1
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Wang J, Sadeghi CA, Frock RL. DNA-PKcs suppresses illegitimate chromosome rearrangements. Nucleic Acids Res 2024; 52:5048-5066. [PMID: 38412274 PMCID: PMC11109964 DOI: 10.1093/nar/gkae140] [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: 07/11/2023] [Revised: 02/09/2024] [Accepted: 02/14/2024] [Indexed: 02/29/2024] Open
Abstract
Two DNA repair pathways, non-homologous end joining (NHEJ) and alternative end joining (A-EJ), are involved in V(D)J recombination and chromosome translocation. Previous studies reported distinct repair mechanisms for chromosome translocation, with NHEJ involved in humans and A-EJ in mice predominantly. NHEJ depends on DNA-PKcs, a critical partner in synapsis formation and downstream component activation. While DNA-PKcs inhibition promotes chromosome translocations harboring microhomologies in mice, its synonymous effect in humans is not known. We find partial DNA-PKcs inhibition in human cells leads to increased translocations and the continued involvement of a dampened NHEJ. In contrast, complete DNA-PKcs inhibition substantially increased microhomology-mediated end joining (MMEJ), thus bridging the two different translocation mechanisms between human and mice. Similar to a previous study on Ku70 deletion, DNA-PKcs deletion in G1/G0-phase mouse progenitor B cell lines, significantly impairs V(D)J recombination and generated higher rates of translocations as a consequence of dysregulated coding and signal end joining. Genetic DNA-PKcs inhibition suppresses NHEJ entirely, with repair phenotypically resembling Ku70-deficient A-EJ. In contrast, we find DNA-PKcs necessary in generating the near-exclusive MMEJ associated with Lig4 deficiency. Our study underscores DNA-PKcs in suppressing illegitimate chromosome rearrangement while also contributing to MMEJ in both species.
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Affiliation(s)
- Jinglong Wang
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Cheyenne A Sadeghi
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Richard L Frock
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA
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2
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Goff NJ, Brenière M, Buehl CJ, de Melo AJ, Huskova H, Ochi T, Blundell TL, Mao W, Yu K, Modesti M, Meek K. Catalytically inactive DNA ligase IV promotes DNA repair in living cells. Nucleic Acids Res 2022; 50:11058-11071. [PMID: 36263813 PMCID: PMC9638927 DOI: 10.1093/nar/gkac913] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 10/18/2022] [Indexed: 11/17/2022] Open
Abstract
DNA double strand breaks (DSBs) are induced by external genotoxic agents (ionizing radiation or genotoxins) or by internal processes (recombination intermediates in lymphocytes or by replication errors). The DNA ends induced by these genotoxic processes are often not ligatable, requiring potentially mutagenic end-processing to render ends compatible for ligation by non-homologous end-joining (NHEJ). Using single molecule approaches, Loparo et al. propose that NHEJ fidelity can be maintained by restricting end-processing to a ligation competent short-range NHEJ complex that 'maximizes the fidelity of DNA repair'. These in vitro studies show that although this short-range NHEJ complex requires DNA ligase IV (Lig4), its catalytic activity is dispensable. Here using cellular models, we show that inactive Lig4 robustly promotes DNA repair in living cells. Compared to repair products from wild-type cells, those isolated from cells with inactive Lig4 show a somewhat increased fraction that utilize micro-homology (MH) at the joining site consistent with alternative end-joining (a-EJ). But unlike a-EJ in the absence of NHEJ, a large percentage of joints isolated from cells with inactive Lig4 occur with no MH - thus, clearly distinct from a-EJ. Finally, biochemical assays demonstrate that the inactive Lig4 complex promotes the activity of DNA ligase III (Lig3).
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Affiliation(s)
- Noah J Goff
- College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA,Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA,Department of Pathobiology & Diagnostic Investigation, Michigan State University, East Lansing, MI 48824, USA
| | - Manon Brenière
- Centre de Recherche en Cancérologie de Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Universiteé, Marseille, France
| | - Christopher J Buehl
- College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA,Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA,Department of Pathobiology & Diagnostic Investigation, Michigan State University, East Lansing, MI 48824, USA
| | - Abinadabe J de Melo
- Centre de Recherche en Cancérologie de Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Universiteé, Marseille, France
| | - Hana Huskova
- Centre de Recherche en Cancérologie de Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Universiteé, Marseille, France
| | - Takashi Ochi
- The Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9TJ, UK
| | - Tom L Blundell
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Weifeng Mao
- College of Human Medicine, Michigan State University, East Lansing, MI 48824, USA,Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - Kefei Yu
- College of Human Medicine, Michigan State University, East Lansing, MI 48824, USA,Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - Mauro Modesti
- Correspondence may also be addressed to Mauro Modesti.
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3
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Uncovering bleomycin-induced genomic alterations and underlying mechanisms in yeast. Appl Environ Microbiol 2021; 88:e0170321. [PMID: 34731050 DOI: 10.1128/aem.01703-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bleomycin (BLM) is a widely used chemotherapeutic drug. BLM-treated cells showed an elevated rate of mutations, but the underlying mechanisms remained unclear. In this study, the global genomic alterations in BLM-treated cells were explored in the yeast Saccharomyces cerevisiae. Using genetic assay and whole-genome sequencing, we found that the mutation rate could be greatly elevated in S. cerevisiae cells that underwent ZeocinTM (a BLM member) treatment. One-base deletion and T to G substitution at the 5'-GT-3' motif was the most striking signature of ZeocinTM-induced mutations. This was mainly the result of translesion DNA synthesis involving Rev1 and polymerase ζ. ZeocinTM treatment led to the frequent loss of heterozygosity and chromosomal rearrangements in the diploid strains. The breakpoints of recombination events were significantly associated with certain chromosomal elements. Lastly, we identified multiple genomic alterations that contributed to BLM resistance in the ZeocinTM-treated mutants. Overall, this study provides new insights into the genotoxicity and evolutional effects of BLM. Importance Bleomycin is an antitumor antibiotic that can mutate genomic DNA. Using yeast models in combination with genome sequencing, the mutational signatures of ZeocinTM (a member of the bleomycin family) are disclosed. Translesion-synthesis polymerases are crucial for the viability of ZeocinTM-treated yeast cells at the sacrifice of a higher mutation rate. We also confirmed that multiple genomic alterations were associated with the improved resistance to ZeocinTM, providing novel insights into how bleomycin resistance is developed in cells.
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4
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Meek K. Activation of DNA-PK by hairpinned DNA ends reveals a stepwise mechanism of kinase activation. Nucleic Acids Res 2020; 48:9098-9108. [PMID: 32716029 PMCID: PMC7498359 DOI: 10.1093/nar/gkaa614] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 07/08/2020] [Accepted: 07/14/2020] [Indexed: 12/12/2022] Open
Abstract
As its name implies, the DNA dependent protein kinase (DNA-PK) requires DNA double-stranded ends for enzymatic activation. Here, I demonstrate that hairpinned DNA ends are ineffective for activating the kinase toward many of its well-studied substrates (p53, XRCC4, XLF, HSP90). However, hairpinned DNA ends robustly stimulate certain DNA-PK autophosphorylations. Specifically, autophosphorylation sites within the ABCDE cluster are robustly phosphorylated when DNA-PK is activated by hairpinned DNA ends. Of note, phosphorylation of the ABCDE sites is requisite for activation of the Artemis nuclease that associates with DNA-PK to mediate hairpin opening. This finding suggests a multi-step mechanism of kinase activation. Finally, I find that all non-homologous end joining (NHEJ) defective cells (whether deficient in components of the DNA-PK complex or components of the ligase complex) are similarly deficient in joining DNA double-stranded breaks (DSBs) with hairpinned termini.
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Affiliation(s)
- Katheryn Meek
- Department of Microbiology & Molecular Genetics, and Department of Pathobiology & Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA
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5
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Lees-Miller JP, Cobban A, Katsonis P, Bacolla A, Tsutakawa SE, Hammel M, Meek K, Anderson DW, Lichtarge O, Tainer JA, Lees-Miller SP. Uncovering DNA-PKcs ancient phylogeny, unique sequence motifs and insights for human disease. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 163:87-108. [PMID: 33035590 PMCID: PMC8021618 DOI: 10.1016/j.pbiomolbio.2020.09.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 09/12/2020] [Accepted: 09/29/2020] [Indexed: 01/26/2023]
Abstract
DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a key member of the phosphatidylinositol-3 kinase-like (PIKK) family of protein kinases with critical roles in DNA-double strand break repair, transcription, metastasis, mitosis, RNA processing, and innate and adaptive immunity. The absence of DNA-PKcs from many model organisms has led to the assumption that DNA-PKcs is a vertebrate-specific PIKK. Here, we find that DNA-PKcs is widely distributed in invertebrates, fungi, plants, and protists, and that threonines 2609, 2638, and 2647 of the ABCDE cluster of phosphorylation sites are highly conserved amongst most Eukaryotes. Furthermore, we identify highly conserved amino acid sequence motifs and domains that are characteristic of DNA-PKcs relative to other PIKKs. These include residues in the Forehead domain and a novel motif we have termed YRPD, located in an α helix C-terminal to the ABCDE phosphorylation site loop. Combining sequence with biochemistry plus structural data on human DNA-PKcs unveils conserved sequence and conformational features with functional insights and implications. The defined generally progressive DNA-PKcs sequence diversification uncovers conserved functionality supported by Evolutionary Trace analysis, suggesting that for many organisms both functional sites and evolutionary pressures remain identical due to fundamental cell biology. The mining of cancer genomic data and germline mutations causing human inherited disease reveal that robust DNA-PKcs activity in tumors is detrimental to patient survival, whereas germline mutations compromising function are linked to severe immunodeficiency and neuronal degeneration. We anticipate that these collective results will enable ongoing DNA-PKcs functional analyses with biological and medical implications.
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Affiliation(s)
- James P Lees-Miller
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1, Canada
| | - Alexander Cobban
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1, Canada
| | - Panagiotis Katsonis
- Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Albino Bacolla
- Departments of Cancer Biology and of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, 6767 Bertner Avenue, Houston, TX, 77030, USA
| | - Susan E Tsutakawa
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Michal Hammel
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Katheryn Meek
- College of Veterinary Medicine, Department of Microbiology & Molecular Genetics, And Department of Pathobiology & Diagnostic Investigation, Michigan State University, East Lansing, MI, 48824, USA
| | - Dave W Anderson
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1, Canada
| | - Olivier Lichtarge
- Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - John A Tainer
- Departments of Cancer Biology and of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, 6767 Bertner Avenue, Houston, TX, 77030, USA; Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Susan P Lees-Miller
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1, Canada.
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Neal JA, Dunger K, Geith K, Meek K. Deciphering the role of distinct DNA-PK phosphorylations at collapsed replication forks. DNA Repair (Amst) 2020; 94:102925. [PMID: 32674014 PMCID: PMC7494621 DOI: 10.1016/j.dnarep.2020.102925] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 06/29/2020] [Accepted: 07/06/2020] [Indexed: 11/29/2022]
Abstract
It has recently been established that the marked sensitivity of ATM deficient cells to topoisomerase poisons like camptothecin (Cpt) results from unrestrained end-joining of DNA ends at collapsed replication forks that is mediated by the non-homologous end joining [NHEJ] pathway and results in the induction of copious numbers of genomic alterations, termed "toxic NHEJ". Ablation of core components of the NHEJ pathway reverses the Cpt sensitivity of ATM deficient cells, but inhibition of DNA-PKcs does not. Here, we show that complete ablation of DNA-PKcs partially reverses the Cpt sensitivity of ATM deficient cells; thus, ATM deficient cells lacking DNA-PKcs are more resistant to Cpt than cells expressing DNA-PKcs. However, the relative sensitivity of DNA-PKcs proficient ATM deficient cells is inversely proportional to DNA-PKcs expression levels. These data suggest that DNA-PK may phosphorylate an ATM target (that contributes to Cpt resistance), explaining partial rescue of Cpt sensitivity in cells expressing high levels of DNA-PKcs. Although crippling NHEJ function by mutagenic blockade of the critical ABCDE autophosphorylation sites in DNA-PKcs also sensitizes cells to Cpt, this sensitization apparently occurs by a distinct mechanism from ATM ablation because blockade of these sites actually rescues ATM deficient cells from toxic NHEJ. These data are consistent with autophosphorylation of the ABCDE sites (and not ATM mediated phosphorylation) in response to Cpt-induced damage. In contrast, blockade of S3205 (an ATM dependent phosphorylation site in DNA-PKcs) that minimally impacts NHEJ, increases Cpt sensitivity. In sum, these data suggest that ATM and DNA-PK cooperate to facilitate Cpt-induced DNA damage, and that ATM phosphorylation of S3205 facilitates appropriate repair at collapsed replication forks.
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Affiliation(s)
- Jessica A Neal
- College of Veterinary Medicine, Department of Microbiology & Molecular Genetics, Department of Pathobiology & Diagnostic Investigation, Michigan State University, East Lansing, MI 48824, USA
| | - Krista Dunger
- College of Veterinary Medicine, Department of Microbiology & Molecular Genetics, Department of Pathobiology & Diagnostic Investigation, Michigan State University, East Lansing, MI 48824, USA
| | - Kelly Geith
- College of Veterinary Medicine, Department of Microbiology & Molecular Genetics, Department of Pathobiology & Diagnostic Investigation, Michigan State University, East Lansing, MI 48824, USA
| | - Katheryn Meek
- College of Veterinary Medicine, Department of Microbiology & Molecular Genetics, Department of Pathobiology & Diagnostic Investigation, Michigan State University, East Lansing, MI 48824, USA.
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7
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Britton S, Chanut P, Delteil C, Barboule N, Frit P, Calsou P. ATM antagonizes NHEJ proteins assembly and DNA-ends synapsis at single-ended DNA double strand breaks. Nucleic Acids Res 2020; 48:9710-9723. [PMID: 32890395 PMCID: PMC7515714 DOI: 10.1093/nar/gkaa723] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 07/29/2020] [Accepted: 08/21/2020] [Indexed: 12/15/2022] Open
Abstract
Two DNA repair pathways operate at DNA double strand breaks (DSBs): non-homologous end-joining (NHEJ), that requires two adjacent DNA ends for ligation, and homologous recombination (HR), that resects one DNA strand for invasion of a homologous duplex. Faithful repair of replicative single-ended DSBs (seDSBs) is mediated by HR, due to the lack of a second DNA end for end-joining. ATM stimulates resection at such breaks through multiple mechanisms including CtIP phosphorylation, which also promotes removal of the DNA-ends sensor and NHEJ protein Ku. Here, using a new method for imaging the recruitment of the Ku partner DNA-PKcs at DSBs, we uncover an unanticipated role of ATM in removing DNA-PKcs from seDSBs in human cells. Phosphorylation of DNA-PKcs on the ABCDE cluster is necessary not only for DNA-PKcs clearance but also for the subsequent MRE11/CtIP-dependent release of Ku from these breaks. We propose that at seDSBs, ATM activity is necessary for the release of both Ku and DNA-PKcs components of the NHEJ apparatus, and thereby prevents subsequent aberrant interactions between seDSBs accompanied by DNA-PKcs autophosphorylation and detrimental commitment to Lig4-dependent end-joining.
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Affiliation(s)
- Sébastien Britton
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
- Equipe Labellisée Ligue contre le Cancer 2018, Toulouse, France
| | - Pauline Chanut
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
- Equipe Labellisée Ligue contre le Cancer 2018, Toulouse, France
| | - Christine Delteil
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
- Equipe Labellisée Ligue contre le Cancer 2018, Toulouse, France
| | - Nadia Barboule
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
- Equipe Labellisée Ligue contre le Cancer 2018, Toulouse, France
| | - Philippe Frit
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
- Equipe Labellisée Ligue contre le Cancer 2018, Toulouse, France
| | - Patrick Calsou
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
- Equipe Labellisée Ligue contre le Cancer 2018, Toulouse, France
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8
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DNA-PKcs phosphorylation at the T2609 cluster alters the repair pathway choice during immunoglobulin class switch recombination. Proc Natl Acad Sci U S A 2020; 117:22953-22961. [PMID: 32868446 DOI: 10.1073/pnas.2007455117] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The DNA-dependent protein kinase (DNA-PK), which is composed of the KU heterodimer and the large catalytic subunit (DNA-PKcs), is a classical nonhomologous end-joining (cNHEJ) factor. Naïve B cells undergo class switch recombination (CSR) to generate antibodies with different isotypes by joining two DNA double-strand breaks at different switching regions via the cNHEJ pathway. DNA-PK and the cNHEJ pathway play important roles in the DNA repair phase of CSR. To initiate cNHEJ, KU binds to DNA ends and recruits and activates DNA-PK. Activated DNA-PK phosphorylates DNA-PKcs at the S2056 and T2609 clusters. Loss of T2609 cluster phosphorylation increases radiation sensitivity but whether T2609 phosphorylation has a role in physiological DNA repair remains elusive. Using the DNA-PKcs 5A mouse model carrying alanine substitutions at the T2609 cluster, here we show that loss of T2609 phosphorylation of DNA-PKcs does not affect the CSR efficiency. Yet, the CSR junctions recovered from DNA-PKcs 5A/5A B cells reveal increased chromosomal translocations, extensive use of distal switch regions (consistent with end resection), and preferential usage of microhomology-all signs of the alternative end-joining pathway. Thus, these results uncover a role of DNA-PKcs T2609 phosphorylation in promoting cNHEJ repair pathway choice during CSR.
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9
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Wang XS, Lee BJ, Zha S. The recent advances in non-homologous end-joining through the lens of lymphocyte development. DNA Repair (Amst) 2020; 94:102874. [PMID: 32623318 DOI: 10.1016/j.dnarep.2020.102874] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 05/16/2020] [Accepted: 05/24/2020] [Indexed: 12/17/2022]
Abstract
Lymphocyte development requires ordered assembly and subsequent modifications of the antigen receptor genes through V(D)J recombination and Immunoglobulin class switch recombination (CSR), respectively. While the programmed DNA cleavage events are initiated by lymphocyte-specific factors, the resulting DNA double-strand break (DSB) intermediates activate the ATM kinase-mediated DNA damage response (DDR) and rely on the ubiquitously expressed classical non-homologous end-joining (cNHEJ) pathway including the DNA-dependent protein kinase (DNA-PK), and, in the case of CSR, also the alternative end-joining (Alt-EJ) pathway, for repair. Correspondingly, patients and animal models with cNHEJ or DDR defects develop distinct types of immunodeficiency reflecting their specific DNA repair deficiency. The unique end-structure, sequence context, and cell cycle regulation of V(D)J recombination and CSR also provide a valuable platform to study the mechanisms of, and the interplay between, cNHEJ and DDR. Here, we compare and contrast the genetic consequences of DNA repair defects in V(D)J recombination and CSR with a focus on the newly discovered cNHEJ factors and the kinase-dependent structural roles of ATM and DNA-PK in animal models. Throughout, we try to highlight the pending questions and emerging differences that will extend our understanding of cNHEJ and DDR in the context of primary immunodeficiency and lymphoid malignancies.
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Affiliation(s)
- Xiaobin S Wang
- Institute for Cancer Genetics, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States; Graduate Program of Pathobiology and Molecular Medicine, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States
| | - Brian J Lee
- Institute for Cancer Genetics, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States
| | - Shan Zha
- Institute for Cancer Genetics, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States; Department of Pediatrics, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States; Department of Pathology and Cell Biology, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States; Department of Immunology and Microbiology, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States.
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10
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Liu Y, Efimova EV, Ramamurthy A, Kron SJ. Repair-independent functions of DNA-PKcs protect irradiated cells from mitotic slippage and accelerated senescence. J Cell Sci 2019; 132:jcs229385. [PMID: 31189537 PMCID: PMC6633392 DOI: 10.1242/jcs.229385] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 05/27/2019] [Indexed: 12/21/2022] Open
Abstract
The binding of DNA-dependent protein kinase catalytic subunit (DNA-PKcs, also known as PRKDC) to Ku proteins at DNA double-strand breaks (DSBs) has long been considered essential for non-homologous end joining (NHEJ) repair, providing a rationale for use of DNA-PKcs inhibitors as cancer therapeutics. Given lagging clinical translation, we reexamined mechanisms and observed instead that DSB repair can proceed independently of DNA-PKcs. While repair of radiation-induced DSBs was blocked in cells expressing shRNAs targeting Ku proteins or other NHEJ core factors, DSBs were repaired on schedule despite targeting DNA-PKcs. Although we failed to observe a DSB repair defect, the γH2AX foci that formed at sites of DNA damage persisted indefinitely after irradiation, leading to cytokinesis failure and accumulation of binucleated cells. Following this mitotic slippage, cells with decreased DNA-PKcs underwent accelerated cellular senescence. We identified downregulation of ataxia-telangiectasia mutated kinase (ATM) as the critical role of DNA-PKcs in recovery from DNA damage, insofar as targeting ATM restored γH2AX foci resolution and cytokinesis. Considering the lack of direct impact on DSB repair and emerging links between senescence and resistance to cancer therapy, these results suggest reassessing DNA-PKcs as a target for cancer treatment.
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Affiliation(s)
- Yue Liu
- Department of Molecular Genetics and Cell Biology and Ludwig Center for Metastasis Research, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Elena V Efimova
- Department of Molecular Genetics and Cell Biology and Ludwig Center for Metastasis Research, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Aishwarya Ramamurthy
- Department of Molecular Genetics and Cell Biology and Ludwig Center for Metastasis Research, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Stephen J Kron
- Department of Molecular Genetics and Cell Biology and Ludwig Center for Metastasis Research, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
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