1
|
Kalweit K, Gölling V, Kosan C, Jungnickel B. Role of Rad18 in B cell activation and lymphomagenesis. Sci Rep 2024; 14:7066. [PMID: 38528023 PMCID: PMC10963733 DOI: 10.1038/s41598-024-57018-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Accepted: 03/13/2024] [Indexed: 03/27/2024] Open
Abstract
Maintenance of genome integrity is instrumental in preventing cancer. In addition to DNA repair pathways that prevent damage to DNA, damage tolerance pathways allow for the survival of cells that encounter DNA damage during replication. The Rad6/18 pathway is instrumental in this process, mediating damage bypass by ubiquitination of proliferating cell nuclear antigen. Previous studies have shown different roles of Rad18 in vivo and in tumorigenesis. Here, we show that B cells induce Rad18 expression upon proliferation induction. We have therefore analysed the role of Rad18 in B cell activation as well as in B cell lymphomagenesis mediated by an Eµ-Myc transgene. We find no activation defects or survival differences between Rad18 WT mice and two different models of Rad18 deficient tumour mice. Also, tumour subtypes do not differ between the mouse models. Accordingly, functions of Rad18 in B cell activation and tumorigenesis may be compensated for by other pathways in B cells.
Collapse
Affiliation(s)
- Kevin Kalweit
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Hans Knöll Strasse 2, 07745, Jena, Germany
| | - Vanessa Gölling
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Hans Knöll Strasse 2, 07745, Jena, Germany
| | - Christian Kosan
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Hans Knöll Strasse 2, 07745, Jena, Germany
| | - Berit Jungnickel
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Hans Knöll Strasse 2, 07745, Jena, Germany.
| |
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
|
Yan X, He Y, Yang S, Zeng T, Hua Y, Bao S, Yang F, Duan N, Sun C, Liang Y, Fu Z, Huang X, Li W, Yin Y. A positive feedback loop: RAD18-YAP-TGF-β between triple-negative breast cancer and macrophages regulates cancer stemness and progression. Cell Death Dis 2022; 8:196. [PMID: 35413945 PMCID: PMC9005530 DOI: 10.1038/s41420-022-00968-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 03/09/2022] [Accepted: 03/21/2022] [Indexed: 12/24/2022]
Abstract
As a key regulator of the DNA translesion synthesis (TLS) pathway, RAD18 is error-prone and contributes to the accumulation of DNA mutations. Our previous study showed that it plays an essential role in the progression of multiple tumors. However, the mechanism through which RAD18 influences triple-negative breast cancer (TNBC), especially the interaction between tumor cells and the tumor microenvironment, remains elusive. In this study, we showed that RAD18 expression is markedly higher in patients with high T stage TNBC and inversely correlated with prognosis. High expression of RAD18 facilitated a highly stem-cell phenotype through the Hippo/YAP pathway, which supports the proliferation of TNBC. In addition, the cytokine byproduct TGF-β activates macrophages to have an M2-like tumor-associated macrophage (TAM) phenotype. Reciprocally, TGF-β from TAMs activated RAD18 in TNBC to enhance tumor stemness, forming a positive feedback loop. Inhibition of YAP or TGF-β breaks this loop and suppresses cancer stemness and proliferation In nude mice, RAD18 promoted subcutaneous transplanted tumor growth and M2-type TAM recruitment. Collectively, the RAD18-YAP-TGF-β loop is essential for the promotion of the stemness phenotype by TNBC and could be a potential therapeutic target for TNBC.
Collapse
Affiliation(s)
- Xueqi Yan
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Yaozhou He
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Shikun Yang
- Hepatobiliary/Liver Transplantation Center, The First Affiliated Hospital of Nanjing Medical University; Key Laboratory of Liver Transplantation, Chinese Academy of Medical Sciences, 210029, Nanjing, China
| | - Tianyu Zeng
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Yijia Hua
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Shengnan Bao
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Fan Yang
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Ningjun Duan
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Chunxiao Sun
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Yan Liang
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Ziyi Fu
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Xiang Huang
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Wei Li
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China.
| | - Yongmei Yin
- Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China. .,Jiangsu Key Lab of Cancer Biomarkers, Prevention and Treatment, Collaborative Innovation Center for Personalized Cancer Medicine, Nanjing Medical University, 211166, Nanjing, China.
| |
Collapse
|
4
|
Böttcher K, Braunschmidt K, Hirth G, Schärich K, Klassert TE, Stock M, Sorgatz J, Fischer-Burkart S, Ullrich S, Frankenberger S, Kritsch D, Kosan C, Küppers R, Strobl LJ, Slevogt H, Zimber-Strobl U, Jungnickel B. Context-dependent regulation of immunoglobulin mutagenesis by p53. Mol Immunol 2021; 138:128-136. [PMID: 34392111 DOI: 10.1016/j.molimm.2021.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 07/22/2021] [Accepted: 08/04/2021] [Indexed: 10/20/2022]
Abstract
p53 plays a major role in genome maintenance. In addition to multiple p53 functions in the control of DNA repair, a regulation of DNA damage bypass via translesion synthesis has been implied in vitro. Somatic hypermutation of immunoglobulin genes for affinity maturation of antibody responses is based on aberrant translesion polymerase action and must be subject to stringent control to prevent genetic alterations and lymphomagenesis. When studying the role of p53 in somatic hypermutation in vivo, we found altered translesion polymerase-mediated A:T mutagenesis in mice lacking p53 in all organs, but notably not in mice with B cell-specific p53 inactivation, implying that p53 functions in non-B cells may alter mutagenesis in B cells. During class switch recombination, when p53 prevents formation of chromosomal translocations, we in addition detected a B cell-intrinsic role for p53 in altering G:C and A:T mutagenesis. Thus, p53 regulates translesion polymerase activity and shows differential activity during somatic hypermutation versus class switch recombination in vivo. Finally, p53 inhibition leads to increased somatic hypermutation in human B lymphoma cells. We conclude that loss of p53 function may promote genetic instability via multiple routes during antibody diversification in vivo.
Collapse
Affiliation(s)
- Katrin Böttcher
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany.
| | - Kerstin Braunschmidt
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany; Institute of Clinical Molecular Biology, Helmholtz Center Munich, German Research Center for Environmental Health, Munich, Germany.
| | - Gianna Hirth
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany.
| | - Karsten Schärich
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany.
| | - Tilman E Klassert
- Host Septomics, ZIK Septomics, Jena University Hospital, Jena, Germany.
| | - Magdalena Stock
- Host Septomics, ZIK Septomics, Jena University Hospital, Jena, Germany.
| | - Janine Sorgatz
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany.
| | - Sabine Fischer-Burkart
- Institute of Clinical Molecular Biology, Helmholtz Center Munich, German Research Center for Environmental Health, Munich, Germany.
| | - Steffen Ullrich
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany.
| | - Samantha Frankenberger
- Institute of Clinical Molecular Biology, Helmholtz Center Munich, German Research Center for Environmental Health, Munich, Germany
| | - Daniel Kritsch
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany; Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany.
| | - Christian Kosan
- Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany.
| | - Ralf Küppers
- Institute of Cell Biology (Cancer Research), University of Duisburg-Essen, Medical School, Essen, Germany.
| | - Lothar J Strobl
- Department of Gene Vectors, Helmholtz Center Munich, German Research Center for Environmental Health, Munich, Germany.
| | - Hortense Slevogt
- Host Septomics, ZIK Septomics, Jena University Hospital, Jena, Germany.
| | - Ursula Zimber-Strobl
- Department of Gene Vectors, Helmholtz Center Munich, German Research Center for Environmental Health, Munich, Germany.
| | - Berit Jungnickel
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany; Institute of Clinical Molecular Biology, Helmholtz Center Munich, German Research Center for Environmental Health, Munich, Germany.
| |
Collapse
|
5
|
Haralambieva IH, Eberhard KG, Ovsyannikova IG, Grill DE, Schaid DJ, Kennedy RB, Poland GA. Transcriptional signatures associated with rubella virus-specific humoral immunity after a third dose of MMR vaccine in women of childbearing age. Eur J Immunol 2021; 51:1824-1838. [PMID: 33818775 PMCID: PMC9841595 DOI: 10.1002/eji.202049054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 03/03/2021] [Accepted: 12/17/2020] [Indexed: 01/19/2023]
Abstract
Multiple factors linked to host genetics/inherent biology play a role in interindividual variability in immune response outcomes after rubella vaccination. In order to identify these factors, we conducted a study of rubella-specific humoral immunity before (Baseline) and after (Day 28) a third dose of MMR-II vaccine in a cohort of 109 women of childbearing age. We performed mRNA-Seq profiling of PBMCs after rubella virus in vitro stimulation to delineate genes associated with post-vaccination rubella humoral immunity and to define genes mediating the association between prior immune response status (high or low antibody) and subsequent immune response outcome. Our study identified novel genes that mediated the association between prior immune response and neutralizing antibody titer after a third MMR vaccine dose. These genes included the following: CDC34; CSNK1D; APOBEC3F; RAD18; AAAS; SLC37A1; FAS; and JAK2. The encoded proteins are involved in innate antiviral response, IFN/cytokine signaling, B cell repertoire generation, the clonal selection of B lymphocytes in germinal centers, and somatic hypermutation/antibody affinity maturation to promote optimal antigen-specific B cell immune function. These data advance our understanding of how subjects' prior immune status and/or genetic propensity to respond to rubella/MMR vaccination ultimately affects innate immunity and humoral immune outcomes after vaccination.
Collapse
Affiliation(s)
| | | | | | - Diane E. Grill
- Department of Health Sciences Research, Mayo Clinic, Rochester, MN 55905, USA
| | - Daniel J. Schaid
- Department of Health Sciences Research, Mayo Clinic, Rochester, MN 55905, USA
| | - Richard B. Kennedy
- Mayo Clinic Vaccine Research Group, Mayo Clinic, Rochester, MN 55905, USA
| | - Gregory A. Poland
- Mayo Clinic Vaccine Research Group, Mayo Clinic, Rochester, MN 55905, USA
| |
Collapse
|
6
|
Tomi NS, Davari K, Grotzky D, Loos F, Böttcher K, Frankenberger S, Jungnickel B. Analysis of SHPRH functions in DNA repair and immunoglobulin diversification. DNA Repair (Amst) 2014; 24:63-72. [PMID: 25311267 DOI: 10.1016/j.dnarep.2014.09.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 08/29/2014] [Accepted: 09/23/2014] [Indexed: 12/18/2022]
Abstract
During replication, bypass of DNA lesions is orchestrated by the Rad6 pathway. Monoubiquitination of proliferating cell nuclear antigen (PCNA) by Rad6/Rad18 leads to recruitment of translesion polymerases for direct and potentially mutagenic damage bypass. An error-free bypass pathway may be initiated via K63-linked PCNA polyubiquitination by Ubc13/Mms2 and the E3 ligase Rad5 in yeast, or HLTF/SHPRH in vertebrates. For the latter two enzymes, redundancy with a third E3 ligase and alternative functions have been reported. We have previously shown that the Rad6 pathway is involved in somatic hypermutation of immunoglobulin genes in B lymphocytes. Here, we have used knockout strategies targeting expression of the entire SHPRH protein or functionally significant domains in chicken DT40 cells that do not harbor a HLTF ortholog. We show that SHPRH is apparently redundant with another E3 ligase during DNA damage-induced PCNA modification. SHPRH plays no substantial role in cellular resistance to drugs initiating excision repair and the Rad6 pathway, but is important in survival of topoisomerase II inhibitor treatment. Removal of only the C-terminal RING domain does not interfere with this SHPRH function. SHPRH inactivation does not substantially impact on the overall efficacy of Ig diversification. Redundancy of E3 ligases in the Rad6 pathway may be linked to its different functions in genome maintenance and genetic plasticity.
Collapse
Affiliation(s)
- Nils-Sebastian Tomi
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Center for Molecular Biomedicine, Friedrich-Schiller University Jena, Hans-Knoell-Strasse 2, 07745 Jena, Germany
| | - Kathrin Davari
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Center for Molecular Biomedicine, Friedrich-Schiller University Jena, Hans-Knoell-Strasse 2, 07745 Jena, Germany
| | - David Grotzky
- Institute of Clinical and Molecular Biology, Helmholtz Center Munich, Marchioninistrasse 25, 81377 Munich, Germany
| | - Friedemann Loos
- Institute of Clinical and Molecular Biology, Helmholtz Center Munich, Marchioninistrasse 25, 81377 Munich, Germany
| | - Katrin Böttcher
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Center for Molecular Biomedicine, Friedrich-Schiller University Jena, Hans-Knoell-Strasse 2, 07745 Jena, Germany
| | - Samantha Frankenberger
- Institute of Clinical and Molecular Biology, Helmholtz Center Munich, Marchioninistrasse 25, 81377 Munich, Germany
| | - Berit Jungnickel
- Department of Cell Biology, Institute of Biochemistry and Biophysics, Center for Molecular Biomedicine, Friedrich-Schiller University Jena, Hans-Knoell-Strasse 2, 07745 Jena, Germany.
| |
Collapse
|
7
|
Saribasak H, Gearhart PJ. Does DNA repair occur during somatic hypermutation? Semin Immunol 2012; 24:287-92. [PMID: 22728014 DOI: 10.1016/j.smim.2012.05.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 05/18/2012] [Indexed: 11/25/2022]
Abstract
Activation-induced deaminase (AID) initiates a flood of DNA damage in the immunoglobulin loci, leading to abasic sites, single-strand breaks and mismatches. It is compelling that some proteins in the canonical base excision and mismatch repair pathways have been hijacked to increase mutagenesis during somatic hypermutation. Thus, the AID-induced mutagenic pathways involve a mix of DNA repair proteins and low fidelity DNA polymerases to create antibody diversity. In this review, we analyze the roles of base excision repair, mismatch repair, and mutagenesis during somatic hypermutation of rearranged variable genes. The emerging view is that faithful base excision repair occurs simultaneously with mutagenesis, whereas faithful mismatch repair is mostly absent.
Collapse
Affiliation(s)
- Huseyin Saribasak
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, United States
| | | |
Collapse
|
8
|
Chahwan R, Edelmann W, Scharff MD, Roa S. Mismatch-mediated error prone repair at the immunoglobulin genes. Biomed Pharmacother 2011; 65:529-36. [PMID: 22100214 DOI: 10.1016/j.biopha.2011.09.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022] Open
Abstract
The generation of effective antibodies depends upon somatic hypermutation (SHM) and class-switch recombination (CSR) of antibody genes by activation induced cytidine deaminase (AID) and the subsequent recruitment of error prone base excision and mismatch repair. While AID initiates and is required for SHM, more than half of the base changes that accumulate in V regions are not due to the direct deamination of dC to dU by AID, but rather arise through the recruitment of the mismatch repair complex (MMR) to the U:G mismatch created by AID and the subsequent perversion of mismatch repair from a high fidelity process to one that is very error prone. In addition, the generation of double-strand breaks (DSBs) is essential during CSR, and the resolution of AID-generated mismatches by MMR to promote such DSBs is critical for the efficiency of the process. While a great deal has been learned about how AID and MMR cause hypermutations and DSBs, it is still unclear how the error prone aspect of these processes is largely restricted to antibody genes. The use of knockout models and mice expressing mismatch repair proteins with separation-of-function point mutations have been decisive in gaining a better understanding of the roles of each of the major MMR proteins and providing further insight into how mutation and repair are coordinated. Here, we review the cascade of MMR factors and repair signals that are diverted from their canonical error free role and hijacked by B cells to promote genetic diversification of the Ig locus. This error prone process involves AID as the inducer of enzymatically-mediated DNA mismatches, and a plethora of downstream MMR factors acting as sensors, adaptors and effectors of a complex and tightly regulated process from much of which is not yet well understood.
Collapse
Affiliation(s)
- Richard Chahwan
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave-Chanin 404, Bronx, NY 10461, United States
| | | | | | | |
Collapse
|
9
|
Recombinase-mediated cassette exchange as a novel method to study somatic hypermutation in Ramos cells. mBio 2011; 2:mBio.00186-11. [PMID: 21990614 PMCID: PMC3190358 DOI: 10.1128/mbio.00186-11] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Activation-induced cytidine deaminase (AID) mediates the somatic hypermutation (SHM) of immunoglobulin (Ig) variable (V) regions that is required for the generation of antibody diversity and for the affinity maturation of the antibody response against infectious agents and toxic substances. AID preferentially targets WRC (W = A/T, R = A/G) hot spot motifs, particularly WGCW motifs that create overlapping hot spots on both strands. In order to gain a better understanding of the generation of antibody diversity and to create a platform for the in vitro generation of affinity-matured antibodies, we have established a system involving recombinase-mediated cassette exchange (RMCE) to replace the V region and its flanking sequences. This makes it possible to easily manipulate the sequence of the Ig gene within the endogenous heavy chain of the Ramos human Burkitt’s lymphoma cell line. Here we show that the newly integrated wild-type (WT) VH regions introduced by RMCE undergo SHM similarly to non-RMCE-modified Ramos cells. Most importantly, we have shown that introducing a cluster of WGCW motifs into the complementary determining region 2 (CDR2) of the human heavy chain V region significantly raised the mutation frequency and number of mutations per sequence compared to WT controls. Thus, we have demonstrated a novel platform in Ramos cells whereby we can easily and quickly manipulate the endogenous human VH region to further explore the regulation and targeting of SHM. This platform will be useful for generating human antibodies with changes in affinity and specificity in vitro. An effective immune response requires a highly diverse repertoire of affinity-matured antibodies. Activation-induced cytidine deaminase (AID) is required for somatic hypermutation (SHM) of immunoglobulin (Ig) genes. Although a great deal has been learned about the regulation of AID, it remains unclear how it is preferentially targeted to particular motifs, to certain locations within the Ig gene and not to other highly expressed genes in the germinal center B cell. This is an important question because AID is highly mutagenic and is sometimes mistargeted to other highly expressed genes, including proto-oncogenes, leading to B cell lymphomas. Here we describe how we utilize recombinase-mediated cassette exchange (RMCE) to modify the sequence of the endogenous heavy chain locus in the Ramos Burkitt’s lymphoma cell line. This platform can be used to explore the regulation and targeting of SHM and to generate human antibodies with changes in affinity and specificity in vitro.
Collapse
|
10
|
Marianes AE, Zimmerman AM. Targets of somatic hypermutation within immunoglobulin light chain genes in zebrafish. Immunology 2010; 132:240-55. [PMID: 21070232 DOI: 10.1111/j.1365-2567.2010.03358.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
In mammals, somatic hypermutation (SHM) of immunoglobulin (Ig) genes is critical for the generation of high-affinity antibodies and effective immune responses. Knowledge of sequence-specific biases in the targeting of somatic mutations can be useful for studies aimed at understanding antibody repertoires produced in response to infections, B-cell neoplasms, or autoimmune disease. To evaluate potential nucleotide targets of somatic mutation in zebrafish (Danio rerio), an enriched IgL cDNA library was constructed and > 250 randomly selected clones were sequenced and analysed. In total, 55 unique VJ-C sequences were identified encoding a total of 125 mutations. Mutations were most prevalent in V(L) with a bias towards single base transitions and increased mutation in the complementarity-determining regions (CDRs). Overall, mutations were overrepresented at WRCH/DGYW motifs suggestive of activation-induced cytidine deaminase (AID) targeting which is common in mice and humans. In contrast to mammalian models, N and P addition was not observed and mutations at AID hotspots were largely restricted to palindromic WRCH/DGYW motifs. Mutability indexes for di- and trinucleotide combinations confirmed C/G targets within WRCH/DGYW motifs to be statistically significant mutational hotspots and showed trinucleotides ATC and ATG to be mutation coldspots. Additive mutations in VJ-C sequences revealed patterns of clonal expansion consistent with affinity maturation responses seen in higher vertebrates. Taken together, the data reveal specific nucleotide targets of SHM in zebrafish and suggest that AID and affinity maturation contribute to antibody diversification in this emerging immunological model.
Collapse
Affiliation(s)
- Alexis E Marianes
- Department of Biology, College of Charleston, Charleston, SC 29424, USA
| | | |
Collapse
|
11
|
Abstract
In response to an assault by foreign organisms, peripheral B cells can change their antibody affinity and isotype by somatically mutating their genomic DNA. The ability of a cell to modify its DNA is exceptional in light of the potential consequences of genetic alterations to cause human disease and cancer. Thus, as expected, this mechanism of antibody diversity is tightly regulated and coordinated through one protein, activation-induced deaminase (AID). AID produces diversity by converting cytosine to uracil within the immunoglobulin loci. The deoxyuracil residue is mutagenic when paired with deoxyguanosine, since it mimics thymidine during DNA replication. Additionally, B cells can manipulate the DNA repair pathways so that deoxyuracils are not faithfully repaired. Therefore, an intricate balance exists which is regulated at multiple stages to promote mutation of immunoglobulin genes, while retaining integrity of the rest of the genome. Here we discuss and summarize the current understanding of how AID functions to cause somatic hypermutation.
Collapse
Affiliation(s)
- Robert W Maul
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, USA
| | | |
Collapse
|
12
|
Borchert GM, Holton NW, Edwards KA, Vogel LA, Larson ED. Histone H2A and H2B are monoubiquitinated at AID-targeted loci. PLoS One 2010; 5:e11641. [PMID: 20661291 PMCID: PMC2905439 DOI: 10.1371/journal.pone.0011641] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 06/18/2010] [Indexed: 11/24/2022] Open
Abstract
Background Somatic hypermutation introduces base substitutions into the rearranged and expressed immunoglobulin (Ig) variable regions to promote immunity. This pathway requires and is initiated by the Activation Induced Deaminase (AID) protein, which deaminates cytidine to produce uracils and UG mismatches at the Ig genes. Subsequent processing of uracil by mismatch repair and base excision repair factors contributes to mutagenesis. While selective for certain genomic targets, the chromatin modifications which distinguish hypermutating from non-hypermutating loci are not defined. Methodology/Principal Findings Here, we show that AID-targeted loci in mammalian B cells contain ubiquitinated chromatin. Chromatin immunoprecipitation (ChIP) analysis of a constitutively hypermutating Burkitt's B cell line, Ramos, revealed the presence of monoubiquitinated forms of both histone H2A and H2B at two AID-associated loci, but not at control loci which are expressed but not hypermutated. Similar analysis using LPS activated primary murine splenocytes showed enrichment of the expressed VH and Sγ3 switch regions upon ChIP with antibody specific to AID and to monoubiquitinated H2A and H2B. In the mechanism of mammalian hypermutation, AID may interact with ubiquitinated chromatin because confocal immunofluorescence microscopy visualized AID colocalized with monoubiquitinated H2B within discrete nuclear foci. Conclusions/Significance Our results indicate that monoubiquitinated histones accompany active somatic hypermutation, revealing part of the histone code marking AID-targeted loci. This expands the current view of the chromatin state during hypermutation by identifying a specific nucleosome architecture associated with somatic hypermutation.
Collapse
Affiliation(s)
- Glen M. Borchert
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Nathaniel W. Holton
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Kevin A. Edwards
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Laura A. Vogel
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Erik D. Larson
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
- * E-mail:
| |
Collapse
|
13
|
Ertongur I, Tomi NS, Kutzera A, Fischer-Burkart S, Jungnickel B. Ubc13 dosage is critical for immunoglobulin gene conversion and gene targeting in vertebrate cells. Nucleic Acids Res 2010; 38:4701-7. [PMID: 20223767 PMCID: PMC2919702 DOI: 10.1093/nar/gkq154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In contrast to lower eukaryotes, most vertebrate cells are characterized by a moderate efficiency of homologous recombination (HR) and limited feasibility of targeted genetic modifications. As a notable exception, the chicken DT40 B cell line is distinguished by efficient homology-mediated repair of DNA lesions during Ig gene conversion, and also shows exceptionally high gene-targeting efficiencies. The molecular basis of these phenomena is elusive. Here we show that the activity levels of Ubc13, the E2 enzyme responsible for non-canonical K63-linked polyubiquitination, are critical for high efficiency of Ig gene conversion and gene targeting in DT40. Ubc13(+/-) cells show substantially lower homology-mediated repair, yet do not display changes in somatic hypermutation, overall DNA repair or cell proliferation. Our results suggest that modulation of the activity of K63-linked polyubiquitination may be used to customize HR efficiencies in vertebrate cells.
Collapse
Affiliation(s)
- Isin Ertongur
- Institute of Clinical Molecular Biology, Helmholtz Center Munich, German Research Center for Environmental Health, Munich, Germany
| | | | | | | | | |
Collapse
|
14
|
Arakawa H, Buerstedde JM. Activation-induced cytidine deaminase-mediated hypermutation in the DT40 cell line. Philos Trans R Soc Lond B Biol Sci 2009; 364:639-44. [PMID: 19008193 DOI: 10.1098/rstb.2008.0202] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Depending on the species and the developmental stage of B cells, activation-induced cytidine deaminase (AID) triggers immunoglobulin (Ig) gene diversification by gene conversion, hypermutation or switch recombination. The bursal B cell line DT40 usually diversifies its rearranged Ig light chain (IgL) gene by gene conversion, but disruption of the RAD51 gene paralogues or deletion of the psiV conversion donors induces hypermutation. Although not all aspects of somatic hypermutation can be studied in DT40, the compact size of the chicken IgL locus and the ability to modify the genome by targeted integration are powerful experimental advantages. We review here how the studies in DT40 contributed to understanding how AID initiates Ig gene diversification and how AID-induced uracils are subsequently processed by uracil DNA glycosylase, proliferating cell nuclear antigens and error-prone polymerases. We also discuss the on-going research on the Ig locus specificity of hypermutation and the possibility of using hypermutation for the artificial evolution of proteins and regulatory sequences in DT40.
Collapse
Affiliation(s)
- Hiroshi Arakawa
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute for Molecular Radiobiology, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany
| | | |
Collapse
|
15
|
Liu M, Schatz DG. Balancing AID and DNA repair during somatic hypermutation. Trends Immunol 2009; 30:173-81. [PMID: 19303358 DOI: 10.1016/j.it.2009.01.007] [Citation(s) in RCA: 155] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Revised: 01/27/2009] [Accepted: 01/28/2009] [Indexed: 11/25/2022]
Abstract
Somatic hypermutation (SHM) of Ig genes in B cells is crucial for antibody affinity maturation. The reaction is initiated by cytosine deamination of Ig loci by activation induced deaminase (AID) and is completed by error-prone DNA repair enzyme processing of AID-generated uracils. The mechanisms that target SHM specifically to Ig loci are poorly understood. Recently, it has been demonstrated that although AID preferentially targets Ig loci, it acts surprisingly widely on non-Ig loci, many of which are protected from mutation accumulation by high-fidelity DNA repair. We propose that breakdown of this high fidelity repair process helps explain oncogene mutations observed in B-cell tumors, and further, that many oncogenes are vulnerable to AID-mediated DNA breaks and translocations in normal activated B cells.
Collapse
Affiliation(s)
- Man Liu
- Department of Immunobiology and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
| | | |
Collapse
|
16
|
Ubiquitylated PCNA plays a role in somatic hypermutation and class-switch recombination and is required for meiotic progression. Proc Natl Acad Sci U S A 2008; 105:16248-53. [PMID: 18854411 DOI: 10.1073/pnas.0808182105] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Somatic hypermutation (SHM) and class-switch recombination (CSR) of Ig genes are dependent upon activation-induced cytidine deaminase (AID)-induced mutations. The scaffolding properties of proliferating cell nuclear antigen (PCNA) and ubiquitylation of its residue K164 have been suggested to play an important role organizing the error-prone repair events that contribute to the AID-induced diversification of the Ig locus. We generated knockout mice for PCNA (Pcna(-/-)), which were embryonic lethal. Expression of PCNA with the K164R mutation rescued the lethal phenotype, but the mice (Pcna(-/-)tg(K164R)) displayed a meiotic defect in early pachynema and were sterile. B cells proliferated normally in Pcna(-/-)tg(K164R) mice, but a PCNA-K164R mutation resulted in impaired ex vivo CSR to IgG1 and IgG3, which was associated with reduced mutation frequency at the switch regions and a bias toward blunt junctions. Analysis of the heavy chain V186.2 region after NP-immunization showed in Pcna(-/-)tg(K164R) mice a significant reduction in the mutation frequency of A:T residues in WA motifs preferred by polymerase-eta (Poleta), and a strand-biased increase in the mutation frequency of G residues, preferentially in the context of AID-targeted GYW motifs. The phenotype of Pcna(-/-)tg(K164R) mice supports the idea that ubiquitylation of PCNA participates directly in the meiotic process and the diversification of the Ig locus through class-switch recombination (CSR) and somatic hypermutation (SHM).
Collapse
|
17
|
Masuda K, Ouchida R, Yokoi M, Hanaoka F, Azuma T, Wang JY. DNA polymerase η is a limiting factor for A:T mutations in Ig genes and contributes to antibody affinity maturation. Eur J Immunol 2008; 38:2796-805. [DOI: 10.1002/eji.200838502] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
18
|
Mierau M, Drexler GA, Kutzera A, Braunschmidt K, Ellwart J, Eckardt-Schupp F, Fritz E, Bachl J, Jungnickel B. Non-conservative homologous recombination in human B lymphocytes is promoted by activation-induced cytidine deaminase and transcription. Nucleic Acids Res 2008; 36:5591-601. [PMID: 18757891 PMCID: PMC2553578 DOI: 10.1093/nar/gkn542] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
During secondary immunoglobulin (Ig) diversification in vertebrates, the sequence of the variable region of Ig genes may be altered by templated or non-templated mechanisms. In both cases, cytidine deamination by activation-induced cytidine deaminase (AID) in the transcribed Ig loci leads to DNA lesions, which are repaired by conservative homologous recombination (HR) during Ig gene conversion, or by non-templated mutagenesis during somatic hypermutation. The molecular basis for the differential use of these two pathways in different species is unclear. While experimental ablation of HR in avian cells performing Ig gene conversion may promote a switch to somatic hypermutation, the activity of HR processes in intrinsically hypermutating mammalian cells has not been measured to date. Employing a functional HR assay in human germinal centre like B cell lines, we detect elevated HR activity that can be enhanced by transcription and AID. Products of such recombination events mostly arise through non-conservative HR pathways, while the activity of conservative HR is low to absent. Our results identify non-conservative HR as a novel DNA transaction pathway promoted by AID and suggest that somatic hypermutation in germinal centre B cells may be based on a physiological suppression of conservative HR.
Collapse
Affiliation(s)
- Maren Mierau
- Institute of Clinical Molecular Biology and Tumor Genetics, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Institute of Radiobiology, Helmholtz Center Munich, National Research Center for Environmental Health, D-85764 Neuherberg, Radiobiological Institute, Ludwig-Maximilians-University, D-80336 Munich, Institute of Molecular Immunology, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Leibniz Institute for Age Research, Fritz Lipmann Institute, D-07745 Jena and 4-Antibody, WRO-1096.3, Schwarzwaldallee 215, CH-4002 Basel, Switzerland
| | - Guido A. Drexler
- Institute of Clinical Molecular Biology and Tumor Genetics, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Institute of Radiobiology, Helmholtz Center Munich, National Research Center for Environmental Health, D-85764 Neuherberg, Radiobiological Institute, Ludwig-Maximilians-University, D-80336 Munich, Institute of Molecular Immunology, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Leibniz Institute for Age Research, Fritz Lipmann Institute, D-07745 Jena and 4-Antibody, WRO-1096.3, Schwarzwaldallee 215, CH-4002 Basel, Switzerland
| | - André Kutzera
- Institute of Clinical Molecular Biology and Tumor Genetics, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Institute of Radiobiology, Helmholtz Center Munich, National Research Center for Environmental Health, D-85764 Neuherberg, Radiobiological Institute, Ludwig-Maximilians-University, D-80336 Munich, Institute of Molecular Immunology, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Leibniz Institute for Age Research, Fritz Lipmann Institute, D-07745 Jena and 4-Antibody, WRO-1096.3, Schwarzwaldallee 215, CH-4002 Basel, Switzerland
| | - Kerstin Braunschmidt
- Institute of Clinical Molecular Biology and Tumor Genetics, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Institute of Radiobiology, Helmholtz Center Munich, National Research Center for Environmental Health, D-85764 Neuherberg, Radiobiological Institute, Ludwig-Maximilians-University, D-80336 Munich, Institute of Molecular Immunology, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Leibniz Institute for Age Research, Fritz Lipmann Institute, D-07745 Jena and 4-Antibody, WRO-1096.3, Schwarzwaldallee 215, CH-4002 Basel, Switzerland
| | - Joachim Ellwart
- Institute of Clinical Molecular Biology and Tumor Genetics, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Institute of Radiobiology, Helmholtz Center Munich, National Research Center for Environmental Health, D-85764 Neuherberg, Radiobiological Institute, Ludwig-Maximilians-University, D-80336 Munich, Institute of Molecular Immunology, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Leibniz Institute for Age Research, Fritz Lipmann Institute, D-07745 Jena and 4-Antibody, WRO-1096.3, Schwarzwaldallee 215, CH-4002 Basel, Switzerland
| | - Friederike Eckardt-Schupp
- Institute of Clinical Molecular Biology and Tumor Genetics, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Institute of Radiobiology, Helmholtz Center Munich, National Research Center for Environmental Health, D-85764 Neuherberg, Radiobiological Institute, Ludwig-Maximilians-University, D-80336 Munich, Institute of Molecular Immunology, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Leibniz Institute for Age Research, Fritz Lipmann Institute, D-07745 Jena and 4-Antibody, WRO-1096.3, Schwarzwaldallee 215, CH-4002 Basel, Switzerland
| | - Eberhard Fritz
- Institute of Clinical Molecular Biology and Tumor Genetics, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Institute of Radiobiology, Helmholtz Center Munich, National Research Center for Environmental Health, D-85764 Neuherberg, Radiobiological Institute, Ludwig-Maximilians-University, D-80336 Munich, Institute of Molecular Immunology, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Leibniz Institute for Age Research, Fritz Lipmann Institute, D-07745 Jena and 4-Antibody, WRO-1096.3, Schwarzwaldallee 215, CH-4002 Basel, Switzerland
| | - Jürgen Bachl
- Institute of Clinical Molecular Biology and Tumor Genetics, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Institute of Radiobiology, Helmholtz Center Munich, National Research Center for Environmental Health, D-85764 Neuherberg, Radiobiological Institute, Ludwig-Maximilians-University, D-80336 Munich, Institute of Molecular Immunology, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Leibniz Institute for Age Research, Fritz Lipmann Institute, D-07745 Jena and 4-Antibody, WRO-1096.3, Schwarzwaldallee 215, CH-4002 Basel, Switzerland
| | - Berit Jungnickel
- Institute of Clinical Molecular Biology and Tumor Genetics, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Institute of Radiobiology, Helmholtz Center Munich, National Research Center for Environmental Health, D-85764 Neuherberg, Radiobiological Institute, Ludwig-Maximilians-University, D-80336 Munich, Institute of Molecular Immunology, Helmholtz Center Munich, National Research Center for Environmental Health, D-81377 Munich, Leibniz Institute for Age Research, Fritz Lipmann Institute, D-07745 Jena and 4-Antibody, WRO-1096.3, Schwarzwaldallee 215, CH-4002 Basel, Switzerland
- *To whom correspondence should be addressed. Tel: +49 89 7099 209; Fax: +49 89 7099 500;
| |
Collapse
|
19
|
Peled JU, Kuang FL, Iglesias-Ussel MD, Roa S, Kalis SL, Goodman MF, Scharff MD. The biochemistry of somatic hypermutation. Annu Rev Immunol 2008; 26:481-511. [PMID: 18304001 DOI: 10.1146/annurev.immunol.26.021607.090236] [Citation(s) in RCA: 368] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Affinity maturation of the humoral response is mediated by somatic hypermutation of the immunoglobulin (Ig) genes and selection of higher-affinity B cell clones. Activation-induced cytidine deaminase (AID) is the first of a complex series of proteins that introduce these point mutations into variable regions of the Ig genes. AID deaminates deoxycytidine residues in single-stranded DNA to deoxyuridines, which are then processed by DNA replication, base excision repair (BER), or mismatch repair (MMR). In germinal center B cells, MMR, BER, and other factors are diverted from their normal roles in preserving genomic integrity to increase diversity within the Ig locus. Both AID and these components of an emerging error-prone mutasome are regulated on many levels by complex mechanisms that are only beginning to be elucidated.
Collapse
Affiliation(s)
- Jonathan U Peled
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
| | | | | | | | | | | | | |
Collapse
|
20
|
Abstract
The immunoglobulin (Ig) repertoire achieves functional diversification through several somatic alterations of the Ig locus. One of these processes, somatic hypermutation (SHM), deposits point mutations into the variable region of the Ig gene to generate higher-affinity variants. Activation-induced cytidine deaminase (AID) converts cytidine to uridine to initiate the hypermutation process. Error-prone versions of DNA repair are believed to then process these lesions into a diverse spectrum of point mutations. We review the current understanding of the molecular mechanisms and regulation of SHM, and also discuss emerging ideas which merit further exploration.
Collapse
Affiliation(s)
- Grace Teng
- Laboratory of Lymphocyte Biology, The Rockefeller University, New York, NY 10021, USA
| | | |
Collapse
|
21
|
Abstract
Damage tolerance mechanisms, which allow the bypass of DNA lesions during replication, are controlled in eukaryotic cells by mono- and poly-ubiquitination of the DNA polymerase cofactor PCNA (proliferating-cell nuclear antigen). In the present review, I will summarize our current knowledge of the enzymatic machinery for ubiquitination of PCNA and the way in which the modifications affect PCNA function during replication and lesion bypass in different organisms. Using the budding yeast as a reference model, I will highlight some of the species-specific differences, but also point out the common principles that emerge from the genetic and biochemical studies of damage tolerance in a range of experimental systems.
Collapse
|
22
|
Abstract
Exposure brings risk to all living organisms. Using a remarkably effective strategy, higher vertebrates mitigate risk by mounting a complex and sophisticated immune response to counter the potentially toxic invasion by a virtually limitless army of chemical and biological antagonists. Mutations are almost always deleterious, but in the case of antibody diversification there are mutations occurring at hugely elevated rates within the variable (V) and switch regions (SR) of the immunoglobulin (Ig) genes that are responsible for binding to and neutralizing foreign antigens throughout the body. These mutations are truly purposeful. This chapter is centered on activation-induced cytidine deaminase (AID). AID is required for initiating somatic hypermutation (SHM) in the V regions and class switch recombination (CSR) in the SR portions of Ig genes. By converting C --> U, while transcription takes place, AID instigates a cascade of mutational events involving error-prone DNA polymerases, base excision and mismatch repair enzymes, and recombination pathways. Together, these processes culminate in highly mutated antibody genes and the B cells expressing antibodies that have achieved optimal antigenic binding undergo positive selection in germinal centers. We will discuss the biological role of AID in this complex process, primarily in terms of its biochemical properties in relation to SHM in vivo. The chapter also discusses recent advances in experimental methods to characterize antibody dynamics as a function of SHM to help elucidate the role that the AID-induced mutations play in tailoring molecular recognition. The emerging experimental techniques help to address long-standing conundrums concerning evolution-imposed constraints on antibody structure and function.
Collapse
Affiliation(s)
- Myron F Goodman
- Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | | | | |
Collapse
|
23
|
Arakawa H, Moldovan GL, Saribasak H, Saribasak NN, Jentsch S, Buerstedde JM. A role for PCNA ubiquitination in immunoglobulin hypermutation. PLoS Biol 2006; 4:e366. [PMID: 17105346 PMCID: PMC1618868 DOI: 10.1371/journal.pbio.0040366] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Accepted: 09/05/2006] [Indexed: 12/15/2022] Open
Abstract
Proliferating cell nuclear antigen (PCNA) is a DNA polymerase cofactor and regulator of replication-linked functions. Upon DNA damage, yeast and vertebrate PCNA is modified at the conserved lysine K164 by ubiquitin, which mediates error-prone replication across lesions via translesion polymerases. We investigated the role of PCNA ubiquitination in variants of the DT40 B cell line that are mutant in K164 of PCNA or in Rad18, which is involved in PCNA ubiquitination. Remarkably, the PCNAK164R mutation not only renders cells sensitive to DNA-damaging agents, but also strongly reduces activation induced deaminase-dependent single-nucleotide substitutions in the immunoglobulin light-chain locus. This is the first evidence, to our knowledge, that vertebrates exploit the PCNA-ubiquitin pathway for immunoglobulin hypermutation, most likely through the recruitment of error-prone DNA polymerases. Vertebrate DT40 cells with a mutation inPCNA that prevents the protein's ubiquitylation and SUMOylation are sensitive to DNA damage and are dramatically deficient in AID-induced hypermutation.
Collapse
Affiliation(s)
- Hiroshi Arakawa
- Gesellschaft für Strahlen Forschung, Institute for Molecular Radiobiology, Neuherberg-Munich, Germany
| | - George-Lucian Moldovan
- Max Planck Institute of Biochemistry, Department of Molecular Cell Biology, Martinsried-Munich, Germany
| | - Huseyin Saribasak
- Gesellschaft für Strahlen Forschung, Institute for Molecular Radiobiology, Neuherberg-Munich, Germany
| | - Nesibe Nur Saribasak
- Gesellschaft für Strahlen Forschung, Institute for Molecular Radiobiology, Neuherberg-Munich, Germany
| | - Stefan Jentsch
- Max Planck Institute of Biochemistry, Department of Molecular Cell Biology, Martinsried-Munich, Germany
| | - Jean-Marie Buerstedde
- Gesellschaft für Strahlen Forschung, Institute for Molecular Radiobiology, Neuherberg-Munich, Germany
- * To whom correspondence should be addressed. E-mail:
| |
Collapse
|