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Bekker-Jensen S, Lukas C, Melander F, Bartek J, Lukas J. Dynamic assembly and sustained retention of 53BP1 at the sites of DNA damage are controlled by Mdc1/NFBD1. ACTA ACUST UNITED AC 2005; 170:201-11. [PMID: 16009723 PMCID: PMC2171401 DOI: 10.1083/jcb.200503043] [Citation(s) in RCA: 222] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
53BP1 is a key component of the genome surveillance network activated by DNA double strand breaks (DSBs). Despite its known accumulation at the DSB sites, the spatiotemporal aspects of 53BP1 interaction with DSBs and the role of other DSB regulators in this process remain unclear. Here, we used real-time microscopy to study the DSB-induced redistribution of 53BP1 in living cells. We show that within minutes after DNA damage, 53BP1 becomes progressively, yet transiently, immobilized around the DSB-flanking chromatin. Quantitative imaging of single cells revealed that the assembly of 53BP1 at DSBs significantly lagged behind Mdc1/NFBD1, another DSB-interacting checkpoint mediator. Furthermore, short interfering RNA-mediated ablation of Mdc1/NFBD1 drastically impaired 53BP1 redistribution to DSBs and triggered premature dissociation of 53BP1 from these regions. Collectively, these in vivo measurements identify Mdc1/NFBD1 as a key upstream determinant of 53BP1's interaction with DSBs from its dynamic assembly at the DSB sites through sustained retention within the DSB-flanking chromatin up to the recovery from the checkpoint.
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Affiliation(s)
- Simon Bekker-Jensen
- Institute of Cancer Biology and Centre for Genotoxic Stress Research, Danish Cancer Society, DK-2100, Copenhagen, Denmark
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52
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Pryde F, Khalili S, Robertson K, Selfridge J, Ritchie AM, Melton DW, Jullien D, Adachi Y. 53BP1 exchanges slowly at the sites of DNA damage and appears to require RNA for its association with chromatin. J Cell Sci 2005; 118:2043-55. [PMID: 15840649 DOI: 10.1242/jcs.02336] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
53BP1 protein is re-localized to the sites of DNA damage after ionizing radiation (IR) and is involved in DNA-damage-checkpoint signal transduction. We examined the dynamics of GFP-53BP1 in living cells. The protein starts to accumulate at the sites of DNA damage 2-3 minutes after damage induction. Fluorescence recovery after photobleaching experiments showed that GFP-53BP1 is highly mobile in non-irradiated cells. Upon binding to the IR-induced nuclear foci, the mobility of 53BP1 reduces greatly. The minimum (M) domain of 53BP1 essential for targeting to IR induced foci consists of residues 1220-1703. GFP-M protein forms foci in mouse embryonic fibroblast cells lacking functional endogenous 53BP1. The M domain contains a tandem repeat of Tudor motifs and an arginine- and glycine-rich domain (RG stretch), which are often found in proteins involved in RNA metabolism, the former being essential for targeting. RNase A treatment dissociates 53BP1 from IR-induced foci. In HeLa cells, dissociation of the M domain without the RG stretch by RNase A treatment can be restored by re-addition of nuclear RNA in the early stages of post-irradiation. 53BP1 immunoprecipitates contain some RNA molecules. Our results suggest a possible involvement of RNA in the binding of 53BP1 to chromatin damaged by IR.
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Affiliation(s)
- Fiona Pryde
- The Wellcome Trust Centre for Cell Biology, The Institute of Cell and Molecular Biology, The University of Edinburgh, The King's Buildings, Edinburgh, EH9 3JR, UK
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53
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Akhter S, Richie CT, Deng JM, Brey E, Zhang X, Patrick C, Behringer RR, Legerski RJ. Deficiency in SNM1 abolishes an early mitotic checkpoint induced by spindle stress. Mol Cell Biol 2005; 24:10448-55. [PMID: 15542852 PMCID: PMC529044 DOI: 10.1128/mcb.24.23.10448-10455.2004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Spindle poisons represent an important class of anticancer drugs that act by interfering with microtubule polymerization and dynamics and thereby induce mitotic checkpoints and apoptosis. Here we show that mammalian SNM1 functions in an early mitotic stress checkpoint that is distinct from the well-characterized spindle checkpoint that regulates the metaphase-to-anaphase transition. Specifically, we found that compared to wild-type cells, Snm1-deficient mouse embryonic fibroblasts exposed to spindle poisons exhibited elevated levels of micronucleus formation, decreased mitotic delay, a failure to arrest in mitosis prior to chromosome condensation, supernumerary centrosomes, and decreased viability. In addition, we show that both Snm1 and 53BP1, previously shown to interact, coimmunoprecipitate with components of the anaphase-promoting complex (APC)/cyclosome. These findings suggest that Snm1 is a component of a mitotic stress checkpoint that negatively targets the APC prior to chromosome condensation.
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Affiliation(s)
- Shamima Akhter
- University of Texas M. D. Anderson Cancer Center, Department of Molecular Genetics, 1515 Holcombe Blvd., Houston, TX 77030, USA
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54
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Vogel C, Kienitz A, Hofmann I, Müller R, Bastians H. Crosstalk of the mitotic spindle assembly checkpoint with p53 to prevent polyploidy. Oncogene 2004; 23:6845-53. [PMID: 15286707 DOI: 10.1038/sj.onc.1207860] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Treatment of cells with microtubule inhibitors results in activation of the mitotic spindle assembly checkpoint, leading to mitotic arrest before anaphase. Upon prolonged treatment, however, cells can adapt and exit mitosis aberrantly, resulting in the occurrence of tetraploid cells in G1. Those cells subsequently arrest in postmitotic G1 due to the activation of a p53-dependent G1 checkpoint. Failure of the G1 checkpoint leads to endoreduplication and further polyploidization. Using HCT116 and isogenic p53-deficient or spindle checkpoint compromised derivatives, we show here that not only p53 but also a functional spindle assembly checkpoint is required for postmitotic G1 checkpoint function. During transient mitotic arrest, p53 stabilization and activation is triggered by a pathway independent of ATM/ATR, Chk1 and Chk2. We further show that a prolonged spindle checkpoint-mediated mitotic arrest is required for proper postmitotic G1 checkpoint function. In addition, we demonstrate that polyploid cells are inhibited to re-enter mitosis by an additional checkpoint acting in G2. Thus, during a normal cell cycle, polyploidization and subsequent aneuploidization is prevented by the function of the mitotic spindle checkpoint, a p53-dependent G1 checkpoint and an additional G2 checkpoint.
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Affiliation(s)
- Celia Vogel
- Institute for Molecular Biology and Tumor Research, Philipps University Marburg, Emil-Mannkopff-Strasse 2, D-35037 Marburg, Germany
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55
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Charier G, Couprie J, Alpha-Bazin B, Meyer V, Quéméneur E, Guérois R, Callebaut I, Gilquin B, Zinn-Justin S. The Tudor Tandem of 53BP1. Structure 2004; 12:1551-62. [PMID: 15341721 DOI: 10.1016/j.str.2004.06.014] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Revised: 06/18/2004] [Accepted: 06/19/2004] [Indexed: 01/09/2023]
Abstract
53BP1 is a key transducer of the DNA damage checkpoint signal, which is required for phosphorylation of a subset of ATM substrates and p53 accumulation. After cell irradiation, the 53BP1 N-terminal region is phosphorylated. Its two C-terminal BRCT motifs interact with p53. Its central region is required and sufficient for 53BP1 foci formation at DNA strand breaks and for 53BP1 binding to the kinetochore. It contains an RG-rich segment and interacts with DNA in vitro. Here we show that the major globular domain of the 53BP1 central region adopts a new structural motif composed of two tightly packed Tudor domains and a C-terminal alpha helix. A unique surface essentially located on the first Tudor domain is involved in the binding to 53BP1 RG-rich sequence and to DNA, suggesting that the Tudor tandem can act as an adaptor mediating intramolecular as well as intermolecular protein-protein interactions and protein-nucleic acid associations.
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Affiliation(s)
- Gaëlle Charier
- Département d'Ingénierie et d'Etudes des Protéines, 91191 Gif-sur-Yvette, France
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56
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Abstract
The ability to sense DNA damage and activate response pathways that coordinate cell cycle progression and DNA repair is essential for the maintenance of genomic integrity and the viability of organisms. During the last couple of years, several proteins have been identified that participate very early in the DNA damage response. Here we review the current understanding of the mechanisms by which mammalian cells detect DNA lesions, especially double-strand breaks, and mediate the signal to downstream transducers.
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Affiliation(s)
- Irene Ward
- Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA
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57
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Xu X, Stern DF. NFBD1/MDC1 regulates ionizing radiation‐induced focus formation by DNA checkpoint signaling and repair factors. FASEB J 2003; 17:1842-8. [PMID: 14519663 DOI: 10.1096/fj.03-0310com] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
NFBD1/MDC1 (mediator of DNA damage checkpoint 1) is a nuclear factor with an amino-terminal FHA (forkhead-associated) domain and a tandem repeat of BRCT (breast cancer susceptibility gene-1 carboxyl terminus) domains. We have previously shown that NFBD1 is an early participant in DNA damage signaling pathways and that ionizing radiation-induced nuclear foci (IRIF) of NFBD1 colocalize with several DNA checkpoint signaling and repair factors. We report here that NFBD1 physically associates with ATM, p53, components of the MRE11-RAD50-NBS1 (MRN) complex, and gamma-H2AX. An overexpressed FHA domain-containing fragment of NFBD1 binds to endogenous NFBD1 and components of the MRN complex, but not to gamma-H2AX. This fragment interferes with IRIF formation by endogenous NFBD1, MRE11, or NBS1. A BRCT domain-containing fragment of NFBD1 binds to gamma-H2AX and 53BP1, but not to components of the MRN complex, and abolishes IRIF formation by NFBD1, MRE11, NBS1, 53BP1, CHK2 phospho-T68, gamma-H2AX, and possible ATM/ATR substrates recognized by anti-phospho-SQ/TQ antibody. These results suggest that NFBD1 is an ATM/ATR-dependent organizer that recruits DNA checkpoint signaling and repair proteins to the sites of DNA damage.
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Affiliation(s)
- Xingzhi Xu
- Department of Pathology, School of Medicine, Yale University, 310 Cedar St., BML342, New Haven, Connecticut 06510, USA
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58
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Iwabuchi K, Basu BP, Kysela B, Kurihara T, Shibata M, Guan D, Cao Y, Hamada T, Imamura K, Jeggo PA, Date T, Doherty AJ. Potential role for 53BP1 in DNA end-joining repair through direct interaction with DNA. J Biol Chem 2003; 278:36487-95. [PMID: 12824158 DOI: 10.1074/jbc.m304066200] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Upon DNA damage, p53-binding protein 1 (53BP1) relocalizes to sites of DNA double-strand breaks and forms discrete nuclear foci, suggesting its role in DNA damage responses. We show that 53BP1 changed its localization from the detergent soluble to insoluble fraction after treatment of cells with x-ray, but not with ultraviolet or hydroxyurea. Either DNase or phosphatase treatment of the insoluble fraction released 53BP1 into the soluble fraction, showing that 53BP1 binds to chromatin in a phosphorylation-dependent manner after X-irradiation of cells. 53BP1 was retained at discrete nuclear foci in X-irradiated cells even after detergent extraction of cells, showing that the chromatin binding of 53BP1 occurs at sites of DNA double-strand breaks. The minimal domain for focus formation was identified by immunofluorescence staining of cells ectopically expressed with 53BP1 deletion mutants. This domain consisted of conserved Tudor and Myb motifs. The Tudor plus Myb domain possessed chromatin binding activity in vivo and bound directly to both double-stranded and single-stranded DNA in vitro. This domain also stimulated end-joining by DNA ligase IV/Xrcc4, but not by T4 DNA ligase in vitro. We conclude that 53BP1 has the potential to participate directly in the repair of DNA double-strand breaks.
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Affiliation(s)
- Kuniyoshi Iwabuchi
- Department of Biochemistry, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Kahoku-gun, Ishikawa 920-0293, Japan
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59
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Ward IM, Minn K, Jorda KG, Chen J. Accumulation of checkpoint protein 53BP1 at DNA breaks involves its binding to phosphorylated histone H2AX. J Biol Chem 2003; 278:19579-82. [PMID: 12697768 DOI: 10.1074/jbc.c300117200] [Citation(s) in RCA: 273] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
53BP1 participates in the cellular response to DNA damage. Like many proteins involved in the DNA damage response, 53BP1 becomes hyperphosphorylated after radiation and colocalizes with phosphorylated H2AX in megabase regions surrounding the sites of DNA strand breaks. However, it is not yet clear whether the phosphorylation status of 53BP1 determines its localization or vice versa. In this study we mapped a region upstream of the 53BP1 C terminus that is required and sufficient for the recruitment of 53BP1 to these DNA break areas. In vitro assays revealed that this region binds to phosphorylated but not unphosphorylated H2AX. Moreover, using H2AX-deficient cells reconstituted with wild-type or a phosphorylation-deficient mutant of H2AX, we have shown that phosphorylation of H2AX at serine 140 is critical for efficient 53BP1 foci formation, implying that a direct interaction between 53BP1 and phosphorylated H2AX is required for the accumulation of 53BP1 at DNA break sites. On the other hand, radiation-induced phosphorylation of the 53BP1 N terminus by the ATM (ataxia-telangiectasia mutated) kinase is not essential for 53BP1 foci formation and takes place independently of 53BP1 redistribution. Thus, these two damage-induced events, hyperphosphorylation and relocalization of 53BP1, occur independently in the cell.
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Affiliation(s)
- Irene M Ward
- Department of Oncology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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60
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Morales JC, Xia Z, Lu T, Aldrich MB, Wang B, Rosales C, Kellems RE, Hittelman WN, Elledge SJ, Carpenter PB. Role for the BRCA1 C-terminal repeats (BRCT) protein 53BP1 in maintaining genomic stability. J Biol Chem 2003; 278:14971-7. [PMID: 12578828 DOI: 10.1074/jbc.m212484200] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
p53-binding protein-1 (53BP1) is phosphorylated in response to DNA damage and rapidly relocalizes to presumptive sites of DNA damage along with Mre11 and the phosphorylated histone 2A variant, gamma-H2AX. 53BP1 associates with the BRCA1 tumor suppressor, and knock-down experiments with small interfering RNA have revealed a role for the protein in the checkpoint response to DNA damage. By generating mice defective in m53BP1 (m53BP1(tr/tr)), we have created an animal model to further explore its biochemical and genetic roles in vivo. We find that m53BP1(tr/tr) animals are growth-retarded and show various immune deficiencies including a specific reduction in thymus size and T cell count. Consistent with a role in responding to DNA damage, we find that m53BP1(tr/tr) mice are sensitive to ionizing radiation (gamma-IR), and cells from these animals exhibit chromosomal abnormalities consistent with defects in DNA repair. Thus, 53BP1 is a critical element in the DNA damage response and plays an integral role in maintaining genomic stability.
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Affiliation(s)
- Julio C Morales
- Department of Biochemistry and Molecular Biology, University of Texas Health Sciences Center, Houston, Texas 77030, USA
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61
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Ward IM, Minn K, van Deursen J, Chen J. p53 Binding protein 53BP1 is required for DNA damage responses and tumor suppression in mice. Mol Cell Biol 2003; 23:2556-63. [PMID: 12640136 PMCID: PMC150747 DOI: 10.1128/mcb.23.7.2556-2563.2003] [Citation(s) in RCA: 377] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
53BP1 is a p53 binding protein of unknown function that binds to the central DNA-binding domain of p53. It relocates to the sites of DNA strand breaks in response to DNA damage and is a putative substrate of the ataxia telangiectasia-mutated (ATM) kinase. To study the biological role of 53BP1, we disrupted the 53BP1 gene in the mouse. We show that, similar to ATM(-/-) mice, 53BP1-deficient mice were growth retarded, immune deficient, radiation sensitive, and cancer prone. 53BP1(-/-) cells show a slight S-phase checkpoint defect and prolonged G(2)/M arrest after treatment with ionizing radiation. Moreover, 53BP1(-/-) cells feature a defective DNA damage response with impaired Chk2 activation. These data indicate that 53BP1 acts downstream of ATM and upstream of Chk2 in the DNA damage response pathway and is involved in tumor suppression.
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Affiliation(s)
- Irene M Ward
- Department of Oncology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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62
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Richie CT, Peterson C, Lu T, Hittelman WN, Carpenter PB, Legerski RJ. hSnm1 colocalizes and physically associates with 53BP1 before and after DNA damage. Mol Cell Biol 2002; 22:8635-47. [PMID: 12446782 PMCID: PMC139863 DOI: 10.1128/mcb.22.24.8635-8647.2002] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2002] [Revised: 05/07/2002] [Accepted: 09/19/2002] [Indexed: 11/20/2022] Open
Abstract
snm1 mutants of Saccharomyces cerevisiae have been shown to be specifically sensitive to DNA interstrand crosslinking agents but not sensitive to monofunctional alkylating agents, UV, or ionizing radiation. Five homologs of SNM1 have been identified in the mammalian genome and are termed SNM1, SNM1B, Artemis, ELAC2, and CPSF73. To explore the functional role of human Snm1 in response to DNA damage, we characterized the cellular distribution and dynamics of human Snm1 before and after exposure to DNA-damaging agents. Human Snm1 was found to localize to the cell nucleus in three distinct patterns. A particular cell showed diffuse nuclear staining, multiple nuclear foci, or one or two larger bodies confined to the nucleus. Upon exposure to ionizing radiation or an interstrand crosslinking agent, the number of cells exhibiting Snm1 bodies was reduced, while the population of cells with foci increased dramatically. Indirect immunofluorescence studies also indicated that the human Snm1 protein colocalized with 53BP1 before and after exposure to ionizing radiation, and a physical interaction was confirmed by coimmunoprecipitation assays. Furthermore, human Snm1 foci formed after ionizing radiation were largely coincident with foci formed by human Mre11 and to a lesser extent with those formed by BRCA1, but not with those formed by human Rad51. Finally, we mapped a region of human Snm1 of approximately 220 amino acids that was sufficient for focus formation when attached to a nuclear localization signal. Our results indicate a novel function for human Snm1 in the cellular response to double-strand breaks formed by ionizing radiation.
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Affiliation(s)
- Christopher T Richie
- Department of Molecular Genetics, M. D. Anderson Cancer Center, Houston, Texas 77030, USA
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