1
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Tang C, Krantsevich A, MacCarthy T. Deep learning model of somatic hypermutation reveals importance of sequence context beyond hotspot targeting. iScience 2022; 25:103668. [PMID: 35036866 PMCID: PMC8749460 DOI: 10.1016/j.isci.2021.103668] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 11/08/2021] [Accepted: 12/16/2021] [Indexed: 11/23/2022] Open
Abstract
B cells undergo somatic hypermutation (SHM) of the Immunoglobulin (Ig) variable region to generate high-affinity antibodies. SHM relies on the activity of activation-induced deaminase (AID), which mutates C>U preferentially targeting WRC (W=A/T, R=A/G) hotspots. Downstream mutations at WA Polymerase η hotspots contribute further mutations. Computational models of SHM can describe the probability of mutations essential for vaccine responses. Previous studies using short subsequences (k-mers) failed to explain divergent mutability for the same k-mer. We developed the DeepSHM (Deep learning on SHM) model using k-mers of size 5-21, improving accuracy over previous models. Interpretation of DeepSHM identified an extended WWRCT motif with particularly high mutability. Increased mutability was further associated with lower surrounding G content. Our model also discovered a conserved AGYCTGGGGG (Y=C/T) motif within FW1 of IGHV3 family genes with unusually high T>G substitution rates. Thus, a wider sequence context increases predictive power and identifies features that drive mutational targeting.
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Affiliation(s)
- Catherine Tang
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY 11794, USA
| | - Artem Krantsevich
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY 11794, USA
| | - Thomas MacCarthy
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY 11794, USA
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, USA
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2
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Geronimo I, Vidossich P, Donati E, Vivo M. Computational investigations of polymerase enzymes: Structure, function, inhibition, and biotechnology. WIREs Comput Mol Sci 2021. [DOI: 10.1002/wcms.1534] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Inacrist Geronimo
- Laboratory of Molecular Modelling and Drug Discovery, Istituto Italiano di Tecnologia Genoa Italy
| | - Pietro Vidossich
- Laboratory of Molecular Modelling and Drug Discovery, Istituto Italiano di Tecnologia Genoa Italy
| | - Elisa Donati
- Laboratory of Molecular Modelling and Drug Discovery, Istituto Italiano di Tecnologia Genoa Italy
| | - Marco Vivo
- Laboratory of Molecular Modelling and Drug Discovery, Istituto Italiano di Tecnologia Genoa Italy
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3
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Saha P, Mandal T, Talukdar AD, Kumar D, Kumar S, Tripathi PP, Wang QE, Srivastava AK. DNA polymerase eta: A potential pharmacological target for cancer therapy. J Cell Physiol 2020; 236:4106-4120. [PMID: 33184862 DOI: 10.1002/jcp.30155] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 10/21/2020] [Accepted: 11/02/2020] [Indexed: 12/24/2022]
Abstract
In the last two decades, intensive research has been carried out to improve the survival rates of cancer patients. However, the development of chemoresistance that ultimately leads to tumor relapse poses a critical challenge for the successful treatment of cancer patients. Many cancer patients experience tumor relapse and ultimately die because of treatment failure associated with acquired drug resistance. Cancer cells utilize multiple lines of self-defense mechanisms to bypass chemotherapy and radiotherapy. One such mechanism employed by cancer cells is translesion DNA synthesis (TLS), in which specialized TLS polymerases bypass the DNA lesion with the help of monoubiquitinated proliferating cell nuclear antigen. Among all TLS polymerases (Pol η, Pol ι, Pol κ, REV1, Pol ζ, Pol μ, Pol λ, Pol ν, and Pol θ), DNA polymerase eta (Pol η) is well studied and majorly responsible for the bypass of cisplatin and UV-induced DNA damage. TLS polymerases contribute to chemotherapeutic drug-induced mutations as well as therapy resistance. Therefore, targeting these polymerases presents a novel therapeutic strategy to combat chemoresistance. Mounting evidence suggests that inhibition of Pol η may have multiple impacts on cancer therapy such as sensitizing cancer cells to chemotherapeutics, suppressing drug-induced mutagenesis, and inhibiting the development of secondary tumors. Herein, we provide a general introduction of Pol η and its clinical implications in blocking acquired drug resistance. In addition; this review addresses the existing gaps and challenges of Pol η mediated TLS mechanisms in human cells. A better understanding of the Pol η mediated TLS mechanism will not merely establish it as a potential pharmacological target but also open possibilities to identify novel drug targets for future therapy.
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Affiliation(s)
- Priyanka Saha
- Cancer Biology & Inflammatory Disorder Division, CSIR-Indian Institute of Chemical Biology, Kolkata, West Bengal, India
| | - Tanima Mandal
- Cancer Biology & Inflammatory Disorder Division, CSIR-Indian Institute of Chemical Biology, Kolkata, West Bengal, India
| | - Anupam D Talukdar
- Department of Life Science and Bioinformatics, Assam University, Silchar, Assam, India
| | - Deepak Kumar
- Organic & Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata, West Bengal, India
| | - Sanjay Kumar
- Division of Biology, Indian Institute of Science Education and Research (IISER) Tirupati, Andhra Pradesh, India
| | - Prem P Tripathi
- Cell Biology & Physiology Division, CSIR-Indian Institute of Chemical Biology, Kolkata, West Bengal, India
| | - Qi-En Wang
- Department of Radiation Oncology, Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio, USA
| | - Amit K Srivastava
- Cancer Biology & Inflammatory Disorder Division, CSIR-Indian Institute of Chemical Biology, Kolkata, West Bengal, India
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4
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Hoitsma NM, Whitaker AM, Schaich MA, Smith MR, Fairlamb MS, Freudenthal BD. Structure and function relationships in mammalian DNA polymerases. Cell Mol Life Sci 2019; 77:35-59. [PMID: 31722068 DOI: 10.1007/s00018-019-03368-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 10/11/2019] [Accepted: 10/31/2019] [Indexed: 12/19/2022]
Abstract
DNA polymerases are vital for the synthesis of new DNA strands. Since the discovery of DNA polymerase I in Escherichia coli, a diverse library of mammalian DNA polymerases involved in DNA replication, DNA repair, antibody generation, and cell checkpoint signaling has emerged. While the unique functions of these DNA polymerases are differentiated by their association with accessory factors and/or the presence of distinctive catalytic domains, atomic resolution structures of DNA polymerases in complex with their DNA substrates have revealed mechanistic subtleties that contribute to their specialization. In this review, the structure and function of all 15 mammalian DNA polymerases from families B, Y, X, and A will be reviewed and discussed with special emphasis on the insights gleaned from recently published atomic resolution structures.
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Affiliation(s)
- Nicole M Hoitsma
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Amy M Whitaker
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Matthew A Schaich
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Mallory R Smith
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Max S Fairlamb
- 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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5
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Costello R, Cantillo JF, Kenter AL. Chicken MBD4 Regulates Immunoglobulin Diversification by Somatic Hypermutation. Front Immunol 2019; 10:2540. [PMID: 31736964 PMCID: PMC6838969 DOI: 10.3389/fimmu.2019.02540] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 10/14/2019] [Indexed: 01/21/2023] Open
Abstract
Immunoglobulin (Ig) diversification occurs via somatic hypermutation (SHM) and class switch recombination (CSR), and is initiated by activation-induced deaminase (AID), which converts cytosine to uracil. Variable (V) region genes undergo SHM to create amino acid substitutions that produce antibodies with higher affinity for antigen. The conversion of cytosine to uracil in DNA promotes mutagenesis. Two distinct DNA repair mechanisms regulate uracil processing in Ig genes. The first involves base removal by the uracil DNA glycosylase (UNG), and the second detects uracil via the mismatch repair (MMR) complex. Methyl binding domain protein 4 (MBD4) is a uracil glycosylase and an intriguing candidate for involvement in somatic hypermutation because of its interaction with the MMR MutL homolog 1 (MLH1). We found that the DNA uracil glycosylase domain of MBD4 is highly conserved among mammals, birds, shark, and insects. Conservation of the human and chicken MBD4 uracil glycosylase domain structure is striking. Here we examined the function of MBD4 in chicken DT40 B cells which undergo constitutive SHM. We constructed structural variants of MBD4 DT40 cells using CRISPR/Cas9 genome editing. Disruption of the MBD4 uracil glycosylase catalytic region increased SHM frequency in IgM loss assays. We propose that MBD4 plays a role in SHM.
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Affiliation(s)
- Ryan Costello
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, United States
| | - Jose F Cantillo
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, United States
| | - Amy L Kenter
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, United States
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6
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Kenter AL, Kumar S, Wuerffel R, Grigera F. AID hits the jackpot when missing the target. Curr Opin Immunol 2016; 39:96-102. [PMID: 26845615 DOI: 10.1016/j.coi.2016.01.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 01/12/2016] [Accepted: 01/14/2016] [Indexed: 01/07/2023]
Abstract
Activation induced deaminase is the single B cell specific factor mediating class switch recombination and somatic hypermutation. Numerous studies have shown that AID preferentially targets Ig substrates and also attacks non-Ig substrates to create DNA damage that contributes to lymphomagenesis. AID targeting to Ig loci is linked to transcription but the mechanism governing this process has been obscure. Here we discuss research that illustrates the connection between AID targeting to DNA substrates and transcription processes to reveal rules governing the specificity of AID attack. These observations are woven together to provide a integrated view of AID function and a surprising linkage with global regulation of gene expression.
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7
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Zanotti KJ, Gearhart PJ. Antibody diversification caused by disrupted mismatch repair and promiscuous DNA polymerases. DNA Repair (Amst) 2016; 38:110-116. [PMID: 26719140 PMCID: PMC4740194 DOI: 10.1016/j.dnarep.2015.11.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/30/2015] [Indexed: 10/25/2022]
Abstract
The enzyme activation-induced deaminase (AID) targets the immunoglobulin loci in activated B cells and creates DNA mutations in the antigen-binding variable region and DNA breaks in the switch region through processes known, respectively, as somatic hypermutation and class switch recombination. AID deaminates cytosine to uracil in DNA to create a U:G mismatch. During somatic hypermutation, the MutSα complex binds to the mismatch, and the error-prone DNA polymerase η generates mutations at A and T bases. During class switch recombination, both MutSα and MutLα complexes bind to the mismatch, resulting in double-strand break formation and end-joining. This review is centered on the mechanisms of how the MMR pathway is commandeered by B cells to generate antibody diversity.
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Affiliation(s)
- Kimberly J Zanotti
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
| | - Patricia J Gearhart
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
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8
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Katsura M, Cyou-Nakamine H, Zen Q, Zen Y, Nansai H, Amagasa S, Kanki Y, Inoue T, Kaneki K, Taguchi A, Kobayashi M, Kaji T, Kodama T, Miyagawa K, Wada Y, Akimitsu N, Sone H. Effects of Chronic Low-Dose Radiation on Human Neural Progenitor Cells. Sci Rep 2016; 6:20027. [PMID: 26795421 PMCID: PMC4726121 DOI: 10.1038/srep20027] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 10/19/2015] [Indexed: 12/24/2022] Open
Abstract
The effects of chronic low-dose radiation on human health have not been well established. Recent studies have revealed that neural progenitor cells are present not only in the fetal brain but also in the adult brain. Since immature cells are generally more radiosensitive, here we investigated the effects of chronic low-dose radiation on cultured human neural progenitor cells (hNPCs) derived from embryonic stem cells. Radiation at low doses of 31, 124 and 496 mGy per 72 h was administered to hNPCs. The effects were estimated by gene expression profiling with microarray analysis as well as morphological analysis. Gene expression was dose-dependently changed by radiation. By thirty-one mGy of radiation, inflammatory pathways involving interferon signaling and cell junctions were altered. DNA repair and cell adhesion molecules were affected by 124 mGy of radiation while DNA synthesis, apoptosis, metabolism, and neural differentiation were all affected by 496 mGy of radiation. These in vitro results suggest that 496 mGy radiation affects the development of neuronal progenitor cells while altered gene expression was observed at a radiation dose lower than 100 mGy. This study would contribute to the elucidation of the clinical and subclinical phenotypes of impaired neuronal development induced by chronic low-dose radiation.
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Affiliation(s)
- Mari Katsura
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
| | - Hiromasa Cyou-Nakamine
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
- Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Japan
- Faculty of Pharmaceutical Sciences, Department of Pharmacy, Tokyo University of Science, Noda, Japan
| | - Qin Zen
- Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Japan
| | - Yang Zen
- Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Japan
| | - Hiroko Nansai
- Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Japan
| | - Shota Amagasa
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
| | - Yasuharu Kanki
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
| | - Tsuyoshi Inoue
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
- Division of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Kiyomi Kaneki
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Akashi Taguchi
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Mika Kobayashi
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Toshiyuki Kaji
- Faculty of Pharmaceutical Sciences, Department of Pharmacy, Tokyo University of Science, Noda, Japan
| | - Tatsuhiko Kodama
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Kiyoshi Miyagawa
- Laboratory of Molecular Radiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Japan
| | - Youichiro Wada
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | | | - Hideko Sone
- Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Japan
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9
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Abstract
This chapter describes some of the recent, exciting developments that have characterized and connected processes that modify DNA bases with DNA repair pathways. It begins with AID/APOBEC or TET family members that covalently modify bases within DNA. The modified bases, such as uracil or 5-formylcytosine, are then excised by DNA glycosylases including UNG or TDG to initiate base excision repair (BER). BER is known to preserve genome integrity by removing damaged bases. The newer studies underscore the necessity of BER following enzymes that deliberately damage DNA. This includes the role of BER in antibody diversification and more recently, its requirement for demethylation of 5-methylcytosine in mammalian cells. The recent advances have shed light on mechanisms of DNA demethylation, and have raised many more questions. The potential hazards of these processes have also been revealed. Dysregulation of the activity of base modifying enzymes, and resolution by unfaithful or corrupt means can be a driver of genome instability and tumorigenesis. The understanding of both DNA and histone methylation and demethylation is now revealing the true extent to which epigenetics influence normal development and cancer, an abnormal development.
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Affiliation(s)
- Michael D Wyatt
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina, USA.
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10
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Abstract
Wolf-Hirschhorn syndrome (WHS) is a genetic disease with characteristic facial features and developmental disorders. Of interest, loss of the MMSET gene (also known as WHSC1) is considered to be responsible for the core phenotypes of this disease. Patients with WHS also display Ab deficiency, although the underlying cause of this deficiency is unclear. Recent studies suggest that the histone methyltransferase activity of MMSET plays an important role in the DNA damage response by facilitating the recruitment of 53BP1 to sites of DNA damage. We hypothesize that MMSET also regulates class switch recombination (CSR) through its effect on 53BP1. In this study, we show that MMSET indeed plays an important role in CSR through its histone methyltransferase activity. Knocking down MMSET expression impaired 53BP1 recruitment as well as the germline transcription of the Igh switch regions, resulting in defective CSR but no effect on cell growth and viability. These results suggest that defective CSR caused by MMSET deficiency could be a cause of Ab deficiency in WHS patients.
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Affiliation(s)
- Huadong Pei
- Division of Oncology Research, Mayo Clinic, Rochester, MN 55905, USA
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11
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Conde-Pérezprina JC, Luna-López A, González-Puertos VY, Zenteno-Savín T, León-Galván MÁ, Königsberg M. DNA MMR systems, microsatellite instability and antioxidant activity variations in two species of wild bats: Myotis velifer and Desmodus rotundus, as possible factors associated with longevity. Age (Dordr) 2012; 34:1473-1492. [PMID: 22453932 PMCID: PMC3528369 DOI: 10.1007/s11357-012-9399-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Accepted: 02/22/2012] [Indexed: 05/31/2023]
Abstract
The accumulation of oxidative damage to biomolecules, such as DNA, is known to induce alterations in the cell's mechanisms and structure that might lead to the aging process. DNA mismatch repair system (MMR) corrects base mismatches generated during DNA replication that have escaped the proofreading process. In addition, antioxidant enzymes can reduce reactive oxygen species effects in order to protect cells from oxidizing damage. In order to determine the importance of these associated factors during the aging process, in this study, levels of MMR proteins MSH2 and MLH1, as well as microsatellite markers, were compared in liver, lung, and brain of juvenile, adult, and old, both female and male, individuals from two species of wild bats: the short-lived Myotis velifer and the longer lived Desmodus rotundus. Catalase, glutathione peroxidase, and superoxide dismutase were also analyzed to determine if the antioxidant protection correlates negatively with DNA damage. Antioxidant activities were higher in the longer lived D. rotundus than in M. velifer. Furthermore, old M. velifer but not old D. rotundus bats had reduced MMR levels and increased microsatellite instability. Therefore, although our results correlate the reduced MMR efficiency, the deficient antioxidant activity, and the increase in DNA damage with the aging process, this is not always true for all living organisms.
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Affiliation(s)
- Juan C. Conde-Pérezprina
- />Departamento de Ciencias de la Salud, División de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana Iztapalapa, A.P. 55–535, 09340 México, DF Mexico
| | | | - Viridiana Y. González-Puertos
- />Departamento de Ciencias de la Salud, División de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana Iztapalapa, A.P. 55–535, 09340 México, DF Mexico
| | - Tania Zenteno-Savín
- />Programa de Planeación Ambiental y Conservación, Centro de Investigaciones Biológicas del Noroeste, S.C., La Paz, Baja California Sur Mexico
| | - Miguel Ángel León-Galván
- />Departamento de Biología, DCBS, Universidad Autónoma Metropolitana Iztapalapa, A.P. 55–535, 09340 México, DF Mexico
| | - Mina Königsberg
- />Departamento de Ciencias de la Salud, División de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana Iztapalapa, A.P. 55–535, 09340 México, DF Mexico
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12
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Conde-Pérezprina JC, León-Galván MÁ, Konigsberg M. DNA mismatch repair system: repercussions in cellular homeostasis and relationship with aging. Oxid Med Cell Longev 2012; 2012:728430. [PMID: 23213348 DOI: 10.1155/2012/728430] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 09/24/2012] [Accepted: 10/08/2012] [Indexed: 11/18/2022]
Abstract
The mechanisms that concern DNA repair have been studied in the last years due to their consequences in cellular homeostasis. The diverse and damaging stimuli that affect DNA integrity, such as changes in the genetic sequence and modifications in gene expression, can disrupt the steady state of the cell and have serious repercussions to pathways that regulate apoptosis, senescence, and cancer. These altered pathways not only modify cellular and organism longevity, but quality of life (“health-span”). The DNA mismatch repair system (MMR) is highly conserved between species; its role is paramount in the preservation of DNA integrity, placing it as a necessary focal point in the study of pathways that prolong lifespan, aging, and disease. Here, we review different insights concerning the malfunction or absence of the DNA-MMR and its impact on cellular homeostasis. In particular, we will focus on DNA-MMR mechanisms regulated by known repair proteins MSH2, MSH6, PMS2, and MHL1, among others.
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13
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Kenter AL, Feldman S, Wuerffel R, Achour I, Wang L, Kumar S. Three-dimensional architecture of the IgH locus facilitates class switch recombination. Ann N Y Acad Sci 2012; 1267:86-94. [PMID: 22954221 DOI: 10.1111/j.1749-6632.2012.06604.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Immunoglobulin (Ig) class switch recombination (CSR) is responsible for diversification of antibody effector function during an immune response. This region-specific recombination event, between repetitive switch (S) DNA elements, is unique to B lymphocytes and is induced by activationinduced deaminase (AID). CSR is critically dependent on transcription of noncoding RNAs across S regions. However, mechanistic insight regarding this process has remained unclear. New studies indicate that long-range intrachromosomal interactions among IgH transcriptional elements organize the formation of the S/S synaptosome, as a prerequisite for CSR. This three-dimensional chromatin architecture simultaneously brings promoters and enhancers into close proximity to facilitate transcription. Here, we recount how transcription across S DNA promotes accumulation of RNA polymerase II, leading to the introduction of activating chromatin modifications and hyperaccessible chromatin that is amenable to AID activity.
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Affiliation(s)
- Amy L Kenter
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, Illinois, USA.
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14
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Abstract
Activation induced deaminase (AID) is globally targeted to immunoglobulin loci, preferentially focused to switch (S) regions and variable (V) regions, and prone to attack hotspot motifs. Nevertheless, AID deamination is not exclusive to Ig loci and the rules regulating AID targeting remain unclear. Transcription is critically required for class switch recombination and somatic hypermutation. Here, I consider the unique features associated with S region transcription leading to RNA polymerase II pausing, that in turn promote the introduction of activating chromatin remodeling, histone modifications and recruitment of AID to targeted S regions. These findings allow for a better understanding of the interplay between transcription, AID targeting and mistargeting to Ig and non-Ig loci.
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Affiliation(s)
- Amy L Kenter
- Department of Microbiology and Immunology, University of Illinois College of Medicine, 835 S. Wolcott, Chicago, IL 60612-7344, USA.
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15
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Abstract
Gliobastoma multiform (GBM) is the most common and aggressive brain tumor, which is characterized by its infiltrative nature. Current standard therapy for GBMs consists of surgery followed by radiotherapy combined with the alkylating agent temozolomide (TMZ). Recent clinical trials have demonstrated that this chemo-irradiation approach results in a significant increase in survival compared to radiotherapy alone. Nevertheless, due to tumor recurrence, the median survival time is still limited to approximately 15 months. Recently, several studies have focused on aberrant signal transduction in GBM, resistance mechanisms of GBM to TMZ and to radiotherapy. Attention has been focused on molecular targets including phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, protein kinase C (pKC) pathway, Ras/mitogen-activated protein kinase pathway (MAPK), Wnt pathway and intrinsic or extrinsic apoptosis pathways. In addition, research has been directed to radiotherapy and radiosensitizing agents, and cancer gene therapy as well. This article will address several resistance mechanisms of GBM to chemotherapy and radiotherapy and the recent preclinical and clinical studies on targeted therapy.
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Affiliation(s)
- N H Rekers
- Department of Medical Oncology, VU University Medical Center, The Netherlands
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16
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Masutani C. Human DNA Polymerase η and Its Regulatory Mechanisms. Genes Environ 2012. [DOI: 10.3123/jemsge.34.63] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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17
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Abstract
To combat the ever-changing pool of pathogens we face, B cells generate highly optimized antibodies in two distinct steps. A large variety of antibodies are first generated randomly by V(D)J recombination, and then, upon encountering an antigen, antibodies are fine-tuned by somatic hypermutation and class switch recombination--both of which are initiated by the same protein, activation-induced cytidine deaminase (AID). All three processes are highly mutagenic, and mistargeting of each of these has been shown to contribute to tumorigenesis. We study these processes because they provide an excellent model to understand how highly mutagenic reactions are channeled into productive use by cells and the consequent risk this carries. In this review, we will discuss many of the outstanding questions in the field that we grapple with while developing a consistent model for AID action. We will also discuss the complexity added to these models by the recent finding that AID might be part of a demethylase complex.
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Affiliation(s)
- Dana C Upton
- Department of Immunology, Duke University, 312 Edwin L. Jones Bldg., Campus Box # 3010, Durham, NC 27710, USA
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18
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Abstract
The discovery of human DNA polymerase eta (pol η) has a major impact on the fields of DNA replication/repair fields. Since the discovery of human pol η, a number of new DNA polymerases with the ability to bypass various DNA lesions have been discovered. Among these polymerases, pol η is the most extensively studied lesion bypass polymerase with a defined major biological function, that is, to replicate across the cyclobutane pyrimidine dimers introduced by UV irradiation. Cyclobutane pyrimidine dimer is a major DNA lesion that causes distortion of DNA structure and block the replicative DNA polymerases during DNA replication process. Genetic defects in the pol η gene, Rad30, results in a disease called xeroderma pigmentosum variant. This review focuses on the overall properties of pol η and the mechanism that involved in regulating its activity in cells. In addition, the role of pol η in the action of DNA-targeting anticancer compounds is also discussed.
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Affiliation(s)
- Kai-ming Chou
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202, USA.
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Kothapalli NR, Norton DD, Fugmann SD. Classical Mus musculus Igκ enhancers support transcription but not high level somatic hypermutation from a V-lambda promoter in chicken DT40 cells. PLoS One 2011; 6:e18955. [PMID: 21533098 PMCID: PMC3080390 DOI: 10.1371/journal.pone.0018955] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Accepted: 03/21/2011] [Indexed: 01/28/2023] Open
Abstract
Somatic hypermutation (SHM) of immunoglobulin genes is initiated by activation-induced cytidine deaminase (AID) in activated B cells. This process is strictly dependent on transcription. Hence, cis-acting transcriptional control elements have been proposed to target SHM to immunoglobulin loci. The Mus musculus Igκ locus is regulated by the intronic enhancer (iE/MAR) and the 3′ enhancer (3′E), and multiple studies using transgenic and knock-out approaches in mice and cell lines have reported somewhat contradictory results about the function of these enhancers in AID-mediated sequence diversification. Here we show that the M. musculus iE/MAR and 3′E elements are active solely as transcriptional enhancer when placed in the context of the IGL locus in Gallus gallus DT40 cells, but they are very inefficient in targeting AID-mediated mutation events to this locus. This suggests that either key components of the cis-regulatory targeting elements reside outside the murine Igκ transcriptional enhancer sequences, or that the targeting of AID activity to Ig loci occurs by largely species-specific mechanisms.
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Affiliation(s)
- Naga Rama Kothapalli
- Laboratory of Molecular Biology and Immunology, Molecular Immunology Unit, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
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Abstract
Sharks are representatives of the earliest vertebrates that possess an immune system utilizing V(D)J recombination to generate Ag receptors. Their Ab repertoire diversity is based in part on a somatic hypermutation process that introduces adjacent nucleotide substitutions of 2-5 bp. We have isolated mutant nonfunctional Ig rearrangements and intronic flank sequences to characterize the nonselected, intrinsic properties of this phenomenon; changes unique to shark were observed. Duplications and deletions were associated with N additions, suggesting participation of a DNA polymerase with some degree of template independence during the repair of DNA breaks initiated by activation-induced cytidine deaminase. Other mutations were consistent with some in vitro activities of mammalian translesion DNA polymerase η: tandem base substitutions, strand slippage, and small insertions/deletions. The nature of substitution patterns shows that DNA lesions at shark Ig genes recruit DNA repair factors with a species-specific repertoire of activities. We speculate that the tandem mutations are introduced by direct sequential misinsertions and that, in shark B cells, the mispairs tend to be extended rather than proofread. Despite extensive changes undergone by some mutants, the physical range of mutational activity remained restricted to VDJ and within the first 2-kb portion of the 6.8-kb J-C intron, perhaps a self-regulating aspect of activation-induced cytidine deaminase action that is conserved in evolution.
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Affiliation(s)
- Catherine Zhu
- Department of Physiology and Pharmacology, State University of New York, Health Science Center at Brooklyn, Brooklyn, NY 11203-2098, USA
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Chahwan R, Wontakal SN, Roa S. Crosstalk between genetic and epigenetic information through cytosine deamination. Trends Genet 2010; 26:443-8. [DOI: 10.1016/j.tig.2010.07.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 07/16/2010] [Accepted: 07/19/2010] [Indexed: 01/25/2023]
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Biertümpfel C, Zhao Y, Kondo Y, Ramón-Maiques S, Gregory M, Lee JY, Masutani C, Lehmann AR, Hanaoka F, Yang W. Structure and mechanism of human DNA polymerase eta. Nature 2010; 465:1044-8. [PMID: 20577208 DOI: 10.1038/nature09196] [Citation(s) in RCA: 271] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Accepted: 05/21/2010] [Indexed: 12/25/2022]
Abstract
The variant form of human xeroderma pigmentosum syndrome (XPV) is caused by a deficiency in DNA polymerase η (Pol η) that enables replication through sunlight-induced pyrimidine dimers. We report high-resolution crystal structures of human Pol η at four consecutive steps during DNA synthesis through cis-syn cyclobutane thymine dimers. Pol η acts like a molecular splint to stabilize damaged DNA in a normal B-form conformation. An enlarged active site accommodates the thymine dimer with excellent stereochemistry for two-metal ion catalysis. Two residues conserved among Pol η orthologs form specific hydrogen bonds with the lesion and the incoming nucleotide to assist translesion synthesis. Based on the structures, eight Pol η missense mutations causing XPV can be rationalized as undermining the “molecular splint” or perturbing the active-site alignment. The structures also shed light on the role of Pol η in replicating through D loop and DNA fragile sites.
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van Oers JM, Roa S, Werling U, Liu Y, Genschel J, Hou H Jr, Sellers RS, Modrich P, Scharff MD, Edelmann W. PMS2 endonuclease activity has distinct biological functions and is essential for genome maintenance. Proc Natl Acad Sci U S A 2010; 107:13384-9. [PMID: 20624957 DOI: 10.1073/pnas.1008589107] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The DNA mismatch repair protein PMS2 was recently found to encode a novel endonuclease activity. To determine the biological functions of this activity in mammals, we generated endonuclease-deficient Pms2E702K knock-in mice. Pms2EK/EK mice displayed increased genomic mutation rates and a strong cancer predisposition. In addition, class switch recombination, but not somatic hypermutation, was impaired in Pms2EK/EK B cells, indicating a specific role in Ig diversity. In contrast to Pms2-/- mice, Pms2EK/EK male mice were fertile, indicating that this activity is dispensable in spermatogenesis. Therefore, the PMS2 endonuclease activity has distinct biological functions and is essential for genome maintenance and tumor suppression.
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Ramachandran S, Chahwan R, Nepal RM, Frieder D, Panier S, Roa S, Zaheen A, Durocher D, Scharff MD, Martin A. The RNF8/RNF168 ubiquitin ligase cascade facilitates class switch recombination. Proc Natl Acad Sci U S A 2010; 107:809-14. [PMID: 20080757 DOI: 10.1073/pnas.0913790107] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
An effective immune response requires B cells to produce several classes of antibodies through the process of class switch recombination (CSR). Activation-induced cytidine deaminase initiates CSR by deaminating deoxycytidines at switch regions within the Ig locus. This activity leads to double-stranded DNA break formation at the donor and recipient switch regions that are subsequently synapsed and ligated in a 53BP1-dependent process that remains poorly understood. The DNA damage response E3 ubiquitin ligases RNF8 and RNF168 were recently shown to facilitate recruitment of 53BP1 to sites of DNA damage. Here we show that the ubiquitination pathway mediated by RNF8 and RNF168 plays an integral part in CSR. Using the CH12F3-2 mouse B cell line that undergoes CSR to IgA at high rates, we demonstrate that knockdown of RNF8, RNF168, and 53BP1 leads to a significant decrease in CSR. We also show that 53BP1-deficient CH12F3-2 cells are protected from apoptosis mediated by the MDM2 inhibitor Nutlin-3. In contrast, deficiency in either E3 ubiquitin ligase does not protect cells from Nutlin-3-mediated apoptosis, indicating that RNF8 and RNF168 do not regulate all functions of 53BP1.
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