1
|
Weischedel J, Higgins L, Rogers S, Gramalla-Schmitz A, Wyrzykowska P, Borgoni S, MacCarthy T, Chahwan R. Modular cytosine base editing promotes epigenomic and genomic modifications. Nucleic Acids Res 2024; 52:e8. [PMID: 37994786 PMCID: PMC10810192 DOI: 10.1093/nar/gkad1118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 10/06/2023] [Accepted: 11/06/2023] [Indexed: 11/24/2023] Open
Abstract
Prokaryotic and eukaryotic adaptive immunity differ considerably. Yet, their fundamental mechanisms of gene editing via Cas9 and activation-induced deaminase (AID), respectively, can be conveniently complimentary. Cas9 is an RNA targeted dual nuclease expressed in several bacterial species. AID is a cytosine deaminase expressed in germinal centre B cells to mediate genomic antibody diversification. AID can also mediate epigenomic reprogramming via active DNA demethylation. It is known that sequence motifs, nucleic acid structures, and associated co-factors affect AID activity. But despite repeated attempts, deciphering AID's intrinsic catalytic activities and harnessing its targeted recruitment to DNA is still intractable. Even recent cytosine base editors are unable to fully recapitulate AID's genomic and epigenomic editing properties. Here, we describe the first instance of a modular AID-based editor that recapitulates the full spectrum of genomic and epigenomic editing activity. Our 'Swiss army knife' toolbox will help better understand AID biology per se as well as improve targeted genomic and epigenomic editing.
Collapse
Affiliation(s)
- Julian Weischedel
- Institute of Experimental Immunology, University of Zurich, Zurich 8057, Switzerland
| | - Laurence Higgins
- Living Systems Institute, University of Exeter, Exeter EX4 4QD, UK
| | - Sally Rogers
- Living Systems Institute, University of Exeter, Exeter EX4 4QD, UK
| | - Anna Gramalla-Schmitz
- Institute of Experimental Immunology, University of Zurich, Zurich 8057, Switzerland
| | - Paulina Wyrzykowska
- Institute of Experimental Immunology, University of Zurich, Zurich 8057, Switzerland
| | - Simone Borgoni
- Institute of Experimental Immunology, University of Zurich, Zurich 8057, Switzerland
| | - Thomas MacCarthy
- Department of Applied Mathematics & Statistics, Stony Brook University, NY 11794-3600, USA
| | - Richard Chahwan
- Institute of Experimental Immunology, University of Zurich, Zurich 8057, Switzerland
| |
Collapse
|
2
|
Bello A, Hirth G, Voigt S, Tepper S, Jungnickel B. Mechanism and regulation of secondary immunoglobulin diversification. Cell Cycle 2023; 22:2070-2087. [PMID: 37909747 PMCID: PMC10761156 DOI: 10.1080/15384101.2023.2275397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 10/20/2023] [Indexed: 11/03/2023] Open
Abstract
Secondary immunoglobulin diversification by somatic hypermutation and class switch recombination in B cells is instrumental for an adequate adaptive humoral immune response. These genetic events may, however, also introduce aberrations into other cellular genes and thereby cause B cell malignancies. While the basic mechanism of somatic hypermutation and class switch recombination is now well understood, their regulation and in particular the mechanism of their specific targeting to immunoglobulin genes is still rather mysterious. In this review, we summarize the current knowledge on the mechanism and regulation of secondary immunoglobulin diversification and discuss known mechanisms of physiological targeting to immunoglobulin genes and mistargeting to other cellular genes. We summarize open questions in the field and provide an outlook on future research.
Collapse
Affiliation(s)
- Amanda Bello
- Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University, Jena, Germany
| | - Gianna Hirth
- Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University, Jena, Germany
| | - Stefanie Voigt
- Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University, Jena, Germany
| | - Sandra Tepper
- Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University, Jena, Germany
| | - Berit Jungnickel
- Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University, Jena, Germany
| |
Collapse
|
3
|
Wu L, Shukla V, Yadavalli AD, Dinesh RK, Xu D, Rao A, Schatz DG. HMCES protects immunoglobulin genes specifically from deletions during somatic hypermutation. Genes Dev 2022; 36:433-450. [PMID: 35450882 PMCID: PMC9067407 DOI: 10.1101/gad.349438.122] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Accepted: 03/29/2022] [Indexed: 01/07/2023]
Abstract
Somatic hypermutation (SHM) produces point mutations in immunoglobulin (Ig) genes in B cells when uracils created by the activation-induced deaminase are processed in a mutagenic manner by enzymes of the base excision repair (BER) and mismatch repair (MMR) pathways. Such uracil processing creates DNA strand breaks and is susceptible to the generation of deleterious deletions. Here, we demonstrate that the DNA repair factor HMCES strongly suppresses deletions without significantly affecting other parameters of SHM in mouse and human B cells, thereby facilitating the production of antigen-specific antibodies. The deletion-prone repair pathway suppressed by HMCES operates downstream from the uracil glycosylase UNG and is mediated by the combined action of BER factor APE2 and MMR factors MSH2, MSH6, and EXO1. HMCES's ability to shield against deletions during SHM requires its capacity to form covalent cross-links with abasic sites, in sharp contrast to its DNA end-joining role in class switch recombination but analogous to its genome-stabilizing role during DNA replication. Our findings lead to a novel model for the protection of Ig gene integrity during SHM in which abasic site cross-linking by HMCES intercedes at a critical juncture during processing of vulnerable gapped DNA intermediates by BER and MMR enzymes.
Collapse
Affiliation(s)
- Lizhen Wu
- Department of Immunobiology, Yale School of Medicine, New Haven, Connecticut 06520, USA
| | - Vipul Shukla
- Division of Signaling and Gene Expression, La Jolla Institute for Immunology, La Jolla, California 92037, USA
| | | | - Ravi K Dinesh
- Department of Immunobiology, Yale School of Medicine, New Haven, Connecticut 06520, USA
| | - Dijin Xu
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut 06510, USA
| | - Anjana Rao
- Division of Signaling and Gene Expression, La Jolla Institute for Immunology, La Jolla, California 92037, USA
- Department of Pharmacology, Moores Cancer Center, University of California at San Diego, La Jolla, California 92093, USA
- Consortium for Regenerative Medicine, La Jolla, California 92037, USA
| | - David G Schatz
- Department of Immunobiology, Yale School of Medicine, New Haven, Connecticut 06520, USA
| |
Collapse
|
4
|
Tarsalainen A, Maman Y, Meng FL, Kyläniemi MK, Soikkeli A, Budzynska P, McDonald JJ, Šenigl F, Alt FW, Schatz DG, Alinikula J. Ig Enhancers Increase RNA Polymerase II Stalling at Somatic Hypermutation Target Sequences. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2022; 208:143-154. [PMID: 34862258 PMCID: PMC8702490 DOI: 10.4049/jimmunol.2100923] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 10/20/2021] [Indexed: 01/03/2023]
Abstract
Somatic hypermutation (SHM) drives the genetic diversity of Ig genes in activated B cells and supports the generation of Abs with increased affinity for Ag. SHM is targeted to Ig genes by their enhancers (diversification activators [DIVACs]), but how the enhancers mediate this activity is unknown. We show using chicken DT40 B cells that highly active DIVACs increase the phosphorylation of RNA polymerase II (Pol II) and Pol II occupancy in the mutating gene with little or no accompanying increase in elongation-competent Pol II or production of full-length transcripts, indicating accumulation of stalled Pol II. DIVAC has similar effect also in human Ramos Burkitt lymphoma cells. The DIVAC-induced stalling is weakly associated with an increase in the detection of ssDNA bubbles in the mutating target gene. We did not find evidence for antisense transcription, or that DIVAC functions by altering levels of H3K27ac or the histone variant H3.3 in the mutating gene. These findings argue for a connection between Pol II stalling and cis-acting targeting elements in the context of SHM and thus define a mechanistic basis for locus-specific targeting of SHM in the genome. Our results suggest that DIVAC elements render the target gene a suitable platform for AID-mediated mutation without a requirement for increasing transcriptional output.
Collapse
Affiliation(s)
- Alina Tarsalainen
- Unit of Infections and Immunity, Institute of Biomedicine, University of Turku, 20520 Turku, Finland
| | - Yaakov Maman
- The Azrieli Faculty of Medicine, Bar Ilan University, Safed, 1311502, Israel
| | - Fei-Long Meng
- Department of Genetics, Harvard Medical School and Program in Cellular and Molecular Medicine, HHMI, Boston Children’s Hospital, Boston, MA 02115, USA.,Current address: 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 200031, China
| | - Minna K. Kyläniemi
- Unit of Infections and Immunity, Institute of Biomedicine, University of Turku, 20520 Turku, Finland,Current address: Turku Bioscience Centre, University of Turku and Åbo Akademi University, 20520 Turku, Finland
| | - Anni Soikkeli
- Unit of Infections and Immunity, Institute of Biomedicine, University of Turku, 20520 Turku, Finland
| | - Paulina Budzynska
- Unit of Infections and Immunity, Institute of Biomedicine, University of Turku, 20520 Turku, Finland
| | - Jessica J. McDonald
- Department of Immunobiology, Yale School of Medicine, New Haven, CT 06511, USA,Current address: The Annenberg Public Policy Center, Philadelphia, PA 19104-3806, USA
| | - Filip Šenigl
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Praha 4, Czech Republic
| | - Frederic W. Alt
- Department of Genetics, Harvard Medical School and Program in Cellular and Molecular Medicine, HHMI, Boston Children’s Hospital, Boston, MA 02115, USA
| | - David G. Schatz
- Department of Immunobiology, Yale School of Medicine, New Haven, CT 06511, USA,Correspondence should be addressed to and
| | - Jukka Alinikula
- Unit of Infections and Immunity, Institute of Biomedicine, University of Turku, 20520 Turku, Finland,Correspondence should be addressed to and
| |
Collapse
|
5
|
The role of HIRA-dependent H3.3 deposition and its modifications in the somatic hypermutation of immunoglobulin variable regions. Proc Natl Acad Sci U S A 2021; 118:2114743118. [PMID: 34873043 DOI: 10.1073/pnas.2114743118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/27/2021] [Indexed: 12/17/2022] Open
Abstract
The H3.3 histone variant and its chaperone HIRA are involved in active transcription, but their detailed roles in regulating somatic hypermutation (SHM) of immunoglobulin variable regions in human B cells are not yet fully understood. In this study, we show that the knockout (KO) of HIRA significantly decreased SHM and changed the mutation pattern of the variable region of the immunoglobulin heavy chain (IgH) in the human Ramos B cell line without changing the levels of activation-induced deaminase and other major proteins known to be involved in SHM. Except for H3K79me2/3 and Spt5, many factors related to active transcription, including H3.3, were substantively decreased in HIRA KO cells, and this was accompanied by decreased nascent transcription in the IgH locus. The abundance of ZMYND11 that specifically binds to H3.3K36me3 on the IgH locus was also reduced in the HIRA KO. Somewhat surprisingly, HIRA loss increased the chromatin accessibility of the IgH V region locus. Furthermore, stable expression of ectopic H3.3G34V and H3.3G34R mutants that inhibit both the trimethylation of H3.3K36 and the recruitment of ZMYND11 significantly reduced SHM in Ramos cells, while the H3.3K79M did not. Consistent with the HIRA KO, the H3.3G34V mutant also decreased the occupancy of various elongation factors and of ZMYND11 on the IgH variable and downstream switching regions. Our results reveal an unrecognized role of HIRA and the H3.3K36me3 modification in SHM and extend our knowledge of how transcription-associated chromatin structure and accessibility contribute to SHM in human B cells.
Collapse
|
6
|
A Bayesian model based computational analysis of the relationship between bisulfite accessible single-stranded DNA in chromatin and somatic hypermutation of immunoglobulin genes. PLoS Comput Biol 2021; 17:e1009323. [PMID: 34491985 PMCID: PMC8462741 DOI: 10.1371/journal.pcbi.1009323] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 09/24/2021] [Accepted: 08/04/2021] [Indexed: 11/19/2022] Open
Abstract
The B cells in our body generate protective antibodies by introducing somatic hypermutations (SHM) into the variable region of immunoglobulin genes (IgVs). The mutations are generated by activation induced deaminase (AID) that converts cytosine to uracil in single stranded DNA (ssDNA) generated during transcription. Attempts have been made to correlate SHM with ssDNA using bisulfite to chemically convert cytosines that are accessible in the intact chromatin of mutating B cells. These studies have been complicated by using different definitions of "bisulfite accessible regions" (BARs). Recently, deep-sequencing has provided much larger datasets of such regions but computational methods are needed to enable this analysis. Here we leveraged the deep-sequencing approach with unique molecular identifiers and developed a novel Hidden Markov Model based Bayesian Segmentation algorithm to characterize the ssDNA regions in the IGHV4-34 gene of the human Ramos B cell line. Combining hierarchical clustering and our new Bayesian model, we identified recurrent BARs in certain subregions of both top and bottom strands of this gene. Using this new system, the average size of BARs is about 15 bp. We also identified potential G-quadruplex DNA structures in this gene and found that the BARs co-locate with G-quadruplex structures in the opposite strand. Using various correlation analyses, there is not a direct site-to-site relationship between the bisulfite accessible ssDNA and all sites of SHM but most of the highly AID mutated sites are within 15 bp of a BAR. In summary, we developed a novel platform to study single stranded DNA in chromatin at a base pair resolution that reveals potential relationships among BARs, SHM and G-quadruplexes. This platform could be applied to genome wide studies in the future.
Collapse
|
7
|
Role of Dot1L and H3K79 methylation in regulating somatic hypermutation of immunoglobulin genes. Proc Natl Acad Sci U S A 2021; 118:2104013118. [PMID: 34253616 DOI: 10.1073/pnas.2104013118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Somatic hypermutation (SHM) and class-switch recombination (CSR) of the immunoglobulin (Ig) genes allow B cells to make antibodies that protect us against a wide variety of pathogens. SHM is mediated by activation-induced deaminase (AID), occurs at a million times higher frequency than other mutations in the mammalian genome, and is largely restricted to the variable (V) and switch (S) regions of Ig genes. Using the Ramos human Burkitt's lymphoma cell line, we find that H3K79me2/3 and its methyltransferase Dot1L are more abundant on the V region than on the constant (C) region, which does not undergo mutation. In primary naïve mouse B cells examined ex vivo, the H3K79me2/3 modification appears constitutively in the donor Sμ and is inducible in the recipient Sγ1 upon CSR stimulation. Knockout and inhibition of Dot1L in Ramos cells significantly reduces V region mutation and the abundance of H3K79me2/3 on the V region and is associated with a decrease of polymerase II (Pol II) and its S2 phosphorylated form at the IgH locus. Knockout of Dot1L also decreases the abundance of BRD4 and CDK9 (a subunit of the P-TEFb complex) on the V region, and this is accompanied by decreased nascent transcripts throughout the IgH gene. Treatment with JQ1 (inhibitor of BRD4) or DRB (inhibitor of CDK9) decreases SHM and the abundance of Pol II S2P at the IgH locus. Since all these factors play a role in transcription elongation, our studies reinforce the idea that the chromatin context and dynamics of transcription are critical for SHM.
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
Feng Y, Seija N, Di Noia JM, Martin A. AID in Antibody Diversification: There and Back Again. Trends Immunol 2020; 41:586-600. [PMID: 32434680 PMCID: PMC7183997 DOI: 10.1016/j.it.2020.04.009] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 04/16/2020] [Accepted: 04/20/2020] [Indexed: 01/01/2023]
Abstract
Activation-Induced cytidine Deaminase (AID) initiates affinity maturation and isotype switching by deaminating deoxycytidines within immunoglobulin genes, leading to somatic hypermutation (SHM) and class switch recombination (CSR). AID thus potentiates the humoral response to clear pathogens. Marking the 20th anniversary of the discovery of AID, we review the current understanding of AID function. We discuss AID biochemistry and how error-free forms of DNA repair are co-opted to prioritize mutagenesis over accuracy during antibody diversification. We discuss the regulation of DNA double-strand break (DSB) repair pathways during CSR. We describe genomic targeting of AID as a multilayered process involving chromatin architecture, cis- and trans-acting factors, and determining mutagenesis – distinct from AID occupancy at loci that are spared from mutation. Subverted base excision repair (BER) and mismatch repair (MMR) pathways act concertedly to generate antibody sequence diversity during SHM. In CSR, DNA DSBs are repaired by the nonhomologous end-joining pathway involving the 53BP1–Rif1–Shieldin axis, and by an alternative end-joining pathway involving HMCES (5-Hydroxymethylcytosine binding, ES-cell-specific) that binds and protects resected DSB ends. Genomic targeting of AID appears to be multilayered, with inbuilt redundancy, but robust enough to ensure that most of the genome is spared from AID activity. Cis elements and genome topology act together with trans-acting factors involved in transcription and RNA processing to determine AID activity at specific Ig regions. Other loci sharing genomic and transcriptional features with the Ig are collaterally targeted during SHM and CSR.
Collapse
Affiliation(s)
- Yuqing Feng
- Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Noé Seija
- Institute de Recherches Cliniques de Montréal, Montréal, QC, Canada; Molecular Biology Programs, Department of Medicine, University of Montreal, Montréal, QC, Canada
| | - Javier M Di Noia
- Institute de Recherches Cliniques de Montréal, Montréal, QC, Canada; Molecular Biology Programs, Department of Medicine, University of Montreal, Montréal, QC, Canada.
| | - Alberto Martin
- Department of Immunology, University of Toronto, Toronto, ON, Canada.
| |
Collapse
|
10
|
Splicing regulator SRSF1-3 that controls somatic hypermutation of IgV genes interacts with topoisomerase 1 and AID. Mol Immunol 2019; 116:63-72. [PMID: 31622795 DOI: 10.1016/j.molimm.2019.10.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 09/24/2019] [Accepted: 10/01/2019] [Indexed: 01/27/2023]
Abstract
Somatic hypermutation (SHM) of Ig genes is initiated by activation-induced cytidine deaminase (AID) and requires target gene transcription. A splice isoform of SRSF1, SRSF1-3, is necessary for AID-dependent SHM of IgV genes. Nevertheless, its exact molecular mechanism of action in SHM remains unknown. Our in silico studies show that, unlike SRSF1, SRSF1-3 lacks a strong nuclear localization domain. We show that the absence of RS domain in SRSF1-3 affects its nuclear localization, as compared to SRSF1. Consequently, SRSF1-3 is predominantly present in the cytoplasm. Remarkably, co-immunoprecipitation studies showed that SRSF1-3 interacts with Topoisomerase 1 (TOP1), a crucial regulator of SHM that assists in generating ssDNA for AID activity. Moreover, the immunofluorescence studies confirmed that SRSF1-3 and TOP1 are co-localized in the nucleus. Furthermore, Proximity Ligation Assay corroborated the direct interaction between SRSF1-3 and TOP1. An interaction between SRSF1-3 and TOP1 suggests that SRSF1-3 likely influences the TOP1 activity and consequently can aid in SHM. Accordingly, SRSF1-3 probably acts as a link between TOP1 and SHM, by spatially regulating TOP1 activity at the Ig locus. We also confirmed the interaction between SRSF1-3 and AID in chicken B-cells. Thus, SRSF1-3 shows dual-regulation of SHM, via interacting with AID as well as TOP1.
Collapse
|
11
|
Transient AID expression for in situ mutagenesis with improved cellular fitness. Sci Rep 2018; 8:9413. [PMID: 29925928 PMCID: PMC6010430 DOI: 10.1038/s41598-018-27717-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 06/07/2018] [Indexed: 12/13/2022] Open
Abstract
Activation induced cytidine deaminase (AID) in germinal center B cells introduces somatic DNA mutations in transcribed immunoglobulin genes to increase antibody diversity. Ectopic expression of AID coupled with selection has been successfully employed to develop proteins with desirable properties. However, this process is laborious and time consuming because many rounds of selection are typically required to isolate the target proteins. AID expression can also adversely affect cell viability due to off target mutagenesis. Here we compared stable and transient expression of AID mutants with different catalytic activities to determine conditions for maximum accumulation of mutations with minimal toxicity. We find that transient (3–5 days) expression of an AID upmutant in the presence of selection pressure could induce a high rate of mutagenesis in reporter genes without affecting cells growth and expansion. Our findings may help improve protein evolution by ectopic expression of AID and other enzymes that can induce DNA mutations.
Collapse
|
12
|
Abstract
Long-term survivors of human immunodeficiency virus (HIV) infection have been shown to have a greatly increased incidence of B cell lymphomas. This increased lymphomagenesis suggests some link between HIV infection and the destabilization of the host B cell genome, a phenomenon also suggested by the extraordinary high frequency of mutation, insertion, and deletion in the broadly neutralizing HIV antibodies. Since HIV does not infect B cells, the molecular mechanisms of this genomic instability remain to be fully defined. Here, we demonstrate that the cell membrane-permeable HIV Tat proteins enhance activation-induced deaminase (AID)-mediated somatic hypermutation (SHM) of antibody V regions through their modulation of the endogenous polymerase II (Pol II) transcriptional process. Extremely small amounts of Tat that could come from bystander HIV-infected cells were sufficient to promote SHM. Our data suggest HIV Tat is one missing link between HIV infection and the overall B cell genomic instability in AIDS patients. Although the introduction of antiretroviral therapy (ART) has successfully controlled primary effects of human immunodeficiency virus (HIV) infection, such as HIV proliferation and HIV-induced immune deficiency, it did not eliminate the increased susceptibility of HIV-infected patients to B cell lymphomas. We find that a secreted HIV protein, Tat, enhances the intrinsic antibody diversification mechanism by increasing the AID-induced somatic mutations at the heavy-chain variable (VH) regions in human B cells. This could contribute to the high rate of mutation in the variable regions of broadly neutralizing anti-HIV antibodies and the genomewide mutations leading to B cell malignancies in HIV carriers.
Collapse
|
13
|
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.
Collapse
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
| |
Collapse
|
14
|
Castiblanco DP, Norton DD, Maul RW, Gearhart PJ. J H6 downstream intronic sequence is dispensable for RNA polymerase II accumulation and somatic hypermutation of the variable gene in Ramos cells. Mol Immunol 2018; 97:101-108. [PMID: 29625296 DOI: 10.1016/j.molimm.2018.03.031] [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: 01/04/2018] [Revised: 03/09/2018] [Accepted: 03/30/2018] [Indexed: 02/03/2023]
Abstract
Activation-induced deaminase (AID) introduces nucleotide substitutions within the variable region of immunoglobulin genes to promote antibody diversity. This activity, which is limited to 1.5 kb downstream of the variable gene promoter, mutates both the coding exon and downstream intronic sequences. We recently reported that RNA polymerase II accumulates in these regions during transcription in mice. This build-up directly correlates with the area that is accessible to AID, and manipulation of RNA polymerase II levels alters the mutation frequency. To address whether the intronic DNA sequence by itself can regulate RNA polymerase II accumulation and promote mutagenesis, we deleted 613 bp of DNA downstream of the JH6 intron in the human Ramos B cell line. The loss of this sequence did not alter polymerase abundance or mutagenesis in the variable gene, suggesting that most of the intronic sequence is dispensable for somatic hypermutation.
Collapse
Affiliation(s)
- Diana P Castiblanco
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Darrell D Norton
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Robert W Maul
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Patricia J Gearhart
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
| |
Collapse
|
15
|
Teater M, Dominguez PM, Redmond D, Chen Z, Ennishi D, Scott DW, Cimmino L, Ghione P, Chaudhuri J, Gascoyne RD, Aifantis I, Inghirami G, Elemento O, Melnick A, Shaknovich R. AICDA drives epigenetic heterogeneity and accelerates germinal center-derived lymphomagenesis. Nat Commun 2018; 9:222. [PMID: 29335468 PMCID: PMC5768781 DOI: 10.1038/s41467-017-02595-w] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 12/13/2017] [Indexed: 12/22/2022] Open
Abstract
Epigenetic heterogeneity is emerging as a feature of tumors. In diffuse large B-cell lymphoma (DLBCL), increased cytosine methylation heterogeneity is associated with poor clinical outcome, yet the underlying mechanisms remain unclear. Activation-induced cytidine deaminase (AICDA), an enzyme that mediates affinity maturation and facilitates DNA demethylation in germinal center (GC) B cells, is required for DLBCL pathogenesis and linked to inferior outcome. Here we show that AICDA overexpression causes more aggressive disease in BCL2-driven murine lymphomas. This phenotype is associated with increased cytosine methylation heterogeneity, but not with increased AICDA-mediated somatic mutation burden. Reciprocally, the cytosine methylation heterogeneity characteristic of normal GC B cells is lost upon AICDA depletion. These observations are relevant to human patients, since DLBCLs with high AICDA expression manifest increased methylation heterogeneity vs. AICDA-low DLBCLs. Our results identify AICDA as a driver of epigenetic heterogeneity in B-cell lymphomas with potential significance for other tumors with aberrant expression of cytidine deaminases. In diffuse large B-cell lymphoma (DLBCL) increased epigenetic heterogeneity in the form of cytosine methylation is known to link to a poor clinical outcome. Here, the authors show that AICDA, an enzyme required for DLBCL pathogenesis, increases cytosine methylation heterogeneity.
Collapse
Affiliation(s)
- Matt Teater
- Department of Medicine, Division of Hematology and Medical Oncology, Weill Cornell Medicine, New York, NY, 10021, USA.,Institute for Computational Biomedicine, Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10021, USA
| | - Pilar M Dominguez
- Department of Medicine, Division of Hematology and Medical Oncology, Weill Cornell Medicine, New York, NY, 10021, USA
| | - David Redmond
- Institute for Computational Biomedicine, Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10021, USA
| | - Zhengming Chen
- Division of Biostatistics and Epidemiology, Weill Cornell Medicine, New York, NY, 10021, USA
| | - Daisuke Ennishi
- Centre for Lymphoid Cancer, British Columbia Cancer Agency, Vancouver, BC V5Z 4E6, Canada
| | - David W Scott
- Centre for Lymphoid Cancer, British Columbia Cancer Agency, Vancouver, BC V5Z 4E6, Canada
| | - Luisa Cimmino
- Department of Pathology, Laura and Isaac Perlmutter Cancer Center, and The Helen L. and Martin S. Kimmel Center for Stem Cell Biology, NYU School of Medicine, New York, NY, 10016, USA
| | - Paola Ghione
- Department of Medicine, Division of Hematology and Medical Oncology, Weill Cornell Medicine, New York, NY, 10021, USA.,Division of Hematology, Department of Experimental Medicine and Oncology, University of Turin, 10124, Turin, Italy
| | - Jayanta Chaudhuri
- Immunology Program, Memorial Sloan-Kettering Cancer Center, Gerstner Sloan-Kettering Graduate School, New York, NY, 10021, USA
| | - Randy D Gascoyne
- Department of Pathology, British Columbia Cancer Agency, Vancouver, BC V5Z 4E6, Canada
| | - Iannis Aifantis
- Department of Pathology, Laura and Isaac Perlmutter Cancer Center, and The Helen L. and Martin S. Kimmel Center for Stem Cell Biology, NYU School of Medicine, New York, NY, 10016, USA
| | - Giorgio Inghirami
- Pathology and Laboratory Medicine Department, Weill Cornell Medicine, New York, NY, 10021, USA
| | - Olivier Elemento
- Institute for Computational Biomedicine, Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10021, USA. .,Caryl and Israel Englander Institute for Precision Medicine, Weill Cornell Medicine, New York, NY, 10021, USA.
| | - Ari Melnick
- Department of Medicine, Division of Hematology and Medical Oncology, Weill Cornell Medicine, New York, NY, 10021, USA.
| | - Rita Shaknovich
- Department of Medicine, Division of Hematology and Medical Oncology, Weill Cornell Medicine, New York, NY, 10021, USA. .,Cancer Genetics, Inc., Rutherford, NJ, 07070, USA.
| |
Collapse
|
16
|
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.
Collapse
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.
| |
Collapse
|
17
|
Saini N, Roberts SA, Sterling JF, Malc EP, Mieczkowski PA, Gordenin DA. APOBEC3B cytidine deaminase targets the non-transcribed strand of tRNA genes in yeast. DNA Repair (Amst) 2017; 53:4-14. [PMID: 28351647 DOI: 10.1016/j.dnarep.2017.03.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 02/23/2017] [Accepted: 03/10/2017] [Indexed: 01/08/2023]
Abstract
Variations in mutation rates across the genome have been demonstrated both in model organisms and in cancers. This phenomenon is largely driven by the damage specificity of diverse mutagens and the differences in DNA repair efficiency in given genomic contexts. Here, we demonstrate that the single-strand DNA-specific cytidine deaminase APOBEC3B (A3B) damages tRNA genes at a 1000-fold higher efficiency than other non-tRNA genomic regions in budding yeast. We found that A3B-induced lesions in tRNA genes were predominantly located on the non-transcribed strand, while no transcriptional strand bias was observed in protein coding genes. Furthermore, tRNA gene mutations were exacerbated in cells where RNaseH expression was completely abolished (Δrnh1Δrnh35). These data suggest a transcription-dependent mechanism for A3B-induced tRNA gene hypermutation. Interestingly, in strains proficient in DNA repair, only 1% of the abasic sites formed upon excision of A3B-deaminated cytosines were not repaired leading to mutations in tRNA genes, while 18% of these lesions failed to be repaired in the remainder of the genome. A3B-induced mutagenesis in tRNA genes was found to be efficiently suppressed by the redundant activities of both base excision repair (BER) and the error-free DNA damage bypass pathway. On the other hand, deficiencies in BER did not have a profound effect on A3B-induced mutations in CAN1, the reporter for protein coding genes. We hypothesize that differences in the mechanisms underlying ssDNA formation at tRNA genes and other genomic loci are the key determinants of the choice of the repair pathways and consequently the efficiency of DNA damage repair in these regions. Overall, our results indicate that tRNA genes are highly susceptible to ssDNA-specific DNA damaging agents. However, increased DNA repair efficacy in tRNA genes can prevent their hypermutation and maintain both genome and proteome homeostasis.
Collapse
Affiliation(s)
- Natalie Saini
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Research Triangle Park, NC, USA
| | - Steven A Roberts
- School of Molecular Biosciences, Washington State University, Pullman, WA, USA
| | - Joan F Sterling
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Research Triangle Park, NC, USA
| | - Ewa P Malc
- Department of Genetics,Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA
| | - Piotr A Mieczkowski
- Department of Genetics,Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA
| | - Dmitry A Gordenin
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Research Triangle Park, NC, USA.
| |
Collapse
|
18
|
Boulianne B, Robinson ME, May PC, Castellano L, Blighe K, Thomas J, Reid A, Müschen M, Apperley JF, Stebbing J, Feldhahn N. Lineage-Specific Genes Are Prominent DNA Damage Hotspots during Leukemic Transformation of B Cell Precursors. Cell Rep 2017; 18:1687-1698. [PMID: 28199841 PMCID: PMC5318656 DOI: 10.1016/j.celrep.2017.01.057] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 11/29/2016] [Accepted: 01/23/2017] [Indexed: 02/07/2023] Open
Abstract
In human leukemia, lineage-specific genes represent predominant targets of deletion, with lymphoid-specific genes frequently affected in lymphoid leukemia and myeloid-specific genes in myeloid leukemia. To investigate the basis of lineage-specific alterations, we analyzed global DNA damage in primary B cell precursors expressing leukemia-inducing oncogenes by ChIP-seq. We identified more than 1,000 sensitive regions, of which B lineage-specific genes constitute the most prominent targets. Identified hotspots at B lineage genes relate to DNA-DSBs, affect genes that harbor genomic lesions in human leukemia, and associate with ectopic deletion in successfully transformed cells. Furthermore, we show that most identified regions overlap with gene bodies of highly expressed genes and that induction of a myeloid lineage phenotype in transformed B cell precursors promotes de novo DNA damage at myeloid loci. Hence, we demonstrate that lineage-specific transcription predisposes lineage-specific genes in transformed B cell precursors to DNA damage, which is likely to promote the frequent alteration of lineage-specific genes in human leukemia.
Collapse
Affiliation(s)
- Bryant Boulianne
- Centre for Haematology, Department of Medicine, Imperial College London, W12 0NN London, UK
| | - Mark E Robinson
- Centre for Haematology, Department of Medicine, Imperial College London, W12 0NN London, UK; Division of Cancer, Department of Surgery and Cancer, Imperial College London, W12 0NN London, UK
| | - Philippa C May
- Centre for Haematology, Department of Medicine, Imperial College London, W12 0NN London, UK; Molecular Pathology, Imperial College Healthcare NHS Trust, W12 0NN London, UK
| | - Leandro Castellano
- Division of Cancer, Department of Surgery and Cancer, Imperial College London, W12 0NN London, UK
| | - Kevin Blighe
- Centre for Haematology, Department of Medicine, Imperial College London, W12 0NN London, UK; Division of Cancer, Department of Surgery and Cancer, Imperial College London, W12 0NN London, UK
| | - Jennifer Thomas
- Centre for Haematology, Department of Medicine, Imperial College London, W12 0NN London, UK; Division of Cancer, Department of Surgery and Cancer, Imperial College London, W12 0NN London, UK
| | - Alistair Reid
- Centre for Haematology, Department of Medicine, Imperial College London, W12 0NN London, UK; Molecular Pathology, Imperial College Healthcare NHS Trust, W12 0NN London, UK
| | - Markus Müschen
- Department of Systems Biology, Beckman Research Institute and City of Hope Comprehensive Cancer Center, Pasadena, CA 91016, USA
| | - Jane F Apperley
- Centre for Haematology, Department of Medicine, Imperial College London, W12 0NN London, UK
| | - Justin Stebbing
- Division of Cancer, Department of Surgery and Cancer, Imperial College London, W12 0NN London, UK
| | - Niklas Feldhahn
- Centre for Haematology, Department of Medicine, Imperial College London, W12 0NN London, UK.
| |
Collapse
|
19
|
Methot S, Di Noia J. Molecular Mechanisms of Somatic Hypermutation and Class Switch Recombination. Adv Immunol 2017; 133:37-87. [DOI: 10.1016/bs.ai.2016.11.002] [Citation(s) in RCA: 165] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
|
20
|
Heinäniemi M, Vuorenmaa T, Teppo S, Kaikkonen MU, Bouvy-Liivrand M, Mehtonen J, Niskanen H, Zachariadis V, Laukkanen S, Liuksiala T, Teittinen K, Lohi O. Transcription-coupled genetic instability marks acute lymphoblastic leukemia structural variation hotspots. eLife 2016; 5. [PMID: 27431763 PMCID: PMC4951197 DOI: 10.7554/elife.13087] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 06/09/2016] [Indexed: 12/11/2022] Open
Abstract
Progression of malignancy to overt disease requires multiple genetic hits. Activation-induced deaminase (AID) can drive lymphomagenesis by generating off-target DNA breaks at loci that harbor highly active enhancers and display convergent transcription. The first active transcriptional profiles from acute lymphoblastic leukemia (ALL) patients acquired here reveal striking similarity at structural variation (SV) sites. Specific transcriptional features, namely convergent transcription and Pol2 stalling, were detected at breakpoints. The overlap was most prominent at SV with recognition motifs for the recombination activating genes (RAG). We present signal feature analysis to detect vulnerable regions and quantified from human cells how convergent transcription contributes to R-loop generation and RNA polymerase stalling. Wide stalling regions were characterized by high DNAse hypersensitivity and unusually broad H3K4me3 signal. Based on 1382 pre-B-ALL patients, the ETV6-RUNX1 fusion positive patients had over ten-fold elevation in RAG1 while high expression of AID marked pre-B-ALL lacking common cytogenetic changes.
Collapse
Affiliation(s)
- Merja Heinäniemi
- School of Medicine, University of Eastern Finland, Kuopio, Finland
| | - Tapio Vuorenmaa
- School of Medicine, University of Eastern Finland, Kuopio, Finland.,A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Susanna Teppo
- School of Medicine, University of Tampere, Tampere, Finland
| | - Minna U Kaikkonen
- A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | | | - Juha Mehtonen
- School of Medicine, University of Eastern Finland, Kuopio, Finland
| | - Henri Niskanen
- A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Vasilios Zachariadis
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | | | | | | | - Olli Lohi
- School of Medicine, University of Tampere, Tampere, Finland.,Tampere University Hospital, Tampere, Finland
| |
Collapse
|
21
|
Abstract
Transcription termination is a fundamental process in which RNA polymerase ceases RNA chain extension and dissociates from the chromatin template, thereby defining the end of the transcription unit. Our understanding of the biological role and functional importance of termination by RNA polymerase II and the range of processes in which it is involved has grown significantly in recent years. A large set of nucleic acid-binding proteins and enzymes have been identified as part of the termination machinery. A greater appreciation for the coupling of termination to RNA processing and metabolism has been recognized. In addition to serving as an essential step at the end of the transcription cycle, termination is involved in the regulation of a broad range of cellular processes. More recently, a role for termination in pervasive transcription, non-coding RNA regulation, genetic stability, chromatin remodeling, the immune response, and disease has come to the fore. Interesting mechanistic questions remain, but the last several years have resulted in significant insights into termination and an increasing recognition of its biological importance.
Collapse
Affiliation(s)
- Travis J Loya
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Daniel Reines
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA
| |
Collapse
|
22
|
Zanotti KJ, Gearhart PJ. Antibody diversification caused by disrupted mismatch repair and promiscuous DNA polymerases. DNA Repair (Amst) 2016; 38:110-116. [PMID: 26719140 PMCID: PMC4740194 DOI: 10.1016/j.dnarep.2015.11.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/30/2015] [Indexed: 10/25/2022]
Abstract
The enzyme activation-induced deaminase (AID) targets the immunoglobulin loci in activated B cells and creates DNA mutations in the antigen-binding variable region and DNA breaks in the switch region through processes known, respectively, as somatic hypermutation and class switch recombination. AID deaminates cytosine to uracil in DNA to create a U:G mismatch. During somatic hypermutation, the MutSα complex binds to the mismatch, and the error-prone DNA polymerase η generates mutations at A and T bases. During class switch recombination, both MutSα and MutLα complexes bind to the mismatch, resulting in double-strand break formation and end-joining. This review is centered on the mechanisms of how the MMR pathway is commandeered by B cells to generate antibody diversity.
Collapse
Affiliation(s)
- Kimberly J Zanotti
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
| | - Patricia J Gearhart
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
| |
Collapse
|
23
|
Abstract
The immunoglobulin diversification processes of somatic hypermutation and class switch recombination critically rely on transcription-coupled targeting of activation-induced cytidine deaminase (AID) to Ig loci in activated B lymphocytes. AID catalyzes deamination of cytidine deoxynucleotides on exposed single-stranded DNA. In addition to driving immunoglobulin diversity, promiscuous targeting of AID mutagenic activity poses a deleterious threat to genomic stability. Recent genome-wide studies have uncovered pervasive AID activity throughout the B cell genome. It is increasingly apparent that AID activity is frequently targeted to genomic loci undergoing early transcription termination where RNA exosome promotes the resolution of stalled transcription complexes via cotranscriptional RNA degradation mechanisms. Here, we review aspects and consequences of eukaryotic transcription that lead to early termination, RNA exosome recruitment, and ultimately targeting of AID mutagenic activity.
Collapse
Affiliation(s)
- Evangelos Pefanis
- Department of Microbiology & Immunology, College of Physicians and Surgeons, Columbia University, New York, USA.
| | - Uttiya Basu
- Department of Microbiology & Immunology, College of Physicians and Surgeons, Columbia University, New York, USA.
| |
Collapse
|
24
|
Stavnezer J, Schrader CE. IgH chain class switch recombination: mechanism and regulation. THE JOURNAL OF IMMUNOLOGY 2015; 193:5370-8. [PMID: 25411432 DOI: 10.4049/jimmunol.1401849] [Citation(s) in RCA: 168] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
IgH class switching occurs rapidly after activation of mature naive B cells, resulting in a switch from expression of IgM and IgD to expression of IgG, IgE, or IgA; this switch improves the ability of Abs to remove the pathogen that induces the humoral immune response. Class switching occurs by a deletional recombination between two switch regions, each of which is associated with a H chain constant region gene. Class switch recombination (CSR) is instigated by activation-induced cytidine deaminase, which converts cytosines in switch regions to uracils. The uracils are subsequently removed by two DNA-repair pathways, resulting in mutations, single-strand DNA breaks, and the double-strand breaks required for CSR. We discuss several aspects of CSR, including how CSR is induced, CSR in B cell progenitors, the roles of transcription and chromosomal looping in CSR, and the roles of certain DNA-repair enzymes in CSR.
Collapse
Affiliation(s)
- Janet Stavnezer
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA 01605
| | - Carol E Schrader
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA 01605
| |
Collapse
|
25
|
Maul RW, Cao Z, Venkataraman L, Giorgetti CA, Press JL, Denizot Y, Du H, Sen R, Gearhart PJ. Spt5 accumulation at variable genes distinguishes somatic hypermutation in germinal center B cells from ex vivo-activated cells. ACTA ACUST UNITED AC 2014; 211:2297-306. [PMID: 25288395 PMCID: PMC4203944 DOI: 10.1084/jem.20131512] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Variable (V) genes of immunoglobulins undergo somatic hypermutation by activation-induced deaminase (AID) to generate amino acid substitutions that encode antibodies with increased affinity for antigen. Hypermutation is restricted to germinal center B cells and cannot be recapitulated in ex vivo-activated splenic cells, even though the latter express high levels of AID. This suggests that there is a specific feature of antigen activation in germinal centers that recruits AID to V genes which is absent in mitogen-activated cultured cells. Using two Igh knock-in mouse models, we found that RNA polymerase II accumulates in V regions in B cells after both types of stimulation for an extended distance of 1.2 kb from the TATA box. The paused polymerases generate abundant single-strand DNA targets for AID. However, there is a distinct accumulation of the initiating form of polymerase, along with the transcription cofactor Spt5 and AID, in the V region from germinal center cells, which is totally absent in cultured cells. These data support a model where mutations are prevalent in germinal center cells, but not in ex vivo cells, because the initiating form of polymerase is retained, which affects Spt5 and AID recruitment.
Collapse
Affiliation(s)
- Robert W Maul
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| | - Zheng Cao
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| | | | | | - Joan L Press
- Department of Biology, Brandeis University, Waltham, MA 02454
| | - Yves Denizot
- Centre National de la Recherche Scientifique UMR 7276, Université de Limoges, 87025 Limoges, France
| | - Hansen Du
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| | - Ranjan Sen
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| | - Patricia J Gearhart
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| |
Collapse
|
26
|
Abstract
Transcription requires unwinding complementary DNA strands, generating torsional stress, and sensitizing the exposed single strands to chemical reactions and endogenous damaging agents. In addition, transcription can occur concomitantly with the other major DNA metabolic processes (replication, repair, and recombination), creating opportunities for either cooperation or conflict. Genetic modifications associated with transcription are a global issue in the small genomes of microorganisms in which noncoding sequences are rare. Transcription likewise becomes significant when one considers that most of the human genome is transcriptionally active. In this review, we focus specifically on the mutagenic consequences of transcription. Mechanisms of transcription-associated mutagenesis in microorganisms are discussed, as is the role of transcription in somatic instability of the vertebrate immune system.
Collapse
Affiliation(s)
- Sue Jinks-Robertson
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710;
| | | |
Collapse
|