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Valente M, Timm J, Castillo-Acosta VM, Ruiz-Pérez LM, Balzarini T, Nettleship JE, Bird LE, Rada H, Wilson KS, González-Pacanowska D. Cell cycle regulation and novel structural features of thymidine kinase, an essential enzyme in Trypanosoma brucei. Mol Microbiol 2016; 102:365-385. [PMID: 27426054 DOI: 10.1111/mmi.13467] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/17/2016] [Indexed: 11/28/2022]
Abstract
Thymidine kinase (TK) is a key enzyme in the pyrimidine salvage pathway which catalyzes the transfer of the γ-phosphate of ATP to 2'-deoxythymidine (dThd) forming thymidine monophosphate (dTMP). Unlike other type II TKs, the Trypanosoma brucei enzyme (TbTK) is a tandem protein with two TK homolog domains of which only the C-terminal one is active. In this study, we establish that TbTK is essential for parasite viability and cell cycle progression, independently of extracellular pyrimidine concentrations. We show that expression of TbTK is cell cycle regulated and that depletion of TbTK leads to strongly diminished dTTP pools and DNA damage indicating intracellular dThd to be an essential intermediate metabolite for the synthesis of thymine-derived nucleotides. In addition, we report the X-ray structure of the catalytically active domain of TbTK in complex with dThd and dTMP at resolutions up to 2.2 Å. In spite of the high conservation of the active site residues, the structures reveal a widened active site cavity near the nucleobase moiety compared to the human enzyme. Our findings strongly support TbTK as a crucial enzyme in dTTP homeostasis and identify structural differences within the active site that could be exploited in the process of rational drug design.
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Affiliation(s)
- Maria Valente
- Instituto de Parasitología y Biomedicina "López-Neyra", Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Jennifer Timm
- York Structural Biology Laboratory, Department of Chemistry, University of York, York, YO10 5DD, UK
| | - Víctor M Castillo-Acosta
- Instituto de Parasitología y Biomedicina "López-Neyra", Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Luis M Ruiz-Pérez
- Instituto de Parasitología y Biomedicina "López-Neyra", Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Tom Balzarini
- Instituto de Parasitología y Biomedicina "López-Neyra", Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Joanne E Nettleship
- The Oxford Protein Production Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, R92 Harwell, Didcot, Oxfordshire, OX11 0FA, UK
| | - Louise E Bird
- The Oxford Protein Production Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, R92 Harwell, Didcot, Oxfordshire, OX11 0FA, UK
| | - Heather Rada
- The Oxford Protein Production Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, R92 Harwell, Didcot, Oxfordshire, OX11 0FA, UK
| | - Keith S Wilson
- York Structural Biology Laboratory, Department of Chemistry, University of York, York, YO10 5DD, UK.
| | - Dolores González-Pacanowska
- Instituto de Parasitología y Biomedicina "López-Neyra", Consejo Superior de Investigaciones Científicas, Granada, Spain.
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McAllister KA, Yasseen AA, McKerr G, Downes CS, McKelvey-Martin VJ. FISH comets show that the salvage enzyme TK1 contributes to gene-specific DNA repair. Front Genet 2014; 5:233. [PMID: 25152750 PMCID: PMC4126492 DOI: 10.3389/fgene.2014.00233] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 06/30/2014] [Indexed: 11/13/2022] Open
Abstract
Thymidine kinase 1 (TK1) is a salvage enzyme that phosphorylates thymidine, imported from surrounding fluids, to create dTMP, which is further phosphorylated to the DNA precursor dTTP. TK1 deficiency has for a long time been known to cause increased cellular sensitivity to DNA damage. We have examined preferential strand break repair of DNA domains in TK1(+) and TK1(-) clones of the Raji cell line, by the Comet-FISH technique, in bulk DNA and in the actively transcribed tumor suppressor (TP53) and human telomerase reverse transcriptase (hTERT) gene regions, over 1 h after 5Gy γ-irradiation. Results showed that repair of the TP53 and hTERT gene regions was more efficient in TK1(+) compared to TK1(-) cells, a trend also reflected to a lesser degree in genomic DNA repair between the cell-lines. The targeted gene-specific repair in TK(+) cells occurred rapidly, mainly over the first 15 min repair-period. Therefore, TK1 is needed for preferential repair of actively transcribed regions, through a previously unsuspected mechanism. In principle, TK1 could exert its protective effects through supply of a supplementary dTTP pool for accurate repair of damaged genes; but Raji TK1(+) cells in thymidine free media still show preferential repair of transcribed regions. TK1 therefore does not exert its protective effects through dTTP pools, but through another unidentified mechanism, which affects sensitivity to and mutagenicity by DNA damaging agents.
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Affiliation(s)
| | - Akeel A Yasseen
- Department of Pathology and Forensic Medicine, Faculty of Medicine, University of Kufa Kufa, Iraq
| | - George McKerr
- School of Biomedical Sciences, University of Ulster Coleraine, UK
| | - C S Downes
- School of Biomedical Sciences, University of Ulster Coleraine, UK
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Chen YL, Eriksson S, Chang ZF. Regulation and functional contribution of thymidine kinase 1 in repair of DNA damage. J Biol Chem 2010; 285:27327-27335. [PMID: 20554529 DOI: 10.1074/jbc.m110.137042] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellular supply of dNTPs is essential in the DNA replication and repair processes. Here we investigated the regulation of thymidine kinase 1 (TK1) in response to DNA damage and found that genotoxic insults in tumor cells cause up-regulation and nuclear localization of TK1. During recovery from DNA damage, TK1 accumulates in p53-null cells due to a lack of mitotic proteolysis as these cells are arrested in the G(2) phase by checkpoint activation. We show that in p53-proficient cells, p21 expression in response to DNA damage prohibits G(1)/S progression, resulting in a smaller G(2) fraction and less TK1 accumulation. Thus, the p53 status of tumor cells affects the level of TK1 after DNA damage through differential cell cycle control. Furthermore, it was shown that in HCT-116 p53(-/-) cells, TK1 is dispensable for cell proliferation but crucial for dTTP supply during recovery from DNA damage, leading to better survival. Depletion of TK1 decreases the efficiency of DNA repair during recovery from DNA damage and generates more cell death. Altogether, our data suggest that more dTTP synthesis via TK1 take place after genotoxic insults in tumor cells, improving DNA repair during G(2) arrest.
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Affiliation(s)
- Yen-Ling Chen
- Graduate Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Section 1, Jen-Ai Road, Taipei 100, Taiwan
| | - Staffan Eriksson
- Department of Anatomy, Physiology and Biochemistry, The Swedish University of Agricultural Sciences, Biomedical Center, S-751 23 Uppsala, Sweden
| | - Zee-Fen Chang
- Graduate Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Section 1, Jen-Ai Road, Taipei 100, Taiwan; Institute of Biochemistry and Molecular Biology, National Yang-Ming University, No. 155, Section 2, Linong Street, Taipei 112, Taiwan.
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Dobrovolsky VN, Bucci T, Heflich RH, Desjardins J, Richardson FC. Mice deficient for cytosolic thymidine kinase gene develop fatal kidney disease. Mol Genet Metab 2003; 78:1-10. [PMID: 12559842 DOI: 10.1016/s1096-7192(02)00224-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The thymidine kinase (Tk) gene codes for a cytosolic protein involved in the pyrimidine nucleotide salvage pathway. A functional Tk gene is not necessary for cells in culture, and a naturally occurring Tk deficient phenotype has not been described in humans or animal models. In order to determine the biological significance of the Tk gene, we created Tk(-/-) knockout (KO) mice through homologous recombination in mouse embryonic stem cells. Tk KO mice have shortened life spans compared with their wild-type or Tk heterozygous (HET) siblings. All Tk KO mice develop sclerosis of kidney glomeruli and die before one year of age of kidney failure. Among other changes in KO animals, the most consistent is a switch from exclusively mucous secretion to predominantly serous secretion in the sublingual salivary gland. HET parents can produce KO mice at a frequency approaching Mendelian inheritance. Other observations in KO animals include an elevated level of serum thymidine, a significant decrease in the cloning efficiency of splenic lymphocytes, an increase in the frequency of hypoxanthine guanine phosphoribosyl transferase gene mutant lymphocytes, and histological alteration in the lymphoid structure of the spleen. In addition, KO animals sporadically exhibit inflammation of the arteries, which taken together with the lymphocyte and spleen abnormalities, suggest an abnormal immune system. Alterations in Tk KO mice indicate that the pyrimidine nucleotide salvage pathway is indispensable in vivo.
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Affiliation(s)
- Vasily N Dobrovolsky
- National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR, USA.
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Branda RF, O'Neill JP, Brooks EM, Trombley LM, Nicklas JA. The effect of folate deficiency on the cytotoxic and mutagenic responses to ethyl methanesulfonate in human lymphoblastoid cell lines that differ in p53 status. Mutat Res 2001; 473:51-71. [PMID: 11166026 DOI: 10.1016/s0027-5107(00)00138-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Folic acid deficiency acts synergistically with alkylating agents to increase genetic damage at the HPRT locus in Chinese hamster ovary cells in vitro and in rat splenocytes in vivo. The present studies extend these observations to human cells and, in addition, investigate the role of p53 activity on mutation induction. The human lymphoblastoid cell lines TK6 and WTK1 are derived from the same parental cell line (WI-L2), but WTK1 expresses mutant p53. Treatment of folate-replete or deficient WTK1 and TK6 cells with increasing concentrations (0-50microg/ml) of ethyl methanesulfonate (EMS) resulted in significantly different HPRT mutation dose-response relationships (P<0.01), indicating that folate deficiency increased the EMS-induced mutant frequency in both cell lines, but with a greater effect in TK6 cells. Molecular analyses of 152 mutations showed that the predominant mutation (65%) in both cell types grown in the presence or absence of folic acid was a G>A transition on the non-transcribed strand. These transitions were mainly at non-CpG sites, particularly when these bases were flanked 3' by a purine or on both sides by G:C base pairs. A smaller number of G>A transitions occurred on the transcribed strand (C>T=14%), resulting in 79% total G:C>A:T transitions. There were more genomic deletions in folate-deficient (15%) as compared to replete cells (4%) of both cell types. Mutations that altered RNA splicing were common in both cell types and under both folate conditions, representing 33% of the total mutations. These studies indicate that cells expressing p53 activity exhibit a higher rate of mutation induction but are more sensitive to the toxic effects of alkylating agents than those lacking p53 activity. Folate deficiency tends to reduce toxicity but increase mutation induction after EMS treatment. The p53 gene product did not have a major influence on the molecular spectrum after treatment with EMS, while folate deficiency increased the frequency of deletions in both cell types.
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Affiliation(s)
- R F Branda
- Department of Medicine and The Vermont Cancer Center, University of Vermont, Burlington, VT 05405, USA.
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Kubota M, Lin YW, Hamahata K, Sawada M, Koishi S, Hirota H, Wakazono Y. Cancer chemotherapy and somatic cell mutation. Mutat Res 2000; 470:93-102. [PMID: 11027962 DOI: 10.1016/s1383-5742(00)00043-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The occurrence of a second neoplasm is one of the major obstacles in cancer chemotherapy. The elucidation of the genotoxic effects induced by anti-cancer drugs is considered to be helpful in identifying the degree of cancer risk. Numerous investigations on cancer patients after chemotherapy have demonstrated: (i) an increase in the in vivo somatic cell mutant frequency (Mf) at three genetic loci, including hypoxanthine-guanine phosphoribosyl-transferase (hprt), glycophorin A (GPA), and the T-cell receptor (TCR), and (ii) alterations in the mutational spectra of hprt mutants. However, the time required for and the degree of such changes are quite variable among patients even if they have received the same chemotherapy, suggesting the existence of underlying genetic factor(s). Accordingly, some cancer patients prior to chemotherapy as well as patients with cancer-prone syndrome have been found to show an elevated Mf. Based on the information obtained from somatic cell mutation assays, an individualized chemotherapy should be considered in order to minimize the risk of a second neoplasm.
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Affiliation(s)
- M Kubota
- Department of Pediatrics, Faculty of Medicine, Kyoto University, Kawahara-cho 54, Shogoin, Sakyo-ku, 606-8507, Kyoto, Japan.
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Greenwood SK, Armstrong MJ, Hill RB, Bradt CI, Johnson TE, Hilliard CA, Galloway SM. Fewer chromosome aberrations and earlier apoptosis induced by DNA synthesis inhibitors, a topoisomerase II inhibitor or alkylating agents in human cells with normal compared with mutant p53. Mutat Res 1998; 401:39-53. [PMID: 9639670 DOI: 10.1016/s0027-5107(97)00272-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The human lymphoblastoid cell lines TK6 (normal p53) and WI-L2-NS or WTK1 (mutant p53) differ in sensitivity to killing and induction of gene mutations and chromosome aberrations by ionizing radiation. This may be related to decreased apoptosis in the cells with mutated p53, such that more damaged cells survive. We compared the response of the two cell types to various chemicals. First, to ensure that the thymidine kinase deficiency does not increase the sensitivity of TK6 tk+/- cells to mutagens, we demonstrated that they were not hypersensitive to aberration induction by altered DNA precursor pools or DNA synthesis inhibition, by aphidicolin (APC), methotrexate, hydroxyurea (HU), cytosine arabinoside and thymidine. TK6 cells were then compared with WI-L2-NS or WTK1 cells. With APC, HU, methyl methanesulfonate (MMS), ethyl nitrosourea (ENU) and etoposide (etop), TK6 cells had more apoptosis in the first two days after treatment. Fewer aberrations were seen in normal p53 TK6 cells than the mutant p53 WI-L2-NS cells, ranging from very little difference between the two cell types with MMS to very large differences with ENU and etop. For MMS and ENU we followed cultures for several days, and found that WI-L2-NS cells underwent delayed apoptosis 3 to 5 days after treatment, in parallel with published observations with ionizing radiation. WI-L2-NS cells also had a delayed increase in aberrations (up to 5 days post-treatment) when no aberrations remained in TK6 cells. Colony forming efficiency was measured for APC, MMS and ENU, and was greater in the p53 mutant cells. Our results show that normal p53 function is required for rapid and efficient apoptosis in these lymphoblastoid cells with DNA synthesis inhibitors, alkylating agents and a topoisomerase II inhibitor, and support the hypothesis that induced levels of aberrations are higher in p53 mutant cells because of a failure to remove damaged cells by apoptosis.
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Affiliation(s)
- S K Greenwood
- Merck Research Laboratories, WP45-305, West Point, PA 19486, USA
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Kubota M, Wakazono Y, Furusho K. Increased cell killing and mutagenecity by DNA alkylating agents in cells with decreased TTP pools. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 431:611-6. [PMID: 9598138 DOI: 10.1007/978-1-4615-5381-6_118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- M Kubota
- Department of Pediatrics, Kyoto University, Japan
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Oliver FJ, Collins MK, López-Rivas A. Overexpression of a heterologous thymidine kinase delays apoptosis induced by factor deprivation and inhibitors of deoxynucleotide metabolism. J Biol Chem 1997; 272:10624-30. [PMID: 9099710 DOI: 10.1074/jbc.272.16.10624] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Perturbing deoxyribonucleoside triphosphate (dNTP) metabolism with inhibitors of the de novo synthesis of dNTP causes apoptosis in the interleukin-3 (IL-3)-dependent pre-B cell line BAF3. Under these conditions apoptosis is prevented when deoxyribonucleosides for dNTP synthesis are supplied in the culture medium. On the other hand, removal of IL-3 from cultures of BAF3 cells resulted in down-regulation of thymidine kinase activity, rapid imbalance in dNTP levels, and apoptosis. In this study we show that overexpression of a heterologous thymidine kinase, herpes simplex virus thymidine kinase (TK), in BAF3 cells protects these cells from apoptosis induced by either inhibitors of dNTP synthesis or IL-3 deprivation. This protection against apoptosis is abrogated by 9-(4-hydroxybutyl)-N2-phenylguanine, a specific inhibitor of herpes simplex virus-1 TK. These results suggest that deoxyribonucleoside kinases, particularly TK, may be important in the regulation of apoptosis in hemopoietic cells.
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Affiliation(s)
- F J Oliver
- Instituto de Parasitología y Biomedicina, Consejo Superior de Investigaciones Científicas, 18001 Granada, Spain
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