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Schmidl D, Jonasson NSW, Menke A, Schneider S, Daumann L. Spectroscopic and in vitro investigations of Fe2+/α-Ketoglutarate-dependent enzymes involved in nucleic acid repair and modification. Chembiochem 2022; 23:e202100605. [PMID: 35040547 PMCID: PMC9401043 DOI: 10.1002/cbic.202100605] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 01/14/2022] [Indexed: 11/08/2022]
Abstract
The activation of molecular oxygen for the highly selective functionalization and repair of DNA and RNA nucleobases is achieved by α-ketoglutarate (α-KG)/iron-dependent dioxygenases. Enzymes of special interest are the human homologs AlkBH of Escherichia coli EcAlkB and ten-eleven translocation (TET) enzymes. These enzymes are involved in demethylation or dealkylation of DNA and RNA, although additional physiological functions are continuously being revealed. Given their importance, studying enzyme-substrate interactions, turnover and kinetic parameters is pivotal for the understanding of the mode of action of these enzymes. Diverse analytical methods, including X-ray crystallography, UV/Vis absorption, electron paramagnetic resonance (EPR), circular dichroism (CD) and NMR spectroscopy have been employed to study the changes in the active site and the overall enzyme structure upon substrate, cofactor and inhibitor addition. Several methods are now available to assess activity of these enzymes. By discussing limitations and possibilities of these techniques for EcAlkB, AlkBH and TET we aim to give a comprehensive synopsis from a bioinorganic point of view, addressing researchers from different disciplines working in the highly interdisciplinary and rapidly evolving field of epigenetic processes and DNA/RNA repair and modification.
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Affiliation(s)
- David Schmidl
- Ludwig-Maximilians-Universität München: Ludwig-Maximilians-Universitat Munchen, Chemistry, GERMANY
| | - Niko S W Jonasson
- Ludwig-Maximilians-Universität München: Ludwig-Maximilians-Universitat Munchen, Chemistry, GERMANY
| | - Annika Menke
- Ludwig-Maximilians-Universität München: Ludwig-Maximilians-Universitat Munchen, Chemistry, GERMANY
| | - Sabine Schneider
- Ludwig-Maximilians-Universität München: Ludwig-Maximilians-Universitat Munchen, Chemistry, GERMANY
| | - Lena Daumann
- Ludwig-Maximilians-Universität München, Department of Chemistry, Butenandtstr. 5-13, 81377, München, GERMANY
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2
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DNA Methylation on N6-Adenine Regulates the Hyphal Development during Dimorphism in the Early-Diverging Fungus Mucor lusitanicus. J Fungi (Basel) 2021; 7:jof7090738. [PMID: 34575776 PMCID: PMC8470550 DOI: 10.3390/jof7090738] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 09/03/2021] [Accepted: 09/06/2021] [Indexed: 12/14/2022] Open
Abstract
The epigenetic modifications control the pathogenicity of human pathogenic fungi, which have been poorly studied in Mucorales, causative agents of mucormycosis. This order belongs to a group referred to as early-diverging fungi that are characterized by high levels of N6-methyldeoxy adenine (6mA) in their genome with dense 6mA clusters associated with actively expressed genes. AlkB enzymes can act as demethylases of 6mA in DNA, with the most remarkable eukaryotic examples being mammalian ALKBH1 and Caenorhabditis elegans NMAD-1. The Mucor lusitanicus (formerly M. circinelloides f. lusitanicus) genome contains one gene, dmt1, and two genes, dmt2 and dmt3, encoding proteins similar to C. elegans NMAD-1 and ALKBH1, respectively. The function of these three genes was analyzed by the generation of single and double deletion mutants for each gene. Multiple processes were studied in the mutants, but defects were only found in single and double deletion mutants for dmt1. In contrast to the wild-type strain, dmt1 mutants showed an increase in 6mA levels during the dimorphic transition, suggesting that 6mA is associated with dimorphism in M. lusitanicus. Furthermore, the spores of dmt1 mutants challenged with macrophages underwent a reduction in polar growth, suggesting that 6mA also has a role during the spore–macrophage interaction that could be important in the infection process.
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3
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Van Deuren V, Plessers S, Robben J. Structural determinants of nucleobase modification recognition in the AlkB family of dioxygenases. DNA Repair (Amst) 2020; 96:102995. [PMID: 33069898 DOI: 10.1016/j.dnarep.2020.102995] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 09/30/2020] [Indexed: 01/29/2023]
Abstract
Iron-dependent dioxygenases of the AlkB protein family found in most organisms throughout the tree of life play a major role in oxidative dealkylation processes. Many of these enzymes have attracted the attention of researchers across different fields and have been subjected to thorough biochemical characterization because of their link to human health and disease. For example, several mammalian AlkB homologues are involved in the direct reversal of alkylation damage in DNA, while others have been shown to play a regulatory role in epigenetic or epitranscriptomic nucleic acid methylation or in post-translational modifications such as acetylation of actin filaments. These studies show that that divergence in amino acid sequence and structure leads to different characteristics and substrate specificities. In this review, we aim to summarize current insights in the structural features involved in the substrate selection of AlkB homologues, with focus on nucleic acid interactions.
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Affiliation(s)
- V Van Deuren
- Department of Chemistry, KU Leuven, Celestijnenlaan 200G, B-3001, Heverlee, Belgium
| | - S Plessers
- Department of Chemistry, KU Leuven, Celestijnenlaan 200G, B-3001, Heverlee, Belgium
| | - J Robben
- Department of Chemistry, KU Leuven, Celestijnenlaan 200G, B-3001, Heverlee, Belgium.
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4
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Müller TA, Tobar MA, Perian MN, Hausinger RP. Biochemical Characterization of AP Lyase and m 6A Demethylase Activities of Human AlkB Homologue 1 (ALKBH1). Biochemistry 2017; 56:1899-1910. [PMID: 28290676 DOI: 10.1021/acs.biochem.7b00060] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Alkbh1 is one of nine mammalian homologues of Escherichia coli AlkB, a 2-oxoglutarate-dependent dioxygenase that catalyzes direct DNA repair by removing alkyl lesions from DNA. Six distinct enzymatic activities have been reported for Alkbh1, including hydroxylation of variously methylated DNA, mRNA, tRNA, or histone substrates along with the cleavage of DNA at apurinic/apyrimidinic (AP) sites followed by covalent attachment to the 5'-product. The studies described here extend the biochemical characterization of two of these enzymatic activities using human ALKBH1: the AP lyase and 6-methyl adenine DNA demethylase activities. The steady-state and single-turnover kinetic parameters for ALKBH1 cleavage of AP sites in DNA were determined and shown to be comparable to those of other AP lyases. The α,β-unsaturated aldehyde of the 5'-product arising from DNA cleavage reacts predominantly with C129 of ALKBH1, but secondary sites also generate covalent adducts. The 6-methyl adenine demethylase activity was examined with a newly developed assay using a methylation-sensitive restriction endonuclease, and the enzymatic rate was found to be very low. Indeed, the demethylase activity was less than half that of the AP lyase activity when ALKBH1 samples were assayed using identical buffer conditions. The two enzymatic activities were examined using a series of site-directed variant proteins, revealing the presence of distinct but partially overlapping active sites for the two reactions. We postulate that the very low 6-methyl adenine oxygenase activity associated with ALKBH1 is unlikely to represent the major function of the enzyme in the cell, while the cellular role of the lyase activity (including its subsequent covalent attachment to DNA) remains uncertain.
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Affiliation(s)
- Tina A Müller
- Department of Microbiology and Molecular Genetics, Michigan State University , East Lansing, Michigan 48824, United States
| | - Michael A Tobar
- Department of Microbiology and Molecular Genetics, Michigan State University , East Lansing, Michigan 48824, United States
| | - Madison N Perian
- Biology Department, Kalamazoo College , Kalamazoo, Michigan 49006, United States
| | - Robert P Hausinger
- Department of Microbiology and Molecular Genetics, Michigan State University , East Lansing, Michigan 48824, United States.,Department of Biochemistry and Molecular Biology, Michigan State University , East Lansing, Michigan 48824, United States
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5
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Fedeles BI, Singh V, Delaney JC, Li D, Essigmann JM. The AlkB Family of Fe(II)/α-Ketoglutarate-dependent Dioxygenases: Repairing Nucleic Acid Alkylation Damage and Beyond. J Biol Chem 2015; 290:20734-20742. [PMID: 26152727 DOI: 10.1074/jbc.r115.656462] [Citation(s) in RCA: 272] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The AlkB family of Fe(II)- and α-ketoglutarate-dependent dioxygenases is a class of ubiquitous direct reversal DNA repair enzymes that remove alkyl adducts from nucleobases by oxidative dealkylation. The prototypical and homonymous family member is an Escherichia coli "adaptive response" protein that protects the bacterial genome against alkylation damage. AlkB has a wide variety of substrates, including monoalkyl and exocyclic bridged adducts. Nine mammalian AlkB homologs exist (ALKBH1-8, FTO), but only a subset functions as DNA/RNA repair enzymes. This minireview presents an overview of the AlkB proteins including recent data on homologs, structural features, substrate specificities, and experimental strategies for studying DNA repair by AlkB family proteins.
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Affiliation(s)
- Bogdan I Fedeles
- Departments of Chemistry and Biological Engineering and the Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Vipender Singh
- Departments of Chemistry and Biological Engineering and the Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - James C Delaney
- Departments of Chemistry and Biological Engineering and the Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Deyu Li
- Departments of Chemistry and Biological Engineering and the Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.
| | - John M Essigmann
- Departments of Chemistry and Biological Engineering and the Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.
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6
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Müller TA, Hausinger RP. AlkB and Its Homologues – DNA Repair and Beyond. 2-OXOGLUTARATE-DEPENDENT OXYGENASES 2015. [DOI: 10.1039/9781782621959-00246] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
AlkB is an Fe(ii)/2-oxoglutarate-dependent dioxygenase that is part of the adaptive response to alkylating agents in Escherichia coli. AlkB hydroxylates a wide variety of alkylated DNA bases producing unstable intermediates which decompose to restore the non-alkylated bases. Homologues exist in other bacteria, metazoa (e.g. nine in humans), plants and viruses, but not in archaea, with many catalysing the same oxidative demethylation reactions as for AlkB. The mammalian enzymes Alkbh2 and Alkbh3 catalyse direct DNA repair, Alkbh5 and FTO (Alkbh9) are RNA demethylases, and Alkbh8 is used to synthesize a tRNA, while the remaining mammalian homologues have alternative functions. Alkbh1 is an apurinic/apyrimidinic lyase in addition to exhibiting demethylase activities, but no clear role for the Alkbh1 protein has emerged. Alkbh4 is involved in cell division and potentially demethylates actin, whereas the mitochondrial homologue Alkbh7 has a role in obesity; however, no enzymatic activity has been linked to Alkbh4 or Alkbh7. Here, we discuss AlkB as the ‘archetype’ of this class of hydroxylases, compare it to Alkbh2 and Alkbh3, and then briefly review the diverse (and largely unknown) functions of Alkbh1, Alkbh4, Alkbh6 and Alkbh7. Alkbh5, Alkbh8 and Alkbh9 (FTO) are described separately.
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Affiliation(s)
- Tina A. Müller
- Department of Microbiology and Molecular Genetics, Michigan State University East Lansing MI 48824 USA
| | - Robert P. Hausinger
- Department of Microbiology and Molecular Genetics, Michigan State University East Lansing MI 48824 USA
- Department of Biochemistry and Molecular Biology, Michigan State University East Lansing MI 48824 USA
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7
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Shivange G, Kodipelli N, Monisha M, Anindya R. A role for Saccharomyces cerevisiae Tpa1 protein in direct alkylation repair. J Biol Chem 2014; 289:35939-52. [PMID: 25381260 DOI: 10.1074/jbc.m114.590216] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Alkylating agents induce cytotoxic DNA base adducts. In this work, we provide evidence to suggest, for the first time, that Saccharomyces cerevisiae Tpa1 protein is involved in DNA alkylation repair. Little is known about Tpa1 as a repair protein beyond the initial observation from a high-throughput analysis indicating that deletion of TPA1 causes methyl methane sulfonate sensitivity in S. cerevisiae. Using purified Tpa1, we demonstrate that Tpa1 repairs both single- and double-stranded methylated DNA. Tpa1 is a member of the Fe(II) and 2-oxoglutarate-dependent dioxygenase family, and we show that mutation of the amino acid residues involved in cofactor binding abolishes the Tpa1 DNA repair activity. Deletion of TPA1 along with the base excision repair pathway DNA glycosylase MAG1 renders the tpa1Δmag1Δ double mutant highly susceptible to methylation-induced toxicity. We further demonstrate that the trans-lesion synthesis DNA polymerase Polζ (REV3) plays a key role in tolerating DNA methyl-base lesions and that tpa1Δmag1revΔ3 triple mutant is extremely susceptible to methylation-induced toxicity. Our results indicate a synergism between the base excision repair pathway and direct alkylation repair by Tpa1 in S. cerevisiae. We conclude that Tpa1 is a hitherto unidentified DNA repair protein in yeast and that it plays a crucial role in reverting alkylated DNA base lesions and cytotoxicity.
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Affiliation(s)
- Gururaj Shivange
- From the Department of Biotechnology, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram 502205, Hyderabad, India
| | - Naveena Kodipelli
- From the Department of Biotechnology, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram 502205, Hyderabad, India
| | - Mohan Monisha
- From the Department of Biotechnology, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram 502205, Hyderabad, India
| | - Roy Anindya
- From the Department of Biotechnology, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram 502205, Hyderabad, India
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8
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Silvestrov P, Müller TA, Clark KN, Hausinger RP, Cisneros GA. Homology modeling, molecular dynamics, and site-directed mutagenesis study of AlkB human homolog 1 (ALKBH1). J Mol Graph Model 2014; 54:123-30. [PMID: 25459764 DOI: 10.1016/j.jmgm.2014.10.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 10/16/2014] [Accepted: 10/21/2014] [Indexed: 02/03/2023]
Abstract
The ability to repair DNA is important for the conservation of genetic information of living organisms. Cells have a number of ways to restore damaged DNA, such as direct DNA repair, base excision repair, and nucleotide excision repair. One of the proteins that can perform direct repair of DNA bases is Escherichia coli AlkB. In humans, there are 9 identified AlkB homologs, including AlkB homolog 1 (ALKBH1). Many of these proteins catalyze the direct oxidative dealkylation of DNA and RNA bases and, as such, have an important role in repairing DNA from damage induced by alkylating agents. In addition to the dealkylase activity, ALKBH1 can also function as an apyrimidinic/apurinic lyase and was proposed to have a distinct lyase active site. To our knowledge, no crystal structure or complete homology model of ALKBH1 protein is available. In this study, we have used homology modeling to predict the structure of ALKBH1 based on AlkB and Duffy-binding-like domain crystal structures as templates. Molecular dynamics simulations were subsequently performed on the predicted structure of ALKBH1. The positions of two disulfide bonds or a zinc-finger motif and a disulfide bond were predicted and the importance of these features was tested by mutagenesis. Possible locations for the lyase active site are proposed based on the analysis of our predicted structures and previous experimental results.
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Affiliation(s)
- Pavel Silvestrov
- Department of Chemistry, Wayne State University, Detroit, MI 48202, United States
| | - Tina A Müller
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, United States
| | - Kristen N Clark
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, United States
| | - Robert P Hausinger
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, United States
| | - G Andrés Cisneros
- Department of Chemistry, Wayne State University, Detroit, MI 48202, United States.
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9
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Lu L, Zhu C, Xia B, Yi C. Oxidative Demethylation of DNA and RNA Mediated by Non-Heme Iron-Dependent Dioxygenases. Chem Asian J 2014; 9:2018-29. [DOI: 10.1002/asia.201402148] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Indexed: 11/10/2022]
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10
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Mielecki D, Grzesiuk E. Ada response - a strategy for repair of alkylated DNA in bacteria. FEMS Microbiol Lett 2014; 355:1-11. [PMID: 24810496 PMCID: PMC4437013 DOI: 10.1111/1574-6968.12462] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 04/04/2014] [Accepted: 05/05/2014] [Indexed: 11/29/2022] Open
Abstract
Alkylating agents are widespread in the environment and also occur endogenously. They can be cytotoxic or mutagenic to the cells introducing alkylated bases to DNA or RNA. All organisms have evolved multiple DNA repair mechanisms to counteract the effects of DNA alkylation: the most cytotoxic lesion, N3-methyladenine (3meA), is excised by AlkA glycosylase initiating base excision repair (BER); toxic N1-methyladenine (1meA) and N3-methylcytosine (3meC), induced in DNA and RNA, are removed by AlkB dioxygenase; and mutagenic and cytotoxic O6-methylguanine (O6meG) is repaired by Ada methyltransferase. In Escherichia coli, Ada response involves the expression of four genes, ada, alkA, alkB, and aidB, encoding respective proteins Ada, AlkA, AlkB, and AidB. The Ada response is conserved among many bacterial species; however, it can be organized differently, with diverse substrate specificity of the particular proteins. Here, an overview of the organization of the Ada regulon and function of individual proteins is presented. We put special effort into the characterization of AlkB dioxygenases, their substrate specificity, and function in the repair of alkylation lesions in DNA/RNA.
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Affiliation(s)
- Damian Mielecki
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warszawa, Poland
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11
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Affiliation(s)
- Guanqun Zheng
- Department of Chemistry and
Institute for Biophysical Dynamics, The
University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United
States
| | - Ye Fu
- Department of Chemistry and
Institute for Biophysical Dynamics, The
University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United
States
| | - Chuan He
- Department of Chemistry and
Institute for Biophysical Dynamics, The
University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United
States
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12
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Affiliation(s)
- Guanqun Zheng
- Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States
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Aik W, Scotti JS, Choi H, Gong L, Demetriades M, Schofield CJ, McDonough MA. Structure of human RNA N⁶-methyladenine demethylase ALKBH5 provides insights into its mechanisms of nucleic acid recognition and demethylation. Nucleic Acids Res 2014; 42:4741-54. [PMID: 24489119 PMCID: PMC3985658 DOI: 10.1093/nar/gku085] [Citation(s) in RCA: 149] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
ALKBH5 is a 2-oxoglutarate (2OG) and ferrous iron-dependent nucleic acid oxygenase (NAOX) that catalyzes the demethylation of N6-methyladenine in RNA. ALKBH5 is upregulated under hypoxia and plays a role in spermatogenesis. We describe a crystal structure of human ALKBH5 (residues 66–292) to 2.0 Å resolution. ALKBH566–292 has a double-stranded β-helix core fold as observed in other 2OG and iron-dependent oxygenase family members. The active site metal is octahedrally coordinated by an HXD…H motif (comprising residues His204, Asp206 and His266) and three water molecules. ALKBH5 shares a nucleotide recognition lid and conserved active site residues with other NAOXs. A large loop (βIV–V) in ALKBH5 occupies a similar region as the L1 loop of the fat mass and obesity-associated protein that is proposed to confer single-stranded RNA selectivity. Unexpectedly, a small molecule inhibitor, IOX3, was observed covalently attached to the side chain of Cys200 located outside of the active site. Modelling substrate into the active site based on other NAOX–nucleic acid complexes reveals conserved residues important for recognition and demethylation mechanisms. The structural insights will aid in the development of inhibitors selective for NAOXs, for use as functional probes and for therapeutic benefit.
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Affiliation(s)
- WeiShen Aik
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK
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14
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A covalent protein-DNA 5'-product adduct is generated following AP lyase activity of human ALKBH1 (AlkB homologue 1). Biochem J 2013; 452:509-18. [PMID: 23577621 DOI: 10.1042/bj20121908] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
ALKBH1 (AlkB homologue 1) is a mammalian AlkB (2-oxoglutarate-dependent dioxygenase) homologue that possesses AP (abasic or apurinic/apyrimidinic) lyase activity. The AP lyase reaction is catalysed by imine formation with an active site lysine residue, and a covalent intermediate can be trapped in the presence of NaBH4. Surprisingly, ALKBH1 also forms a stable protein-DNA adduct in the absence of a reducing agent. Experiments with different substrates demonstrated that the protein covalently binds to the 5' DNA product, i.e. the fragment containing an α,β-unsaturated aldehyde. The N-terminal domain of ALKBH1 was identified as the main site of linkage with DNA. By contrast, mutagenesis studies suggest that the primary catalytic residue forming the imine linkage is Lys133, with Lys154 and other lysine residues in this region serving in opportunistic roles. These findings confirm the classification of ALKBH1 as an AP lyase, identify the primary and a secondary lysine residues involved in the lyase reaction, and demonstrate that the protein forms a covalent adduct with the 5' DNA product. We propose two plausible chemical mechanisms to account for the covalent attachment.
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Fu D, Jordan JJ, Samson LD. Human ALKBH7 is required for alkylation and oxidation-induced programmed necrosis. Genes Dev 2013; 27:1089-100. [PMID: 23666923 DOI: 10.1101/gad.215533.113] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Programmed necrosis has emerged as a crucial modulator of cell death in response to several forms of cellular stress. In one form of programmed necrotic cell death, induced by cytotoxic alkylating agents, hyperactivation of poly-ADP-ribose polymerase (PARP) leads to cellular NAD and ATP depletion, mitochondrial dysfunction, reactive oxygen species formation, and ensuing cell death. Here, we show that the protein encoded by the human AlkB homolog 7 (ALKBH7) gene plays a pivotal role in DNA-damaging agent-induced programmed necrosis by triggering the collapse of mitochondrial membrane potential and large-scale loss of mitochondrial function that lead to energy depletion and cellular demise. Depletion of ALKBH7 suppresses necrotic cell death induced by numerous alkylating and oxidizing agents while having no effect on apoptotic cell death. Like wild-type cells, ALKBH7-depleted cells undergo PARP hyperactivation and NAD depletion after severe DNA damage but, unlike wild-type cells, exhibit rapid recovery of intracellular NAD and ATP levels. Consistent with the recovery of cellular bioenergetics, ALKBH7-depleted cells maintain their mitochondrial membrane potential, plasma membrane integrity, and viability. Our results uncover a novel role for a mammalian AlkB homolog in programmed necrosis, presenting a new target for therapeutic intervention in cancer cells that are resistant to apoptotic cell death.
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Affiliation(s)
- Dragony Fu
- Department of Biological Engineering, Department of Biology, Center for Environmental Health Sciences, David H. Koch Center for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Abstract
Endogenous and exogenous factors constantly challenge cellular DNA, generating cytotoxic and/or mutagenic DNA adducts. As a result, organisms have evolved different mechanisms to defend against the deleterious effects of DNA damage. Among these diverse repair pathways, direct DNA-repair systems provide cells with simple yet efficient solutions to reverse covalent DNA adducts. In this review, we focus on recent advances in the field of direct DNA repair, namely, photolyase-, alkyltransferase-, and dioxygenase-mediated repair processes. We present specific examples to describe new findings of known enzymes and appealing discoveries of new proteins. At the end of this article, we also briefly discuss the influence of direct DNA repair on other fields of biology and its implication on the discovery of new biology.
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Affiliation(s)
- Chengqi Yi
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China
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Mello LV, Rigden DJ. A new family of bacterial DNA repair proteins annotated by the integration of non-homology, distant homology and structural bioinformatic methods. FEBS Lett 2012; 586:3908-13. [DOI: 10.1016/j.febslet.2012.09.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 09/13/2012] [Accepted: 09/14/2012] [Indexed: 10/27/2022]
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