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Kaminski AM, Chiruvella KK, Ramsden DA, Bebenek K, Kunkel TA, Pedersen LC. DNA polymerase λ Loop1 variant yields unexpected gain-of-function capabilities in nonhomologous end-joining. DNA Repair (Amst) 2024; 136:103645. [PMID: 38428373 PMCID: PMC11078337 DOI: 10.1016/j.dnarep.2024.103645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 01/26/2024] [Accepted: 01/31/2024] [Indexed: 03/03/2024]
Abstract
DNA polymerases lambda (Polλ) and mu (Polμ) are X-Family polymerases that participate in DNA double-strand break (DSB) repair by the nonhomologous end-joining pathway (NHEJ). Both polymerases direct synthesis from one DSB end, using template derived from a second DSB end. In this way, they promote the NHEJ ligation step and minimize the sequence loss normally associated with this pathway. The two polymerases differ in cognate substrate, as Polλ is preferred when synthesis must be primed from a base-paired DSB end, while Polμ is required when synthesis must be primed from an unpaired DSB end. We generated a Polλ variant (PolλKGET) that retained canonical Polλ activity on a paired end-albeit with reduced incorporation fidelity. We recently discovered that the variant had unexpectedly acquired the activity previously unique to Polμ-synthesis from an unpaired primer terminus. Though the sidechains of the Loop1 region make no contact with the DNA substrate, PolλKGET Loop1 amino acid sequence is surprisingly essential for its unique activity during NHEJ. Taken together, these results underscore that the Loop1 region plays distinct roles in different Family X polymerases.
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Affiliation(s)
- Andrea M Kaminski
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Dr., Bldg 101, Research Triangle Park, NC 27709, USA
| | - Kishore K Chiruvella
- Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Dale A Ramsden
- Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Katarzyna Bebenek
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Dr., Bldg 101, Research Triangle Park, NC 27709, USA
| | - Thomas A Kunkel
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Dr., Bldg 101, Research Triangle Park, NC 27709, USA
| | - Lars C Pedersen
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Dr., Bldg 101, Research Triangle Park, NC 27709, USA.
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2
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Ye Z, Shi Y, Lees-Miller SP, Tainer JA. Function and Molecular Mechanism of the DNA Damage Response in Immunity and Cancer Immunotherapy. Front Immunol 2021; 12:797880. [PMID: 34970273 PMCID: PMC8712645 DOI: 10.3389/fimmu.2021.797880] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 11/15/2021] [Indexed: 12/21/2022] Open
Abstract
The DNA damage response (DDR) is an organized network of multiple interwoven components evolved to repair damaged DNA and maintain genome fidelity. Conceptually the DDR includes damage sensors, transducer kinases, and effectors to maintain genomic stability and accurate transmission of genetic information. We have recently gained a substantially improved molecular and mechanistic understanding of how DDR components are interconnected to inflammatory and immune responses to stress. DDR shapes both innate and adaptive immune pathways: (i) in the context of innate immunity, DDR components mainly enhance cytosolic DNA sensing and its downstream STimulator of INterferon Genes (STING)-dependent signaling; (ii) in the context of adaptive immunity, the DDR is needed for the assembly and diversification of antigen receptor genes that is requisite for T and B lymphocyte development. Imbalances between DNA damage and repair impair tissue homeostasis and lead to replication and transcription stress, mutation accumulation, and even cell death. These impacts from DDR defects can then drive tumorigenesis, secretion of inflammatory cytokines, and aberrant immune responses. Yet, DDR deficiency or inhibition can also directly enhance innate immune responses. Furthermore, DDR defects plus the higher mutation load in tumor cells synergistically produce primarily tumor-specific neoantigens, which are powerfully targeted in cancer immunotherapy by employing immune checkpoint inhibitors to amplify immune responses. Thus, elucidating DDR-immune response interplay may provide critical connections for harnessing immunomodulatory effects plus targeted inhibition to improve efficacy of radiation and chemotherapies, of immune checkpoint blockade, and of combined therapeutic strategies.
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Affiliation(s)
- Zu Ye
- Department of Molecular and Cellular Oncology, and Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Yin Shi
- Department of Immunology, Zhejiang University School of Medicine, Hangzhou, China
- Division of Pediatrics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Susan P. Lees-Miller
- Department of Biochemistry and Molecular Biology, Robson DNA Science Centre, Charbonneau Cancer Institute, University of Calgary, Calgary, AB, Canada
| | - John A. Tainer
- Department of Molecular and Cellular Oncology, and Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
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Kaminski AM, Pryor JM, Ramsden DA, Kunkel TA, Pedersen LC, Bebenek K. Structural snapshots of human DNA polymerase μ engaged on a DNA double-strand break. Nat Commun 2020; 11:4784. [PMID: 32963245 PMCID: PMC7508851 DOI: 10.1038/s41467-020-18506-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 08/17/2020] [Indexed: 01/07/2023] Open
Abstract
Genomic integrity is threatened by cytotoxic DNA double-strand breaks (DSBs), which must be resolved efficiently to prevent sequence loss, chromosomal rearrangements/translocations, or cell death. Polymerase μ (Polμ) participates in DSB repair via the nonhomologous end-joining (NHEJ) pathway, by filling small sequence gaps in broken ends to create substrates ultimately ligatable by DNA Ligase IV. Here we present structures of human Polμ engaging a DSB substrate. Synapsis is mediated solely by Polμ, facilitated by single-nucleotide homology at the break site, wherein both ends of the discontinuous template strand are stabilized by a hydrogen bonding network. The active site in the quaternary Pol μ complex is poised for catalysis and nucleotide incoporation proceeds in crystallo. These structures demonstrate that Polμ may address complementary DSB substrates during NHEJ in a manner indistinguishable from single-strand breaks.
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Affiliation(s)
- Andrea M. Kaminski
- grid.94365.3d0000 0001 2297 5165Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Dr., Bldg. 101/Rm F338, Research Triangle Park, NC 27709 USA
| | - John M. Pryor
- grid.10698.360000000122483208Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, 32-046 Lineberger Comprehensive Cancer Center, 450 West Dr., CB 7295, Chapel Hill, NC 27599 USA
| | - Dale A. Ramsden
- grid.10698.360000000122483208Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, 32-046 Lineberger Comprehensive Cancer Center, 450 West Dr., CB 7295, Chapel Hill, NC 27599 USA
| | - Thomas A. Kunkel
- grid.94365.3d0000 0001 2297 5165Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Dr., Bldg. 101/Rm F338, Research Triangle Park, NC 27709 USA
| | - Lars C. Pedersen
- grid.94365.3d0000 0001 2297 5165Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Dr., Bldg. 101/Rm F338, Research Triangle Park, NC 27709 USA
| | - Katarzyna Bebenek
- grid.94365.3d0000 0001 2297 5165Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Dr., Bldg. 101/Rm F338, Research Triangle Park, NC 27709 USA
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Zhao B, Watanabe G, Lieber MR. Polymerase μ in non-homologous DNA end joining: importance of the order of arrival at a double-strand break in a purified system. Nucleic Acids Res 2020; 48:3605-3618. [PMID: 32052035 PMCID: PMC7144918 DOI: 10.1093/nar/gkaa094] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 01/14/2020] [Accepted: 02/04/2020] [Indexed: 01/07/2023] Open
Abstract
During non-homologous DNA end joining (NHEJ), bringing two broken dsDNA ends into proximity is an essential prerequisite for ligation by XRCC4:Ligase IV (X4L4). This physical juxtaposition of DNA ends is called NHEJ synapsis. In addition to the key NHEJ synapsis proteins, Ku, X4L4, and XLF, it has been suggested that DNA polymerase mu (pol μ) may also align two dsDNA ends into close proximity for synthesis. Here, we directly observe the NHEJ synapsis by pol μ using a single molecule FRET (smFRET) assay where we can measure the duration of the synapsis. The results show that pol μ alone can mediate efficient NHEJ synapsis of 3′ overhangs that have at least 1 nt microhomology. The abundant Ku protein in cells limits the accessibility of pol μ to DNA ends with overhangs. But X4L4 can largely reverse the Ku inhibition, perhaps by pushing the Ku inward to expose the overhang for NHEJ synapsis. Based on these studies, the mechanistic flexibility known to exist at other steps of NHEJ is now also apparent for the NHEJ synapsis step.
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Affiliation(s)
- Bailin Zhao
- Department of Pathology, Department of Biochemistry & Molecular Biology, Department of Molecular Microbiology & Immunology, and Section of Computational & Molecular Biology, USC Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, 1441 Eastlake Ave, Rm. 5428, Los Angeles, CA 90089, USA
| | - Go Watanabe
- Department of Pathology, Department of Biochemistry & Molecular Biology, Department of Molecular Microbiology & Immunology, and Section of Computational & Molecular Biology, USC Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, 1441 Eastlake Ave, Rm. 5428, Los Angeles, CA 90089, USA
| | - Michael R Lieber
- Department of Pathology, Department of Biochemistry & Molecular Biology, Department of Molecular Microbiology & Immunology, and Section of Computational & Molecular Biology, USC Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, 1441 Eastlake Ave, Rm. 5428, Los Angeles, CA 90089, USA
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Combined immunodeficiency caused by a loss-of-function mutation in DNA polymerase delta 1. J Allergy Clin Immunol 2019; 145:391-401.e8. [PMID: 31629014 DOI: 10.1016/j.jaci.2019.10.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 09/11/2019] [Accepted: 10/04/2019] [Indexed: 01/29/2023]
Abstract
BACKGROUND Mutations affecting DNA polymerases have been implicated in genomic instability and cancer development, but the mechanisms by which they can affect the immune system remain largely unexplored. OBJECTIVE We sought to establish the role of DNA polymerase δ1 catalytic subunit (POLD1) as the cause of a primary immunodeficiency in an extended kindred. METHODS We performed whole-exome and targeted gene sequencing, lymphocyte characterization, molecular and functional analyses of the DNA polymerase δ (Polδ) complex, and T- and B-cell antigen receptor repertoire analysis. RESULTS We identified a missense mutation (c. 3178C>T; p.R1060C) in POLD1 in 3 related subjects who presented with recurrent, especially herpetic, infections and T-cell lymphopenia with impaired T-cell but not B-cell proliferation. The mutation destabilizes the Polδ complex, leading to ineffective recruitment of replication factor C to initiate DNA replication. Molecular dynamics simulation revealed that the R1060C mutation disrupts the intramolecular interaction between the POLD1 CysB motif and the catalytic domain and also between POLD1 and the Polδ subunit POLD2. The patients exhibited decreased numbers of naive CD4 and especially CD8 T cells in favor of effector memory subpopulations. This skewing was associated with oligoclonality and restricted T-cell receptor β-chain V-J pairing in CD8+ but not CD4+ T cells, suggesting that POLD1R1060C differentially affects peripheral CD8+ T-cell expansion and possibly thymic selection. CONCLUSION These results identify gene defects in POLD1 as a novel cause of T-cell immunodeficiency.
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Sarac I, Hollenstein M. Terminal Deoxynucleotidyl Transferase in the Synthesis and Modification of Nucleic Acids. Chembiochem 2019; 20:860-871. [PMID: 30451377 DOI: 10.1002/cbic.201800658] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Indexed: 12/26/2022]
Abstract
The terminal deoxynucleotidyl transferase (TdT) belongs to the X family of DNA polymerases. This unusual polymerase catalyzes the template-independent addition of random nucleotides on 3'-overhangs during V(D)J recombination. The biological function and intrinsic biochemical properties of the TdT have spurred the development of numerous oligonucleotide-based tools and methods, especially if combined with modified nucleoside triphosphates. Herein, we summarize the different applications stemming from the incorporation of modified nucleotides by the TdT. The structural, mechanistic, and biochemical properties of this polymerase are also discussed.
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Affiliation(s)
- Ivo Sarac
- Laboratory for Bioorganic Chemistry of Nucleic Acids, Department of Structural Biology and Chemistry, Institut Pasteur, CNRS UMR3523, 28, rue du Docteur Roux, 75724, Paris Cedex 15, France
| | - Marcel Hollenstein
- Laboratory for Bioorganic Chemistry of Nucleic Acids, Department of Structural Biology and Chemistry, Institut Pasteur, CNRS UMR3523, 28, rue du Docteur Roux, 75724, Paris Cedex 15, France
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Pannunzio NR, Watanabe G, Lieber MR. Nonhomologous DNA end-joining for repair of DNA double-strand breaks. J Biol Chem 2017; 293:10512-10523. [PMID: 29247009 DOI: 10.1074/jbc.tm117.000374] [Citation(s) in RCA: 326] [Impact Index Per Article: 46.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Nonhomologous DNA end-joining (NHEJ) is the predominant double-strand break (DSB) repair pathway throughout the cell cycle and accounts for nearly all DSB repair outside of the S and G2 phases. NHEJ relies on Ku to thread onto DNA termini and thereby improve the affinity of the NHEJ enzymatic components consisting of polymerases (Pol μ and Pol λ), a nuclease (the Artemis·DNA-PKcs complex), and a ligase (XLF·XRCC4·Lig4 complex). Each of the enzymatic components is distinctive for its versatility in acting on diverse incompatible DNA end configurations coupled with a flexibility in loading order, resulting in many possible junctional outcomes from one DSB. DNA ends can either be directly ligated or, if the ends are incompatible, processed until a ligatable configuration is achieved that is often stabilized by up to 4 bp of terminal microhomology. Processing of DNA ends results in nucleotide loss or addition, explaining why DSBs repaired by NHEJ are rarely restored to their original DNA sequence. Thus, NHEJ is a single pathway with multiple enzymes at its disposal to repair DSBs, resulting in a diversity of repair outcomes.
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Affiliation(s)
- Nicholas R Pannunzio
- From the Departments of Pathology, Biochemistry and Molecular Biology, and Molecular Microbiology and Immunology, Section of Molecular and Computational Biology, Department of Biological Sciences, Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California 90033
| | - Go Watanabe
- From the Departments of Pathology, Biochemistry and Molecular Biology, and Molecular Microbiology and Immunology, Section of Molecular and Computational Biology, Department of Biological Sciences, Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California 90033
| | - Michael R Lieber
- From the Departments of Pathology, Biochemistry and Molecular Biology, and Molecular Microbiology and Immunology, Section of Molecular and Computational Biology, Department of Biological Sciences, Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California 90033
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8
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Non-homologous DNA end joining and alternative pathways to double-strand break repair. Nat Rev Mol Cell Biol 2017; 18:495-506. [PMID: 28512351 DOI: 10.1038/nrm.2017.48] [Citation(s) in RCA: 1006] [Impact Index Per Article: 143.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
DNA double-strand breaks (DSBs) are the most dangerous type of DNA damage because they can result in the loss of large chromosomal regions. In all mammalian cells, DSBs that occur throughout the cell cycle are repaired predominantly by the non-homologous DNA end joining (NHEJ) pathway. Defects in NHEJ result in sensitivity to ionizing radiation and the ablation of lymphocytes. The NHEJ pathway utilizes proteins that recognize, resect, polymerize and ligate the DNA ends in a flexible manner. This flexibility permits NHEJ to function on a wide range of DNA-end configurations, with the resulting repaired DNA junctions often containing mutations. In this Review, we discuss the most recent findings regarding the relative involvement of the different NHEJ proteins in the repair of various DNA-end configurations. We also discuss the shunting of DNA-end repair to the auxiliary pathways of alternative end joining (a-EJ) or single-strand annealing (SSA) and the relevance of these different pathways to human disease.
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9
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Lieber MR, Gu J, Lu H, Shimazaki N, Tsai AG. Nonhomologous DNA end joining (NHEJ) and chromosomal translocations in humans. Subcell Biochem 2010; 50:279-96. [PMID: 20012587 DOI: 10.1007/978-90-481-3471-7_14] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Double-strand breaks (DSBs) arise in dividing cells about ten times per cell per day. Causes include replication across a nick, free radicals of oxidative metabolism, ionizing radiation, and inadvertent action by enzymes of DNA metabolism (such as failures of type II topoisomerases or cleavage by recombinases at off-target sites). There are two major double-strand break repair pathways. Homologous recombination (HR) can repair double-strand breaks, but only during S phase and typically only if there are hundreds of base pairs of homology. The more commonly used pathway is nonhomologous DNA end joining, abbreviated NHEJ. NHEJ can repair a DSB at any time during the cell cycle and does not require any homology, although a few nucleotides of terminal microhomology are often utilized by the NHEJ enzymes, if present. The proteins and enzymes of NHEJ include Ku, DNA-PKcs, Artemis, DNA polymerase mu (Pol micro), DNA polymerase lambda (Pol lambda), XLF (also called Cernunnos), XRCC4, and DNA ligase IV. These enzymes constitute what some call the classical NHEJ pathway, and in wild type cells, the vast majority of joining events appear to proceed using these components. NHEJ is present in many prokaryotes, as well as all eukaryotes, and very similar mechanistic flexibility evolved both convergently and divergently. When two double-strand breaks occur on different chromosomes, then the rejoining is almost always done by NHEJ. The causes of DSBs in lymphomas most often involve the RAG or AID enzymes that function in the specialized processes of antigen receptor gene rearrangement.
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Affiliation(s)
- Michael R Lieber
- USC Norris Comprehensive Cancer Center, Los Angeles, CA 90089-9176, USA.
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Moon AF, Garcia-Diaz M, Batra VK, Beard WA, Bebenek K, Kunkel TA, Wilson SH, Pedersen LC. The X family portrait: structural insights into biological functions of X family polymerases. DNA Repair (Amst) 2007; 6:1709-25. [PMID: 17631059 PMCID: PMC2128704 DOI: 10.1016/j.dnarep.2007.05.009] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2007] [Accepted: 05/22/2007] [Indexed: 11/19/2022]
Abstract
The mammalian family X DNA polymerases (DNA polymerases beta, lambda, mu, and TdT) contribute to base excision repair and double-strand break repair by virtue of their ability to fill short gaps in DNA. Structural information now exists for all four of these enzymes, making this the first mammalian polymerase family whose structural portrait is complete. Here we consider how distinctive structural features of these enzymes contribute to their biological functions in vivo.
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Affiliation(s)
- Andrea F. Moon
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences. 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709
| | - Miguel Garcia-Diaz
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences. 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences. 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709
| | - Vinod K. Batra
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences. 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709
| | - William A. Beard
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences. 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709
| | - Katarzyna Bebenek
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences. 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences. 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709
| | - Thomas A. Kunkel
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences. 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences. 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709
| | - Samuel H. Wilson
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences. 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709
| | - Lars C. Pedersen
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences. 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709
- *Corresponding author: Phone: 919-541-0444; Fax: 919-541-7880;
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Moon AF, Garcia-Diaz M, Bebenek K, Davis BJ, Zhong X, Ramsden DA, Kunkel TA, Pedersen LC. Structural insight into the substrate specificity of DNA Polymerase mu. Nat Struct Mol Biol 2006; 14:45-53. [PMID: 17159995 DOI: 10.1038/nsmb1180] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2006] [Accepted: 11/10/2006] [Indexed: 11/08/2022]
Abstract
DNA polymerase mu (Pol mu) is a family X enzyme with unique substrate specificity that contributes to its specialized role in nonhomologous DNA end joining (NHEJ). To investigate Pol mu's unusual substrate specificity, we describe the 2.4 A crystal structure of the polymerase domain of murine Pol mu bound to gapped DNA with a correct dNTP at the active site. This structure reveals substrate interactions with side chains in Pol mu that differ from other family X members. For example, a single amino acid substitution, H329A, has little effect on template-dependent synthesis by Pol mu from a paired primer terminus, but it reduces both template-independent and template-dependent synthesis during NHEJ of intermediates whose 3' ends lack complementary template strand nucleotides. These results provide insight into the substrate specificity and differing functions of four closely related mammalian family X DNA polymerases.
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Affiliation(s)
- Andrea F Moon
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences (National Institutes of Health, US Department of Health and Human Services), 111 T.W. Alexander Drive, MD F3-09, Research Triangle Park, North Carolina 27709, USA
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