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Yuyukina SK, Zharkov DO. Mechanisms of Coronavirus Genome Stability As Potential Targets for Antiviral Drugs. HERALD OF THE RUSSIAN ACADEMY OF SCIENCES 2022; 92:470-478. [PMID: 36091852 PMCID: PMC9447942 DOI: 10.1134/s1019331622040256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 02/25/2022] [Accepted: 03/14/2022] [Indexed: 06/15/2023]
Abstract
The COVID-19 pandemic has made it necessary to create antivirals active against the SARS-CoV-2 coronavirus. One of the widely used strategies to fight off viral infections is the use of modified nucleoside analogues that inhibit viral replication by incorporating DNA or RNA into the growing chain, thus stopping its synthesis. The difficulty of using this method of treatment in the case of SARS-CoV-2 is that coronaviruses have an effective mechanism for maintaining genome stability. Its central element is the nsp14 protein, which is characterized by exonuclease activity, due to which incorrectly included and noncanonical nucleotides are removed from the 3' end of the growing RNA chain. Inhibitors of nsp14 exonuclease and nucleoside analogues resistant to its action are viewed as potential targets for anticoronavirus therapy.
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Affiliation(s)
- S. K. Yuyukina
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
- Novosibirsk State University, Novosibirsk, Russia
| | - D. O. Zharkov
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
- Novosibirsk State University, Novosibirsk, Russia
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2
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Endutkin AV, Yatsenko DD, Zharkov DO. Effect of DNA Methylation on the 3'→5' Exonuclease Activity of Major Human Abasic Site Endonuclease APEX1. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:10-20. [PMID: 35491018 DOI: 10.1134/s0006297922010023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 11/23/2021] [Accepted: 11/24/2021] [Indexed: 06/14/2023]
Abstract
Apurinic/apyrimidinic (AP) endonucleases are the key enzymes in the DNA base excision repair, as they hydrolyze the phosphodiester bond in the AP site formed after removal of the damaged base. Major human AP endonuclease APEX1 also possesses the 3'-phosphodiesterase and 3'→5' exonuclease activities. The biological role of the latter has not been established yet; it is assumed that it corrects DNA synthesis errors during DNA repair. If DNA is damaged at the 3'-side of 5-methylcytosine (mC) residue, the 3'→5' exonuclease activity can change the epigenetic methylation status of the CpG dinucleotide. It remains unclear whether the 3'→5' exonuclease activity of APEX1 contributes to the active epigenetic demethylation or, on the contrary, is limited in the case of methylated CpG dinucleotides in order to preserve the epigenetic status upon repair of accidental DNA damage. Here, we report the results of the first systematic study on the efficiency of removal of 3'-terminal nucleotides from the substrates modeling DNA repair intermediates in the CpG dinucleotides. The best substrates for the 3'→5' exonuclease activity of APEX1 were oligonucleotides with the 3'-terminal bases non-complementary to the template, while the worst substrates contained mC. The presence of mC in the complementary strand significantly reduced the reaction rate even for the non-complementary 3'-ends. Therefore, the efficiency of the 3'→5' exonuclease reaction catalyzed by APEX1 is limited in the case of the methylated CpG dinucleotides, which likely reflects the need to preserve the epigenetic status during DNA repair.
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Affiliation(s)
- Anton V Endutkin
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Darya D Yatsenko
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Dmitry O Zharkov
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia.
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk, 630090, Russia
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3
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A New Method for Exonuclease Activity Analysis of Apurinic/Apyrimidinic Endonuclease 1 and Application in Heavy-polluted Ramie. CHINESE JOURNAL OF ANALYTICAL CHEMISTRY 2021. [DOI: 10.1016/s1872-2040(21)60117-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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4
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Liu TC, Guo KW, Chu JW, Hsiao YY. Understanding APE1 cellular functions by the structural preference of exonuclease activities. Comput Struct Biotechnol J 2021; 19:3682-3691. [PMID: 34285771 PMCID: PMC8258793 DOI: 10.1016/j.csbj.2021.06.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 06/21/2021] [Accepted: 06/22/2021] [Indexed: 12/17/2022] Open
Abstract
Mammalian apurinic/apyrimidinic (AP) endonuclease 1 (APE1) has versatile enzymatic functions, including redox, endonuclease, and exonuclease activities. APE1 is thus broadly associated with pathways in DNA repair, cancer cell growth, and drug resistance. Unlike its AP site-specific endonuclease activity in Base excision repair (BER), the 3′-5′ exonucleolytic cleavage of APE1 using the same active site exhibits complex substrate selection patterns, which are key to the biological functions. This work aims to integrate molecular structural information and biocatalytic properties to deduce the substrate recognition mechanism of APE1 as an exonuclease and make connection to its diverse functionalities in the cell. In particular, an induced space-filling model emerges in which a bridge-like structure is formed by Arg177 and Met270 (RM bridge) upon substrate binding, causing the active site to adopt a long and narrow product pocket for hosting the leaving group of an AP site or the 3′-end nucleotide. Rather than distinguishing bases as other exonucleases, the hydrophobicity and steric hindrance due to the APE1 product pocket provides selectivity for substrate structures, such as matched or mismatched blunt-ended dsDNA, recessed dsDNA, gapped dsDNA, and nicked dsDNA with 3′-end overhang shorter than 2 nucleotides. These dsDNAs are similar to the native substrates in BER proofreading, BER for trinucleotide repeats (TNR), Nucleotide incision repair (NIR), DNA single-strand breaks (SSB), SSB with damaged bases, and apoptosis. Integration of in vivo studies, in vitro biochemical assays, and structural analysis is thus essential for linking the APE1 exonuclease activity to the specific roles in cellular functions.
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Affiliation(s)
- Tung-Chang Liu
- Institute of Molecular Medicine and Bioengineering, National Yang Ming Chiao Tung University, Hsinchu 30068, Taiwan.,Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, Taiwan 30068, Taiwan
| | - Kai-Wei Guo
- Institute of Molecular Medicine and Bioengineering, National Yang Ming Chiao Tung University, Hsinchu 30068, Taiwan.,Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, Taiwan 30068, Taiwan
| | - Jhih-Wei Chu
- Institute of Molecular Medicine and Bioengineering, National Yang Ming Chiao Tung University, Hsinchu 30068, Taiwan.,Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, Taiwan 30068, Taiwan.,Institute of Bioinformatics and Systems Biology, National Yang Ming Chiao Tung University, Hsinchu, 30068, Taiwan.,Center For Intelligent Drug Systems and Smart Bio-devices (IDSB), National Yang Ming Chiao Tung University, Hsinchu, Taiwan
| | - Yu-Yuan Hsiao
- Institute of Molecular Medicine and Bioengineering, National Yang Ming Chiao Tung University, Hsinchu 30068, Taiwan.,Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, Taiwan 30068, Taiwan.,Institute of Bioinformatics and Systems Biology, National Yang Ming Chiao Tung University, Hsinchu, 30068, Taiwan.,Center For Intelligent Drug Systems and Smart Bio-devices (IDSB), National Yang Ming Chiao Tung University, Hsinchu, Taiwan.,Drug Development and Value Creation Research Center, Center for Cancer Research, Kaohsiung Medical University, Kaohsiung, Taiwan
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5
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Liu TC, Lin CT, Chang KC, Guo KW, Wang S, Chu JW, Hsiao YY. APE1 distinguishes DNA substrates in exonucleolytic cleavage by induced space-filling. Nat Commun 2021; 12:601. [PMID: 33504804 PMCID: PMC7841161 DOI: 10.1038/s41467-020-20853-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Accepted: 12/22/2020] [Indexed: 11/09/2022] Open
Abstract
The exonuclease activity of Apurinic/apyrimidinic endonuclease 1 (APE1) is responsible for processing matched/mismatched terminus in various DNA repair pathways and for removing nucleoside analogs associated with drug resistance. To fill in the gap of structural basis for exonucleolytic cleavage, we determine the APE1-dsDNA complex structures displaying end-binding. As an exonuclease, APE1 does not show base preference but can distinguish dsDNAs with different structural features. Integration with assaying enzyme activity and binding affinity for a variety of substrates reveals for the first time that both endonucleolytic and exonucleolytic cleavage can be understood by an induced space-filling model. Binding dsDNA induces RM (Arg176 and Met269) bridge that defines a long and narrow product pocket for exquisite machinery of substrate selection. Our study paves the way to comprehend end-processing of dsDNA in the cell and the drug resistance relating to APE1.
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Affiliation(s)
- Tung-Chang Liu
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, 30068, Taiwan.,Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, 30068, Taiwan
| | - Chun-Ting Lin
- Master's and Doctoral Degree Program for Science and Technology of Accelerator Light Sources, National Chiao Tung University, Hsinchu, 30068, Taiwan
| | - Kai-Cheng Chang
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, 30068, Taiwan
| | - Kai-Wei Guo
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, 30068, Taiwan
| | - Shuying Wang
- Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Department of Biotechnology and Bioindustry Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan
| | - Jhih-Wei Chu
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, 30068, Taiwan.,Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, 30068, Taiwan.,Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsinchu, 30068, Taiwan.,Center For Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Chiao Tung University, Hsinchu, Taiwan
| | - Yu-Yuan Hsiao
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, 30068, Taiwan. .,Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, 30068, Taiwan. .,Master's and Doctoral Degree Program for Science and Technology of Accelerator Light Sources, National Chiao Tung University, Hsinchu, 30068, Taiwan. .,Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsinchu, 30068, Taiwan. .,Center For Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Chiao Tung University, Hsinchu, Taiwan. .,Drug Development and Value Creation Research Center, Center for Cancer Research, Kaohsiung Medical University, Kaohsiung, Taiwan.
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6
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Boeckemeier L, Kraehenbuehl R, Keszthelyi A, Gasasira MU, Vernon EG, Beardmore R, Vågbø CB, Chaplin D, Gollins S, Krokan HE, Lambert SAE, Paizs B, Hartsuiker E. Mre11 exonuclease activity removes the chain-terminating nucleoside analog gemcitabine from the nascent strand during DNA replication. SCIENCE ADVANCES 2020; 6:eaaz4126. [PMID: 32523988 PMCID: PMC7259961 DOI: 10.1126/sciadv.aaz4126] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 03/30/2020] [Indexed: 06/11/2023]
Abstract
The Mre11 nuclease is involved in early responses to DNA damage, often mediated by its role in DNA end processing. MRE11 mutations and aberrant expression are associated with carcinogenesis and cancer treatment outcomes. While, in recent years, progress has been made in understanding the role of Mre11 nuclease activities in DNA double-strand break repair, their role during replication has remained elusive. The nucleoside analog gemcitabine, widely used in cancer therapy, acts as a replication chain terminator; for a cell to survive treatment, gemcitabine needs to be removed from replicating DNA. Activities responsible for this removal have, so far, not been identified. We show that Mre11 3' to 5' exonuclease activity removes gemcitabine from nascent DNA during replication. This contributes to replication progression and gemcitabine resistance. We thus uncovered a replication-supporting role for Mre11 exonuclease activity, which is distinct from its previously reported detrimental role in uncontrolled resection in recombination-deficient cells.
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Affiliation(s)
- L. Boeckemeier
- North West Cancer Research Institute, School of Medical Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, UK
| | - R. Kraehenbuehl
- North West Cancer Research Institute, School of Medical Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, UK
- Centre for Environmental Biotechnology, School of Natural Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, UK
| | - A. Keszthelyi
- North West Cancer Research Institute, School of Medical Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, UK
| | - M. U. Gasasira
- North West Cancer Research Institute, School of Medical Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, UK
| | - E. G. Vernon
- North West Cancer Research Institute, School of Medical Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, UK
| | - R. Beardmore
- North West Cancer Research Institute, School of Medical Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, UK
| | - C. B. Vågbø
- Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - D. Chaplin
- Centre for Environmental Biotechnology, School of Natural Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, UK
| | - S. Gollins
- North West Cancer Research Institute, School of Medical Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, UK
| | - H. E. Krokan
- Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - S. A. E. Lambert
- Institut Curie, Paris-Saclay University, UMR3348, F-91450 Orsay, France
| | - B. Paizs
- Centre for Environmental Biotechnology, School of Natural Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, UK
| | - E. Hartsuiker
- North West Cancer Research Institute, School of Medical Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, UK
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7
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Abstract
Genomic DNA is susceptible to endogenous and environmental stresses that modify DNA structure and its coding potential. Correspondingly, cells have evolved intricate DNA repair systems to deter changes to their genetic material. Base excision DNA repair involves a number of enzymes and protein cofactors that hasten repair of damaged DNA bases. Recent advances have identified macromolecular complexes that assemble at the DNA lesion and mediate repair. The repair of base lesions generally requires five enzymatic activities: glycosylase, endonuclease, lyase, polymerase, and ligase. The protein cofactors and mechanisms for coordinating the sequential enzymatic steps of repair are being revealed through a range of experimental approaches. We discuss the enzymes and protein cofactors involved in eukaryotic base excision repair, emphasizing the challenge of integrating findings from multiple methodologies. The results provide an opportunity to assimilate biochemical findings with cell-based assays to uncover new insights into this deceptively complex repair pathway.
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Affiliation(s)
- William A Beard
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Science, National Institutes of Health, Research Triangle Park, North Carolina 27709-2233, USA;
| | - Julie K Horton
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Science, National Institutes of Health, Research Triangle Park, North Carolina 27709-2233, USA;
| | - Rajendra Prasad
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Science, National Institutes of Health, Research Triangle Park, North Carolina 27709-2233, USA;
| | - Samuel H Wilson
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Science, National Institutes of Health, Research Triangle Park, North Carolina 27709-2233, USA;
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8
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Dyrkheeva NS, Lebedeva NA, Sherstyuk YV, Abramova TV, Silnikov VN, Lavrik OI. Excision of Carbohydrate-Modified dNMP Analogues from DNA 3' end by Human Apurinic/Apyrimidinic Endonuclease 1 (APE1) and Tyrosyl-DNA Phosphodiesterase 1 (TDP1). Mol Biol 2018. [DOI: 10.1134/s0026893318060067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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9
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Abstract
Before a deleterious DNA lesion can be replaced with its undamaged counterpart, the lesion must first be removed from the genome. This process of removing and replacing DNA lesions is accomplished by the careful coordination of several protein factors during DNA repair. One such factor is the multifunctional enzyme human apurinic/apyrimidinic endonuclease 1 (APE1), known best for its DNA backbone cleavage activity at AP sites during base excision repair (BER). APE1 preforms AP site incision with surgical precision and skill, by sculpting the DNA to place the cleavage site in an optimal position for nucleophilic attack within its compact protein active site. APE1, however, has demonstrated broad surgical expertise, and applies its DNA cleavage activity to a wide variety of DNA and RNA substrates. Here, we discuss what is known and unknown about APE1 cleavage mechanisms, focusing on structural and mechanistic considerations. Importantly, disruptions in the biological functions associated with APE1 are linked to numerous human maladies, including cancer and neurodegenerative diseases. The continued elucidation of APE1 mechanisms is required for rational drug design towards novel and strategic ways to target its associated repair pathways.
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Affiliation(s)
- Amy M Whitaker
- Department of Biochemistry and Molecular Biology, Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Bret D Freudenthal
- Department of Biochemistry and Molecular Biology, Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
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10
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Whitaker AM, Flynn TS, Freudenthal BD. Molecular snapshots of APE1 proofreading mismatches and removing DNA damage. Nat Commun 2018; 9:399. [PMID: 29374164 PMCID: PMC5785985 DOI: 10.1038/s41467-017-02175-y] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 11/10/2017] [Indexed: 01/13/2023] Open
Abstract
Human apurinic/apyrimidinic (AP) endonuclease 1 (APE1) is an essential DNA repair enzyme which uses a single active site to process DNA damage via two distinct activities: (1) AP-endonuclease and (2) 3′ to 5′ exonuclease. The AP-endonuclease activity cleaves at AP-sites, while the exonuclease activity excises bulkier 3′ mismatches and DNA damage to generate clean DNA ends suitable for downstream repair. Molecular details of the exonuclease reaction and how one active site can accommodate various toxic DNA repair intermediates remains elusive despite being biologically important. Here, we report multiple high-resolution APE1–DNA structural snapshots revealing how APE1 removes 3′ mismatches and DNA damage by placing the 3′ group within the intra-helical DNA cavity via a non-base flipping mechanism. This process is facilitated by a DNA nick, instability of a mismatched/damaged base, and bending of the DNA. These results illustrate how APE1 cleanses DNA dirty-ends to generate suitable substrates for downstream repair enzymes. The essential DNA repair enzyme apurinic/apyrimidinic endonuclease 1 (APE1) has both endonuclease and exonuclease activities. Here, the authors present DNA bound human APE1 crystal structures which give insights into its exonuclease mechanism.
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Affiliation(s)
- Amy M Whitaker
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Tony S Flynn
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Bret D Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA.
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11
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Shelton J, Lu X, Hollenbaugh JA, Cho JH, Amblard F, Schinazi RF. Metabolism, Biochemical Actions, and Chemical Synthesis of Anticancer Nucleosides, Nucleotides, and Base Analogs. Chem Rev 2016; 116:14379-14455. [PMID: 27960273 DOI: 10.1021/acs.chemrev.6b00209] [Citation(s) in RCA: 238] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Nucleoside, nucleotide, and base analogs have been in the clinic for decades to treat both viral pathogens and neoplasms. More than 20% of patients on anticancer chemotherapy have been treated with one or more of these analogs. This review focuses on the chemical synthesis and biology of anticancer nucleoside, nucleotide, and base analogs that are FDA-approved and in clinical development since 2000. We highlight the cellular biology and clinical biology of analogs, drug resistance mechanisms, and compound specificity towards different cancer types. Furthermore, we explore analog syntheses as well as improved and scale-up syntheses. We conclude with a discussion on what might lie ahead for medicinal chemists, biologists, and physicians as they try to improve analog efficacy through prodrug strategies and drug combinations.
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Affiliation(s)
- Jadd Shelton
- Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine , 1760 Haygood Drive, NE, Atlanta, Georgia 30322, United States
| | - Xiao Lu
- Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine , 1760 Haygood Drive, NE, Atlanta, Georgia 30322, United States
| | - Joseph A Hollenbaugh
- Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine , 1760 Haygood Drive, NE, Atlanta, Georgia 30322, United States
| | - Jong Hyun Cho
- Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine , 1760 Haygood Drive, NE, Atlanta, Georgia 30322, United States
| | - Franck Amblard
- Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine , 1760 Haygood Drive, NE, Atlanta, Georgia 30322, United States
| | - Raymond F Schinazi
- Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine , 1760 Haygood Drive, NE, Atlanta, Georgia 30322, United States
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12
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Distinct catalytic activity and in vivo roles of the ExoIII and EndoIV AP endonucleases from Sulfolobus islandicus. Extremophiles 2016; 20:785-93. [PMID: 27457080 DOI: 10.1007/s00792-016-0867-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 07/12/2016] [Indexed: 10/21/2022]
Abstract
AP endonuclease cleaves the phosphodiester bond 5'- to the AP (apurinic or apyrimidinic) sites and is one of the major enzymes involved in base excision repair. So far, the properties of several archaeal AP endonuclease homologues have been characterized in vitro, but little is known about their functions in vivo. Herein, we report on the biochemical and genetic analysis of two AP endonucleases, SisExoIII and SisEndoIV, from the hyperthermophilic crenarchaeon Sulfolobus islandicus REY15A. Both SisExoIII and SisEndoIV exhibit AP endonuclease activity, but neither of them has 3'-5' exonuclease activity. SisExoIII and SisEndoIV have similar K M values on the substrate containing an AP site, but the latter cleaves the AP substrate at a dramatically higher catalytic rate than the former. Unlike other AP endonucleases identified in archaea, SisExoIII and SisEndoIV do not exhibit any cleavage activity on DNA having oxidative damage (8-oxo-dG) or uracil. Genetic analysis revealed that neither gene is essential for cell viability, and the growth of ∆SiRe_2666 (endoIV), ∆SiRe_0100 (exoIII), and ∆SiRe_0100∆SiRe_2666 is not affected under normal growth conditions. However, ∆SiRe_2666 exhibits higher sensitivity to the alkylating agent methyl methanesulfonate (MMS) than ∆SiRe_0100. Over-expression of SiRe_0100 can partially complement the sensitivity of ∆SiRe_2666 to MMS, suggesting a backup role of SisExoIII in AP site processing in vivo. Intriguingly, over-expression of SisEndoIV renders the strain more sensitive to MMS than the control. Taken together, we conclude that SisEndoIV, but not SisExoIII, is the main AP endonuclease that participates directly in base excision repair in S. islandicus.
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13
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Beaver JM, Lai Y, Xu M, Casin AH, Laverde EE, Liu Y. AP endonuclease 1 prevents trinucleotide repeat expansion via a novel mechanism during base excision repair. Nucleic Acids Res 2015; 43:5948-60. [PMID: 25990721 PMCID: PMC4499148 DOI: 10.1093/nar/gkv530] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 05/10/2015] [Indexed: 01/28/2023] Open
Abstract
Base excision repair (BER) of an oxidized base within a trinucleotide repeat (TNR) tract can lead to TNR expansions that are associated with over 40 human neurodegenerative diseases. This occurs as a result of DNA secondary structures such as hairpins formed during repair. We have previously shown that BER in a TNR hairpin loop can lead to removal of the hairpin, attenuating or preventing TNR expansions. Here, we further provide the first evidence that AP endonuclease 1 (APE1) prevented TNR expansions via its 3′-5′ exonuclease activity and stimulatory effect on DNA ligation during BER in a hairpin loop. Coordinating with flap endonuclease 1, the APE1 3′-5′ exonuclease activity cleaves the annealed upstream 3′-flap of a double-flap intermediate resulting from 5′-incision of an abasic site in the hairpin loop. Furthermore, APE1 stimulated DNA ligase I to resolve a long double-flap intermediate, thereby promoting hairpin removal and preventing TNR expansions.
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Affiliation(s)
- Jill M Beaver
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA Biochemistry Ph.D. Program, Florida International University, Miami, FL 33199, USA
| | - Yanhao Lai
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Meng Xu
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Astrid H Casin
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Eduardo E Laverde
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Yuan Liu
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA Biochemistry Ph.D. Program, Florida International University, Miami, FL 33199, USA Biomolecular Sciences Institute, School of Integrated Sciences and Humanities, Florida International University, Miami, FL 33199, USA
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14
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Abstract
SIGNIFICANCE Human apurinic/apyrimidinic endonuclease 1 (APE1, also known as REF-1) was isolated based on its ability to cleave at AP sites in DNA or activate the DNA binding activity of certain transcription factors. We review herein topics related to this multi-functional DNA repair and stress-response protein. RECENT ADVANCES APE1 displays homology to Escherichia coli exonuclease III and is a member of the divalent metal-dependent α/β fold-containing phosphoesterase superfamily of enzymes. APE1 has acquired distinct active site and loop elements that dictate substrate selectivity, and a unique N-terminus which at minimum imparts nuclear targeting and interaction specificity. Additional activities ascribed to APE1 include 3'-5' exonuclease, 3'-repair diesterase, nucleotide incision repair, damaged or site-specific RNA cleavage, and multiple transcription regulatory roles. CRITICAL ISSUES APE1 is essential for mouse embryogenesis and contributes to cell viability in a genetic background-dependent manner. Haploinsufficient APE1(+/-) mice exhibit reduced survival, increased cancer formation, and cellular/tissue hyper-sensitivity to oxidative stress, supporting the notion that impaired APE1 function associates with disease susceptibility. Although abnormal APE1 expression/localization has been seen in cancer and neuropathologies, and impaired-function variants have been described, a causal link between an APE1 defect and human disease remains elusive. FUTURE DIRECTIONS Ongoing efforts aim at delineating the biological role(s) of the different APE1 activities, as well as the regulatory mechanisms for its intra-cellular distribution and participation in diverse molecular pathways. The determination of whether APE1 defects contribute to human disease, particularly pathologies that involve oxidative stress, and whether APE1 small-molecule regulators have clinical utility, is central to future investigations.
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Affiliation(s)
- Mengxia Li
- Intramural Research Program, Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health , Baltimore, Maryland
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15
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Abstract
Troxacitabine (Troxatyl; BCH-4556; (-)-2'-deoxy-3'-oxacytadine) is the first synthetic l-nucleoside enantiomer to demonstrate broad spectrum cytotoxic activity. It was obtained by exchanging the sulphur endocyclic atom with oxygen in the structure of lamivudine, following the discovery that this agent had cytotoxic, as well as anti-viral activity. The unique "unnatural" stereochemistry of troxacitabine has produced impressive cytotoxic potency against a wide range of malignancies in the laboratory which led to its selection for clinical development. The initial trials with troxacitabine have established its efficacy in both solid and haematological malignancies, including those resistant to ara-C (cytarabine). This review will consider troxacitabine in terms of its pharmacology, mode of action, pharmacokinetics, tolerability and clinical efficacy.
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Affiliation(s)
- R Swords
- Department of Haematology, University College Hospital Galway, Galway, Ireland
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Alvarado Y, Kantarjian HM, Cortes JE, Apostolidou E, Bivins C, Giles FJ. Troxacitabine Activity in Extramedullary Myeloid Leukemia. Hematology 2013; 7:179-85. [PMID: 12243982 DOI: 10.1080/1024533021000008155] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Troxacitabine is a novel L-enantiomer nucleoside analog with unique properties in terms of its structure, pharmacokinetics, intracellular transport, and susceptibility to mechanisms of resistance. Troxacitabine has significant activity in patients with refractory myeloid leukemias, both as a single agent and when combined with standard anti-leukemia agents. In a cohort of 170 patients with refractory myeloid leukemia treated with troxacitabine-based regimens on Phase 1 or 2 studies, 10 (6%) had biopsy-proven extramedullary disease, either with or without bone marrow involvement. Six of these patients who received single-agent troxacitabine, 4 received a combination of troxacitabine and cytarabine. Complete response and disappearance of all extramedullary lesions were observed in 6 (60%) of these 10 patients. Two of the 6 responding patients relapsed within 3 months, 2 patients had remissions of 8 and 9 months duration, respectively, 1 patient is in on-going remission at 3, and 1 patient is lost to follow-up. Troxacitabine-based therapy had significant antileukemic activity in extramedullary myeloid leukemias and warrants further investigation in this clinical situation.
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Affiliation(s)
- Yesid Alvarado
- Department of Leukemia, M.D. Anderson Cancer Center, The University of Texas, Houston 77030, USA
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17
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Insight into mechanisms of 3'-5' exonuclease activity and removal of bulky 8,5'-cyclopurine adducts by apurinic/apyrimidinic endonucleases. Proc Natl Acad Sci U S A 2013; 110:E3071-80. [PMID: 23898172 DOI: 10.1073/pnas.1305281110] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
8,5'-cyclo-2'-deoxyadenosine (cdA) and 8,5'-cyclo-2'-deoxyguanosine generated in DNA by both endogenous oxidative stress and ionizing radiation are helix-distorting lesions and strong blocks for DNA replication and transcription. In duplex DNA, these lesions are repaired in the nucleotide excision repair (NER) pathway. However, lesions at DNA strand breaks are most likely poor substrates for NER. Here we report that the apurinic/apyrimidinic (AP) endonucleases--Escherichia coli Xth and human APE1--can remove 5'S cdA (S-cdA) at 3' termini of duplex DNA. In contrast, E. coli Nfo and yeast Apn1 are unable to carry out this reaction. None of these enzymes can remove S-cdA adduct located at 1 or more nt away from the 3' end. To understand the structural basis of 3' repair activity, we determined a high-resolution crystal structure of E. coli Nfo-H69A mutant bound to a duplex DNA containing an α-anomeric 2'-deoxyadenosine:T base pair. Surprisingly, the structure reveals a bound nucleotide incision repair (NIR) product with an abortive 3'-terminal dC close to the scissile position in the enzyme active site, providing insight into the mechanism for Nfo-catalyzed 3'→5' exonuclease function and its inhibition by 3'-terminal S-cdA residue. This structure was used as a template to model 3'-terminal residues in the APE1 active site and to explain biochemical data on APE1-catalyzed 3' repair activities. We propose that Xth and APE1 may act as a complementary repair pathway to NER to remove S-cdA adducts from 3' DNA termini in E. coli and human cells, respectively.
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Ruiz FM, Francis SM, Tintoré M, Ferreira R, Gil-Redondo R, Morreale A, Ortiz ÁR, Eritja R, Fàbrega C. Receptor-based virtual screening and biological characterization of human apurinic/apyrimidinic endonuclease (Ape1) inhibitors. ChemMedChem 2012; 7:2168-78. [PMID: 23109358 DOI: 10.1002/cmdc.201200372] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 09/26/2012] [Indexed: 12/25/2022]
Abstract
The endonucleolytic activity of human apurinic/apyrimidinic endonuclease (AP endo, Ape1) is a major factor in maintaining the integrity of the genome. Conversely, as an undesired effect, Ape1 overexpression has been linked to resistance to radio- and chemotherapeutic treatments in several human tumors. Inhibition of Ape1 using siRNA or the expression of a dominant negative form of the protein has been shown to sensitize cells to DNA-damaging agents, including various chemotherapeutic agents. Therefore, inhibition of the enzymatic activity of Ape1 might result in a potent antitumor therapy. A number of small molecules have been described as Ape1 inhibitors; however, those compounds are in the early stages of development. Herein we report the identification of new compounds as potential Ape1 inhibitors through a docking-based virtual screening technique. Some of the compounds identified have in vitro activities in the low-to-medium micromolar range. Interaction of these compounds with the Ape1 protein was observed by mass spectrometry. These molecules also potentiate the cytotoxicity of the chemotherapeutic agent methyl methanesulfonate in fibrosarcoma cells. This study demonstrates the power of docking and virtual screening techniques as initial steps in the design of new drugs, and opens the door to the development of a new generation of Ape1 inhibitors.
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Kelley MR, Georgiadis MM, Fishel ML. APE1/Ref-1 role in redox signaling: translational applications of targeting the redox function of the DNA repair/redox protein APE1/Ref-1. Curr Mol Pharmacol 2012; 5:36-53. [PMID: 22122463 DOI: 10.2174/1874467211205010036] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Revised: 08/18/2010] [Accepted: 08/25/2010] [Indexed: 12/22/2022]
Abstract
The heterogeneity of most cancers diminishes the treatment effectiveness of many cancer-killing regimens. Thus, treatments that hold the most promise are ones that block multiple signaling pathways essential to cancer survival. One of the most promising proteins in that regard is APE1, whose reduction-oxidation activity influences multiple cancer survival mechanisms, including growth, proliferation, metastasis, angiogenesis, and stress responses. With the continued research using APE1 redox specific inhibitors alone or coupled with developing APE1 DNA repair inhibitors it will now be possible to further delineate the role of APE1 redox, repair and protein-protein interactions. Previously, use of siRNA or over expression approaches, while valuable, do not give a clear picture of the two major functions of APE1 since both techniques severely alter the cellular milieu. Additionally, use of the redox-specific APE1 inhibitor, APX3330, now makes it possible to study how inhibition of APE1's redox signaling can affect multiple tumor pathways and can potentiate the effectiveness of existing cancer regimens. Because APE1 is an upstream effector of VEGF, as well as other molecules that relate to angiogenesis and the tumor microenvironment, it is also being studied as a possible treatment for agerelated macular degeneration and diabetic retinopathy. This paper reviews all of APE1's functions, while heavily focusing on its redox activities. It also discusses APE1's altered expression in many cancers and the therapeutic potential of selective inhibition of redox regulation, which is the subject of intense preclinical studies.
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Affiliation(s)
- Mark R Kelley
- Department of Pediatrics (Section of Hematology/Oncology), Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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20
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A genetic variant in the APE1/Ref-1 gene promoter -141T/G may modulate risk of glioblastoma in a Chinese Han population. BMC Cancer 2011; 11:104. [PMID: 21429202 PMCID: PMC3072948 DOI: 10.1186/1471-2407-11-104] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 03/23/2011] [Indexed: 01/03/2023] Open
Abstract
Background The human apurinic/apyrimidinic endonuclease 1/Redox effector factor-1 (APE1/Ref-1) is implicated in tumor development and progression. Recently, the APE1/Ref-1 promoter -141T/G variant (rs1760944) has been reported to be associated with lung cancer risk. Given the importance of APE1/Ref-1 in both DNA repair and redox activity, we speculate that the -141T/G polymorphism may confer individual susceptibility to gliomas or its subtypes. Methods The APE1/Ref-1 -141T/G polymorphism was analyzed in a case-control study including 766 glioma patients (among them 241 glioblastoma, 284 astrocytomas except for glioblastoma and 241 other gliomas) and 824 cancer-free controls from eastern China. Genotyping was performed with Sequenom MassARRAY iPLEX platform by use of allele-specific MALDI-TOF mass spectrometry assay. We estimated odds ratios (ORs) and 95% confidence intervals (95% CIs) using unconditional logistic regression. A test of trend was calculated using the genotype as an ordinal variable in the regression model. For each statistically significant association identified, we estimated the false positive reporting probability (FPRP). FPRP values less than 0.2 were consider to indicate robust associations. Results The significant association between the APE1/Ref-1 promoter -141T/G polymorphism and glioma risk was not observed. However, the stratified analysis by histology revealed the variant allele G significantly decreased glioblastoma risk (OR = 0.80, 95% CI = 0.65-0.98, P = 0.032). Individuals with the homozygous -141GG genotype exhibited 46% reduced risk of glioblastoma (adjusted OR = 0.54, 95% CI 0.34-0.87, P = 0.012), compared with the TT homozygote. This result remained robust given the prior probabilities of 25% (FPRP = 0.052) and 10% (FPRP = 0.140), but not with a prior probability of 1% (FPRP = 0.643). The P-associated with the trend test was 0.014. Conclusions Our results suggest that a specific genetic variant located in the APE1/Ref-1 promoter may modulate risk of glioblastoma, but not for other histological gliomas. Larger studies with more APE1 polymorphisms are required to validate these preliminary findings.
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21
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Wilson DM, Simeonov A. Small molecule inhibitors of DNA repair nuclease activities of APE1. Cell Mol Life Sci 2010; 67:3621-31. [PMID: 20809131 PMCID: PMC2956791 DOI: 10.1007/s00018-010-0488-2] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 07/28/2010] [Indexed: 10/19/2022]
Abstract
APE1 is a multifunctional protein that possesses several nuclease activities, including the ability to incise at apurinic/apyrimidinic (AP) sites in DNA or RNA, to excise 3'-blocking termini from DNA ends, and to cleave at certain oxidized base lesions in DNA. Pre-clinical and clinical data indicate a role for APE1 in the pathogenesis of cancer and in resistance to DNA-interactive drugs, particularly monofunctional alkylators and antimetabolites. In an effort to improve the efficacy of therapeutic compounds, such as temozolomide, groups have begun to develop high-throughput screening assays and to identify small molecule inhibitors against APE1 repair nuclease activities. It is envisioned that such inhibitors will be used in combinatorial treatment paradigms to enhance the efficacy of DNA-interactive drugs that introduce relevant cytotoxic DNA lesions. In this review, we summarize the current state of the efforts to design potent and selective inhibitors against APE1 AP site incision activity.
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Affiliation(s)
- David M Wilson
- Laboratory of Molecular Gerontology, Biomedical Research Center, National Institute on Aging, NIH, IRP, 251 Bayview Boulevard, Baltimore, MD 21224, USA
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22
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El-Kawy OA, Hashem AM, Amin MA, El-Wetery AS. Preparation and evaluation of [125I]troxacitabine: L-nucleoside model of a potential agent for tumor diagnosis and radiotherapy. J Labelled Comp Radiopharm 2010. [DOI: 10.1002/jlcr.1820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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23
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Abbotts R, Madhusudan S. Human AP endonuclease 1 (APE1): from mechanistic insights to druggable target in cancer. Cancer Treat Rev 2010; 36:425-35. [PMID: 20056333 DOI: 10.1016/j.ctrv.2009.12.006] [Citation(s) in RCA: 164] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 12/02/2009] [Accepted: 12/07/2009] [Indexed: 01/16/2023]
Abstract
DNA base excision repair (BER) is critically involved in the processing of DNA base damage induced by alkylating agents. Pharmacological inhibition of BER (using PARP inhibitors), either alone or in combination with chemotherapy has recently shown promise in clinical trials. Human apurinic/apyrimidinic endonuclease 1(APE1) is an essential BER protein that is involved in the processing of potentially cytotoxic abasic sites that are obligatory intermediates in BER. Here we provide a summary of the basic mechanistic role of APE1 in DNA repair and redox regulation and highlight preclinical and clinical data that confirm APE1 as a valid anticancer drug target. Development of small molecule inhibitors of APE1 is an area of intense research and current evidence using APE1 inhibitors has demonstrated potentiation of cytotoxicity of alkylating agents in preclinical models implying translational applications in cancer patients.
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Affiliation(s)
- Rachel Abbotts
- Translational DNA Repair Group, Laboratory of Molecular Oncology, Academic Unit of Oncology, School of Molecular Medical Sciences, University of Nottingham, Nottingham, UK
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24
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Abstract
The efficient turnover of messenger RNA represents an important mechanism that allows the cell to control gene expression. Until recently, the mechanism of mRNA decay was mainly attributed to exonucleases, comprising enzymes that degrade RNAs from the ends of the molecules. This article summarizes the endoribonucleases, comprising enzymes that cleave RNA molecules internally, which were identified in more recent years in eukaryotic mRNA metabolism. Endoribonucleases have received little attention in the past, based on the difficulty in their identification and a lack of understanding of their physiological significance. This review aims to compare the similarities and differences among this group of enzymes, as well as their known cellular functions. Despite the many differences in protein structure, and thus difficulties in identifying them based on amino acid sequence, most endoribonucleases possess essential cellular functions and have been shown to play an important role in mRNA turnover.
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Affiliation(s)
- Wai Ming Li
- Chemistry Program, University of Northern British Columbia, Prince George, BC, Canada
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25
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Parker WB. Enzymology of purine and pyrimidine antimetabolites used in the treatment of cancer. Chem Rev 2009; 109:2880-93. [PMID: 19476376 DOI: 10.1021/cr900028p] [Citation(s) in RCA: 388] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- William B Parker
- Southern Research Institute, 2000 Ninth Avenue, South Birmingham, Alabama 35205, USA.
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26
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Vose JM, Panwalkar A, Belanger R, Coiffier B, Baccarani M, Gregory SA, Facon T, Fanin R, Caballero D, Ben-Yehuda D, Giles F. A phase II multicenter study of troxacitabine in relapsed or refractory lymphoproliferative neoplasms or multiple myeloma. Leuk Lymphoma 2009; 48:39-45. [PMID: 17325846 DOI: 10.1080/10428190600909578] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Options for patients with relapsed/refractory lymphoproliferative disorders and multiple myeloma are currently limited. Troxacitabine has shown promise in preclinical studies in a variety of malignancies; hence, the current study was conducted to evaluate the activity of troxacitabine in relapsed or refractory lymphoid malignancies. This was a phase II, open-label, multinational, multicenter study of patients with relapsed or refractory lymphoproliferative disorders or multiple myeloma. Thirty-four adults were enrolled in the study and received the study drug at either 5.4 mg/m2 (n = 16) or 4.3 mg/m2 (n = 18). The dose was decided in a phase I study, during which dose escalation was carried to reach a maximum tolerated dose with an acceptable toxicity profile. Two separate phase I studies were performed in Europe and the US. Troxacitabine was administered by intravenous infusion over 30 min daily for days 1 - 5 every 4 weeks. Treatment was continued to disease progression or until the subjects met criteria for withdrawal or unacceptable toxicities were evident as outlined in the protocol. Two patients had a partial response (PR) to treatment with troxacitabine to yield an overall response rate of 13%. There were no complete responses seen with the drug. Stable disease was achieved in 15 patients (44%). All patients had at least one treatment related adverse event, which led to six withdrawals from the study. Hematologic toxicity constituted the most common adverse events. Serious adverse effects were seen in 62% of patients. None of the 13 deaths were attributed directly to troxacitabine. As a single agent, troxacitabine has limited benefit in patients with advanced lymphoproliferative disorders or multiple myeloma. Future studies will be needed to address modified dosing according to emerging pharmacokinetic and pharmacodynamic data and combination therapy which may lead to improved clinical benefit for troxacitabine in hematologic malignancies.
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Affiliation(s)
- Julie M Vose
- University of Nebraska Medical Center, Omaha, NE 68198-7680, USA.
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27
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Timofeyeva NA, Koval VV, Knorre DG, Zharkov DO, Saparbaev MK, Ishchenko AA, Fedorova OS. Conformational dynamics of human AP endonuclease in base excision and nucleotide incision repair pathways. J Biomol Struct Dyn 2009; 26:637-52. [PMID: 19236113 DOI: 10.1080/07391102.2009.10507278] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
APE1 is a multifunctional enzyme that plays a central role in base excision repair (BER) of DNA. APE1 is also involved in the alternative nucleotide incision repair (NIR) pathway. We present an analysis of conformational dynamics and kinetic mechanisms of the full-length APE1 and truncated NDelta61-APE1 lacking the N-terminal 61 amino acids (REF1 domain) in BER and NIR pathways. The action of both enzyme forms were described by identical kinetic schemes, containing four stages corresponding to formation of the initial enzyme-substrate complex and isomerization of this complex; when a damaged substrate was present, these stages were followed by an irreversible catalytic stage resulting in the formation of the enzyme-product complex and the equilibrium stage of product release. For the first time we showed, that upon binding AP-containing DNA, the APE1 structure underwent conformational changes before the chemical cleavage step. Under BER conditions, the REF1 domain of APE1 influenced the stability of both the enzyme-substrate and enzyme-product complexes, as well as the isomerization rate, but did not affect the rates of initial complex formation or catalysis. Under NIR conditions, the REF1 domain affected both the rate of formation and the stability of the initial complex. In comparison with the full-length protein, NDelta61-APE1 did not display a decrease in NIR activity with a dihydrouracil-containing substrate. BER conditions decrease the rate of catalysis and strongly inhibit the rate of isomerization step for the NIR substrates. Under NIR conditions AP-endonuclease activity is still very efficient.
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Affiliation(s)
- N A Timofeyeva
- Institute of Chemical Biology and Fundamental Medicine, Novosibirsk State University, Russia.
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28
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McNeill DR, Lam W, DeWeese TL, Cheng YC, Wilson DM. Impairment of APE1 function enhances cellular sensitivity to clinically relevant alkylators and antimetabolites. Mol Cancer Res 2009; 7:897-906. [PMID: 19470598 DOI: 10.1158/1541-7786.mcr-08-0519] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Base excision repair (BER) is the major pathway for removing mutagenic and cytotoxic oxidative and alkylation DNA modifications. Using a catalytically inactive, dominant negative protein form of human APE1, termed ED, which binds with high affinity to substrate DNA and blocks subsequent repair steps, we assessed the role of BER in mediating cellular resistance to clinically relevant alkylating drugs and antimetabolites. Colony formation assays revealed that ED expression enhanced cellular sensitivity to melphalan not at all; to decarbazine, thiotepa, busulfan and carmustine moderately (1.2- to 2.4-fold); and to streptozotocin and temozolomide significantly (2.0- to 5.3-fold). The effectiveness of ED to promote enhanced cytotoxicity generally correlated with the agent's (a) monofunctional nature, (b) capacity to induce N(7)-guanine and N(3)-adenine modifications, and (c) inability to generate O(6)-guanine adducts or DNA cross-links. ED also enhanced the cell killing potency of the antimetabolite troxacitabine, apparently by blocking the processing of DNA strand breaks, yet had no effect on the cytotoxicity of gemcitabine, results that agree well with the known efficiency of APE1 to excise these nucleoside analogues from DNA. Most impressively, ED expression produced an approximately 5- and 25-fold augmentation of the cell killing effect of 5-fluorouracil and 5-fluorodeoxyuridine, respectively, implicating BER in the cellular response to such antimetabolites; the increased 5-fluorouracil sensitivity was associated with an accumulation of abasic sites and active caspase-positive staining. Our data suggest that APE1, and BER more broadly, is a potential target for inactivation in anticancer treatment paradigms that involve select alkylating agents or antimetabolites.
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Affiliation(s)
- Daniel R McNeill
- Biomedical Research Center, National Institute on Aging, NIH, Baltimore, MD 21224, USA
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29
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Lin CC, Beeram M, Rowinsky EK, Takimoto CH, Ng CM, Geyer CE, Denis LJ, De Bono JS, Hao D, Tolcher AW, Rha SY, Jolivet J, Patnaik A. Phase I and pharmacokinetic study of cisplatin and troxacitabine administered intravenously every 28 days in patients with advanced solid malignancies. Cancer Chemother Pharmacol 2009; 65:167-75. [DOI: 10.1007/s00280-009-1020-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Accepted: 04/27/2009] [Indexed: 10/20/2022]
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30
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Abstract
The DNA base excision repair (BER) pathway repairs alkylation and oxidative DNA damage caused by endogenous and exogenous agents, including chemotherapeutic agents. Upon removal of the damaged base AP endonuclease 1 (Ape1), a critical component of the pathway cleaves the abasic site to facilitate repair. Ape1 is a multifunctional protein which plays a role not only in DNA repair but it also functions as a reduction-oxidation factor, known as Ref-1 in the literature, to increase the DNA binding ability of several transcription factors involved in different growth signaling pathways. Elevated levels of Ape1 have been linked to resistance to chemotherapy, poor prognosis, and poor survival. Reducing the amount of Ape1 protein in cancer cells and tumors using RNA interference and anti-sense oligonucleotide technology sensitizes mammalian tumor cells to a variety of laboratory and chemotherapeutic agents. Therefore, selective inhibition of Ape1's DNA repair activity is a promising avenue to develop novel cancer therapeutics.
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Affiliation(s)
- Aditi Bapat
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA
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31
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Lam W, Bussom S, Cheng YC. Effect of hypoxia on the expression of phosphoglycerate kinase and antitumor activity of troxacitabine and gemcitabine in non-small cell lung carcinoma. Mol Cancer Ther 2009; 8:415-23. [PMID: 19208827 DOI: 10.1158/1535-7163.mct-08-0692] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Beta-L-dioxolane-cytidine (L-OddC; BCH-4556; troxacitabine), a novel L-configuration deoxycytidine analogue, was under clinical trials for treating cancer. The cytotoxicity of L-OddC is dependent on its phosphorylation to L-OddCTP by phosphoglycerate kinase (PGK) and its subsequent addition into nuclear DNA. Because PGK is induced with hypoxia, the expression of hypoxia-inducible factor-1alpha and PGK of H460 cells (human non-small cell lung carcinoma) in vitro and in vivo was studied. In culture, hypoxic treatment induced the protein expression of PGK by 3-fold but had no effect on the protein expression of other L-OddC metabolism-associated enzymes such as apurinic/apyrimidinic endonuclease-1, deoxycytidine kinase, CMP kinase, and nM23 H1. Using a clonogenic assay, hypoxic treatment of H460 cells rendered cells 4-fold more susceptible to L-OddC but not to gemcitabine (dFdC) following exposure to drugs for one generation. Using hypoxia response element-luciferase reporter system, Western blotting, and immunohistochemistry, it was found that hypoxia-inducible factor-1alpha and PGK expression increased and could be correlated to tumor size. Despite dFdC being more toxic than L-OddC in cell culture, L-OddC (300 mg/kg i.p.) had a stronger antitumor activity than dFdC in H460 xenograft-bearing nude mice. Furthermore, L-OddC retained approximately 50% of its antitumor activity with oral gavage compared with i.p. delivery. Oral administration of L-OddC (600 mg/kg p.o.) had a similar area under the curve value compared with i.p. injection of dFdC (300 mg/kg i.p.). In conclusion, the hypoxia, which commonly exists in non-small cell lung carcinoma or other solid tumors resistant to radiotherapy or chemotherapy, is a favorable determinant to enhance the antitumor activity of L-OddC in vivo.
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Affiliation(s)
- Wing Lam
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510, USA
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Abstract
Nucleoside analogs are structurally similar antimetabolites that have a broad range of action and are clinically active in both solid tumors and hematological malignancies. Many of these agents are incorporated into DNA by polymerases during normal DNA synthesis, an action that blocks further extension of the nascent strand and causes stalling of replication forks. The molecular mechanisms that sense stalled replication forks activate cell cycle checkpoints and DNA repair processes, which may contribute to drug resistance. When replication forks are not stabilized by these molecules or when subsequent DNA repair processes are overwhelmed, apoptosis is initiated either by these same DNA damage sensors or by alternative mechanisms. Recently, strategies aimed at targeting DNA damage checkpoints or DNA repair processes have demonstrated effectiveness in sensitizing cells to nucleoside analogs, thus offering a means to elude drug resistance. In addition to their DNA synthesis-directed actions many nucleoside analogs trigger apoptosis by unique mechanisms, such as causing epigenetic modifications or by direct activation of the apoptosome. A review of the cellular and molecular responses to clinically relevant agents provides an understanding of the mechanisms that cause apoptosis and may provide rationale for the development of novel therapeutic strategies.
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Luo M, Delaplane S, Jiang A, Reed A, He Y, Fishel M, Nyland RL, Borch RF, Qiao X, Georgiadis MM, Kelley MR. Role of the multifunctional DNA repair and redox signaling protein Ape1/Ref-1 in cancer and endothelial cells: small-molecule inhibition of the redox function of Ape1. Antioxid Redox Signal 2008; 10:1853-67. [PMID: 18627350 PMCID: PMC2587278 DOI: 10.1089/ars.2008.2120] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The DNA base excision-repair pathway is responsible for the repair of DNA damage caused by oxidation/alkylation and protects cells against the effects of endogenous and exogenous agents. Removal of the damaged base creates a baseless (AP) site. AP endonuclease1 (Ape1) acts on this site to continue the BER-pathway repair. Failure to repair baseless sites leads to DNA strand breaks and cytotoxicity. In addition to the repair role of Ape1, it also functions as a major redox-signaling factor to reduce and activate transcription factors such as AP1, p53, HIF-1alpha, and others that control the expression of genes important for cell survival and cancer promotion and progression. Thus, the Ape1 protein interacts with proteins involved in DNA repair, growth-signaling pathways, and pathways involved in tumor promotion and progression. Although knockdown studies with siRNA have been informative in studying the role of Ape1 in both normal and cancer cells, knocking down Ape1 does not reveal the individual role of the redox or repair functions of Ape1. The identification of small-molecule inhibitors of specific Ape1 functions is critical for mechanistic studies and translational applications. Here we discuss small-molecule inhibition of Ape1 redox and its effect on both cancer and endothelial cells.
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Affiliation(s)
- Meihua Luo
- Department of Pediatrics (Section of Hematology/Oncology), Herman B Wells Center for Pediatric Research, Indianapolis, Indiana 46202, USA
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Characterization of a Bacillus subtilis 64-kDa DNA polymerase X potentially involved in DNA repair. J Mol Biol 2008; 384:1019-28. [PMID: 18938175 DOI: 10.1016/j.jmb.2008.09.081] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 09/18/2008] [Accepted: 09/26/2008] [Indexed: 11/20/2022]
Abstract
Bacillus subtilis gene yshC encodes a 64-kDa family X DNA polymerase (PolXBs), which contains all the critical residues involved in DNA and nucleotide binding as well as those responsible for catalysis of DNA polymerization, conserved in most family X members. Biochemical analyses of the purified enzyme indicate that PolXBs is a monomeric and strictly template-directed DNA polymerase, preferentially acting on DNA structures containing gaps from one to a few nucleotides and bearing a phosphate group at the 5' end of the downstream DNA. The fact that PolXBs is able to conduct filling of a single-nucleotide gap, allowing further sealing of the resulting nick by a DNA ligase, points to a putative role in base excision repair during the B. subtilis life cycle.
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Ewald B, Sampath D, Plunkett W. ATM and the Mre11-Rad50-Nbs1 complex respond to nucleoside analogue-induced stalled replication forks and contribute to drug resistance. Cancer Res 2008; 68:7947-55. [PMID: 18829552 PMCID: PMC2631429 DOI: 10.1158/0008-5472.can-08-0971] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The Mre11-Rad50-Nbs1 complex and autophosphorylated Ser(1981)-ATM are involved in recognizing and repairing DNA damage, such as double-strand breaks (DSB). However, the role of these factors in response to stalled replication forks is not clear. Nucleoside analogues are agents that are incorporated into DNA during replication, which cause stalling of replication forks. The molecular mechanisms that sense these events may signal for DNA repair and contribute to survival but are poorly understood. Cellular responses to both DSBs and stalled replication forks are marked by H2AX phosphorylation on Ser(139) (gamma-H2AX), which forms nuclear foci at sites of DNA damage. Here, concentrations of the nucleoside analogues 1-beta-d-arabinofuranosylcytosine (cytarabine; ara-C), gemcitabine, and troxacitabine, which inhibited DNA synthesis by 90% within 2 hours, were determined for each agent. Using gamma-H2AX as a marker for changes in chromatin structure, we show that Mre11, Rad50, Nbs1, and phosphorylated ATM respond to nucleoside analogue-induced stalled replication forks by forming nuclear foci that colocalize with gamma-H2AX within 2 hours. Because neither DSBs nor single-strand breaks were detectable after nucleoside analogue exposure, we conclude that this molecular response is not due to the presence of DNA breaks. Deficiencies in ATM, Mre11, or Rad50 led to a 2- to 5-fold increase in clonogenic sensitization to gemcitabine, whereas Nbs1 and H2AX deficiency did not affect reproductive growth. Taken together, these results suggest that ATM, Mre11, and Rad50 are required for survival after replication fork stalling, whereas Nbs1 and H2AX are inconsequential.
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Affiliation(s)
- Brett Ewald
- Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas and The University of Texas Health Science Center at Houston Graduate School of Biomedical Sciences, Houston, Texas
| | - Deepa Sampath
- Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas and The University of Texas Health Science Center at Houston Graduate School of Biomedical Sciences, Houston, Texas
| | - William Plunkett
- Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas and The University of Texas Health Science Center at Houston Graduate School of Biomedical Sciences, Houston, Texas
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Dyrkheeva NS, Khodyreva SN, Lavrik OI. [Quantitative parameters of the 3'-5'-exonuclease reaction of human apurinic/apyrimidinic endonuclease 1 and DNA with single-strand breaks containing dYMP or their modified analogues]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2008; 34:210-9. [PMID: 18522277 DOI: 10.1134/s1068162008020088] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Human apurinic/apyrimidinic (AP) endonuclease 1 (APE1) is a multifunctional enzyme. In addition to its main AP endonuclease activity, the cleavage of DNA 5' to the AP site, it displays other weak enzymatic activities. One of them is 3'-5' exonuclease activity, which is most effectively pronounced for DNA duplexes containing modified or mismatched nucleotides at the 3' end of the primer chain. There is a presumption that APE1 can correct the DNA synthesis catalyzed by DNA polymerase beta during the base excision repair process. We determined the quantitative parameters of the 3'-5' exonuclease reaction in dependence on the reaction conditions to reveal the detailed mechanism of this process. The kinetic parameters of APE1 exonuclease excision of mismatched dCMP and dTMP from the 3' terminus of single-strand DNA and from photoreactive dCMP analogues applied for photoaffinity modification of proteins and DNA in recombinant systems and cell/nuclear extracts were determined. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2008, vol. 34, no. 2; see also http://www.maik.ru.
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Kelley MR, Fishel ML. DNA repair proteins as molecular targets for cancer therapeutics. Anticancer Agents Med Chem 2008; 8:417-25. [PMID: 18473726 DOI: 10.2174/187152008784220294] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cancer therapeutics include an ever-increasing array of tools at the disposal of clinicians in their treatment of this disease. However, cancer is a tough opponent in this battle and current treatments which typically include radiotherapy, chemotherapy and surgery are not often enough to rid the patient of his or her cancer. Cancer cells can become resistant to the treatments directed at them and overcoming this drug resistance is an important research focus. Additionally, increasing discussion and research is centering on targeted and individualized therapy. While a number of approaches have undergone intensive and close scrutiny as potential approaches to treat and kill cancer (signaling pathways, multidrug resistance, cell cycle checkpoints, anti-angiogenesis, etc.), much less work has focused on blocking the ability of a cancer cell to recognize and repair the damaged DNA which primarily results from the front line cancer treatments; chemotherapy and radiation. More recent studies on a number of DNA repair targets have produced proof-of-concept results showing that selective targeting of these DNA repair enzymes has the potential to enhance and augment the currently used chemotherapeutic agents and radiation as well as overcoming drug resistance. Some of the targets identified result in the development of effective single-agent anti-tumor molecules. While it is inherently convoluted to think that inhibiting DNA repair processes would be a likely approach to kill cancer cells, careful identification of specific DNA repair proteins is increasingly appearing to be a viable approach in the cancer therapeutic cache.
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Affiliation(s)
- Mark R Kelley
- Department of Pediatrics, Section of Hematology/Oncology, Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, 1044 W Walnut St. R4-W302C, Indianapolis, IN 46202, USA.
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Chimeric adenoviral vector Ad5/F35-mediated APE1 siRNA enhances sensitivity of human colorectal cancer cells to radiotherapy in vitro and in vivo. Cancer Gene Ther 2008; 15:625-35. [DOI: 10.1038/cgt.2008.30] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Dyrkheeva NS, Khodyreva SN, Lavrik OI. Interaction of APE1 and other repair proteins with DNA duplexes imitating intermediates of DNA repair and replication. BIOCHEMISTRY (MOSCOW) 2008; 73:261-72. [PMID: 18393760 DOI: 10.1134/s0006297908030048] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Interactions of APE1 (human apurinic/apyrimidinic endonuclease 1) and DNA polymerase beta with various DNA structures imitating intermediates of DNA repair and replication were investigated by gel retardation and photoaffinity labeling. Photoaffinity labeling of APE1 and DNA polymerase beta was accomplished by DNA containing photoreactive group at the 3 -end in mouse embryonic fibroblast (MEF) cell extract or for purified proteins. On the whole, modification efficiency was the same for MEF-extract proteins and for purified APE1 and DNA polymerase beta depending on the nature of the 5 -group of a nick/gap in the DNA substrate. Some of DNA duplexes used in this work can be considered as short-patch (DNA with the 5 -phosphate group in the nick/gap) or long-patch (DNA containing 5 -sugar phosphate or 5 -flap) base excision repair (BER) intermediates. Other DNA duplexes (3 -recessed DNA and DNA with the 5 -hydroxyl group in the nick/gap) have no relation to intermediates forming in the course of BER. As shown by both methods, APE1 binds with the highest efficiency to DNA substrate containing 5 -sugar phosphate group in the nick/gap, whereas DNA polymerase beta binds to DNA duplex with a mononucleotide gap flanked by the 5 -p group. When APE1 and DNA polymerase beta are both present, a ternary complex APE1-DNA polymerase beta-DNA is formed with the highest efficiency with DNA product of APE1 endonuclease activity and with DNA containing 5 -flap or mononucleotide-gapped DNA with 5 -p group. It was found that APE1 stimulates DNA synthesis catalyzed by DNA polymerase beta, and a human X-ray repair cross-complementing group 1 protein (XRCC1) stimulates APE1 3 -5 exonuclease activity on 3 -recessed DNA duplex.
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Affiliation(s)
- N S Dyrkheeva
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, pr. Lavrentieva 8, Novosibirsk, Russia.
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40
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Wang Y, Liu X, Matsuda A, Plunkett W. Repair of 2′-C-Cyano-2′-Deoxy-1-β-d-arabino-Pentofuranosylcytosine–Induced DNA Single-Strand Breaks by Transcription-Coupled Nucleotide Excision Repair. Cancer Res 2008; 68:3881-9. [DOI: 10.1158/0008-5472.can-07-6885] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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41
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Adema AD, Radi M, Daft J, Narayanasamy J, Hoebe EK, Alexander LE, Chu CK, Peters GJ. Troxacitabine prodrugs for pancreatic cancer. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2008; 26:1073-7. [PMID: 18058539 DOI: 10.1080/15257770701515591] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Troxacitabine is a cytotoxic deoxycytidine analogue with an unnatural L-configuration, which is activated by deoxycytidine kinase (dCK). The configuration is responsible for differences in the uptake and metabolism of troxacitabine compared to other deoxynucleoside analogues. The main drawback in the use of most nucleoside anticancer agents originates from their hydrophilic nature, which property requires a high and frequent dosage for an intravenous administration. To overcome this problem several troxacitabine prodrugs modified in the aminogroup with a linear aliphatic chain with a higher lipophilicity were developed. To determine whether these prodrugs have an advantage over Troxacitabine pancreatic cancer cell lines were exposed to Troxacitabine and the lipophilic prodrugs. The addition of linear aliphatic chains to troxacitabine increased sensitivity of pancreatic cancer cell lines to the drug > 100-fold, possibly due to a better uptake and retention of the drug.
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Affiliation(s)
- A D Adema
- Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands
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42
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Wilson DM. Processing of nonconventional DNA strand break ends. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2007; 48:772-782. [PMID: 17948279 DOI: 10.1002/em.20346] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Single-strand breaks (SSBs) are one of the most common forms of genetic damage, arising from attack of DNA by reactive oxygen species or as intended or inadvertent products of normal cellular DNA metabolic events. Recent evidence linking defects in the enzymatic processing of nonconventional DNA SSBs, i.e., lesions incompatible with polymerase or ligase reactions, with inherited neurodegenerative disorders, reveals the importance of SSB repair in disease manifestation. I review herein the major eukaryotic enzymes (with an emphasis on the human proteins) responsible for the "clean-up" of DNA breaks harboring 3'- or 5'-blocking termini, and the cellular and disease ramifications of unrepaired SSB damage.
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Affiliation(s)
- David M Wilson
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, Baltimore, MD 21224, USA.
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43
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Wang D, Zhong ZY, Li MX, Xiang DB, Li ZP. Vector-based Ape1 small interfering RNA enhances the sensitivity of human osteosarcoma cells to endostatin in vivo. Cancer Sci 2007; 98:1993-2001. [PMID: 17892509 PMCID: PMC11159197 DOI: 10.1111/j.1349-7006.2007.00616.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Osteosarcoma is a highly vascular and extremely destructive malignancy, and the survival of patients with osteosarcoma has not improved significantly in recent years. Antiangiogenic therapy currently holds great potential in conjunction with conventional treatment modalities for osteosarcoma. However, there are examples of gradual loss of response, and perhaps acquired resistance to antiangiogenic drugs. The acquired resistance of antiangiogenesis may be associated with a lot of hypoxia-response genes. The human apurinic/apyrimidinic endonuclease (Ape1) protein, a bifunctional redox factor and apurinic/apyrimidinic (AP) endonuclease, plays a crucial role in protecting against cell death due to hypoxia. We therefore hypothesized that Ape1 may contribute to the resistance of antiangiogenic therapy. To investigate the effect of Ape1 on the sensitivity of human osteosarcoma cells to endostatin, we constructed an Ape1 small interfering RNA expression vector, pSilenceApe1. Transfection of human osteosarcoma 9901 and HOS cells with pSilenceApe1 resulted in a dose-dependent loss of Ape1 protein. pSilenceApe1 also significantly suppressed the expression of vascular endothelial growth factor (VEGF) protein in the 9901 cells. Combined treatment with pSilenceApe1 and recombinant human endostatin (rhES) showed potent antiangiogenic effects in the transwell chamber invasion assay. Then, 20 nude mice bearing 9901 xenografts were divided into four groups: the phosphate-buffered saline treatment control group; the rhES treatment group (1.5 mg/kg, daily); the pSilenceApe1 treatment group (20 microg, once every 3 days); and the combination of rhES and pSilenceApe1 treatment group. pSilenceApe1 significantly suppressed the expression of Ape1 and VEGF protein in the 9901 xenografts. The tumor-inhibition rate of the pSilenceApe1, rhES, and combination of rhES and pSilenceApe1 treatment groups was 38.23, 35.29, and 62.18%, respectively. Furthermore, a significant decrease in microvessel density with an increase in apoptosis was observed following combined treatment with pSilenceApe1 and rhES, compared with control and either agent alone in 9901 xenografts. These results indicate that Ape1 small interfering RNA could enhance the sensitivity of osteosarcoma cells to endostatin.
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Affiliation(s)
- Dong Wang
- Cancer Center, and Department of Pathology, Daping Hospital and Research Institute of Surgery, Third Military Medical University, Chongqing 400042, China.
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44
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Vidal AE, Harkiolaki M, Gallego C, Castillo-Acosta VM, Ruiz-Pérez LM, Wilson K, González-Pacanowska D. Crystal Structure and DNA Repair Activities of the AP Endonuclease from Leishmania major. J Mol Biol 2007; 373:827-38. [PMID: 17870086 DOI: 10.1016/j.jmb.2007.08.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Revised: 07/24/2007] [Accepted: 08/01/2007] [Indexed: 12/31/2022]
Abstract
Apurinic/apyrimidinic endonucleases initiate the repair of abasic sites produced either spontaneously, from attack of bases by reactive oxygen species or as intermediates during base excision repair. The catalytic properties and crystal structure of Leishmania major apurinic/apyrimidinic endonuclease are described and compared with those of human APE1 and bacterial exonuclease III. The purified enzyme is shown to possess apurinic/apyrimidinic endonuclease activity of the same order as eukaryotic and prokaryotic counterparts and an equally robust 3'-phosphodiesterase activity. Consistent with this, expression of the L. major endonuclease confers resistance to both methyl methane sulphonate and H2O2 in Escherichia coli repair-deficient mutants while expression of the human homologue only reverts methyl methane sulphonate sensitivity. Structural analyses and modelling of the enzyme-DNA complex demonstrates a high degree of conservation to previously characterized homologues, although subtle differences in the active site geometry might account for the high 3'-phosphodiesterase activity. Our results confirm that the L. major's enzyme is a key element in mediating repair of apurinic/apyrimidinic sites and 3'-blocked termini and therefore must play an important role in the survival of kinetoplastid parasites after exposure to the highly oxidative environment within the host macrophage.
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Affiliation(s)
- Antonio E Vidal
- Instituto de Parasitología y Biomedicina López-Neyra, Consejo Superior de Investigaciones Científicas, Avda. del Conocimiento s/n, 18100 Armilla, Granada, Spain
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Chen MJ, Dumitrache LC, Wangsa D, Ma SM, Padilla-Nash H, Ried T, Hasty P. Cisplatin depletes TREX2 and causes Robertsonian translocations as seen in TREX2 knockout cells. Cancer Res 2007; 67:9077-83. [PMID: 17909011 DOI: 10.1158/0008-5472.can-07-1146] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cisplatin, an anticancer drug, forms DNA interstrand cross-links (ICL) that interfere with replication, whereas TREX2 is a 3'-->5' exonuclease that removes 3' mismatched nucleotides and promotes cellular proliferation. Here, we show that TREX2 is depleted in human cells derived from cancer after exposure to cisplatin but not other genotoxins including another cross-linking agent, mitomycin C (MMC), indicating a potential role for TREX2 depletion in cisplatin-induced cytotoxicity. To better understand TREX2 cellular function, we deleted TREX2 in mouse embryonic stem (ES) cells by gene targeting and find these cells exhibit reduced proliferation and gross chromosomal rearrangements including Robertsonian translocations (RbT). Quite interestingly, ES cells exposed to cisplatin also exhibit RbTs. By contrast, RbTs are not observed for ES cells exposed to MMC, indicating that RbTs are not caused by ICLs but instead TREX2 depletion by either cisplatin exposure or mutation. Taken together, our results show that cisplatin depletes TREX2 and causes genomic instability that is similarly observed in TREX2-mutant cells. Thus, cisplatin has two potential cytotoxic activities: (a) the generation of ICLs and (b) the depletion of TREX2.
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Affiliation(s)
- Ming-Jiu Chen
- Department of Molecular Medicine/Institute of Biotechnology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78245-3207, USA
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Synergistic activity of troxacitabine (Troxatyl) and gemcitabine in pancreatic cancer. BMC Cancer 2007; 7:121. [PMID: 17608948 PMCID: PMC1948004 DOI: 10.1186/1471-2407-7-121] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Accepted: 07/03/2007] [Indexed: 11/10/2022] Open
Abstract
Background Gemcitabine, a deoxycytidine nucleoside analog, is the current standard chemotherapy used as first-line treatment for patients with locally advanced or metastatic cancer of the pancreas, and extends life survival by 5.7 months. Advanced pancreatic cancer thus remains a highly unmet medical need and new therapeutic agents are required for this patient population. Troxacitabine (Troxatyl™) is the first unnatural L-nucleoside analog to show potent preclinical antitumor activity and is currently under clinical investigation. Troxacitabine was recently evaluated as a first-line therapy in 54 patients with advanced adenocarcinoma of the pancreas and gave comparable overall results to those reported with gemcitabine in recently published randomized trials. Methods The human pancreatic adenocarcinoma cell lines, AsPC-1, Capan-2, MIA PaCa-2 and Panc-1, were exposed to troxacitabine or gemcitabine alone or in combination, for 72 h, and the effects on cell growth were determined by electronic particle counting. Synergistic efficacy was determined by the isobologram and combination-index methods of Chou and Talalay. Mechanistic studies addressed incorporation of troxacitabine into DNA and intracellular levels of troxacitabine and gemcitabine metabolites. For in vivo studies, we evaluated the effect of both drugs, alone and in combination, on the growth of established human pancreatic (AsPC-1) tumors implanted subcutaneously in nude mice. Statistical analysis was calculated by a one-way ANOVA with Dunnett as a post-test and the two-tailed unpaired t test using GraphPad prism software. Results Synergy, evaluated using the CalcuSyn Software, was observed in all four cell-lines at multiple drug concentrations resulting in combination indices under 0.7 at Fa of 0.5 (50% reduction of cell growth). The effects of drug exposures on troxacitabine and gemcitabine nucleotide pools were analyzed, and although gemcitabine reduced phosphorylation of troxacitabine when cells were exposed at equal drug concentrations, there was no effect on phosphorylated pools at drug combinations that were synergistic. The amount of troxacitabine incorporated into DNA was also not affected by the presence of gemcitabine. In vivo testing against a human pancreatic (AsPC-1) xenograft mouse tumor model indicated that both drugs were more than additive at well-tolerated doses and schedule. The biological basis for this synergy is unclear as we did not observe changes in apoptosis, DNA repair, troxacitabine incorporation into DNA or troxacitabine metabolism in the presence of gemcitabine. Conclusion These data, together with phase I clinical data showing tolerability of both agents when combined, suggest combination therapy with troxacitabine and gemcitabine warrants further evaluation in advanced pancreatic cancer patients.
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Lam W, Leung CH, Bussom S, Cheng YC. The Impact of Hypoxic Treatment on the Expression of Phosphoglycerate Kinase and the Cytotoxicity of Troxacitabine and Gemcitabine. Mol Pharmacol 2007; 72:536-44. [PMID: 17565005 DOI: 10.1124/mol.106.033472] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
beta-L-Dioxolane-cytidine (L-OddC, Troxacitabine, BCH-4556), a novel L-configuration deoxycytidine analog, is under clinical trials for treating cancer. The cytotoxicity of L-OddC is dependent on the amount of the triphosphate form (L-OddCTP) in nuclear DNA. Phosphoglycerate kinase (PGK), a downstream protein of hypoxia-inducible-factor-1alpha (HIF-1alpha), is responsible for the phosphorylation of the diphosphate to the triphosphate of L-OddC. In this study, we studied the impact of hypoxia on the metabolism and the cytotoxicity of L-OddC and beta-d-2',2'-difluorodeoxycytidine (dFdC) in several human tumor cell lines including HepG2, Hep3B, A673, Panc-1, and RKO. Hypoxic treatment induced the protein expression of PGK 3-fold but had no effect on the protein expression of APE-1, dCK, CMPK, and nM23 H1. Hypoxic treatment increased L-OddCTP formation and incorporation of L-OddC into DNA, but it decreased the uptake and incorporation of dFdC, which correlated with the reduction of hENT1, hENT2, and hCNT2 expression. Using a clonogenic assay, hypoxic treatment of cells made them 2- to 3-fold more susceptible to L-OddC but not to dFdC after exposure to drugs for one generation. Dimethyloxallyl glycine enhanced the cytotoxicity of L-OddC but not dFdC in Panc-1 cells under normoxic conditions. Overexpression or down-regulation of PGK using transient transfection of pcDNA5-PGK or inducible shRNA in RKO cells affected the cytotoxicity of L-OddC but not that of dFdC. The knockdown of HIF-1alpha in inducible shRNA in RKO cells reduced the cytotoxicity of L-OddC but not dFdC under hypoxic conditions. In conclusion, hypoxia is an important factor that may potentiate the activity of L-OddC.
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Affiliation(s)
- Wing Lam
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
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48
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Dyrkheeva NS, Khodyreva SN, Lavrik OI. Multifunctional human apurinic/apyrimidinic endonuclease 1: Role of additional functions. Mol Biol 2007. [DOI: 10.1134/s0026893307030065] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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49
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Fishel ML, Kelley MR. The DNA base excision repair protein Ape1/Ref-1 as a therapeutic and chemopreventive target. Mol Aspects Med 2007; 28:375-95. [PMID: 17560642 DOI: 10.1016/j.mam.2007.04.005] [Citation(s) in RCA: 205] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Accepted: 04/15/2007] [Indexed: 10/23/2022]
Abstract
With our growing understanding of the pathways involved in cell proliferation and signaling, targeted therapies, in the treatment of cancer are entering the clinical arena. New and emerging targets are proteins involved in DNA repair pathways. Inhibition of various proteins in the DNA repair pathways sensitizes cancer cells to DNA damaging agents such as chemotherapy and/or radiation. We study the apurinic endonuclease 1/redox factor-1 (Ape1/Ref-1) and believe that its crucial function in DNA repair and reduction-oxidation or redox signaling make it an excellent target for sensitizing tumor cells to chemotherapy. Ape1/Ref-1 is an essential enzyme in the base excision repair (BER) pathway which is responsible for the repair of DNA caused by oxidative and alkylation damage. As importantly, Ape1/Ref-1 also functions as a redox factor maintaining transcription factors in an active reduced state. Ape1/Ref-1 stimulates the DNA binding activity of numerous transcription factors that are involved in cancer promotion and progression such as AP-1 (Fos/Jun), NFkappaB, HIF-1alpha, CREB, p53 and others. We will discuss what is known regarding the pharmacological targeting of the DNA repair activity, as well as the redox activity of Ape1/Ref-1, and explore the budding clinical utility of inhibition of either of these functions in cancer treatment. A brief discussion of the effect of polymorphisms in its DNA sequence is included because of Ape1/Ref-1's importance to maintenance and integrity of the genome. Experimental modification of Ape1/Ref-1 activity changes the response of cells and of organisms to DNA damaging agents, suggesting that Ape1/Ref-1 may also be a productive target of chemoprevention. In this review, we will provide an overview of Ape1/Ref-1's activities and explore the potential of this protein as a target in cancer treatment as well as its role in chemoprevention.
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Affiliation(s)
- Melissa L Fishel
- Department of Pediatrics (Section of Hematology/Oncology), Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, United States
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Chen MJ, Ma SM, Dumitrache LC, Hasty P. Biochemical and cellular characteristics of the 3' -> 5' exonuclease TREX2. Nucleic Acids Res 2007; 35:2682-94. [PMID: 17426129 PMCID: PMC1885668 DOI: 10.1093/nar/gkm151] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
TREX2 is an autonomous nonprocessive 3' --> 5' exonuclease, suggesting that it maintains genome integrity. To investigate TREX2's biochemical and cellular properties, we show that endogenous TREX2 is expressed widely in mouse tissues and human cell lines. Unexpectedly, endogenous human TREX2 is predominantly expressed as a 30-kDa protein (not 26 kDa, as previously believed), which is likely encoded by longer isoforms (TREX2(L1) and/or TREX2(L2)) that possess similar capacity for self-association, DNA binding and catalytic activity. Site-directed mutagenesis analysis shows that the three functional activities of TREX2 are distinct, yet integrated. Mutation of amino acids putatively important for homodimerization significantly impairs both DNA binding and exonuclease activity, while mutation of amino acids (except R163) in the DNA binding and exonuclease domains affects their corresponding activities. Interestingly, however, DNA-binding domain mutations do not impact catalytic activity, while exonuclease domain mutations diminish DNA binding. To understand TREX2 cellular properties, we find endogenous TREX2 is down regulated during G2/M and nuclear TREX2 displays a punctate staining pattern. Furthermore, TREX2 knockdown reduces cell proliferation. Taken together, our results suggest that TREX2 plays an important function during DNA metabolism and cellular proliferation.
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Affiliation(s)
- Ming-Jiu Chen
- The Department of Molecular Medicine/Institute of Biotechnology, The University of Texas Health Science Center, San Antonio, TX 78245-3207, USA.
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