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Pham P, Malik S, Mak C, Calabrese PC, Roeder RG, Goodman MF. AID-RNA polymerase II transcription-dependent deamination of IgV DNA. Nucleic Acids Res 2020; 47:10815-10829. [PMID: 31566237 PMCID: PMC6846656 DOI: 10.1093/nar/gkz821] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 09/09/2019] [Accepted: 09/13/2019] [Indexed: 12/16/2022] Open
Abstract
Activation-induced deoxycytidine deaminase (AID) initiates somatic hypermutation (SHM) in immunoglobulin variable (IgV) genes to produce high-affinity antibodies. SHM requires IgV transcription by RNA polymerase II (Pol II). A eukaryotic transcription system including AID has not been reported previously. Here, we reconstitute AID-catalyzed deamination during Pol II transcription elongation in conjunction with DSIF transcription factor. C→T mutations occur at similar frequencies on non-transcribed strand (NTS) and transcribed strand (TS) DNA. In contrast, bacteriophage T7 Pol generates NTS mutations predominantly. AID-Pol II mutations are strongly favored in WRC and WGCW overlapping hot motifs (W = A or T, R = A or G) on both DNA strands. Single mutations occur on 70% of transcribed DNA clones. Mutations are correlated over a 15 nt distance in multiply mutated clones, suggesting that deaminations are catalyzed processively within a stalled or backtracked transcription bubble. Site-by-site comparisons for biochemical and human memory B-cell mutational spectra in an IGHV3-23*01 target show strongly favored deaminations occurring in the antigen-binding complementarity determining regions (CDR) compared to the framework regions (FW). By exhibiting consistency with B-cell SHM, our in vitro data suggest that biochemically defined reconstituted Pol II transcription systems can be used to investigate how, when and where AID is targeted.
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Affiliation(s)
- Phuong Pham
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Sohail Malik
- Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY 10065, USA
| | - Chiho Mak
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA
| | - Peter C Calabrese
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Robert G Roeder
- Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY 10065, USA
| | - Myron F Goodman
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA.,Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA
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Marchalot A, Ashi MO, Lambert JM, Carrion C, Lecardeur S, Srour N, Delpy L, Le Pennec S. Uncoupling Splicing From Transcription Using Antisense Oligonucleotides Reveals a Dual Role for I Exon Donor Splice Sites in Antibody Class Switching. Front Immunol 2020; 11:780. [PMID: 32477332 PMCID: PMC7233311 DOI: 10.3389/fimmu.2020.00780] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/06/2020] [Indexed: 01/08/2023] Open
Abstract
Class switch recombination (CSR) changes antibody isotype by replacing Cμ constant exons with different constant exons located downstream on the immunoglobulin heavy (IgH) locus. During CSR, transcription through specific switch (S) regions and processing of non-coding germline transcripts (GLTs) are essential for the targeting of activation-induced cytidine deaminase (AID). While CSR to IgG1 is abolished in mice lacking an Iγ1 exon donor splice site (dss), many questions remain regarding the importance of I exon dss recognition in CSR. To further clarify the role of I exon dss in CSR, we first evaluated RNA polymerase II (RNA pol II) loading and chromatin accessibility in S regions after activation of mouse B cells lacking Iγ1 dss. We found that deletion of Iγ1 dss markedly reduced RNA pol II pausing and active chromatin marks in the Sγ1 region. We then challenged the post-transcriptional function of I exon dss in CSR by using antisense oligonucleotides (ASOs) masking I exon dss on GLTs. Treatment of stimulated B cells with an ASO targeting Iγ1 dss, in the acceptor Sγ1 region, or Iμ dss, in the donor Sμ region, did not decrease germline transcription but strongly inhibited constitutive splicing and CSR to IgG1. Supporting a global effect on CSR, we also observed that the targeting of Iμ dss reduced CSR to IgG3 and, to a lesser extent, IgG2b isotypes. Altogether, this study reveals that the recognition of I exon dss first supports RNA pol II pausing and the opening of chromatin in targeted S regions and that GLT splicing events using constitutive I exon dss appear mandatory for the later steps of CSR, most likely by guiding AID to S regions.
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Affiliation(s)
- Anne Marchalot
- Unité Mixte de Recherche CNRS 7276, INSERM 1262, Université de Limoges, Limoges, France
| | - Mohamad Omar Ashi
- Unité Mixte de Recherche CNRS 7276, INSERM 1262, Université de Limoges, Limoges, France
| | - Jean-Marie Lambert
- Unité Mixte de Recherche CNRS 7276, INSERM 1262, Université de Limoges, Limoges, France
| | - Claire Carrion
- Unité Mixte de Recherche CNRS 7276, INSERM 1262, Université de Limoges, Limoges, France
| | - Sandrine Lecardeur
- Unité Mixte de Recherche CNRS 7276, INSERM 1262, Université de Limoges, Limoges, France
| | - Nivine Srour
- Unité Mixte de Recherche CNRS 7276, INSERM 1262, Université de Limoges, Limoges, France
- Segal Cancer Center, Lady Davis Institute for Medical Research and Departments of Oncology and Medicine, McGill University, Montréal, QC, Canada
| | - Laurent Delpy
- Unité Mixte de Recherche CNRS 7276, INSERM 1262, Université de Limoges, Limoges, France
| | - Soazig Le Pennec
- Unité Mixte de Recherche CNRS 7276, INSERM 1262, Université de Limoges, Limoges, France
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Zhang B, Zhao N, Jia L, Che J, He X, Liu K, Bao B. Identification and application of piwi-interacting RNAs from seminal plasma exosomes in Cynoglossus semilaevis. BMC Genomics 2020; 21:302. [PMID: 32293248 PMCID: PMC7158113 DOI: 10.1186/s12864-020-6660-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 03/09/2020] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Piwi-interacting RNAs (piRNAs) have been linked to epigenetic and post-transcriptional gene silencing of retrotransposons in germ line cells, particularly in spermatogenesis. Exosomes are important mediators of vesicle transport, and the piRNAs in exosomes might play an important role in cell communication and signal pathway regulation. Moreover, exosomic piRNAs are promising biomarkers for disease diagnosis and physiological status indication. We used Cynoglossus semilaevis because of its commercial value and its sexual dimorphism, particularly the sex reversed "pseudomales" who have a female karyotype, produce sperm, and copulate with normal females to produce viable offspring. RESULTS To determine whether piRNAs from fish germ line cells have similar features, seminal plasma exosomes from half-smooth tongue sole, C. semilaevis, were identified, and their small RNAs were sequenced and analysed. We identified six signature piRNAs as biomarkers in exosomes of seminal plasma from males and pseudomale C. semilaevis. Bioinformatic analysis showed that all six signatures were sex-related, and four were DNA methylation-related and transposition-related piRNAs. Their expression profiles were verified using real-time quantitative PCR. The expression of the signature piRNAs was markedly higher in males than in pseudomales. The signature piRNAs could be exploited as male-specific biomarkers in this fish. CONCLUSIONS These signatures provide an effective tool to explore the regulatory mechanism of sex development in C. semilaevis and may provide guidance for future research on the function of piRNAs in the generative mechanism of sex reversed "pseudomales" in C. semilaevis.
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Affiliation(s)
- Bo Zhang
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources (Shanghai Ocean University), Ministry of Education; International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology; National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, 201306, China.,Tianjin Sea Fisheries Research Institute, Tianjin, China
| | - Na Zhao
- Tianjin Medicine Biotechnology Co, Ltd, Tianjin, China
| | - Lei Jia
- Tianjin Sea Fisheries Research Institute, Tianjin, China
| | - Jinyuan Che
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources (Shanghai Ocean University), Ministry of Education; International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology; National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, 201306, China
| | - Xiaoxu He
- Tianjin Sea Fisheries Research Institute, Tianjin, China
| | - Kefeng Liu
- Tianjin Sea Fisheries Research Institute, Tianjin, China
| | - Baolong Bao
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources (Shanghai Ocean University), Ministry of Education; International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology; National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, 201306, China.
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54
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Iveland TS, Hagen L, Sharma A, Sousa MML, Sarno A, Wollen KL, Liabakk NB, Slupphaug G. HDACi mediate UNG2 depletion, dysregulated genomic uracil and altered expression of oncoproteins and tumor suppressors in B- and T-cell lines. J Transl Med 2020; 18:159. [PMID: 32264925 PMCID: PMC7137348 DOI: 10.1186/s12967-020-02318-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 03/27/2020] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND HDAC inhibitors (HDACi) belong to a new group of chemotherapeutics that are increasingly used in the treatment of lymphocyte-derived malignancies, but their mechanisms of action remain poorly understood. Here we aimed to identify novel protein targets of HDACi in B- and T-lymphoma cell lines and to verify selected candidates across several mammalian cell lines. METHODS Jurkat T- and SUDHL5 B-lymphocytes were treated with the HDACi SAHA (vorinostat) prior to SILAC-based quantitative proteome analysis. Selected differentially expressed proteins were verified by targeted mass spectrometry, RT-PCR and western analysis in multiple mammalian cell lines. Genomic uracil was quantified by LC-MS/MS, cell cycle distribution analyzed by flow cytometry and class switch recombination monitored by FACS in murine CH12F3 cells. RESULTS SAHA treatment resulted in differential expression of 125 and 89 proteins in Jurkat and SUDHL5, respectively, of which 19 were commonly affected. Among these were several oncoproteins and tumor suppressors previously not reported to be affected by HDACi. Several key enzymes determining the cellular dUTP/dTTP ratio were downregulated and in both cell lines we found robust depletion of UNG2, the major glycosylase in genomic uracil sanitation. UNG2 depletion was accompanied by hyperacetylation and mediated by increased proteasomal degradation independent of cell cycle stage. UNG2 degradation appeared to be ubiquitous and was observed across several mammalian cell lines of different origin and with several HDACis. Loss of UNG2 was accompanied by 30-40% increase in genomic uracil in freely cycling HEK cells and reduced immunoglobulin class-switch recombination in murine CH12F3 cells. CONCLUSION We describe several oncoproteins and tumor suppressors previously not reported to be affected by HDACi in previous transcriptome analyses, underscoring the importance of proteome analysis to identify cellular effectors of HDACi treatment. The apparently ubiquitous depletion of UNG2 and PCLAF establishes DNA base excision repair and translesion synthesis as novel pathways affected by HDACi treatment. Dysregulated genomic uracil homeostasis may aid interpretation of HDACi effects in cancer cells and further advance studies on this class of inhibitors in the treatment of APOBEC-expressing tumors, autoimmune disease and HIV-1.
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Affiliation(s)
- Tobias S Iveland
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health, Norwegian University of Science and Technology, 7491, Trondheim, Norway.,Cancer Clinic, St. Olav's Hospital, Trondheim, Norway
| | - Lars Hagen
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health, Norwegian University of Science and Technology, 7491, Trondheim, Norway.,Clinic of Laboratory Medicine, St. Olav's Hospital, Trondheim, Norway.,Proteomics and Modomics Experimental Core, PROMEC, at NTNU and the Central Norway Regional Health Authority, Stjørdal, Norway
| | - Animesh Sharma
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health, Norwegian University of Science and Technology, 7491, Trondheim, Norway.,Clinic of Laboratory Medicine, St. Olav's Hospital, Trondheim, Norway.,Proteomics and Modomics Experimental Core, PROMEC, at NTNU and the Central Norway Regional Health Authority, Stjørdal, Norway
| | - Mirta M L Sousa
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health, Norwegian University of Science and Technology, 7491, Trondheim, Norway.,Clinic of Laboratory Medicine, St. Olav's Hospital, Trondheim, Norway
| | - Antonio Sarno
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health, Norwegian University of Science and Technology, 7491, Trondheim, Norway.,Clinic of Laboratory Medicine, St. Olav's Hospital, Trondheim, Norway
| | - Kristian Lied Wollen
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health, Norwegian University of Science and Technology, 7491, Trondheim, Norway
| | - Nina Beate Liabakk
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health, Norwegian University of Science and Technology, 7491, Trondheim, Norway.,Clinic of Laboratory Medicine, St. Olav's Hospital, Trondheim, Norway
| | - Geir Slupphaug
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health, Norwegian University of Science and Technology, 7491, Trondheim, Norway. .,Clinic of Laboratory Medicine, St. Olav's Hospital, Trondheim, Norway. .,Proteomics and Modomics Experimental Core, PROMEC, at NTNU and the Central Norway Regional Health Authority, Stjørdal, Norway.
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55
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Kazadi D, Lim J, Rothschild G, Grinstein V, Laffleur B, Becherel O, Lavin MJ, Basu U. Effects of senataxin and RNA exosome on B-cell chromosomal integrity. Heliyon 2020; 6:e03442. [PMID: 32195383 PMCID: PMC7075999 DOI: 10.1016/j.heliyon.2020.e03442] [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: 08/16/2019] [Revised: 01/07/2020] [Accepted: 02/13/2020] [Indexed: 11/10/2022] Open
Abstract
Loss of function of senataxin (SETX), a bona-fide RNA/DNA helicase, is associated with neuronal degeneration leading to Ataxia and Ocular Apraxia (AOA) in human patients. SETX is proposed to promote transcription termination, DNA replication, DNA repair, and to unwind deleterious RNA:DNA hybrids in the genome. In all the above-mentioned mechanisms, SETX unwinds transcription complex-associated nascent RNA which is then degraded by the RNA exosome complex. Here we have used B cells isolated from a SETX mutant mouse model and compared genomic instability and immunoglobulin heavy chain locus (IgH) class switch recombination (CSR) to evaluate aberrant and programmed genomic rearrangements, respectively. Similar to RNA exosome mutant primary B cells, SETX mutant primary B cells display genomic instability but a modest decrease in efficiency of CSR. Furthermore, knockdown of Setx mRNAs from CH12–F3 B-cell lines leads to a defect in IgA CSR and accumulation of aberrant patterns of mutations in IgH switch sequences. Given that SETX mutant mice do not recapitulate the AOA neurodegenerative phenotype, it is possible that some aspects of SETX biology are rescued by redundant helicases in mice. Overall, our study provides new insights into the role of the SETX/RNA exosome axis in suppressing genomic instability so that programmed DNA breaks are properly orchestrated.
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Affiliation(s)
- David Kazadi
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Junghyun Lim
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Gerson Rothschild
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Veronika Grinstein
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Brice Laffleur
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Olivier Becherel
- Centre for Clinical Research, University of Queensland, Brisbane, Qld, Australia
| | - Martin J Lavin
- Centre for Clinical Research, University of Queensland, Brisbane, Qld, Australia
| | - Uttiya Basu
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
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56
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Urulangodi M, Mohanty A. DNA damage response and repair pathway modulation by non-histone protein methylation: implications in neurodegeneration. J Cell Commun Signal 2020; 14:31-45. [PMID: 31749026 PMCID: PMC7176765 DOI: 10.1007/s12079-019-00538-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 11/14/2019] [Indexed: 12/11/2022] Open
Abstract
Protein post-translational modifications (PTMs) have emerged to be combinatorial, essential mechanisms used by eukaryotic cells to regulate local chromatin structure, diversify and extend their protein functions and dynamically coordinate complex intracellular signalling processes. Most common types of PTMs include enzymatic addition of small chemical groups resulting in phosphorylation, glycosylation, poly(ADP-ribosyl)ation, nitrosylation, methylation, acetylation or covalent attachment of complete proteins such as ubiquitin and SUMO. Protein arginine methyltransferases (PRMTs) and protein lysine methyltransferases (PKMTs) enzymes catalyse the methylation of arginine and lysine residues in target proteins, respectively. Rapid progress in quantitative proteomic analysis and functional assays have not only documented the methylation of histone proteins post-translationally but also identified their occurrence in non-histone proteins which dynamically regulate a plethora of cellular functions including DNA damage response and repair. Emerging advances have now revealed the role of both histone and non-histone methylations in the regulating the DNA damage response (DDR) proteins, thereby modulating the DNA repair pathways both in proliferating and post-mitotic neuronal cells. Defects in many cellular DNA repair processes have been found primarily manifested in neuronal tissues. Moreover, fine tuning of the dynamicity of methylation of non-histone proteins as well as the perturbations in this dynamic methylation processes have recently been implicated in neuronal genomic stability maintenance. Considering the impact of methylation on chromatin associated pathways, in this review we attempt to link the evidences in non-histone protein methylation and DDR with neurodegenerative research.
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Affiliation(s)
- Madhusoodanan Urulangodi
- Department of Biochemistry, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, Kerala, PIN-695011, India.
| | - Abhishek Mohanty
- Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, PIN-110085, India.
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57
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Singh AK, Tamrakar A, Jaiswal A, Kanayama N, Kodgire P. SRSF1-3, a splicing and somatic hypermutation regulator, controls transcription of IgV genes via chromatin regulators SATB2, UBN1 and histone variant H3.3. Mol Immunol 2020; 119:69-82. [DOI: 10.1016/j.molimm.2020.01.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 01/01/2020] [Accepted: 01/11/2020] [Indexed: 12/21/2022]
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58
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Abstract
In this review, Mirman et al. summarize the current understanding of the role of 53BP1 in DSB repair at deprotected telomeres, in class switch recombination in the immune system, and in the context of PARPi-treated BRCA1-deficient cells. They argue that the primary function of 53BP1 is not to regulate the choice between c-NHEJ and HDR, but to ensure the fidelity of DSB repair, a function that is corrupted in diseases where DNA repair is rewired. 53BP1 is an enigmatic DNA damage response factor that gained prominence because it determines the efficacy of PARP1 inhibitory drugs (PARPi) in BRCA1-deficient cancers. Recent studies have elevated 53BP1 from its modest status of (yet another) DNA damage factor to master regulator of double-strand break (DSB) repair pathway choice. Our review of the literature suggests an alternative view. We propose that 53BP1 has evolved to avoid mutagenic repair outcomes and does so by controlling the processing of DNA ends and the dynamics of DSBs. The consequences of 53BP1 deficiency, such as diminished PARPi efficacy in BRCA1-deficient cells and altered repair of damaged telomeres, can be explained from this viewpoint. We further propose that some of the fidelity functions of 53BP1 coevolved with class switch recombination (CSR) in the immune system. We speculate that, rather than being deterministic in DSB repair pathway choice, 53BP1 functions as a DSB escort that guards against illegitimate and potentially tumorigenic recombination.
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Affiliation(s)
- Zachary Mirman
- Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, New York 10065, USA
| | - Titia de Lange
- Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, New York 10065, USA
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Regulation of long non-coding RNAs and genome dynamics by the RNA surveillance machinery. Nat Rev Mol Cell Biol 2020; 21:123-136. [PMID: 32020081 DOI: 10.1038/s41580-019-0209-0] [Citation(s) in RCA: 131] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/19/2019] [Indexed: 02/07/2023]
Abstract
Much of the mammalian genome is transcribed, generating long non-coding RNAs (lncRNAs) that can undergo post-transcriptional surveillance whereby only a subset of the non-coding transcripts is allowed to attain sufficient stability to persist in the cellular milieu and control various cellular functions. Paralleling protein turnover by the proteasome complex, lncRNAs are also likely to exist in a dynamic equilibrium that is maintained through constant monitoring by the RNA surveillance machinery. In this Review, we describe the RNA surveillance factors and discuss the vital role of lncRNA surveillance in orchestrating various biological processes, including the protection of genome integrity, maintenance of pluripotency of embryonic stem cells, antibody-gene diversification, coordination of immune cell activation and regulation of heterochromatin formation. We also discuss examples of human diseases and developmental defects associated with the failure of RNA surveillance mechanisms, further highlighting the importance of lncRNA surveillance in maintaining cell and organism functions and health.
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60
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Franklin A, Steele EJ, Lindley RA. A proposed reverse transcription mechanism for (CAG)n and similar expandable repeats that cause neurological and other diseases. Heliyon 2020; 6:e03258. [PMID: 32140575 PMCID: PMC7044655 DOI: 10.1016/j.heliyon.2020.e03258] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 09/26/2019] [Accepted: 01/15/2020] [Indexed: 12/12/2022] Open
Abstract
The mechanism of (CAG)n repeat generation, and related expandable repeat diseases in non-dividing cells, is currently understood in terms of a DNA template-based DNA repair synthesis process involving hairpin stabilized slippage, local error-prone repair via MutSβ (MSH2-MSH3) hairpin protective stabilization, then nascent strand extension by DNA polymerases-β and -δ. We advance a very similar slipped hairpin-stabilized model involving MSH2-MSH3 with two key differences: the copying template may also be the nascent pre-mRNA with the repair pathway being mediated by the Y-family error-prone enzymes DNA polymerase-η and DNA polymerase-κ acting as reverse transcriptases. We argue that both DNA-based and RNA-based mechanisms could well be activated in affected non-dividing brain cells in vivo. Here, we compare the advantages of the RNA/RT-based model proposed by us as an adjunct to previously proposed models. In brief, our model depends upon dysregulated innate and adaptive immunity cascades involving AID/APOBEC and ADAR deaminases that are known to be involved in normal locus-specific immunoglobulin somatic hypermutation, cancer progression and somatic mutations at many off-target non-immunoglobulin sites across the genome: we explain how these processes could also play an active role in repeat expansion diseases at RNA polymerase II-transcribed genes.
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Affiliation(s)
- Andrew Franklin
- Medical Department, Novartis Pharmaceuticals UK Limited, 200 Frimley Business Park, Frimley, Surrey, GU16 7SR, United Kingdom
| | - Edward J. Steele
- Melville Analytics Pty Ltd, Melbourne, Vic, 3004, Australia
- CYO’Connor ERADE Village Foundation, Perth, WA, Australia
| | - Robyn A. Lindley
- GMDxgenomics, Melbourne, Vic, Australia
- Department of Clinical Pathology, Faculty of Medicine, Dentistry & Health Sciences, University of Melbourne, Vic, Australia
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61
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Abstract
The evolutionarily conserved RNA exosome is a multisubunit ribonuclease complex that processes and/or degrades numerous RNAs. Recently, mutations in genes encoding both structural and catalytic subunits of the RNA exosome have been linked to human disease. Mutations in the structural exosome gene EXOSC2 cause a distinct syndrome that includes retinitis pigmentosa, hearing loss, and mild intellectual disability. In contrast, mutations in the structural exosome genes EXOSC3 and EXOSC8 cause pontocerebellar hypoplasia type 1b (PCH1b) and type 1c (PCH1c), respectively, which are related autosomal recessive, neurodegenerative diseases. In addition, mutations in the structural exosome gene EXOSC9 cause a PCH-like disease with cerebellar atrophy and spinal motor neuronopathy. Finally, mutations in the catalytic exosome gene DIS3 have been linked to multiple myeloma, a neoplasm of plasma B cells. How mutations in these RNA exosome genes lead to distinct, tissue-specific diseases is not currently well understood. In this chapter, we examine the role of the RNA exosome complex in human disease and discuss the mechanisms by which mutations in different exosome subunit genes could impair RNA exosome function and give rise to diverse diseases.
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Affiliation(s)
- Milo B Fasken
- Department of Biology, RRC 1021, Emory University, Atlanta, GA, USA.
| | - Derrick J Morton
- Department of Biology, RRC 1021, Emory University, Atlanta, GA, USA
| | - Emily G Kuiper
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Stephanie K Jones
- Department of Biology, RRC 1021, Emory University, Atlanta, GA, USA
- Genetics and Molecular Biology Graduate Program, Emory University, Atlanta, GA, USA
| | - Sara W Leung
- Department of Biology, RRC 1021, Emory University, Atlanta, GA, USA
| | - Anita H Corbett
- Department of Biology, RRC 1021, Emory University, Atlanta, GA, USA.
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Dinesh RK, Barnhill B, Ilanges A, Wu L, Michelson DA, Senigl F, Alinikula J, Shabanowitz J, Hunt DF, Schatz DG. Transcription factor binding at Ig enhancers is linked to somatic hypermutation targeting. Eur J Immunol 2019; 50:380-395. [PMID: 31821534 DOI: 10.1002/eji.201948357] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 10/05/2019] [Accepted: 12/02/2019] [Indexed: 01/15/2023]
Abstract
Secondary diversification of the Ig repertoire occurs through somatic hypermutation (SHM), gene conversion (GCV), and class switch recombination (CSR)-three processes that are initiated by activation-induced cytidine deaminase (AID). AID targets Ig genes at orders of magnitude higher than the rest of the genome, but the basis for this specificity is poorly understood. We have previously demonstrated that enhancers and enhancer-like sequences from Ig genes are capable of stimulating SHM of neighboring genes in a capacity distinct from their roles in increasing transcription. Here, we use an in vitro proteomics approach to identify E-box, MEF2, Ets, and Ikaros transcription factor family members as potential binders of these enhancers. ChIP assays in the hypermutating Ramos B cell line confirmed that many of these factors bound the endogenous Igλ enhancer and/or the IgH intronic enhancer (Eμ) in vivo. Further investigation using SHM reporter assays identified binding sites for E2A and MEF2B in Eμ and demonstrated an association between loss of factor binding and decreases in the SHM stimulating activity of Eμ mutants. Our results provide novel insights into trans-acting factors that dictate SHM targeting and link their activity to specific DNA binding sites within Ig enhancers.
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Affiliation(s)
- Ravi K Dinesh
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA
| | - Benjamin Barnhill
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
| | - Anoj Ilanges
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA
| | - Lizhen Wu
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA
| | - Daniel A Michelson
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA
| | - Filip Senigl
- Institute of Molecular Genetics, Czech Academy of Sciences, Videnska 1083, CZ-14220, Prague 4, Czech Republic
| | - Jukka Alinikula
- Institute of Biomedicine, University of Turku, Turku, Finland
| | | | - Donald F Hunt
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA.,Department of Pathology, University of Virginia, Charlottesville, VA, USA
| | - David G Schatz
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA
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63
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Cortez LM, Brown AL, Dennis MA, Collins CD, Brown AJ, Mitchell D, Mertz TM, Roberts SA. APOBEC3A is a prominent cytidine deaminase in breast cancer. PLoS Genet 2019; 15:e1008545. [PMID: 31841499 PMCID: PMC6936861 DOI: 10.1371/journal.pgen.1008545] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 12/30/2019] [Accepted: 12/01/2019] [Indexed: 11/19/2022] Open
Abstract
APOBEC cytidine deaminases are the second-most prominent source of mutagenesis in sequenced tumors. Previous studies have proposed that APOBEC3B (A3B) is the major source of mutagenesis in breast cancer (BRCA). We show that APOBEC3A (A3A) is the only APOBEC whose expression correlates with APOBEC-induced mutation load and that A3A expression is responsible for cytidine deamination in multiple BRCA cell lines. Comparative analysis of A3A and A3B expression by qRT-PCR, RSEM-normalized RNA-seq, and unambiguous RNA-seq validated the use of RNA-seq to measure APOBEC expression, which indicates that A3A is the primary correlate with APOBEC-mutation load in primary BRCA tumors. We also demonstrate that A3A has >100-fold more cytidine deamination activity than A3B in the presence of cellular RNA, likely explaining why higher levels of A3B expression contributes less to mutagenesis in BRCA. Our findings identify A3A as a major source of cytidine deaminase activity in breast cancer cells and possibly a prominent contributor to the APOBEC mutation signature.
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Affiliation(s)
- Luis M. Cortez
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, United States of America
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, United States of America
| | - Amber L. Brown
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, United States of America
| | - Madeline A. Dennis
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, United States of America
| | - Christopher D. Collins
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, United States of America
| | - Alexander J. Brown
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, United States of America
- School of Molecular Biosciences, Washington State University-Vancouver, Vancouver, WA, United States of America
| | - Debra Mitchell
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, United States of America
| | - Tony M. Mertz
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, United States of America
| | - Steven A. Roberts
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, United States of America
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64
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Serebrenik AA, Starrett GJ, Leenen S, Jarvis MC, Shaban NM, Salamango DJ, Nilsen H, Brown WL, Harris RS. The deaminase APOBEC3B triggers the death of cells lacking uracil DNA glycosylase. Proc Natl Acad Sci U S A 2019; 116:22158-22163. [PMID: 31611371 PMCID: PMC6825264 DOI: 10.1073/pnas.1904024116] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Human cells express up to 9 active DNA cytosine deaminases with functions in adaptive and innate immunity. Many cancers manifest an APOBEC mutation signature and APOBEC3B (A3B) is likely the main enzyme responsible. Although significant numbers of APOBEC signature mutations accumulate in tumor genomes, the majority of APOBEC-catalyzed uracil lesions are probably counteracted in an error-free manner by the uracil base excision repair pathway. Here, we show that A3B-expressing cells can be selectively killed by inhibiting uracil DNA glycosylase 2 (UNG) and that this synthetic lethal phenotype requires functional mismatch repair (MMR) proteins and p53. UNG knockout human 293 and MCF10A cells elicit an A3B-dependent death. This synthetic lethal phenotype is dependent on A3B catalytic activity and reversible by UNG complementation. A3B expression in UNG-null cells causes a buildup of genomic uracil, and the ensuing lethality requires processing of uracil lesions (likely U/G mispairs) by MSH2 and MLH1 (likely noncanonical MMR). Cancer cells expressing high levels of endogenous A3B and functional p53 can also be killed by expressing an UNG inhibitor. Taken together, UNG-initiated base excision repair is a major mechanism counteracting genomic mutagenesis by A3B, and blocking UNG is a potential strategy for inducing the selective death of tumors.
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Affiliation(s)
- Artur A Serebrenik
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
| | - Gabriel J Starrett
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
- Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, MD 20892
| | - Sterre Leenen
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
- Department of Radiation Oncology, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands
| | - Matthew C Jarvis
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
| | - Nadine M Shaban
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
| | - Daniel J Salamango
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
| | - Hilde Nilsen
- Department of Clinical Molecular Biology, University of Oslo, 1478 Lørenskog, Norway
- Akershus University Hospital, 1478 Lørenskog, Norway
| | - William L Brown
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
| | - Reuben S Harris
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455;
- Howard Hughes Medical Institute, Minneapolis, MN 55455
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65
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Steele EJ, Gorczynski RM, Lindley RA, Liu Y, Temple R, Tokoro G, Wickramasinghe DT, Wickramasinghe NC. Lamarck and Panspermia - On the Efficient Spread of Living Systems Throughout the Cosmos. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2019; 149:10-32. [PMID: 31445944 DOI: 10.1016/j.pbiomolbio.2019.08.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Revised: 08/14/2019] [Accepted: 08/21/2019] [Indexed: 02/06/2023]
Abstract
We review the main lines of evidence (molecular, cellular and whole organism) published since the 1970s demonstrating Lamarckian Inheritance in animals, plants and microorganisms viz. the transgenerational inheritance of environmentally-induced acquired characteristics. The studies in animals demonstrate the genetic permeability of the soma-germline Weismann Barrier. The widespread nature of environmentally-directed inheritance phenomena reviewed here contradicts a key pillar of neo-Darwinism which affirms the rigidity of the Weismann Barrier. These developments suggest that neo-Darwinian evolutionary theory is in need of significant revision. We argue that Lamarckian inheritance strategies involving environmentally-induced rapid directional genetic adaptations make biological sense in the context of cosmic Panspermia allowing the efficient spread of living systems and genetic innovation throughout the Universe. The Hoyle-Wickramasinghe Panspermia paradigm also developed since the 1970s, unlike strictly geocentric neo-Darwinism provides a cogent biological rationale for the actual widespread existence of Lamarckian modes of inheritance - it provides its raison d'être. Under a terrestrially confined neo-Darwinian viewpoint such an association may have been thought spurious in the past. Our aim is to outline the conceptual links between rapid Lamarckian-based evolutionary hypermutation processes dependent on reverse transcription-coupled mechanisms among others and the effective cosmic spread of living systems. For example, a viable, or cryo-preserved, living system travelling through space in a protective matrix will need of necessity to rapidly adapt and proliferate on landing in a new cosmic niche. Lamarckian mechanisms thus come to the fore and supersede the slow (blind and random) genetic processes expected under a traditional neo-Darwinian evolutionary paradigm.
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Affiliation(s)
- Edward J Steele
- C.Y.O'Connor ERADE Village Foundation, Piara Waters, Perth, 6112, WA, Australia; Centre for Astrobiology, University of Ruhuna, Matara, Sri Lanka; Melville Analytics Pty Ltd, Melbourne, Vic, Australia.
| | | | - Robyn A Lindley
- Department of Clinical Pathology, Faculty of Medicine, Dentistry & Health Sciences, University of MelbourneVic, Australia; GMDx Group Ltd, Melbourne, Vic, Australia
| | - Yongsheng Liu
- Henan Collaborative Innovation Center of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, 453003, China
| | - Robert Temple
- The History of Chinese Science and Culture Foundation, Conway Hall, London, UK
| | - Gensuke Tokoro
- Centre for Astrobiology, University of Ruhuna, Matara, Sri Lanka; Institute for the Study of Panspermia and Astrobiology, Gifu, Japan
| | - Dayal T Wickramasinghe
- Centre for Astrobiology, University of Ruhuna, Matara, Sri Lanka; College of Physical and Mathematical Sciences, Australian National University, Canberra, Australia
| | - N Chandra Wickramasinghe
- Centre for Astrobiology, University of Ruhuna, Matara, Sri Lanka; Institute for the Study of Panspermia and Astrobiology, Gifu, Japan; Buckingham Centre for Astrobiology, University of Buckingham, UK
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66
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Yu K, Lieber MR. Current insights into the mechanism of mammalian immunoglobulin class switch recombination. Crit Rev Biochem Mol Biol 2019; 54:333-351. [PMID: 31509023 PMCID: PMC6856442 DOI: 10.1080/10409238.2019.1659227] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 08/13/2019] [Accepted: 08/20/2019] [Indexed: 12/12/2022]
Abstract
Immunoglobulin (Ig) class switch recombination (CSR) is the gene rearrangement process by which B lymphocytes change the Ig heavy chain constant region to permit a switch of Ig isotype from IgM to IgG, IgA, or IgE. At the DNA level, CSR occurs via generation and joining of DNA double strand breaks (DSBs) at intronic switch regions located just upstream of each of the heavy chain constant regions. Activation-induced deaminase (AID), a B cell specific enzyme, catalyzes cytosine deaminations (converting cytosines to uracils) as the initial DNA lesions that eventually lead to DSBs and CSR. Progress on AID structure integrates very well with knowledge about Ig class switch region nucleic acid structures that are supported by functional studies. It is an ideal time to review what is known about the mechanism of Ig CSR and its relation to somatic hypermutation. There have been many comprehensive reviews on various aspects of the CSR reaction and regulation of AID expression and activity. This review is focused on the relation between AID and switch region nucleic acid structures, with a particular emphasis on R-loops.
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Affiliation(s)
- Kefei Yu
- Michigan State University, Department of Microbiology & Molecular Genetics, 5175 Biomedical Physical Sciences, East Lansing, MI 48824
| | - Michael R. Lieber
- USC Norris Comprehensive Cancer Ctr., Departments of Pathology, of Molecular Microbiology & Immunology, of Biochemistry & Molecular Biology, and of the Section of Molecular & Computational Biology within the Department of Biological Sciences, 1441 Eastlake Ave., NTT5428, Los Angeles, CA 90089-9176
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67
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Pan H, Pan J, Song S, Ji L, Lv H, Yang Z. EXOSC5 as a Novel Prognostic Marker Promotes Proliferation of Colorectal Cancer via Activating the ERK and AKT Pathways. Front Oncol 2019; 9:643. [PMID: 31380280 PMCID: PMC6659499 DOI: 10.3389/fonc.2019.00643] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 07/01/2019] [Indexed: 12/24/2022] Open
Abstract
Background and Objective: Exosome component 5 (EXOSC5) is a novel cancer-related gene that is aberrantly expressed in various malignances. However, the molecular mechanism and biological role of EXOSC5 have not been explored in colorectal cancer (CRC). In this study, we investigated the functions and mechanisms by which EXOSC5 promotes the progression of CRC. Methods: EXOSC5 expressions in CRC cell lines and paired CRC and adjacent normal tissues were measured via quantitative real-time PCR (qRT-PCR), Western blot and immunohistochemistry (IHC). In vitro experiments including colony formation, Cell Counting Kit-8 (CCK-8), and flow cytometry and in vivo tumorigenesis assay were performed to explore the effects of EXOSC5 on growth of CRC. The impacts of EXOSC5 on ERK and Akt signaling pathways were measured by Western blot. Results: The mRNA and protein expression levels of EXOSC5 were up-regulated in CRC as compared to adjacent normal tissues. IHC analysis indicated that high EXOSC5 level was positively associated with poor prognosis. EXOSC5 overexpression facilitated the growth of CRC cells, while EXOSC5 knockdown led to decreased proliferation, G1/S phase transition arrest. The oncogenic functions of EXOSC5 were associated with activation of the ERK and Akt pathways in CRC. Conclusion: EXOSC5 is overexpressed in CRC and promotes CRC growth partly through activation of ERK and Akt signaling pathways. Accordingly, EXOSC5 may be a novel oncogene, and acts as a therapeutic target, or prognostic factor for CRC.
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Affiliation(s)
- Hongda Pan
- Department of Gastric Surgery, Fudan University Shanghai Cancer Center, Fudan University, Shanghai, China.,Department of Hematology, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.,Department of Gastrointestinal Surgery, Beijing Hospital, Beijing, China
| | - Jingxin Pan
- Department of Hematology, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China
| | - Shibo Song
- Department of Gastrointestinal Surgery, Beijing Hospital, Beijing, China
| | - Lei Ji
- Department of Gastric Surgery, Fudan University Shanghai Cancer Center, Fudan University, Shanghai, China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Hong Lv
- Department of Gastric Surgery, Fudan University Shanghai Cancer Center, Fudan University, Shanghai, China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Zhangru Yang
- Department of Gastric Surgery, Fudan University Shanghai Cancer Center, Fudan University, Shanghai, China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
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68
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Telekawa C, Boisvert FM, Bachand F. Proteomic profiling and functional characterization of post-translational modifications of the fission yeast RNA exosome. Nucleic Acids Res 2019; 46:11169-11183. [PMID: 30321377 PMCID: PMC6265454 DOI: 10.1093/nar/gky915] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 10/11/2018] [Indexed: 12/11/2022] Open
Abstract
The RNA exosome is a conserved multi-subunit complex essential for processing and degradation of several types of RNAs. Although many of the functions of the RNA exosome are well established, whether the activity of this complex is regulated remains unclear. Here we performed a proteomic analysis of the RNA exosome complex purified from Schizosaccharomyces pombe and identified 39 post-translational modifications (PTMs), including phosphorylation, methylation, and acetylation sites. Interestingly, most of the modifications were identified in Dis3, a catalytic subunit of the RNA exosome, as well as in the exosome-associated RNA helicase, Mtr4. Functional analysis of selected PTM sites using modification-deficient and -mimetic versions of exosome subunits revealed substitutions that affected cell growth and exosome functions. Notably, our results suggest that site-specific phosphorylation in the catalytic center of Dis3 and in the helical bundle domain of Mtr4 control their activity. Our findings support a view in which post-translational modifications fine-tune exosome activity and add a layer of regulation to RNA degradation.
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Affiliation(s)
- Caroline Telekawa
- RNA Group, Department of Biochemistry, Université de Sherbrooke, Sherbrooke, QC, Canada
| | | | - François Bachand
- RNA Group, Department of Biochemistry, Université de Sherbrooke, Sherbrooke, QC, Canada
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69
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Abstract
DNA damage occurs on exposure to genotoxic agents and during physiological DNA transactions. DNA double-strand breaks (DSBs) are particularly dangerous lesions that activate DNA damage response (DDR) kinases, leading to initiation of a canonical DDR (cDDR). This response includes activation of cell cycle checkpoints and engagement of pathways that repair the DNA DSBs to maintain genomic integrity. In adaptive immune cells, programmed DNA DSBs are generated at precise genomic locations during the assembly and diversification of lymphocyte antigen receptor genes. In innate immune cells, the production of genotoxic agents, such as reactive nitrogen molecules, in response to pathogens can also cause genomic DNA DSBs. These DSBs in adaptive and innate immune cells activate the cDDR. However, recent studies have demonstrated that they also activate non-canonical DDRs (ncDDRs) that regulate cell type-specific processes that are important for innate and adaptive immune responses. Here, we review these ncDDRs and discuss how they integrate with other signals during immune system development and function.
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Affiliation(s)
- Jeffrey J Bednarski
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, USA
| | - Barry P Sleckman
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, USA.
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70
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Abstract
Class switch recombination (CSR) generates isotype-switched antibodies with distinct effector functions essential for mediating effective humoral immunity. CSR is catalyzed by activation-induced deaminase (AID) that initiates DNA lesions in the evolutionarily conserved switch (S) regions at the immunoglobulin heavy chain (Igh) locus. AID-initiated DNA lesions are subsequently converted into DNA double stranded breaks (DSBs) in the S regions of Igh locus, repaired by non-homologous end-joining to effect CSR in mammalian B lymphocytes. While molecular mechanisms of CSR are well characterized, it remains less well understood how upstream signaling pathways regulate AID expression and CSR. B lymphocytes express multiple receptors including the B cell antigen receptor (BCR) and co-receptors (e.g., CD40). These receptors may share common signaling pathways or may use distinct signaling elements to regulate CSR. Here, we discuss how signals emanating from different receptors positively or negatively regulate AID expression and CSR.
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Affiliation(s)
- Zhangguo Chen
- Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States.
| | - Jing H Wang
- Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States.
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71
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Yeap LS, Meng FL. Cis- and trans-factors affecting AID targeting and mutagenic outcomes in antibody diversification. Adv Immunol 2019; 141:51-103. [PMID: 30904133 DOI: 10.1016/bs.ai.2019.01.002] [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] [Indexed: 02/06/2023]
Abstract
Antigen receptor diversification is a hallmark of adaptive immunity which allows specificity of the receptor to particular antigen. B cell receptor (BCR) or its secreted form, antibody, is diversified through antigen-independent and antigen-dependent mechanisms. During B cell development in bone marrow, BCR is diversified via V(D)J recombination mediated by RAG endonuclease. Upon stimulation by antigen, B cell undergo somatic hypermutation (SHM) to allow affinity maturation and class switch recombination (CSR) to change the effector function of the antibody. Both SHM and CSR are initiated by activation-induced cytidine deaminase (AID). Repair of AID-initiated lesions through different DNA repair pathways results in diverse mutagenic outcomes. Here, we focus on discussing cis- and trans-factors that target AID to its substrates and factors that affect different outcomes of AID-initiated lesions. The knowledge of mechanisms that govern AID targeting and outcomes could be harnessed to elicit rare functional antibodies and develop ex vivo antibody diversification approaches with diversifying base editors.
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Affiliation(s)
- Leng-Siew Yeap
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Fei-Long Meng
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.
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72
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Laffleur B, Basu U. Biology of RNA Surveillance in Development and Disease. Trends Cell Biol 2019; 29:428-445. [PMID: 30755352 DOI: 10.1016/j.tcb.2019.01.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 01/03/2019] [Accepted: 01/10/2019] [Indexed: 01/09/2023]
Abstract
The 'RNA world', in which RNA molecules stored information and acquired enzymatic properties, has been proposed to have preceded organism life. RNA is now recognized for its central role in biology, with accumulating evidence implicating coding and noncoding (nc)RNAs in myriad mechanisms regulating cellular physiology and disequilibrium in transcriptomes resulting in pathological conditions. Nascently synthesized RNAs are subjected to stringent regulation by sophisticated RNA surveillance pathways. In this review, we integrate these pathways from a developmental viewpoint, proposing RNA surveillance as the convergence of mechanisms that ensure the exact titration of RNA molecules in a spatiotemporally controlled manner, leading to development without the onset of pathological conditions, including cancer.
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Affiliation(s)
- Brice Laffleur
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
| | - Uttiya Basu
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
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73
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Chakraborty P, Huang JTJ, Hiom K. DHX9 helicase promotes R-loop formation in cells with impaired RNA splicing. Nat Commun 2018; 9:4346. [PMID: 30341290 PMCID: PMC6195550 DOI: 10.1038/s41467-018-06677-1] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 09/06/2018] [Indexed: 01/05/2023] Open
Abstract
R-loops are stable nucleic acid structures that have important physiological functions, but which also pose a significant threat to genomic stability. Increased R-loops cause replication stress and chromosome fragility and have been associated with diseases such as neurodegeneration and cancer. Although excessive R-loops are a feature of cells that are defective in RNA processing, what causes them to form is unclear. Here, we demonstrate that DHX9 (RNA helicase A) promotes the formation of pathological and non-pathological R-loops. In the absence of splicing factors, formation of R-loops correlates with the prolonged association of DHX9 with RNA Polymerase II (RNA Pol II). This leads to the production of DNA–RNA hybrid, which traps RNA Pol II on chromatin with the potential to block DNA replication. Our data provide a molecular mechanism for the formation of R-loops that is relevant to neurodegenerative diseases and cancers in which deregulated RNA processing is a feature. Unresolved R-loops can represent a threat to genome stability. Here the authors reveal that DHX9 helicase can promote R-loop formation in the absence of splicing factors SFPQ and SF3B3.
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Affiliation(s)
- Prasun Chakraborty
- Division of Cellular Medicine, School of Medicine, University of Dundee, Scotland, UK
| | - Jeffrey T J Huang
- Biomarker and Drug Analysis Core Facility, School of Medicine, University of Dundee, Scotland, UK
| | - Kevin Hiom
- Division of Cellular Medicine, School of Medicine, University of Dundee, Scotland, UK.
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74
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Liu WT, Lv YJ, Yang RC, Fu JY, Liu L, Wang H, Cao Q, Tan C, Chen HC, Wang XR. New insights into meningitic Escherichia coli infection of brain microvascular endothelial cells from quantitative proteomics analysis. J Neuroinflammation 2018; 15:291. [PMID: 30340642 PMCID: PMC6195690 DOI: 10.1186/s12974-018-1325-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Accepted: 10/02/2018] [Indexed: 01/08/2023] Open
Abstract
Background Bacterial meningitis remains a big threat to the integrity of the central nervous system (CNS), despite the advancements in antimicrobial reagents. Escherichia coli is a bacterial pathogen that can disrupt the CNS function, especially in neonates. E. coli meningitis occurs after bacteria invade the brain microvascular endothelial cells (BMECs) that form a direct and essential barrier restricting the entry of circulating microbes and toxins to the brain. Previous studies have reported on several cellular proteins that function during meningitic E. coli infections; however, more comprehensive investigations to elucidate the potential targets involved in E. coli meningitis are essential to better understand this disease and discover new treatments for it. Methods The isobaric tags for relative and absolute quantification (iTRAQ) approach coupled with LC-MS/MS were applied to compare and characterize the different proteomic profiles of BMECs in response to meningitic or non-meningitic E. coli strains. KEGG and gene ontology annotations, ingenuity pathways analysis, and functional experiments were combined to identify the key host molecules involved in the meningitic E. coli-induced tight junction breakdown and neuroinflammatory responses. Results A total of 13 cellular proteins were found to be differentially expressed by meningitic E. coli strains PCN033 and RS218, including one that was also affected by HB101, a non-meningitic E. coli strain. Through bioinformatics analysis, we identified the macrophage migration inhibitory factor (MIF), granzyme A, NF-κB signaling, and mitogen-activated protein kinase (MAPK) pathways as being biologically involved in the meningitic E. coli-induced tight junction breakdown and neuroinflammation. Functionally, we showed that MIF facilitated meningitic E. coli-induced production of cytokines and chemokines and also helped to disrupt the blood-brain barrier by decreasing the expression of tight junction proteins like ZO-1, occludin. Moreover, we demonstrated the significant activation of NF-κB and MAPK signaling in BMECs in response to meningitic E. coli strains, which dominantly determined the generation of the proinflammatory cytokines including IL-6, IL-8, TNF-α, and IL-1β. Conclusions Our work identified 12 host cellular targets that are affected by meningitic E. coli strains and revealed MIF to be an important contributor to meningitic E. coli-induced cytokine production and tight junction disruption, and also the NF-κB and MAPK signaling pathways that are mainly involved in the infection-induced cytokines production. Characterization of these distinct proteins and pathways in BMECs will facilitate further elucidation of meningitis-causing mechanisms in humans and animals, thereby enabling the development of novel preventative and therapeutic strategies against infection with meningitic E. coli. Electronic supplementary material The online version of this article (10.1186/s12974-018-1325-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Wen-Tong Liu
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, 430070, Hubei, China
| | - Yu-Jin Lv
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, 430070, Hubei, China.,College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, 450046, Henan, China
| | - Rui-Cheng Yang
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, 430070, Hubei, China
| | - Ji-Yang Fu
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, 430070, Hubei, China
| | - Lu Liu
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, 430070, Hubei, China
| | - Huan Wang
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, 430070, Hubei, China
| | - Qi Cao
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, 430070, Hubei, China
| | - Chen Tan
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, 430070, Hubei, China.,State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, Hubei, China
| | - Huan-Chun Chen
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, 430070, Hubei, China.,State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, Hubei, China
| | - Xiang-Ru Wang
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan, 430070, Hubei, China. .,State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, Hubei, China.
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75
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Human mitochondrial degradosome prevents harmful mitochondrial R loops and mitochondrial genome instability. Proc Natl Acad Sci U S A 2018; 115:11024-11029. [PMID: 30301808 DOI: 10.1073/pnas.1807258115] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
R loops are nucleic acid structures comprising an DNA-RNA hybrid and a displaced single-stranded DNA. These structures may occur transiently during transcription, playing essential biological functions. However, persistent R loops may become pathological as they are important drivers of genome instability and have been associated with human diseases. The mitochondrial degradosome is a functionally conserved complex from bacteria to human mitochondria. It is composed of the ATP-dependent RNA and DNA helicase SUV3 and the PNPase ribonuclease, playing a central role in mitochondrial RNA surveillance and degradation. Here we describe a new role for the mitochondrial degradosome in preventing the accumulation of pathological R loops in the mitochondrial DNA, in addition to preventing dsRNA accumulation. Our data indicate that, similar to the molecular mechanisms acting in the nucleus, RNA surveillance mechanisms in the mitochondria are crucial to maintain its genome integrity by counteracting pathological R-loop accumulation.
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76
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The splicing factor SRSF3 is functionally connected to the nuclear RNA exosome for intronless mRNA decay. Sci Rep 2018; 8:12901. [PMID: 30150655 PMCID: PMC6110769 DOI: 10.1038/s41598-018-31078-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 07/24/2018] [Indexed: 12/22/2022] Open
Abstract
The RNA exosome fulfills important functions in the processing and degradation of numerous RNAs species. However, the mechanisms of recruitment to its various nuclear substrates are poorly understood. Using Epstein-Barr virus mRNAs as a model, we have discovered a novel function for the splicing factor SRSF3 in the quality control of nuclear mRNAs. We have found that viral mRNAs generated from intronless genes are particularly unstable due to their degradation by the nuclear RNA exosome. This effect is counteracted by the viral RNA-binding protein EB2 which stabilizes these mRNAs in the nucleus and stimulates both their export to the cytoplasm and their translation. In the absence of EB2, SRSF3 participates in the destabilization of these viral RNAs by interacting with both the RNA exosome and its adaptor complex NEXT. Taken together, our results provide direct evidence for a connection between the splicing machinery and mRNA decay mediated by the RNA exosome. Our results suggest that SRSF3 aids the nuclear RNA exosome and the NEXT complex in the recognition and degradation of certain mRNAs.
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77
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Chen J, Cai Z, Bai M, Yu X, Zhang C, Cao C, Hu X, Wang L, Su R, Wang D, Wang L, Yao Y, Ye R, Hou B, Yu Y, Yu S, Li J, Xue Y. The RNA-binding protein ROD1/PTBP3 cotranscriptionally defines AID-loading sites to mediate antibody class switch in mammalian genomes. Cell Res 2018; 28:981-995. [PMID: 30143796 PMCID: PMC6170407 DOI: 10.1038/s41422-018-0076-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Revised: 07/08/2018] [Accepted: 07/16/2018] [Indexed: 02/06/2023] Open
Abstract
Activation-induced cytidine deaminase (AID) mediates class switching by binding to a small fraction of single-stranded DNA (ssDNA) to diversify the antibody repertoire. The precise mechanism for highly selective AID targeting in the genome has remained elusive. Here, we report an RNA-binding protein, ROD1 (also known as PTBP3), that is both required and sufficient to define AID-binding sites genome-wide in activated B cells. ROD1 interacts with AID via an ultraconserved loop, which proves to be critical for the recruitment of AID to ssDNA using bi-directionally transcribed nascent RNAs as stepping stones. Strikingly, AID-specific mutations identified in human patients with hyper-IgM syndrome type 2 (HIGM2) completely disrupt the AID interacting surface with ROD1, thereby abolishing the recruitment of AID to immunoglobulin (Ig) loci. Together, our results suggest that bi-directionally transcribed RNA traps the RNA-binding protein ROD1, which serves as a guiding system for AID to load onto specific genomic loci to induce DNA rearrangement during immune responses.
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Affiliation(s)
- Juan Chen
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Zhaokui Cai
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Meizhu Bai
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, 320 Yueyang Road, 200031, Shanghai, China.,School of Life Science and Technology, ShanghaiTech University, 100 Haike Road, 201210, Shanghai, China
| | - Xiaohua Yu
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Chao Zhang
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China
| | - Changchang Cao
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Xihao Hu
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Lei Wang
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.,College of Life Sciences, Institute for Conservation and Utilization of Agro-bioresources in Dabie Mountains, Xinyang Normal University, 464000, Xinyang, China
| | - Ruibao Su
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Di Wang
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Lei Wang
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Yingpeng Yao
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, People's Republic of China
| | - Rong Ye
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Baidong Hou
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China
| | - Yang Yu
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China
| | - Shuyang Yu
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, People's Republic of China
| | - Jinsong Li
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, 320 Yueyang Road, 200031, Shanghai, China.,School of Life Science and Technology, ShanghaiTech University, 100 Haike Road, 201210, Shanghai, China
| | - Yuanchao Xue
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China. .,University of Chinese Academy of Sciences, 100049, Beijing, China.
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78
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Recaldin T, Hobson PS, Mann EH, Ramadani F, Cousins DJ, Lavender P, Fear DJ. miR-29b directly targets activation-induced cytidine deaminase in human B cells and can limit its inappropriate expression in naïve B cells. Mol Immunol 2018; 101:419-428. [PMID: 30081328 DOI: 10.1016/j.molimm.2018.07.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 06/08/2018] [Accepted: 07/23/2018] [Indexed: 11/25/2022]
Abstract
Class-switch recombination (CSR) is an essential B cell process that alters the isotype of antibody produced by the B cell, tailoring the immune response to the nature of the invading pathogen. CSR requires the activity of the mutagenic enzyme AID (encoded by AICDA) to generate chromosomal lesions within the immunoglobulin genes that initiate the class switching recombination event. These AID-mediated mutations also participate in somatic-hypermutation of the immunoglobulin variable region, driving affinity maturation. As such, AID poses a significant oncogenic threat if it functions outside of the immunoglobulin locus. We found that expression of the microRNA, miR-29b, was repressed in B cells isolated from tonsil tissue, relative to circulating naïve B cells. Further investigation revealed that miR-29b was able to directly initiate the degradation of AID mRNA. Enforced overexpression of miR-29b in human B cells precipitated a reduction in overall AID protein and a corresponding diminution in CSR to IgE. Given miR-29b's ability to potently target AID, a mutagenic molecule that can initiate chromosomal translocations and "off-target" mutations, we propose that miR-29b acts to silence premature AID expression in naïve B cells, thus reducing the likelihood of inappropriate and potentially dangerous deamination activity.
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Affiliation(s)
- Timothy Recaldin
- School of Immunology & Microbial Sciences, King's College London, UK; Medical Research Council and Asthma UK Centre, Allergic Mechanisms in Asthma, London, UK
| | - Philip S Hobson
- Medical Research Council and Asthma UK Centre, Allergic Mechanisms in Asthma, London, UK
| | - Elizabeth H Mann
- Medical Research Council and Asthma UK Centre, Allergic Mechanisms in Asthma, London, UK
| | - Faruk Ramadani
- Medical Research Council and Asthma UK Centre, Allergic Mechanisms in Asthma, London, UK; School of Basic & Medical Biosciences, King's College London, UK
| | - David J Cousins
- Medical Research Council and Asthma UK Centre, Allergic Mechanisms in Asthma, London, UK; Leicester Respiratory Biomedical Research Unit, Leicester University, UK
| | - Paul Lavender
- School of Immunology & Microbial Sciences, King's College London, UK; Medical Research Council and Asthma UK Centre, Allergic Mechanisms in Asthma, London, UK
| | - David J Fear
- School of Immunology & Microbial Sciences, King's College London, UK; Medical Research Council and Asthma UK Centre, Allergic Mechanisms in Asthma, London, UK.
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79
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Singh P, Saha U, Paira S, Das B. Nuclear mRNA Surveillance Mechanisms: Function and Links to Human Disease. J Mol Biol 2018; 430:1993-2013. [PMID: 29758258 DOI: 10.1016/j.jmb.2018.05.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 04/30/2018] [Accepted: 05/07/2018] [Indexed: 01/05/2023]
Abstract
Production of export-competent mRNAs involves transcription and a series of dynamic processing and modification events of pre-messenger RNAs in the nucleus. Mutations in the genes encoding the transcription and mRNP processing machinery and the complexities involved in the biogenesis events lead to the formation of aberrant messages. These faulty transcripts are promptly eliminated by the nuclear RNA exosome and its cofactors to safeguard the cells and organisms from genetic catastrophe. Mutations in the components of the core nuclear exosome and its cofactors lead to the tissue-specific dysfunction of exosomal activities, which are linked to diverse human diseases and disorders. In this article, we examine the structure and function of both the yeast and human RNA exosome complex and its cofactors, discuss the nature of the various altered amino acid residues implicated in these diseases with the speculative mechanisms of the mutation-induced disorders and project the frontier and prospective avenues of the future research in this field.
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Affiliation(s)
- Pragyan Singh
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
| | - Upasana Saha
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
| | - Sunirmal Paira
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
| | - Biswadip Das
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India.
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80
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81
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Ribeiro de Almeida C, Dhir S, Dhir A, Moghaddam AE, Sattentau Q, Meinhart A, Proudfoot NJ. RNA Helicase DDX1 Converts RNA G-Quadruplex Structures into R-Loops to Promote IgH Class Switch Recombination. Mol Cell 2018; 70:650-662.e8. [PMID: 29731414 PMCID: PMC5971202 DOI: 10.1016/j.molcel.2018.04.001] [Citation(s) in RCA: 113] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 03/02/2018] [Accepted: 03/30/2018] [Indexed: 12/20/2022]
Abstract
Class switch recombination (CSR) at the immunoglobulin heavy-chain (IgH) locus is associated with the formation of R-loop structures over switch (S) regions. While these often occur co-transcriptionally between nascent RNA and template DNA, we now show that they also form as part of a post-transcriptional mechanism targeting AID to IgH S-regions. This depends on the RNA helicase DDX1 that is also required for CSR in vivo. DDX1 binds to G-quadruplex (G4) structures present in intronic switch transcripts and converts them into S-region R-loops. This in turn targets the cytidine deaminase enzyme AID to S-regions so promoting CSR. Notably R-loop levels over S-regions are diminished by chemical stabilization of G4 RNA or by the expression of a DDX1 ATPase-deficient mutant that acts as a dominant-negative protein to reduce CSR efficiency. In effect, we provide evidence for how S-region transcripts interconvert between G4 and R-loop structures to promote CSR in the IgH locus.
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Affiliation(s)
| | - Somdutta Dhir
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, OX1 3RE Oxford, UK
| | - Ashish Dhir
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, OX1 3RE Oxford, UK
| | - Amin E Moghaddam
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, OX1 3RE Oxford, UK
| | - Quentin Sattentau
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, OX1 3RE Oxford, UK
| | - Anton Meinhart
- Department of Biomolecular Mechanisms, Max-Planck-Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany
| | - Nicholas J Proudfoot
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, OX1 3RE Oxford, UK.
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82
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Yewdell WT, Chaudhuri J. A transcriptional serenAID: the role of noncoding RNAs in class switch recombination. Int Immunol 2018; 29:183-196. [PMID: 28535205 DOI: 10.1093/intimm/dxx027] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 05/22/2017] [Indexed: 12/31/2022] Open
Abstract
During an immune response, activated B cells may undergo class switch recombination (CSR), a molecular rearrangement that allows B cells to switch from expressing IgM and IgD to a secondary antibody heavy chain isotype such as IgG, IgA or IgE. Secondary antibody isotypes provide the adaptive immune system with distinct effector functions to optimally combat various pathogens. CSR occurs between repetitive DNA elements within the immunoglobulin heavy chain (Igh) locus, termed switch (S) regions and requires the DNA-modifying enzyme activation-induced cytidine deaminase (AID). AID-mediated DNA deamination within S regions initiates the formation of DNA double-strand breaks, which serve as biochemical beacons for downstream DNA repair pathways that coordinate the ligation of DNA breaks. Myriad factors contribute to optimal AID targeting; however, many of these factors also localize to genomic regions outside of the Igh locus. Thus, a current challenge is to explain the specific targeting of AID to the Igh locus. Recent studies have implicated noncoding RNAs in CSR, suggesting a provocative mechanism that incorporates Igh-specific factors to enable precise AID targeting. Here, we chronologically recount the rich history of noncoding RNAs functioning in CSR to provide a comprehensive context for recent and future discoveries. We present a model for the RNA-guided targeting of AID that attempts to integrate historical and recent findings, and highlight potential caveats. Lastly, we discuss testable hypotheses ripe for current experimentation, and explore promising ideas for future investigations.
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Affiliation(s)
- William T Yewdell
- Immunology Program, Memorial Sloan Kettering Cancer, New York, NY 10065, USA
| | - Jayanta Chaudhuri
- Immunology Program, Memorial Sloan Kettering Cancer, New York, NY 10065, USA.,Immunology and Microbial Pathogenesis Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA
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83
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Nicolas L, Cols M, Choi JE, Chaudhuri J, Vuong B. Generating and repairing genetically programmed DNA breaks during immunoglobulin class switch recombination. F1000Res 2018; 7:458. [PMID: 29744038 PMCID: PMC5904731 DOI: 10.12688/f1000research.13247.1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/09/2018] [Indexed: 01/03/2023] Open
Abstract
Adaptive immune responses require the generation of a diverse repertoire of immunoglobulins (Igs) that can recognize and neutralize a seemingly infinite number of antigens. V(D)J recombination creates the primary Ig repertoire, which subsequently is modified by somatic hypermutation (SHM) and class switch recombination (CSR). SHM promotes Ig affinity maturation whereas CSR alters the effector function of the Ig. Both SHM and CSR require activation-induced cytidine deaminase (AID) to produce dU:dG mismatches in the Ig locus that are transformed into untemplated mutations in variable coding segments during SHM or DNA double-strand breaks (DSBs) in switch regions during CSR. Within the Ig locus, DNA repair pathways are diverted from their canonical role in maintaining genomic integrity to permit AID-directed mutation and deletion of gene coding segments. Recently identified proteins, genes, and regulatory networks have provided new insights into the temporally and spatially coordinated molecular interactions that control the formation and repair of DSBs within the Ig locus. Unravelling the genetic program that allows B cells to selectively alter the Ig coding regions while protecting non-Ig genes from DNA damage advances our understanding of the molecular processes that maintain genomic integrity as well as humoral immunity.
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Affiliation(s)
- Laura Nicolas
- Immunology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Montserrat Cols
- Immunology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Jee Eun Choi
- Department of Biology, The City College of New York and The Graduate Center of The City University of New York, New York, NY, USA
| | - Jayanta Chaudhuri
- Immunology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Bao Vuong
- Department of Biology, The City College of New York and The Graduate Center of The City University of New York, New York, NY, USA
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84
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A licensing step links AID to transcription elongation for mutagenesis in B cells. Nat Commun 2018; 9:1248. [PMID: 29593215 PMCID: PMC5871760 DOI: 10.1038/s41467-018-03387-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 02/08/2018] [Indexed: 01/01/2023] Open
Abstract
Activation-induced deaminase (AID) mutates the immunoglobulin (Ig) genes to initiate somatic hypermutation (SHM) and class switch recombination (CSR) in B cells, thus underpinning antibody responses. AID mutates a few hundred other loci, but most AID-occupied genes are spared. The mechanisms underlying productive deamination versus non-productive AID targeting are unclear. Here we show that three clustered arginine residues define a functional AID domain required for SHM, CSR, and off-target activity in B cells without affecting AID deaminase activity or Escherichia coli mutagenesis. Both wt AID and mutants with single amino acid replacements in this domain broadly associate with Spt5 and chromatin and occupy the promoter of AID target genes. However, mutant AID fails to occupy the corresponding gene bodies and loses association with transcription elongation factors. Thus AID mutagenic activity is determined not by locus occupancy but by a licensing mechanism, which couples AID to transcription elongation. Activation-induced deaminase (AID) is important for inducing desirable mutations at the B cell receptor genes for effective antibody responses. Here the authors show that three key arginine residues of AID link AID-chromatin association with transcription elongation to license AID for specific mutagenesis in B cells.
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85
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Abstract
The nuclear RNA exosome is an essential and versatile machinery that regulates maturation and degradation of a huge plethora of RNA species. The past two decades have witnessed remarkable progress in understanding the whole picture of its RNA substrates and the structural basis of its functions. In addition to the exosome itself, recent studies focusing on associated co-factors have been elucidating how the exosome is directed towards specific substrates. Moreover, it has been gradually realized that loss-of-function of exosome subunits affect multiple biological processes such as the DNA damage response, R-loop resolution, maintenance of genome integrity, RNA export, translation and cell differentiation. In this review, we summarize the current knowledge of the mechanisms of nuclear exosome-mediated RNA metabolism and discuss their physiological significance.
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86
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Adolph MB, Love RP, Chelico L. Biochemical Basis of APOBEC3 Deoxycytidine Deaminase Activity on Diverse DNA Substrates. ACS Infect Dis 2018; 4:224-238. [PMID: 29347817 DOI: 10.1021/acsinfecdis.7b00221] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The Apolipoprotein B mRNA editing complex (APOBEC) family of enzymes contains single-stranded polynucleotide cytidine deaminases. These enzymes catalyze the deamination of cytidine in RNA or single-stranded DNA, which forms uracil. From this 11 member enzyme family in humans, the deamination of single-stranded DNA by the seven APOBEC3 family members is considered here. The APOBEC3 family has many roles, such as restricting endogenous and exogenous retrovirus replication and retrotransposon insertion events and reducing DNA-induced inflammation. Similar to other APOBEC family members, the APOBEC3 enzymes are a double-edged sword that can catalyze deamination of cytosine in genomic DNA, which results in potential genomic instability due to the many mutagenic fates of uracil in DNA. Here, we discuss how these enzymes find their single-stranded DNA substrate in different biological contexts such as during human immunodeficiency virus (HIV) proviral DNA synthesis, retrotransposition of the LINE-1 element, and the "off-target" genomic DNA substrate. The enzymes must be able to efficiently deaminate transiently available single-stranded DNA during reverse transcription, replication, or transcription. Specific biochemical characteristics promote deamination in each situation to increase enzyme efficiency through processivity, rapid enzyme cycling between substrates, or oligomerization state. The use of biochemical data to clarify biological functions and alignment with cellular data is discussed. Models to bridge knowledge from biochemical, structural, and single molecule experiments are presented.
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Affiliation(s)
- Madison B Adolph
- Department of Microbiology and Immunology, College of Medicine , University of Saskatchewan , 107 Wiggins Road , Saskatoon , Saskatchewan S7N 5E5 , Canada
| | - Robin P Love
- Department of Microbiology and Immunology, College of Medicine , University of Saskatchewan , 107 Wiggins Road , Saskatoon , Saskatchewan S7N 5E5 , Canada
| | - Linda Chelico
- Department of Microbiology and Immunology, College of Medicine , University of Saskatchewan , 107 Wiggins Road , Saskatoon , Saskatchewan S7N 5E5 , Canada
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87
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Sheppard EC, Morrish RB, Dillon MJ, Leyland R, Chahwan R. Epigenomic Modifications Mediating Antibody Maturation. Front Immunol 2018. [PMID: 29535729 PMCID: PMC5834911 DOI: 10.3389/fimmu.2018.00355] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Epigenetic modifications, such as histone modifications, DNA methylation status, and non-coding RNAs (ncRNA), all contribute to antibody maturation during somatic hypermutation (SHM) and class-switch recombination (CSR). Histone modifications alter the chromatin landscape and, together with DNA primary and tertiary structures, they help recruit Activation-Induced Cytidine Deaminase (AID) to the immunoglobulin (Ig) locus. AID is a potent DNA mutator, which catalyzes cytosine-to-uracil deamination on single-stranded DNA to create U:G mismatches. It has been shown that alternate chromatin modifications, in concert with ncRNAs and potentially DNA methylation, regulate AID recruitment and stabilize DNA repair factors. We, hereby, assess the combination of these distinct modifications and discuss how they contribute to initiating differential DNA repair pathways at the Ig locus, which ultimately leads to enhanced antibody–antigen binding affinity (SHM) or antibody isotype switching (CSR). We will also highlight how misregulation of epigenomic regulation during DNA repair can compromise antibody development and lead to a number of immunological syndromes and cancer.
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Affiliation(s)
- Emily C Sheppard
- Living Systems Institute, University of Exeter, Exeter, United Kingdom
| | | | - Michael J Dillon
- Living Systems Institute, University of Exeter, Exeter, United Kingdom
| | | | - Richard Chahwan
- Living Systems Institute, University of Exeter, Exeter, United Kingdom
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88
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Wang R, Zhang X, Ding H, Qiao Y, Han X, Geng W, Guan G, Cui H, Zhao B, Wu Y, Liang G, Shang H. AID recruits the RNA exosome to degrade HIV-1 nascent transcripts through interaction with the Tat-P-TEFb-TAR RNP complex. FEBS Lett 2018; 592:284-294. [PMID: 29266200 DOI: 10.1002/1873-3468.12954] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 10/31/2017] [Accepted: 11/17/2017] [Indexed: 01/11/2023]
Abstract
Activation-induced cytidine deaminase (AID), a member of the APOBEC family that induces antibody diversification, has been shown to inhibit the replication of hepatitis B virus, Kaposi's sarcoma-associated herpesvirus, and retro-transposons. However, whether AID can inhibit human immunodeficiency virus 1 (HIV-1) replication remains unclear. Here, we report that AID impairs the synthesis of HIV-1 components by interacting with the complex of Tat. This interaction recruits the RNA exosome to degrade the nascent HIV-1 transcript. AID also targets the HIV-1-integrated genome via the Tat-P-TEFb-TAR complex. Thus, we propose a novel function for AID as an adaptor protein that represses viral transcription. Our findings provide insights into developing anti-HIV therapeutics and understanding how host cells restrict integrated virus replication.
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Affiliation(s)
- Ruixuan Wang
- Key Laboratory of AIDS Immunology of the National Health and Family Planning Commission, Department of Laboratory Medicine, China Medical University, Shenyang, China
| | - Xiaowei Zhang
- The Core Laboratory for Public Health Science and Practice, China Medical University, Shenyang, China
| | - Haibo Ding
- Key Laboratory of AIDS Immunology of the National Health and Family Planning Commission, Department of Laboratory Medicine, China Medical University, Shenyang, China
| | - Ying Qiao
- The Core Laboratory for Public Health Science and Practice, China Medical University, Shenyang, China
| | - Xiaoxu Han
- Key Laboratory of AIDS Immunology of the National Health and Family Planning Commission, Department of Laboratory Medicine, China Medical University, Shenyang, China
| | - Wenqing Geng
- Key Laboratory of AIDS Immunology of the National Health and Family Planning Commission, Department of Laboratory Medicine, China Medical University, Shenyang, China
| | - Gefei Guan
- Department of Neurosurgery, The First Affiliated Hospital, China Medical University, Shenyang, China
| | - Hualu Cui
- Key Laboratory of AIDS Immunology of the National Health and Family Planning Commission, Department of Laboratory Medicine, China Medical University, Shenyang, China
| | - Bin Zhao
- Key Laboratory of AIDS Immunology of the National Health and Family Planning Commission, Department of Laboratory Medicine, China Medical University, Shenyang, China
| | - Yuntao Wu
- National Center for Biodefense and Infectious Diseases, Department of Molecular and Microbiology, George Mason University, Manassas, VA, USA
| | - Guoxin Liang
- Key Laboratory of AIDS Immunology of the National Health and Family Planning Commission, Department of Laboratory Medicine, China Medical University, Shenyang, China
| | - Hong Shang
- Key Laboratory of AIDS Immunology of the National Health and Family Planning Commission, Department of Laboratory Medicine, China Medical University, Shenyang, China
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89
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Liu X, Meng FL. Generation of Genomic Alteration from Cytidine Deamination. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1044:49-64. [DOI: 10.1007/978-981-13-0593-1_5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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90
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The Antiviral and Cancer Genomic DNA Deaminase APOBEC3H Is Regulated by an RNA-Mediated Dimerization Mechanism. Mol Cell 2017; 69:75-86.e9. [PMID: 29290613 DOI: 10.1016/j.molcel.2017.12.010] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 10/25/2017] [Accepted: 12/13/2017] [Indexed: 01/23/2023]
Abstract
Human APOBEC3H and homologous single-stranded DNA cytosine deaminases are unique to mammals. These DNA-editing enzymes function in innate immunity by restricting the replication of viruses and transposons. APOBEC3H also contributes to cancer mutagenesis. Here, we address the fundamental nature of RNA in regulating human APOBEC3H activities. APOBEC3H co-purifies with RNA as an inactive protein, and RNase A treatment enables strong DNA deaminase activity. RNA-binding-defective mutants demonstrate clear separation of function by becoming DNA hypermutators. Biochemical and crystallographic data demonstrate a mechanism in which double-stranded RNA mediates enzyme dimerization. Additionally, APOBEC3H separation-of-function mutants show that RNA binding is required for cytoplasmic localization, packaging into HIV-1 particles, and antiviral activity. Overall, these results support a model in which structured RNA negatively regulates the potentially harmful DNA deamination activity of APOBEC3H while, at the same time, positively regulating its antiviral activity.
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91
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Adolph MB, Love RP, Feng Y, Chelico L. Enzyme cycling contributes to efficient induction of genome mutagenesis by the cytidine deaminase APOBEC3B. Nucleic Acids Res 2017; 45:11925-11940. [PMID: 28981865 PMCID: PMC5714209 DOI: 10.1093/nar/gkx832] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 09/11/2017] [Indexed: 02/06/2023] Open
Abstract
The single-stranded DNA cytidine deaminases APOBEC3B, APOBEC3H haplotype I, and APOBEC3A can contribute to cancer through deamination of cytosine to form promutagenic uracil in genomic DNA. The enzymes must access single-stranded DNA during the dynamic processes of DNA replication or transcription, but the enzymatic mechanisms enabling this activity are not known. To study this, we developed a method to purify full length APOBEC3B and characterized it in comparison to APOBEC3A and APOBEC3H on substrates relevant to cancer mutagenesis. We found that the ability of an APOBEC3 to cycle between DNA substrates determined whether it was able to efficiently deaminate single-stranded DNA produced by replication and single-stranded DNA bound by replication protein A (RPA). APOBEC3 deaminase activity during transcription had a size limitation that inhibited APOBEC3B tetramers, but not APOBEC3A monomers or APOBEC3H dimers. Altogether, the data support a model in which the availability of single-stranded DNA is necessary, but alone not sufficient for APOBEC3-induced mutagenesis in cells because there is also a dependence on the inherent biochemical properties of the enzymes. The biochemical properties identified in this study can be used to measure the mutagenic potential of other APOBEC enzymes in the genome.
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Affiliation(s)
- Madison B Adolph
- Department of Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Robin P Love
- Department of Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Yuqing Feng
- Department of Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Linda Chelico
- Department of Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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92
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DNA Replication Origins in Immunoglobulin Switch Regions Regulate Class Switch Recombination in an R-Loop-Dependent Manner. Cell Rep 2017; 17:2927-2942. [PMID: 27974207 DOI: 10.1016/j.celrep.2016.11.041] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 09/07/2016] [Accepted: 11/11/2016] [Indexed: 11/22/2022] Open
Abstract
Class switch recombination (CSR) at the immunoglobulin heavy chain (IgH) locus generates antibody isotypes. CSR depends on double-strand breaks (DSBs) induced by activation-induced cytidine deaminase (AID). Although DSB formation and repair machineries are active in G1 phase, efficient CSR is dependent on cell proliferation and S phase entry; however, the underlying mechanisms are obscure. Here, we show that efficient CSR requires the replicative helicase, the Mcm complex. Mcm proteins are enriched at IgH switch regions during CSR, leading to assembly of facultative replication origins that require Mcm helicase function for productive CSR. Assembly of CSR-associated origins is facilitated by R loops and promotes the physical proximity (synapsis) of recombining switch regions, which is reduced by R loop inhibition or Mcm complex depletion. Thus, R loops contribute to replication origin specification that promotes DSB resolution in CSR. This suggests a mechanism for the dependence of CSR on S phase and cell division.
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93
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Steele EJ. Reverse Transcriptase Mechanism of Somatic Hypermutation: 60 Years of Clonal Selection Theory. Front Immunol 2017; 8:1611. [PMID: 29218047 PMCID: PMC5704389 DOI: 10.3389/fimmu.2017.01611] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 11/07/2017] [Indexed: 01/24/2023] Open
Abstract
The evidence for the reverse transcriptase mechanism of somatic hypermutation is substantial and multifactorial. In this 60th anniversary year of the publication of Sir MacFarlane Burnet's Clonal Selection Theory, the evidence is briefly reviewed and updated.
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Affiliation(s)
- Edward J. Steele
- CYO’Connor ERADE Village Foundation Inc., Piara Waters, WA, Australia
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94
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Histone methyltransferase MMSET promotes AID-mediated DNA breaks at the donor switch region during class switch recombination. Proc Natl Acad Sci U S A 2017; 114:E10560-E10567. [PMID: 29158395 DOI: 10.1073/pnas.1701366114] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In B cells, Ig class switch recombination (CSR) is initiated by activation-induced cytidine deaminase (AID), the activity of which leads to DNA double-strand breaks (DSBs) within IgH switch (S) regions. Preferential targeting of AID-mediated DSBs to S sequences is critical for allowing diversification of antibody functions, while minimizing potential off-target oncogenic events. Here, we used gene targeted inactivation of histone methyltransferase (HMT) multiple myeloma SET domain (MMSET) in mouse B cells and the CH12F3 cell line to explore its role in CSR. We find that deletion of MMSET-II, the isoform containing the catalytic SET domain, inhibits CSR without affecting either IgH germline transcription or joining of DSBs within S regions by classical nonhomologous end joining (C-NHEJ). Instead, we find that MMSET-II inactivation leads to decreased AID recruitment and DSBs at the upstream donor Sμ region. Our findings suggest a role for the HMT MMSET in promoting AID-mediated DNA breaks during CSR.
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95
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Abdouni HS, King JJ, Ghorbani A, Fifield H, Berghuis L, Larijani M. DNA/RNA hybrid substrates modulate the catalytic activity of purified AID. Mol Immunol 2017; 93:94-106. [PMID: 29161581 DOI: 10.1016/j.molimm.2017.11.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 11/10/2017] [Accepted: 11/11/2017] [Indexed: 11/28/2022]
Abstract
Activation-induced cytidine deaminase (AID) converts cytidine to uridine at Immunoglobulin (Ig) loci, initiating somatic hypermutation and class switching of antibodies. In vitro, AID acts on single stranded DNA (ssDNA), but neither double-stranded DNA (dsDNA) oligonucleotides nor RNA, and it is believed that transcription is the in vivo generator of ssDNA targeted by AID. It is also known that the Ig loci, particularly the switch (S) regions targeted by AID are rich in transcription-generated DNA/RNA hybrids. Here, we examined the binding and catalytic behavior of purified AID on DNA/RNA hybrid substrates bearing either random sequences or GC-rich sequences simulating Ig S regions. If substrates were made up of a random sequence, AID preferred substrates composed entirely of DNA over DNA/RNA hybrids. In contrast, if substrates were composed of S region sequences, AID preferred to mutate DNA/RNA hybrids over substrates composed entirely of DNA. Accordingly, AID exhibited a significantly higher affinity for binding DNA/RNA hybrid substrates composed specifically of S region sequences, than any other substrates composed of DNA. Thus, in the absence of any other cellular processes or factors, AID itself favors binding and mutating DNA/RNA hybrids composed of S region sequences. AID:DNA/RNA complex formation and supporting mutational analyses suggest that recognition of DNA/RNA hybrids is an inherent structural property of AID.
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Affiliation(s)
- Hala S Abdouni
- Program in immunology and Infectious Diseases, Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, A1 B 3V6, Canada
| | - Justin J King
- Program in immunology and Infectious Diseases, Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, A1 B 3V6, Canada
| | - Atefeh Ghorbani
- Program in immunology and Infectious Diseases, Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, A1 B 3V6, Canada
| | - Heather Fifield
- Program in immunology and Infectious Diseases, Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, A1 B 3V6, Canada
| | - Lesley Berghuis
- Program in immunology and Infectious Diseases, Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, A1 B 3V6, Canada
| | - Mani Larijani
- Program in immunology and Infectious Diseases, Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, A1 B 3V6, Canada.
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96
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Choudhary M, Tamrakar A, Singh AK, Jain M, Jaiswal A, Kodgire P. AID Biology: A pathological and clinical perspective. Int Rev Immunol 2017; 37:37-56. [PMID: 28933967 DOI: 10.1080/08830185.2017.1369980] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Activation-induced cytidine deaminase (AID), primarily expressed in activated mature B lymphocytes in germinal centers, is the key factor in adaptive immune response against foreign antigens. AID is responsible for producing high-affinity and high-specificity antibodies against an infectious agent, through the physiological DNA alteration processes of antibody genes by somatic hypermutation (SHM) and class-switch recombination (CSR) and functions by deaminating deoxycytidines (dC) to deoxyuridines (dU), thereby introducing point mutations and double-stranded chromosomal breaks (DSBs). The beneficial physiological role of AID in antibody diversification is outweighed by its detrimental role in the genesis of several chronic immune diseases, under non-physiological conditions. This review offers a comprehensive and better understanding of AID biology and its pathological aspects, as well as addresses the challenges involved in AID-related cancer therapeutics, based on various recent advances and evidence available in the literature till date. In this article, we discuss ways through which our interpretation of AID biology may reflect upon novel clinical insights, which could be successfully translated into designing clinical trials and improving patient prognosis and disease management.
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Affiliation(s)
- Meenal Choudhary
- a Centre for Biosciences and Biomedical Engineering , Indian Institute of Technology Indore , Simrol , Indore , Madhya Pradesh , India
| | - Anubhav Tamrakar
- a Centre for Biosciences and Biomedical Engineering , Indian Institute of Technology Indore , Simrol , Indore , Madhya Pradesh , India
| | - Amit Kumar Singh
- a Centre for Biosciences and Biomedical Engineering , Indian Institute of Technology Indore , Simrol , Indore , Madhya Pradesh , India
| | - Monika Jain
- a Centre for Biosciences and Biomedical Engineering , Indian Institute of Technology Indore , Simrol , Indore , Madhya Pradesh , India
| | - Ankit Jaiswal
- a Centre for Biosciences and Biomedical Engineering , Indian Institute of Technology Indore , Simrol , Indore , Madhya Pradesh , India
| | - Prashant Kodgire
- a Centre for Biosciences and Biomedical Engineering , Indian Institute of Technology Indore , Simrol , Indore , Madhya Pradesh , India
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97
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Thientosapol ES, Sharbeen G, Lau KKE, Bosnjak D, Durack T, Stevanovski I, Weninger W, Jolly CJ. Proximity to AGCT sequences dictates MMR-independent versus MMR-dependent mechanisms for AID-induced mutation via UNG2. Nucleic Acids Res 2017; 45:3146-3157. [PMID: 28039326 PMCID: PMC5389528 DOI: 10.1093/nar/gkw1300] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 12/16/2016] [Indexed: 11/30/2022] Open
Abstract
AID deaminates C to U in either strand of Ig genes, exclusively producing C:G/G:C to T:A/A:T transition mutations if U is left unrepaired. Error-prone processing by UNG2 or mismatch repair diversifies mutation, predominantly at C:G or A:T base pairs, respectively. Here, we show that transversions at C:G base pairs occur by two distinct processing pathways that are dictated by sequence context. Within and near AGCT mutation hotspots, transversion mutation at C:G was driven by UNG2 without requirement for mismatch repair. Deaminations in AGCT were refractive both to processing by UNG2 and to high-fidelity base excision repair (BER) downstream of UNG2, regardless of mismatch repair activity. We propose that AGCT sequences resist faithful BER because they bind BER-inhibitory protein(s) and/or because hemi-deaminated AGCT motifs innately form a BER-resistant DNA structure. Distal to AGCT sequences, transversions at G were largely co-dependent on UNG2 and mismatch repair. We propose that AGCT-distal transversions are produced when apyrimidinic sites are exposed in mismatch excision patches, because completion of mismatch repair would require bypass of these sites.
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Affiliation(s)
- Eddy Sanchai Thientosapol
- Centenary Institute, Royal Prince Alfred Hospital, Camperdown NSW 2050, and Sydney Medical School, The University of Sydney, Sydney NSW 2006, Australia
| | - George Sharbeen
- Centenary Institute, Royal Prince Alfred Hospital, Camperdown NSW 2050, and Sydney Medical School, The University of Sydney, Sydney NSW 2006, Australia
| | - K K Edwin Lau
- Centenary Institute, Royal Prince Alfred Hospital, Camperdown NSW 2050, and Sydney Medical School, The University of Sydney, Sydney NSW 2006, Australia
| | - Daniel Bosnjak
- Centenary Institute, Royal Prince Alfred Hospital, Camperdown NSW 2050, and Sydney Medical School, The University of Sydney, Sydney NSW 2006, Australia
| | - Timothy Durack
- Centenary Institute, Royal Prince Alfred Hospital, Camperdown NSW 2050, and Sydney Medical School, The University of Sydney, Sydney NSW 2006, Australia
| | - Igor Stevanovski
- Centenary Institute, Royal Prince Alfred Hospital, Camperdown NSW 2050, and Sydney Medical School, The University of Sydney, Sydney NSW 2006, Australia
| | - Wolfgang Weninger
- Centenary Institute, Royal Prince Alfred Hospital, Camperdown NSW 2050, and Sydney Medical School, The University of Sydney, Sydney NSW 2006, Australia
| | - Christopher J Jolly
- Centenary Institute, Royal Prince Alfred Hospital, Camperdown NSW 2050, and Sydney Medical School, The University of Sydney, Sydney NSW 2006, Australia
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98
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Wasmuth EV, Zinder JC, Zattas D, Das M, Lima CD. Structure and reconstitution of yeast Mpp6-nuclear exosome complexes reveals that Mpp6 stimulates RNA decay and recruits the Mtr4 helicase. eLife 2017; 6. [PMID: 28742025 PMCID: PMC5553935 DOI: 10.7554/elife.29062] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 07/21/2017] [Indexed: 11/20/2022] Open
Abstract
Nuclear RNA exosomes catalyze a range of RNA processing and decay activities that are coordinated in part by cofactors, including Mpp6, Rrp47, and the Mtr4 RNA helicase. Mpp6 interacts with the nine-subunit exosome core, while Rrp47 stabilizes the exoribonuclease Rrp6 and recruits Mtr4, but it is less clear if these cofactors work together. Using biochemistry with Saccharomyces cerevisiae proteins, we show that Rrp47 and Mpp6 stimulate exosome-mediated RNA decay, albeit with unique dependencies on elements within the nuclear exosome. Mpp6-exosomes can recruit Mtr4, while Mpp6 and Rrp47 each contribute to Mtr4-dependent RNA decay, with maximal Mtr4-dependent decay observed with both cofactors. The 3.3 Å structure of a twelve-subunit nuclear Mpp6 exosome bound to RNA shows the central region of Mpp6 bound to the exosome core, positioning its Mtr4 recruitment domain next to Rrp6 and the exosome central channel. Genetic analysis reveals interactions that are largely consistent with our model. DOI:http://dx.doi.org/10.7554/eLife.29062.001
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Affiliation(s)
- Elizabeth V Wasmuth
- Structural Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, United States
| | - John C Zinder
- Structural Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, United States.,Tri-Institutional Training Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Dimitrios Zattas
- Structural Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Mom Das
- Structural Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Christopher D Lima
- Structural Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, United States.,Howard Hughes Medical Institute, Memorial Sloan Kettering Cancer Center, New York, United States
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99
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Lim J, Giri PK, Kazadi D, Laffleur B, Zhang W, Grinstein V, Pefanis E, Brown LM, Ladewig E, Martin O, Chen Y, Rabadan R, Boyer F, Rothschild G, Cogné M, Pinaud E, Deng H, Basu U. Nuclear Proximity of Mtr4 to RNA Exosome Restricts DNA Mutational Asymmetry. Cell 2017; 169:523-537.e15. [PMID: 28431250 DOI: 10.1016/j.cell.2017.03.043] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 01/19/2017] [Accepted: 03/27/2017] [Indexed: 11/16/2022]
Abstract
The distribution of sense and antisense strand DNA mutations on transcribed duplex DNA contributes to the development of immune and neural systems along with the progression of cancer. Because developmentally matured B cells undergo biologically programmed strand-specific DNA mutagenesis at focal DNA/RNA hybrid structures, they make a convenient system to investigate strand-specific mutagenesis mechanisms. We demonstrate that the sense and antisense strand DNA mutagenesis at the immunoglobulin heavy chain locus and some other regions of the B cell genome depends upon localized RNA processing protein complex formation in the nucleus. Both the physical proximity and coupled activities of RNA helicase Mtr4 (and senataxin) with the noncoding RNA processing function of RNA exosome determine the strand-specific distribution of DNA mutations. Our study suggests that strand-specific DNA mutagenesis-associated mechanisms will play major roles in other undiscovered aspects of organismic development.
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Affiliation(s)
- Junghyun Lim
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Pankaj Kumar Giri
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
| | - David Kazadi
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Brice Laffleur
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Wanwei Zhang
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Veronika Grinstein
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Evangelos Pefanis
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Lewis M Brown
- Department of Biological Sciences, Quantitative Proteomics Center, Columbia University, New York, NY 10027, USA
| | - Erik Ladewig
- Departments of Systems Biology and Biomedical Informatics, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Ophélie Martin
- Université de Limoges, Centre National de la Recherche Scientifique, CHU Limoges, CRIBL, UMR 7276, 87000 Limoges, France
| | - Yuling Chen
- School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Raul Rabadan
- Departments of Systems Biology and Biomedical Informatics, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - François Boyer
- Université de Limoges, Centre National de la Recherche Scientifique, CHU Limoges, CRIBL, UMR 7276, 87000 Limoges, France
| | - Gerson Rothschild
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Michel Cogné
- Université de Limoges, Centre National de la Recherche Scientifique, CHU Limoges, CRIBL, UMR 7276, 87000 Limoges, France
| | - Eric Pinaud
- Université de Limoges, Centre National de la Recherche Scientifique, CHU Limoges, CRIBL, UMR 7276, 87000 Limoges, France
| | - Haiteng Deng
- School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Uttiya Basu
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
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100
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Pavri R. R Loops in the Regulation of Antibody Gene Diversification. Genes (Basel) 2017; 8:E154. [PMID: 28574479 PMCID: PMC5485518 DOI: 10.3390/genes8060154] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 05/24/2017] [Accepted: 05/31/2017] [Indexed: 01/06/2023] Open
Abstract
For nearly three decades, R loops have been closely linked with class switch recombination (CSR), the process that generates antibody isotypes and that occurs via a complex cascade initiated by transcription-coupled mutagenesis in switch recombination sequences. R loops form during transcription of switch recombination sequences in vitro and in vivo, and there is solid evidence that R loops are required for efficient class switching. The classical model of R loops posits that they boost mutation rates by generating stable and long tracts of single-stranded DNA that serve as the substrate for activation induced deaminase (AID), the enzyme that initiates the CSR reaction cascade by co-transcriptionally mutating ssDNA in switch recombination sequences. Though logical and compelling, this model has not been supported by in vivo evidence. Indeed, several reports suggest that R loops may not be involved in recruiting AID activity to switch regions, meaning that R loops probably serve other unanticipated roles in CSR. Here, I review the key findings in this field to date and propose hypotheses that could help towards elucidating the precise function of R loops in CSR.
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Affiliation(s)
- Rushad Pavri
- Research Institute of Molecular Pathology (IMP), Campus Vienna Biocenter-1, Vienna Biocenter, Vienna 1030, Austria.
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