisted of a series of acidic proteins which were recognized by antibodies against rat AMPA receptor subunits. These 106 kDa proteins were also recognized by wheatgerm agglutinin and concanavalin A; in addition, peptide N-glycosidase F treatment of these preparations decreased their size to 99 kDa. Our results suggest that the putative glutamate receptors isolated here are likely to belong to the AMPA subtype of glutamate receptors in pig brain. Using the purification procedure reported here, 5 micrograms of AMPA receptor proteins can be isolated from 250 g of pig brain tissue.
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Affiliation(s)
- Y C Chang
- Institute of Life Science, National Tsing Hua University, Hsinchu, Taiwan, Republic of China
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Oh HK, Teo AK, Ali RB, Lim A, Ayi TC, Yarosh DB, Li BF. Conformational change in human DNA repair enzyme O6-methylguanine-DNA methyltransferase upon alkylation of its active site by SN1 (indirect-acting) and SN2 (direct-acting) alkylating agents: breaking a "salt-link". Biochemistry 1996; 35:12259-66. [PMID: 8823159 DOI: 10.1021/bi9603635] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Human O6-methylguanine-DNA methyltransferase (MGMT) repairs DNA by transferring alkyl (R-) adducts from O6-alkylguanine (6RG) in DNA to its own cysteine residue at codon 145 (formation of R-MGMT). We show here that R-MGMT in cell extracts, which is sensitive to protease V8 cleavage at the glutamic acid residues at codons 30 (E30) and 172 (E172), can be specifically immunoprecipitated with an MGMT monoclonal antibody, Mab.3C7. This Mab recognizes an epitope of human MGMT including the lysine 107 (K107) which is within the most basic region that is highly conserved among mammalian MGMTs. Surprisingly, the K107L mutant protein is repair-deficient and readily cleaved by protease V8 similar to R-MGMT. We propose that R-MGMT adopted an altered conformation which exposed the Mab.3C7 epitope and rendered that protein sensitive to protease V8 attack. This proposal could be explained by the disruption of a structural "salt-link" within the molecule based on the available structural and biochemical data. The specific binding of Mab.3C7 to R-MGMT has been compared with the protease V8 method in the detection of R-MGMT in extracts of cells treated with low dosages of methyliodide (SN2) and O6-benzylguanine. Their identical behaviors in producing protease V8 sensitive R-MGMT and Mab.3C7 immunoprecipitates suggest that probably methyl iodide (an ineffective agent in producing 6RG in DNA) can directly alkylate the active site of cellular MGMT similar to O6-benzylguanine. The effectiveness of MeI in producing R-MGMT, i.e., inactivation of cellular MGMT, indicates that this agent can increase the effectiveness of environmental and endogenously produced alkylating carcinogens in producing the mutagenic O6-alkylguanine residues in DNA in vivo.
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Affiliation(s)
- H K Oh
- Chemical Carcinogenesis Laboratory, National University of Singapore, Republic of Singapore
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Lim A, Li BF. The nuclear targeting and nuclear retention properties of a human DNA repair protein O6-methylguanine-DNA methyltransferase are both required for its nuclear localization: the possible implications. EMBO J 1996; 15:4050-60. [PMID: 8670909 PMCID: PMC452125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Human O6-methylguanine-DNA methyltransferase (MGMT) protects human cells from the mutagenic effects of alkylating agents by repairing the O6-alkylguanine residues formed by these agents in the nuclear DNA. We report here a study showing a possible two-step model for the nuclear localization of the 21 kDa human protein. The first step is the translocation of the protein from the cytosol to the nucleus. This appears to require the nuclear targeting property associated with the holoprotein in combination with a cellular factor(s) to effect the nuclear translocation of MGMT. The second step involves the nuclear retention of MGMT (to prevent its export from the nucleus). This requires a basic region (PKAAR, codons 124-128) that can bind to the non-diffusible DNA elements in the nucleus. Supporting data for such mechanisms are: (i) the holoprotein can target the cytosolic 110 kDa beta-galactosidase into the nucleus; (ii) purified recombinant MGMT requires a cellular factor for transport across the nuclear membrane; (iii) nuclear MGMT can be removed selectively by DNase I; (iv) the repair-positive K125L mutant, which alters the PKAAR motif, remains in the cytosol and fails to bind DNA in vitro; and (v) polypeptide containing the PKAAR motif has no nuclear targeting property. Interestingly, mutants in another basic region, KLLKVVK (codons 101-107) are DNA binding and repair deficient but entirely nuclear. As these substitutions affect the functional properties of human MGMT, they are potential targets for genetic screening of individuals for risk assessment to alkylating agents.
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Affiliation(s)
- A Lim
- Chemical Carcinogenesis Laboratory, Institute of Molecular and Cell Biology, National University of Singapore, Kent Ridge, Singapore 0511, Singapore
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15
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Sumegi J, Wang JY, Zhen DK, Eudy JD, Talmadge CB, Li BF, Berglund P, Weston MD, Yao SF, Ma-Edmonds M, Overbeck L, Kelley PM, Zabarovsky E, Uzvolgyi E, Stanbridge EJ, Klein G, Kimberling WJ. The construction of a yeast artificial chromosome (YAC) contig in the vicinity of the Usher syndrome type IIa (USH2A) gene in 1q41. Genomics 1996; 35:79-86. [PMID: 8661107 DOI: 10.1006/geno.1996.0325] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The gene for Usher syndrome type II (USH2A), an autosomal recessive syndromic deafness, has been mapped to a region of 1q41 flanked proximally by D1S217 and distally by D1S439. Using sequence-tagged sites (STSs) within the region, a total of 21 yeast artificial chromosome (YAC) clones were isolated and ordered into a single contig that spans approximately 11.0 Mb. The order of microsatellite and STS markers in this region was established as D1S505-D1S425-DXS217-D1S556-D1S237-D1S4 74-EB1-EB2-KB6-AFM144XF2-KB1-K B4-D1S229-D1S490-D1S227-TGFbeta2-D1S439. Analysis of newly positioned polymorphic markers in recombinant individuals in two Usher syndrome type IIa families has enabled us to identify DXS474 and AFM144XF2 as two flanking markers for the Usher type IIa locus. The physical distance between the two markers is 1.0 Mb. This region is covered by eight YACs from the CEPH library: 945f7, 867g9, 762a6, 919h3, 794b8, 785h4, 848b9, and 841g2. A long-range physical map of the Usher type IIa critical region, using MluI, BssHII, NotI, EagI, and SacII, has been developed.
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Affiliation(s)
- J Sumegi
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, 68198, USA
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16
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Chuang LS, Ng HH, Chia JN, Li BF. Characterisation of independent DNA and multiple Zn-binding domains at the N terminus of human DNA-(cytosine-5) methyltransferase: modulating the property of a DNA-binding domain by contiguous Zn-binding motifs. J Mol Biol 1996; 257:935-48. [PMID: 8632476 DOI: 10.1006/jmbi.1996.0213] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We report here a detailed mapping and characterisation of a DNA-binding domain at the N terminus of human DNA-(cytosine-5) methyltransferase. A small region, B1 (codon 202 to 369), was first identified by its Zn- and gross DNA-binding properties. Further fine-mapping using deletion and point mutation analysis shows that the DNA- and Zn-binding domains involve separate peptide motifs, KRRKTTPKEPTEKK (codons 202 to 215) for a bipartite DNA-binding oligopeptide (DB1) and CX2CX13HX2D(X)23EX2EX13CX3H (codons 232 to 297) for possibly two contiguous Zn-binding domains (AZn), which can function independently. However, B1 (containing DB1 and AZn) differs from DB1 because it does not bind to a 30 base-pair duplex. Interestingly, H3 codons 202 to 974, which encloses B1 and B2 (containing the Zn-binding CX2CX2CX4CX2CX2C motif from codon 533 to 550) binds preferentially to 0.8 kb duplexes, as compared with 0.4 to 0.6 kb duplexes. As the homologous murine B1, which targets the murine methylase to replication foci, also binds to DNA and Zn, it is possible that the N terminus of mammalian methylase may be involved in sensing the appropriate length of newly synthesized DNA before methylation by its C terminus. This may enable a time delay for the transient existence of hemi-methylation sites for their unknown biological functions in mammals.
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Affiliation(s)
- L S Chuang
- Chemical Carcinogenesis Laboratory, Institute of Molecular and Cell Biology National University of Singapore, Republic of Singapore
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17
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Belanich M, Randall T, Pastor MA, Kibitel JT, Alas LG, Dolan ME, Schold SC, Gander M, Lejeune FJ, Li BF, White AB, Wasserman P, Citron ML, Yarosh DB. Intracellular Localization and intercellular heterogeneity of the human DNA repair protein O(6)-methylguanine-DNA methyltransferase. Cancer Chemother Pharmacol 1996; 37:547-55. [PMID: 8612308 DOI: 10.1007/s002800050427] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
O(6)-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair protein that removes alkyl adducts from DNA and may be important in tumor resistance to alkylation chemotherapy. MGMT was visualized in human cells and tumor tissues with monoclonal antibodies against MGMT and immunofluorescence microscopy, and fluorescent signals were quantified by digital image analysis. MGMT was found both in the cytoplasm and the nucleus, and in either locale the protein reacts with alkylated DNA bases and becomes inactivated and lost from the cell. Cell lines in culture and xenografts showed a broad normal distribution of nuclear MGMT levels, but human brain tumors often showed a skewed distribution, with a significant fraction of cells with high levels of MGMT. O(6)-Benzylguanine, a suicide substrate inactivator for MGMT activity, reduced MGMT in human cells and in a mouse xenograft to levels undetectable by antibody assay 1 h post-treatment. In melanoma specimens taken from a patient 3 h post-treatment with temozolomide, MGMT levels were reduced by 70%. This quantitative immunofluorescence assay can be used to monitor MGMT and it depletion in human tumors to improve the use of alkylating agents in cancer chemotherapy.
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Affiliation(s)
- M Belanich
- Applied Genetics Inc., Freeport, NY 11520 USA
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18
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Talmadge CB, Zhen DK, Wang JY, Berglund P, Li BF, Weston MD, Kimberling WJ, Zabarovsky ER, Stanbridge EJ, Klein G. Construction and characterization of a NotI linking library from human chromosome region 1q25-qter. Genomics 1995; 29:105-14. [PMID: 8530059 DOI: 10.1006/geno.1995.1220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Chromosome 1q25-qter-specific NotI linking clones have been isolated from a NotI linking library that was constructed using DNA from MCH206.1 somatic cell hybrid cells. These cells contain chromosome 1q25-qter translocated to human chromosome Xp22 as the only human genetic material in mouse background. Sixty-eight NotI linking clones have been mapped by a combination of fluorescence in situ hybridization and R-banding to cytogenetic bands on the long arm of chromosome 1. The relative order of 11 NotI clones and their relation to known chromosome 1 markers have also been determined in 1q32 and 1q41, where the genes of Van der Woude and Usher syndrome type IIa have been previously mapped: cen-chr1.14-chr1.79-chr1.56-chr1.11-chr1.9 5- chr1.58 (chr1.74)-D1S70-chr1.15-chr1.82 (chr1.143)-chr1.62-D1S81-tel. The 1q32- and 1q41-specific NotI linking clones were sequenced in the vicinity of the NotI site. They were analyzed in terms of nucleotide composition, G+C content, frequency of CpG dinucleotides, and protein coding potentials. Most of the 1q32-q41-specific NotI linking clones were derived from CpG islands. Sequences of three NotI linking clones proved to be identical with known genes. Six of the remaining eight had a high potential for coding regions and shared short homologous regions with sequences in the GenBank database. The NotI linking clones and the identified CpG islands will provide valuable resources for constructing a long-range restriction map of chromosome 1q25-q44 and for the eventual isolation of disease genes of Van der Woude syndrome (1q32-q41) and Usher syndrome type IIa (1q41).
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Affiliation(s)
- C B Talmadge
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha 68198-5660, USA
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19
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Zaidi NH, Allay E, Ayi TC, Li BF, Dumenco LL, Sy MS, Gerson SL. The immature thymocyte is protected from N-methylnitrosourea-induced lymphoma by the human MGMT-CD2 transgene. Carcinogenesis 1995; 16:1047-53. [PMID: 7767963 DOI: 10.1093/carcin/16.5.1047] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
N-methylnitrosourea (MNU) induces thymic lymphoma in a high proportion of susceptible C57BL/6xSJL (C57/SJL) mice. Expression of the human DNA repair gene, MGMT cDNA, which encodes O6-methylguanine-DNA-methyltransferase, in transgenic mice effectively prevents MNU-induced thymic lymphomas. In this study, we determined the phenotype of thymocytes expressing the transgene and defined whether the target cell population for MNU induced lymphomas were actually those that expressed the transgene. Transgene expression was characterized by in situ hybridization for MGMT mRNA and immunohistochemistry for the human alkyltransferase protein and was compared to the phenotype of the MNU induced lymphomas. The MGMT transgene was expressed uniformly in immature cortical thymocytes that were CD4+CD8+J11d+ and to a lesser extent in the medullary thymocyte. Lymphomas were induced by single [50 or 80 mg/kg] or multiple doses [30 mg/kg x 5] of MNU to evaluate the dose response of tumor induction and protection by the MGMT-CD2 transgene. Forty-seven of the 108 treated mice developed lymphomas: 38 of 58 nontransgenic and 9 of 50 MGMT+ mice. The T-cell phenotype of thymic lymphomas was established by immunohistochemistry and FACS analysis. Most of the lymphomas were J11d+ (98%), 70% of the tumors were CD4+CD8+, 21% were CD4-CD8+, 9% were CD4-CD8-, and none were CD4-CD8-. All lymphomas in MGMT+ transgenic mice were CD4+CD8+. Since the main phenotype of MNU induced lymphomas in these mice, CD4+CD8+J11d+, is also the cell phenotype which expresses the MGMT-CD2 transgene at high levels, it appears that MGMT-induced protection has occurred in the cell target for MNU induced transformation.
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Affiliation(s)
- N H Zaidi
- Cancer Center, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4937, USA
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20
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Ayi TC, Oh HK, Lee TK, Li BF. A method for simultaneous identification of human active and active-site alkylated O6-methylguanine-DNA methyltransferase and its possible application for monitoring human exposure to alkylating carcinogens. Cancer Res 1994; 54:3726-31. [PMID: 8033092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Cells resist the major mutagenic effects of alkylating agents by the action of O6-methylguanine-DNA methyltransferase (MGMT), which transfers the alkyl (R) group of O6-alkylguanine, produced in DNA by these chemicals, to a cysteine residue in its active site (formation of R-MGMT). We demonstrate that cellular R-MGMT (which represents a record or memory within the cells exposed to these chemicals) can be assayed by its sensitivity toward proteolysis by protease V8. The possible use of this assay for monitoring exposure to alkylating carcinogens was investigated by using cultured cells and a preliminary study with the use of human blood from normal subjects and patients undergoing chemotherapy. Cultured cell experiments show that R-MGMT is sufficiently stable for the monitoring purpose and its level bears a dose-response relationship to the concentrations of the alkylating agent used. Interestingly, experiments with blood from patients undergoing chemotherapy show a gradual formation of R-MGMT in 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea and an induced MGMT deficiency in cyclophosphamide-treated patients. The use of this methodology, which allows for the possible quantification of active MGMT (cellular DNA repair capacity) and R-MGMT (recent exposure) simultaneously, in monitoring human exposure to alkylating carcinogens is discussed.
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Affiliation(s)
- T C Ayi
- Chemical Carcinogenesis Laboratory, National University Hospital, Singapore
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21
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Liem LK, Lim A, Li BF. Specificities of human, rat and E. coli O6-methylguanine-DNA methyltransferases towards the repair of O6-methyl and O6-ethylguanine in DNA. Nucleic Acids Res 1994; 22:1613-9. [PMID: 8202360 PMCID: PMC308037 DOI: 10.1093/nar/22.9.1613] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The behaviour of highly purified bacterial expressed rat O6-methylguanine-DNA methyltransferase (MGMT) towards the repair of CGCm6GAGCTCGCG and CGCe6GAGCTCGCG (km6G/ke6G = 1.45, where k is the second order repair rate constant determined, m6G and e6G are O6-methyl and O6-ethylguanine) is similar to that of E. coli 39kD Ada protein (km6G/ke6G = 1.6). However, the human MGMT is very different (km6G/ke6G = 163). The preferential repair of O6-ethylguanine lesion by the rat MGMT appears not to be related to the lack of the initiator methionine in the expressed protein since similar results were obtained from N-terminal Glutathione-S-transferase (GST) fused protein (GSTMGMT) which retains the methionine. The possible relationship between these findings and the differences observed in the primary amino acid sequence of these proteins is discussed. In addition the preferential repair of O6-ethylguanine substrate by the 39kD Ada protein as compared to the catalytic C-terminus alone (different by 134 times) suggests that the N-terminus plays a crucial role in the repair of O6-ethylguanine. This is in contrast to the minor effects of the GST domain when fused to the N-terminus of mammalian MGMT.
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Affiliation(s)
- L K Liem
- Chemical Carcinogenesis Laboratory, National University of Singapore, Kent Ridge
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22
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Affiliation(s)
- C W Wong
- Chemical Carcinogenesis Laboratory, National University of Singapore, Kent Ridge
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23
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Liem LK, Wong CW, Lim A, Li BF. Factors influencing the repair of the mutagenic lesion O6-methylguanine in DNA by human O6-methylguanine-DNA methyltransferase. J Mol Biol 1993; 231:950-9. [PMID: 8515475 DOI: 10.1006/jmbi.1993.1344] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Oligodeoxynucleotides of various chain lengths (p(Bp)nB, n < or = 9) and the eight possible dinucleotide phosphates (pm6GpB and pBpm6G), each containing a single O6-methylguanine residue (m6G), were used to study the repair kinetics of this lesion by the cloned DNA repair proteins; human 21 kDa O6-methylguanine-DNA methyltransferase (MGMT), human 43 kDa glutathione-S-transferase fused MGMT (GSTMGMT) and the Escherichia coli 39 kDa ada protein. The observed second-order repair rate constants are dependent upon both the chain length of the oligonucleotide substrates for all three proteins and in the case assuming O6-methylguanine is similar to B). The differences observed in the ratios of the rate constants for the substrates with five and four base residues; 125 for the E. coli 39 kDa ada protein, 640 for the human MGMT and 27,800 for the human fusion protein GSTMGMT, suggest that the pentanucleotide phosphate containing this lesion is the "optimal" substrate for the proteins. Surprisingly, the human GSTMGMT is shown to be more effective in the repair of longer substrates with the second-order repair rate constants for TATA-Cm6GTATA being 6.16 x 10(6) for GSTMGMT, 2.00 x 10(6) for MGMT and 0.27 x 10(6) M-1 s-1 for the E. coli 39 kDa ada protein. Thus, the presence of an additional protein domain at the N terminus of human MGMT can alter its selectivity towards certain substrates. Although a number of peptide domains are conserved between the E. coli 39 kDa ada protein and phosphates can also be used to explain the observed sequence specific repair of this lesion within certain DNA sequences.
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Affiliation(s)
- L K Liem
- Chemical Carcinogenesis Laboratory, National University of Singapore
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24
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Abstract
Chemical probing of the structures of a few very similar 30 base-pair duplexes containing a 6-O-methylguanine (meG) residue at the 16th position reveals that the modified base simultaneously perturbs the helical structure in two ways; it preferentially unstacks the 3' neighbouring base residue (thymine in this study) on the same strand and it unstacks the pyrimidine to which it is base-paired. Depending on its neighbouring 5' base residue and the base-pairing pyrimidine, this perturbation can extend to a few base-pairs in both 3' and 5' directions from the abnormal base-pair. These perturbations can be detected by cleavage at the site for the restriction enzyme MaeII. The unstaking of the C in the meG.C and A.C base-pairs may explain the de novo methylation of these helices by the human DNA-(cytosine-5-)methyltransferase. Interestingly, the kinetics of repair of the 6-O-methylguanine-containing dinucleotides by the cloned human methylguanine methyltransferase appears to be largely determined by the strength of the stacking interaction between the 6-O-methylguanine and the 5' neighbouring base.
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Affiliation(s)
- C W Wong
- Chemical Carcinogenesis Laboratory, National University of Singapore
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25
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Ayi TC, Loh KC, Ali RB, Li BF. Intracellular localization of human DNA repair enzyme methylguanine-DNA methyltransferase by antibodies and its importance. Cancer Res 1992; 52:6423-30. [PMID: 1384961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The human DNA repair enzyme, methylguanine-DNA methyltransferase (MGMT, M(r) 21,000), which protects cells against the mutagenic effect of alkylating carcinogens, was found to be localized in the cell nucleus (except the nucleolus) by immunofluorescence staining using polyclonal and monoclonal antibodies. The supporting experiments came from differential staining of the MGMT-deficient (mer-) and -proficient (mer+) cells, Western blotting analysis, and specific antibody depletion studies with the immobilized fusion protein, GSTMGMT-glutathione-Sepharose. Its localization in the nucleus agrees with its biological function and possibly explains the ineffective protection of mammalian cells (mer-) transfected with the Escherichia coli MGMT genes from bifunctional alkylating agents.
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Affiliation(s)
- T C Ayi
- Chemical Carcinogenesis Laboratory, National University of Singapore, Kent Ridge
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26
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Tan NW, Li BF. Interaction of oligonucleotides containing 6-O-methylguanine with human DNA (cytosine-5-)-methyltransferase [published erratumm appears in Biochemistry 1992 Aug 4;31(30):7008]. Biochemistry 1990; 29:9234-40. [PMID: 2271591 DOI: 10.1021/bi00491a018] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Thirty-base-pair synthetic oligonucleotide duplexes containing a single meG.C (meG = 6-O-methylguanine) or A.C base pair at the 16th position (i.e., 5'-CCCGTTTAAATATACXTATACCCGGGTACC-3', where X = A or meG) were used to study de novo methylation by the purified human DNA (cytosine-5)-methyltransferase isolated from CEM cells. Both duplexes containing meG.C and A.C base pairs show enhanced methyl group acceptor properties. Subsequent introduction of hemimethylated sites at the 15th position of the top strand (the C residue next to the abnormal base pair) and the 7th, 15th (which represents the C residue in the 6meG.C and A.C base pairs), and 27th positions of the bottom strand were used to study the maintenance methylation of the hemimethylated duplexes by the methylase. This revealed striking differences in the rate, amount, and sites of methylation, which are dependent on the position of the hemimethylated site in the duplex. The possible mechanism of action of the methylase is discussed. The data show that 6-O-methylguanine residues in DNA can have other genetic effects apart from their miscoding behavior and that meG.C and A.C base pairs exert different effects in terms of methylation.
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Affiliation(s)
- N W Tan
- Institute of Molecular and Cell Biology, National University of Singapore, Kent Ridge
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27
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Kalnik MW, Norman DG, Li BF, Swann PF, Patel DJ. Conformational transitions in thymidine bulge-containing deoxytridecanucleotide duplexes. Role of flanking sequence and temperature in modulating the equilibrium between looped out and stacked thymidine bulge states. J Biol Chem 1990; 265:636-47. [PMID: 2295611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Structural features at extra thymidine bulge sites in DNA duplexes have been elucidated from a two-dimensional NMR analysis of through-bond and through-space connectivities in the otherwise self-complementary d(C-C-G-T-G-A-A-T-T-C-C-G-G) (GTG 13-mer) and d(C-C-G-G-A-A-T-T-C-T-C-G-G) (CTC 13-mer) duplexes in aqueous solution. These studies establish that the extra thymidine flanked by guanosines in the GTG 13-mer duplex is in a conformational equilibrium between looped out and stacked states. The looped-out state is favored at low temperature (0 degrees C), whereas the equilibrium shifts in favor of the stacked state at elevated temperatures (35 degrees C) prior to the onset of the duplex-strand transition. By contrast, the extra thymidine flanked by cytidines in the CTC 13-mer duplex is looped out independent of temperature in the duplex state. Our results demonstrate that temperature and flanking sequence modulate the equilibrium between looped-out and stacked conformations of single base thymidine bulges in DNA oligomer duplexes.
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Affiliation(s)
- M W Kalnik
- Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, New York 10032
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28
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Kalnik MW, Norman DG, Li BF, Swann PF, Patel DJ. Conformational transitions in thymidine bulge-containing deoxytridecanucleotide duplexes. Role of flanking sequence and temperature in modulating the equilibrium between looped out and stacked thymidine bulge states. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)40097-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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29
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Kalnik MW, Li BF, Swann PF, Patel DJ. O6-ethylguanine carcinogenic lesions in DNA: an NMR study of O6etG.T pairing in dodecanucleotide duplexes. Biochemistry 1989; 28:6170-81. [PMID: 2789993 DOI: 10.1021/bi00441a008] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
High-resolution two-dimensional NMR studies are reported on the self-complementary d-(C1-G2-C3-O6etG4-A5-G6-C7-T8-T9-G10-C11-G12) duplex (designated O6etG.T 12-mer) containing two symmetrically related O6etG.T lesion sites located four base pairs in from either end of the duplex. Parallel studies were undertaken on a related sequence containing O6meG.T lesion sites (designated O6meG.T 12-mer) in order to evaluate the influence of the size of the alkyl substituent on the structure of the duplex and were undertaken on a related sequence containing G.T mismatch sites (designated G.T 12-mer duplex), which served as the control duplex. The exchangeable and nonexchangeable proton and the phosphorus nuclei have been assigned from an analysis of two-dimensional nuclear Overhauser enhancement (NOE) and correlated spectra of the O6etG.T 12-mer, O6meG.T 12-mer, and G.T 12-mer duplexes in H2O and D2O solutions. The distance connectivities observed in the NOESY spectra of the O6alkG.T 12-mer duplexes establish that the helix is right-handed and all of the bases adopt an anti conformation of the glycosidic torsion angle including the O6alkG4 and T9 bases at the lesion site. The imino proton of T9 at the O6alkG.T lesion sites resonates at 8.85 ppm in the O6etG.T 12-mer duplex and at 9.47 ppm in the O6meG.T 12-mer duplex. The large upfield shift of the T9 imino proton resonance at the O6alkG4.T9 lesion site relative to that of the same proton in the G4.T9 wobble pair (11.99 ppm) and the A4.T9 Watson-Crick pair (13.95 ppm) in related sequences establishes that the hydrogen bonding of the imino proton of T9 to O6alkG4 is either very weak or absent. The imino proton of T9 develops NOEs to the CH3 protons of the O6etG and O6meG alkyl groups across the base pair, as well as to the imino and H5 protons of the flanking C3.G10 base pair and the imino and CH3 protons of the flanking A5.T8 base pair in the O6alkG.T 12-mer duplexes. These observations establish that the O6alkG4 and T9 residues are stacked into the duplex and that the O6CH3 and O6CH2CH3 groups of O6alkG4 adopt a syn orientation with respect to the N1 of the alkylated guanine.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- M W Kalnik
- Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, New York 10032
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Kalnik MW, Li BF, Swann PF, Patel DJ. O6-ethylguanine carcinogenic lesions in DNA: an NMR study of O6etG.C pairing in dodecanucleotide duplexes. Biochemistry 1989; 28:6182-92. [PMID: 2789994 DOI: 10.1021/bi00441a009] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The pairing of O6etG with C located four base pairs in from either end of the self-complementary d(C1-G2-C3-O6etG4-A5-G6-C7-T8-C9-G10-C11-G12) duplex (designated O6etG.C 12-mer) has been investigated from an analysis of proton and phosphorus two-dimensional NMR experiments. The structural consequences of increasing the alkyl group size were elucidated from a comparative study of the pairing of O6meG4 with C9 in a related sequence (designated O6meG.C 12-mer). The NMR parameters for both O6alkG-containing dodecanucleotides are also compared with those of the control sequence containing G4.C9 base pairs (designated G.C 12-mer). The NOE cross-peaks detected in the two-dimensional NOESY spectra of the O6alkG.C 12-mer duplexes in H2O solution establish that the O6etG4/O6meG4 and C9 bases at the lesion site stack into the helix between the flanking C3.G10 and A5.T8 Watson-Crick base pairs. The amino protons of C9 at the O6alkG4-C9 lesion site resonate as an average resonance at 7.78 and 7.63 ppm in the O6etG.C 12-mer and O6meG.C 12-mer duplexes, respectively. The observed NOEs between the amino protons of C9 and the CH3 protons of O6alkG4 establish a syn orientation of the O6-alkyl group with respect to the N1 of alkylated guanine. A wobble alignment of the O6alkG4.C9 base pair stablized by two hydrogen bonds, one between the amino group of C9 and N1 of O6alkG and the other between the amino group of O6alkG and N3 of C9, is tentatively proposed on the basis of the NOEs between the amino protons of C9 at the lesion site and the imino protons of flanking Watson-Crick base pairs. The proton and phosphorus chemical shift differences between the O6etG.C 12-mer and O6meG.C 12-mer duplexes are small compared to the differences between these O6alkG-containing duplexes and the control G.C 12-mer duplex.
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Affiliation(s)
- M W Kalnik
- Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, New York 10032
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Li BF, Holdup D, Morton CA, Sinnott ML. The catalytic consequences of experimental evolution. Transition-state structure during catalysis by the evolved beta-galactosidases of Escherichia coli (ebg enzymes) changed by a single mutational event. Biochem J 1989; 260:109-14. [PMID: 2505746 PMCID: PMC1138632 DOI: 10.1042/bj2600109] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
1. The first chemical step in the hydrolysis of galactosylpyridinium ions by the evolvant ebg enzyme is less sensitive to leaving-group acidity than in the case of the wild-type ebg enzyme, implying less glycone-aglycone-bond fission at the transition state. 2. The first chemical step in the hydrolysis of aryl galactosides by ebg enzyme is probably less sensitive to leaving-group acidity than in the case of ebg enzyme, possibly as a consequence of resulting in more effective proton donation to the leaving aglycone. 3. alpha-Deuterium kinetic isotope effects of 1.1(0) and beta-deuterium kinetic isotope effects of 1.0(0) were measured for the hydrolysis of galactosyl-enzyme intermediates derived from ebg and ebg enzymes: these effects are not compatible with reaction of the sugar ring through a 4C1-like conformation, or with an ionic glycosyl-enzyme intermediate. 4. The variation with pH of steady-state kinetic parameters for hydrolysis of p-nitrophenyl galactoside by ebg and ebg enzymes and of 3-methylphenyl beta-galactoside, 3,4-dinitrophenyl beta-galactoside and beta-galactosyl-3-bromopyridinium ion by ebg enzyme was measured. The steep, non-classical, fall in activity against p-nitrophenyl galactoside at low pH observed with ebg and ebg enzymes is not observed with ebg enzymes.
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Affiliation(s)
- B F Li
- Department of Organic Chemistry, University of Bristol, Cantocks Close, U.K
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Graves RJ, Li BF, Swann PF. Repair of O6-methylguanine, O6-ethylguanine, O6-isopropylguanine and O4-methylthymine in synthetic oligodeoxynucleotides by Escherichia coli ada gene O6-alkylguanine-DNA-alkyltransferase. Carcinogenesis 1989; 10:661-6. [PMID: 2649264 DOI: 10.1093/carcin/10.4.661] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Self-complementary oligodeoxynucleotides have been synthesized containing O6-methylguanine (O6meG), O6-ethylguanine (O6etG), O6-isopropylguanine (O6iprG) and O4-methylthymine (O4meT). They anneal in solution to give double-stranded DNA. These double helices have been used as substrates for the DNA repair protein O6-alkylguanine-DNA-alkyltransferase coded for by the ada gene of Escherichia coli. The repair followed second-order chemical kinetics. O6meG was repaired by the 19-kd transferase at a rate of 2.54 x 10(7) M-1 s-1 which is close to the theoretical limit for a diffusion-controlled reaction; O6etG and O4meT are repaired 1,000 and 10,000 times more slowly. The 39-kd alkyltransferase (which is precursor to the 19-kd form) and the 19-kd transferase repaired O6etG at similar rates. O6iprG was not repaired. The repair of oligomers containing O6meG was only slightly inhibited by the presence of nonalkylated oligomers. Oligomers containing O6etG were only slightly more effective as inhibitors of repair than the nonalkylated oligomers, indicating that the transferase does not bind selectively to alkylated DNA. Parallel structural studies have shown that O6-alkylguanine:C and O4-alkylthymine:A base pairs have a similar geometry with the alkylated base displaced into the major groove of the DNA in contrast to O6-alkylguanine:T and O4-alkylthymine:G base pairs which retain the Watson-Crick alignment with N1 of the purine juxtaposed to N3 of the pyrimidine. Measurement of the rate of repair of these different base pairs suggests that pairs with the alkyl group exposed in the major groove may be repaired more rapidly than those with the alkyl group more deeply buried in the helix.
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Affiliation(s)
- R J Graves
- Department of Biochemistry, University College and Middlesex School of Medicine, London, UK
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Kouchakdjian M, Li BF, Swann PF, Patel DJ. Pyrimidine.pyrimidine base-pair mismatches in DNA. A nuclear magnetic resonance study of T.T pairing at neutral pH and C.C pairing at acidic pH in dodecanucleotide duplexes. J Mol Biol 1988; 202:139-55. [PMID: 2845094 DOI: 10.1016/0022-2836(88)90526-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Structural features of pyrimidine.pyrimidine mismatches in the interior of oligonucleotide duplexes have been investigated by high resolution two-dimensional proton nuclear magnetic resonance (n.m.r.) spectroscopy. These studies were conducted on the self-complementary d(C-G-C-T-A-G-C-T-T-G-C-G) duplex (designated T.T 12-mer) and the self-complementary d(C-G-C-C-A-G-C-T-C-G-C-G) duplex (designated C.C 12-mer) containing T.T and C.C pairs located at identical positions four base-pairs from either end of the duplex. Proton n.m.r. studies on the T.T 12-mer duplex were undertaken in the neutral pH range, while studies on the C.C 12-mer duplex were recorded at acidic pH. The proton spectra narrowed considerably on lowering the pH below neutrality for the C.C 12-mer duplex. Two-dimensional nuclear Overhauser enhancement spectroscopy (NOESY) data sets have been recorded on the T.T 12-mer and C.C 12-mer duplexes in high salt H2O and D2O solution. The magnitude of the NOE crosspeaks and the directionality of the NOE connectivities demonstrate that both duplexes are right-handed with all bases, including those at the mismatch site, adopting an anti configuration about the glycosidic bond. The observed base and sugar proton chemical shifts suggest structural similarities for the trinucleotide segments centered about the T.T and C.C mismatches. A NOE is detected between the resolved imino protons of T4 and T9 at the mismatch site, consistent with formation of a stacked "wobble" T4(anti).T9(anti) pair in the T.T 12-mer duplex. A comparison of the imino proton chemical shift and NOE data suggests that the imino-carbonyl hydrogen bonds in the wobble T.T mismatch are weaker than the corresponding imino-carbonyl hydrogen bonds in the wobble G.T mismatch. The 4-amino protons of C4 and C9 at the mismatch site in the C.C 12-mer duplex do not exhibit the pattern of hydrogen-bonded and exposed protons separated by approximately 1.5 parts per million characteristic of cytidine amino protons involved in Watson-Crick G.C pairing. The experimental data are insufficient to differentiate between wobble C(anti).C+(anti) and other pairing possibilities for the mismatch in the C.C 12-mer duplex at acidic pH.
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Affiliation(s)
- M Kouchakdjian
- Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, NY 10032
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Kalnik MW, Kouchakdjian M, Li BF, Swann PF, Patel DJ. Base pair mismatches and carcinogen-modified bases in DNA: an NMR study of G.T and G.O4meT pairing in dodecanucleotide duplexes. Biochemistry 1988; 27:108-15. [PMID: 3349021 DOI: 10.1021/bi00401a018] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
High-resolution two-dimensional NMR studies have been completed on the self-complementary d(C-G-C-G-A-G-C-T-T-G-C-G) duplex (designated G.T 12-mer) and the self-complementary d(C-G-C-G-A-G-C-T-O4meT-G-C-G) duplex (designated G.O4meT 12-mer) containing G.T and G.O4meT pairs at identical positions four base pairs in from either end of the duplex. The exchangeable and nonexchangeable proton resonances have been assigned from an analysis of two-dimensional nuclear Overhauser enhancement (NOESY) spectra for the G.T 12-mer and G.O4meT 12-mer duplexes in H2O and D2O solution. The guanosine and thymidine imino protons in the G.T mismatch resonate at 10.57 and 11.98 ppm, respectively, and exhibit a strong NOE between themselves and to imino protons of flanking base pairs in the G.T 12-mer duplex. These results are consistent with wobble pairing at the G.T mismatch site involving two imino proton-carbonyl hydrogen bonds as reported previously [Hare, D. R., Shapiro, L., & Patel, D. J. (1986) Biochemistry 25, 7445-7456]. In contrast, the guanosine imino proton in the G.O4meT pair resonates at 8.67 ppm. The large upfield chemical shift of this proton relative to that of the imino proton resonance of G in the G.T mismatch or in G.C base pairs indicates that hydrogen bonding to O4meT is either very weak or absent. This guanosine imino proton has an NOE to the OCH3 group of O4meT across the pair and NOEs to the imino protons of flanking base pairs.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M W Kalnik
- Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, New York 10032
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Kalnik MW, Kouchakdjian M, Li BF, Swann PF, Patel DJ. Base pair mismatches and carcinogen-modified bases in DNA: an NMR study of A.C and A.O4meT pairing in dodecanucleotide duplexes. Biochemistry 1988; 27:100-8. [PMID: 2831951 DOI: 10.1021/bi00401a017] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Structural features of A.C mismatches and A.O4meT pairs in the interior of oligodeoxynucleotide duplexes have been investigated by high-resolution two-dimensional proton NMR spectroscopy on the self-complementary d(C-G-C-A-A-G-C-T-C-G-C-G) duplex (designated A.C 12-mer) and and the self-complementary d(C-G-C-A-A-G-C-T-O4meT-G-C-G) duplex (designated A.O4meT 12-mer) containing A.C and A.O4meT pairs at identical positions four base pairs in from either end of and A.O4meT pairs at identical positions four base pairs in from either end of the duplex. Proton NMR shows that there are similar pH-dependent changes in the structure in the A.C 12-mer and A.O4meT 12-mer duplexes. Our studies have focused on the low-pH (pH 5.5) conformation where high-quality two-dimensional NOESY data sets were collected from the exchangeable and nonexchangeable protons in these duplexes. The spectral parameters for the A.C 12-mer and the A.O4meT 12-mer duplexes were very similar, indicating that they must have similar structures at this pH in aqueous solution. Both structures are right-handed double helices with all the bases adopting the normal anti configuration about the glycosidic bond. The same atoms are involved in hydrogen-bond pairing for the A.C mismatch and the A.O4meT pair, and these pairs have a similar spatial relationship to flanking base pairs.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M W Kalnik
- Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, New York 10032
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Abstract
The carcinogenicity of N-nitroso compounds is believed to result from the alkylation of DNA, particularly on O-6 of the guanine and O-4 of the thymine residues. In order to study the base-pairing properties of 4-O-methylthymidine (T*) residues and the structural changes produced in DNA by the presence of this alkylated nucleoside, the oligodeoxyribonucleotides T*GCG, CGCAAGCTT*GCG, CGCGAGCTT*GCG, and CGCAAGCTTGCG were synthesized by the phosphotriester approach in solution. The 4-O-methylthymidine required for oligonucleotide synthesis was prepared by treating the 4-(3-nitro-1,2,4-triazolo) derivative of 3',5'-bis-O-(methoxyacetyl)thymidine with 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) in methanol solution. The susceptibility of the 4-O-methyl group of T* toward nucleophiles enables this group of 4-O-methylthymidine-containing oligomers to be labeled by a direct exchange reaction with [13C]- or [14C]methanol in the presence of DBU. Although it has been previously suggested that 4-O-methylthymine forms stable base pairs with guanine, the thermal melting profiles of the double helices formed by these dodecamers suggest that the presence of 4-O-methylthymine paired to either adenine or guanine destablizes the helix. The melting curve of the sequence containing a 4-O-methylthymine residue base paired to guanine was biphasic and similar to that of an analogous sequence containing 6-O-methylguanine paired to thymine.
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