51
|
Wang B, Zhang L, Qiu F, Fang W, Deng J, Zhou Y, Lu J, Yang L. A Newfound association between MDC1 functional polymorphism and lung cancer risk in Chinese. PLoS One 2014; 9:e106794. [PMID: 25198518 PMCID: PMC4157800 DOI: 10.1371/journal.pone.0106794] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 08/02/2014] [Indexed: 12/18/2022] Open
Abstract
Mediator of DNA damage checkpoint protein 1 (MDC1) plays an early and core role in Double-Strand Break Repair (DDR) and ataxia telangiectasia-mutated (ATM) mediated response to DNA double-strand breaks (DSBs), and thus involves the pathogenesis of several DNA damage-related diseases such as cancer. We hypothesized that the single nucleotide polymorphisms (SNPs) of MDC1 which have potencies on affecting MDC1 expression or function were associated with risk of lung cancer. In a two-stage case-control study, we tested the association between 5 putatively functional SNPs of MDC1 and lung cancer risk in a southern Chinese population, and validated the promising association in an eastern Chinese population. We found the SNP rs4713354A>C that is located in the 5′-untranslated region of MDC1 was significantly associated with lung cancer risk in both populations (P = 0.001), with an odds ratio as 1.33(95% confidence interval = 1.14–1.55) for the rs4713354C (CA+CC) genotypes compared to the rs4713354AA genotype. The correct sixth sentence is: The gene-based analysis rested with these SNPs suggested the MDC1 as a susceptible gene for lung cancer (P = 0.057) [corrected]. Moreover, by querying the gene expression database, we further found that the rs4713354C genotypes confer a significantly lower mRNA expression of MDC1 than the rs4713354AA genotype in 260 cases of lymphoblastoid cells (P = 0.002). Our data suggested that the SNP rs4713354A>C of MDC1 may be a functional genetic biomarker for susceptibility to lung cancer in Chinese.
Collapse
Affiliation(s)
- Bo Wang
- The State Key Lab of Respiratory Disease, The Institute for Chemical Carcinogenesis, Guangzhou Medical University, Guangzhou, China
| | - Lisha Zhang
- The State Key Lab of Respiratory Disease, The Institute for Chemical Carcinogenesis, Guangzhou Medical University, Guangzhou, China
| | - Fuman Qiu
- The State Key Lab of Respiratory Disease, The Institute for Chemical Carcinogenesis, Guangzhou Medical University, Guangzhou, China
| | - Wenxiang Fang
- The State Key Lab of Respiratory Disease, The Institute for Chemical Carcinogenesis, Guangzhou Medical University, Guangzhou, China
| | - Jieqiong Deng
- Soochow University Laboratory of Cancer Molecular Genetics, Medical College of Soochow University, Suzhou, China
| | - Yifeng Zhou
- Soochow University Laboratory of Cancer Molecular Genetics, Medical College of Soochow University, Suzhou, China
| | - Jiachun Lu
- The State Key Lab of Respiratory Disease, The Institute for Chemical Carcinogenesis, Guangzhou Medical University, Guangzhou, China
| | - Lei Yang
- The State Key Lab of Respiratory Disease, The Institute for Chemical Carcinogenesis, Guangzhou Medical University, Guangzhou, China
- * E-mail:
| |
Collapse
|
52
|
Svegliati S, Marrone G, Pezone A, Spadoni T, Grieco A, Moroncini G, Grieco D, Vinciguerra M, Agnese S, Jüngel A, Distler O, Musti AM, Gabrielli A, Avvedimento EV. Oxidative DNA damage induces the ATM-mediated transcriptional suppression of the Wnt inhibitor WIF-1 in systemic sclerosis and fibrosis. Sci Signal 2014; 7:ra84. [PMID: 25185156 DOI: 10.1126/scisignal.2004592] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Systemic sclerosis (SSc) is an autoimmune disease characterized by extensive visceral organ and skin fibrosis. SSc patients have increased production of autoreactive antibodies and Wnt signaling activity. We found that expression of the gene encoding Wnt inhibitor factor 1 (WIF-1) was decreased in fibroblasts from SSc patient biopsies. WIF-1 deficiency in SSc patient cells correlated with increased abundance of the Wnt effector β-catenin and the production of collagen. Knocking down WIF-1 in normal fibroblasts increased Wnt signaling and collagen production. WIF-1 loss and DNA damage were induced in normal fibroblasts by either SSc patient immunoglobulins or oxidative DNA-damaging agents, such as ultraviolet light, hydrogen peroxide, or bleomycin. The DNA damage checkpoint kinase ataxia telangiectasia mutated (ATM) mediated WIF-1 silencing through the phosphorylation of the transcription factor c-Jun, which in turn activated the expression of the gene encoding activating transcription factor 3 (ATF3). ATF3 and c-Jun were recruited together with histone deacetylase 3 (HDAC3) to the WIF-1 promoter and inhibited WIF-1 expression. Preventing the accumulation of reactive oxygen species or inhibiting the activation of ATM, c-Jun, or HDACs restored WIF-1 expression in cultured SSc patient cells. Trichostatin A, an HDAC inhibitor, prevented WIF-1 loss, β-catenin induction, and collagen accumulation in an experimental fibrosis model. Our findings suggest that oxidative DNA damage induced by SSc autoreactive antibodies enables Wnt activation that contributes to fibrosis.
Collapse
Affiliation(s)
- Silvia Svegliati
- Dipartimento di Scienze Cliniche e Molecolari, Clinica Medica, Università Politecnica delle Marche, 60126 Ancona, Italy
| | - Giusi Marrone
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di napoli Federico II, 80132 Naples, Italy
| | - Antonio Pezone
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di napoli Federico II, 80132 Naples, Italy
| | - Tatiana Spadoni
- Dipartimento di Scienze Cliniche e Molecolari, Clinica Medica, Università Politecnica delle Marche, 60126 Ancona, Italy
| | - Antonella Grieco
- Dipartimento di Scienze Cliniche e Molecolari, Clinica Medica, Università Politecnica delle Marche, 60126 Ancona, Italy
| | - Gianluca Moroncini
- Dipartimento di Scienze Cliniche e Molecolari, Clinica Medica, Università Politecnica delle Marche, 60126 Ancona, Italy. Dipartimento di Medicina Interna, Ospedali Riuniti, 60126 Ancona, Italy
| | - Domenico Grieco
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di napoli Federico II, 80132 Naples, Italy
| | | | - Savina Agnese
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di napoli Federico II, 80132 Naples, Italy
| | - Astrid Jüngel
- Center of Experimental Rheumatology, Department of Rheumatology, University Hospital Zurich, 8091 Zurich, Switzerland
| | - Oliver Distler
- Center of Experimental Rheumatology, Department of Rheumatology, University Hospital Zurich, 8091 Zurich, Switzerland
| | - Anna Maria Musti
- Dipartimento di Farmacia e Scienze della Salute e della Nutrizione, Università della Calabria, Arcavacata di Rende (CS) 87036, Italy
| | - Armando Gabrielli
- Dipartimento di Scienze Cliniche e Molecolari, Clinica Medica, Università Politecnica delle Marche, 60126 Ancona, Italy. Dipartimento di Medicina Interna, Ospedali Riuniti, 60126 Ancona, Italy.
| | - Enrico V Avvedimento
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di napoli Federico II, 80132 Naples, Italy.
| |
Collapse
|
53
|
Fukumoto Y, Kuki K, Morii M, Miura T, Honda T, Ishibashi K, Hasegawa H, Kubota S, Ide Y, Yamaguchi N, Nakayama Y, Yamaguchi N. Lyn tyrosine kinase promotes silencing of ATM-dependent checkpoint signaling during recovery from DNA double-strand breaks. Biochem Biophys Res Commun 2014; 452:542-7. [DOI: 10.1016/j.bbrc.2014.08.113] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Accepted: 08/21/2014] [Indexed: 11/30/2022]
|
54
|
C646, a selective small molecule inhibitor of histone acetyltransferase p300, radiosensitizes lung cancer cells by enhancing mitotic catastrophe. Radiother Oncol 2014; 111:222-7. [PMID: 24746574 DOI: 10.1016/j.radonc.2014.03.015] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 03/03/2014] [Accepted: 03/18/2014] [Indexed: 11/23/2022]
Abstract
BACKGROUND AND PURPOSE Chromatin remodeling through histone modifications, including acetylation, plays an important role in the appropriate response to DNA damage induced by ionizing radiation (IR). Here we investigated the radiosensitizing effect of C646, a selective small molecule inhibitor of p300 histone acetyltransferase, and explored the underlying mechanisms. MATERIALS AND METHODS A549, H157 and H460 human non-small cell lung carcinoma (NSCLC) cells, and HFL-III human lung fibroblasts were assessed by clonogenic survival assay. Apoptosis and necrosis were assessed by annexin V staining. Senescence was assessed by Senescence-associated β-galactosidase staining. Mitotic catastrophe was assessed by evaluating nuclear morphology with DAPI staining. Cell cycle profiles were analyzed by flow cytometry. Protein expression was analyzed by immunoblotting. RESULTS C646 sensitized A549, H460 and H157 cells to IR with a dose enhancement ratio at 10% surviving fraction of 1.4, 1.2 and 1.2, respectively. C646 did not radiosensitize HFL-III cells. In A549 cells, but not in HFL-III cells, C646 (i) enhanced mitotic catastrophe but not apoptosis, necrosis, or senescence after IR; (ii) increased the hyperploid cell population after IR; and (iii) suppressed the phosphorylation of CHK1 after IR. CONCLUSIONS C646 radiosensitizes NSCLC cells by enhancing mitotic catastrophe through the abrogation of G2 checkpoint maintenance.
Collapse
|
55
|
Zhang G, Pradhan S. Mammalian epigenetic mechanisms. IUBMB Life 2014; 66:240-56. [PMID: 24706538 DOI: 10.1002/iub.1264] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 03/19/2014] [Indexed: 12/31/2022]
Abstract
The mammalian genome is packaged into chromatin that is further compacted into three-dimensional structures consisting of distinct functional domains. The higher order structure of chromatin is in part dictated by enzymatic DNA methylation and histone modifications to establish epigenetic layers controlling gene expression and cellular functions, without altering the underlying DNA sequences. Apart from DNA and histone modifications, non-coding RNAs can also regulate the dynamics of the mammalian gene expression and various physiological functions including cell division, differentiation, and apoptosis. Aberrant epigenetic signatures are associated with abnormal developmental processes and diseases such as cancer. In this review, we will discuss the different layers of epigenetic regulation, including writer enzymes for DNA methylation, histone modifications, non-coding RNA, and chromatin conformation. We will highlight the combinatorial role of these structural and chemical modifications along with their partners in various cellular processes in mammalian cells. We will also address the cis and trans interacting "reader" proteins that recognize these modifications and "eraser" enzymes that remove these marks. Furthermore, an attempt will be made to discuss the interplay between various epigenetic writers, readers, and erasures in the establishment of mammalian epigenetic mechanisms.
Collapse
|
56
|
Fukumoto Y, Morii M, Miura T, Kubota S, Ishibashi K, Honda T, Okamoto A, Yamaguchi N, Iwama A, Nakayama Y, Yamaguchi N. Src family kinases promote silencing of ATR-Chk1 signaling in termination of DNA damage checkpoint. J Biol Chem 2014; 289:12313-29. [PMID: 24634213 DOI: 10.1074/jbc.m113.533752] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The DNA damage checkpoint arrests cell cycle progression to allow time for repair. Once DNA repair is completed, checkpoint signaling is terminated. Currently little is known about the mechanism by which checkpoint signaling is terminated, and the disappearance of DNA lesions is considered to induce the end of checkpoint signaling; however, here we show that the termination of checkpoint signaling is an active process promoted by Src family tyrosine kinases. Inhibition of Src activity delays recovery from the G2 phase DNA damage checkpoint following DNA repair. Src activity is required for the termination of checkpoint signaling, and inhibition of Src activity induces persistent activation of ataxia telangiectasia mutated (ATM)- and Rad3-related (ATR) and Chk1 kinases. Src-dependent nuclear protein tyrosine phosphorylation and v-Src expression suppress the ATR-mediated Chk1 and Rad17 phosphorylation induced by DNA double strand breaks or DNA replication stress. Thus, Src family kinases promote checkpoint recovery through termination of ATR- and Chk1-dependent G2 DNA damage checkpoint. These results suggest a model according to which Src family kinases send a termination signal between the completion of DNA repair and the initiation of checkpoint termination.
Collapse
Affiliation(s)
- Yasunori Fukumoto
- From the Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan and
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
57
|
Shibata A, Jeggo PA. DNA double-strand break repair in a cellular context. Clin Oncol (R Coll Radiol) 2014; 26:243-9. [PMID: 24630811 DOI: 10.1016/j.clon.2014.02.004] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 02/05/2014] [Accepted: 02/10/2014] [Indexed: 12/20/2022]
Abstract
Substantial insight into the mechanisms responding to DNA double-strand breaks has been gained from molecular, biochemical and structural approaches. Attention is now focusing on understanding the interplay between the pathways, how they interface through the cell cycle and the communication with other DNA transactions, such as replication and transcription. Understanding these aspects will facilitate an assessment of how cancer cells have modified these processes to achieve unlimited proliferative capacity and adaptability, and pave the way to identify targets suitable for therapy. Here, we briefly overview the processes responding to double-strand breaks and discuss our current understanding of their interplay in a cellular context.
Collapse
Affiliation(s)
- A Shibata
- Advanced Scientific Research Leaders Development Unit, Gunma University, Maebashi, Gunma, Japan
| | - P A Jeggo
- Genome Damage and Stability Centre, Life Sciences at University of Sussex, Brighton, UK.
| |
Collapse
|
58
|
Shibata A, Moiani D, Arvai AS, Perry J, Harding SM, Genois MM, Maity R, van Rossum-Fikkert S, Kertokalio A, Romoli F, Ismail A, Ismalaj E, Petricci E, Neale MJ, Bristow RG, Masson JY, Wyman C, Jeggo PA, Tainer JA. DNA double-strand break repair pathway choice is directed by distinct MRE11 nuclease activities. Mol Cell 2014; 53:7-18. [PMID: 24316220 PMCID: PMC3909494 DOI: 10.1016/j.molcel.2013.11.003] [Citation(s) in RCA: 426] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Revised: 10/01/2013] [Accepted: 10/29/2013] [Indexed: 12/17/2022]
Abstract
MRE11 within the MRE11-RAD50-NBS1 (MRN) complex acts in DNA double-strand break repair (DSBR), detection, and signaling; yet, how its endo- and exonuclease activities regulate DSBR by nonhomologous end-joining (NHEJ) versus homologous recombination (HR) remains enigmatic. Here, we employed structure-based design with a focused chemical library to discover specific MRE11 endo- or exonuclease inhibitors. With these inhibitors, we examined repair pathway choice at DSBs generated in G2 following radiation exposure. While nuclease inhibition impairs radiation-induced replication protein A (RPA) chromatin binding, suggesting diminished resection, the inhibitors surprisingly direct different repair outcomes. Endonuclease inhibition promotes NHEJ in lieu of HR, while exonuclease inhibition confers a repair defect. Collectively, the results describe nuclease-specific MRE11 inhibitors, define distinct nuclease roles in DSB repair, and support a mechanism whereby MRE11 endonuclease initiates resection, thereby licensing HR followed by MRE11 exonuclease and EXO1/BLM bidirectional resection toward and away from the DNA end, which commits to HR.
Collapse
Affiliation(s)
- Atsushi Shibata
- Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK; Advanced Scientific Research Leaders Development Unit, Gunma University, Maebashi, Gunma 371-8511, Japan
| | - Davide Moiani
- Skaggs Institute of Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA; The Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Andrew S Arvai
- Skaggs Institute of Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA; The Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Jefferson Perry
- Skaggs Institute of Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA; The Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; The School of Biotechnology, Amrita University, Kollam, Kerala 690525, India
| | - Shane M Harding
- Departments of Radiation Oncology and Medical Biophysics, University of Toronto, ON M5G 2M9, Canada
| | - Marie-Michelle Genois
- Genome Stability Laboratory, Laval University Cancer Research Center, Hôtel-Dieu de Québec, 9 McMahon, QC G1R 2J6, Canada
| | - Ranjan Maity
- Genome Stability Laboratory, Laval University Cancer Research Center, Hôtel-Dieu de Québec, 9 McMahon, QC G1R 2J6, Canada
| | - Sari van Rossum-Fikkert
- Department of Radiation Oncology, Department of Genetics, Erasmus University Medical Center, P.O. Box 2040, Rotterdam 3000 CA, the Netherlands
| | - Aryandi Kertokalio
- Department of Radiation Oncology, Department of Genetics, Erasmus University Medical Center, P.O. Box 2040, Rotterdam 3000 CA, the Netherlands
| | - Filippo Romoli
- Dipartimento Farmaco Chimico Tecnologico, Università degli Studi di Siena, Via A. Moro, 53100 Siena, Italy
| | - Amani Ismail
- Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK
| | - Ermal Ismalaj
- Dipartimento Farmaco Chimico Tecnologico, Università degli Studi di Siena, Via A. Moro, 53100 Siena, Italy
| | - Elena Petricci
- Dipartimento Farmaco Chimico Tecnologico, Università degli Studi di Siena, Via A. Moro, 53100 Siena, Italy
| | - Matthew J Neale
- Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK
| | - Robert G Bristow
- Departments of Radiation Oncology and Medical Biophysics, University of Toronto, ON M5G 2M9, Canada
| | - Jean-Yves Masson
- Genome Stability Laboratory, Laval University Cancer Research Center, Hôtel-Dieu de Québec, 9 McMahon, QC G1R 2J6, Canada
| | - Claire Wyman
- Department of Radiation Oncology, Department of Genetics, Erasmus University Medical Center, P.O. Box 2040, Rotterdam 3000 CA, the Netherlands
| | - Penny A Jeggo
- Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK.
| | - John A Tainer
- Skaggs Institute of Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA; The Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
| |
Collapse
|
59
|
Interplay between the cell cycle and double-strand break response in mammalian cells. Methods Mol Biol 2014; 1170:41-59. [PMID: 24906308 DOI: 10.1007/978-1-4939-0888-2_3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The cell cycle is intimately associated with the ability of cells to sense and respond to and repair DNA damage. Understanding how cell cycle progression, particularly DNA replication and cell division, are regulated and how DNA damage can affect these processes has been the subject of intense research. Recent evidence suggests that the repair of DNA damage is regulated by the cell cycle, and that cell cycle factors are closely associated with repair factors and participate in cellular decisions regarding how to respond to and repair damage. Precise regulation of cell cycle progression in the presence of DNA damage is essential to maintain genomic stability and avoid the accumulation of chromosomal aberrations that can promote tumor formation. In this review, we discuss the current understanding of how mammalian cells induce cell cycle checkpoints in response to DNA double-strand breaks. In addition, we discuss how cell cycle factors modulate DNA repair pathways to facilitate proper repair of DNA lesions.
Collapse
|
60
|
Guerra B, Iwabuchi K, Issinger OG. Protein kinase CK2 is required for the recruitment of 53BP1 to sites of DNA double-strand break induced by radiomimetic drugs. Cancer Lett 2013; 345:115-23. [PMID: 24333722 DOI: 10.1016/j.canlet.2013.11.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2013] [Revised: 11/26/2013] [Accepted: 11/29/2013] [Indexed: 12/26/2022]
Abstract
The ataxia telangiectasia mutated (ATM) signaling pathway responds rapidly to DNA double-strand breaks (DSBs) and it is characterized by recruitment of sensor, mediator, transducer and repair proteins to sites of DNA damage. Data suggest that CK2 is implicated in the early cellular response to DSBs. We demonstrate that CK2 binds constitutively the adaptor protein 53BP1 through the tandem Tudor domains and that the interaction is disrupted upon induction of DNA damage. Down-regulation of CK2 results in significant reduction of (i) 53BP1 foci formation, (ii) binding to dimethylated histone H4 and (iii) ATM autophosphorylation. Our data suggest that CK2 is required for 53BP1 accumulation at sites of DSBs which is a prerequisite for efficient activation of the ATM-mediated signaling pathway.
Collapse
Affiliation(s)
- Barbara Guerra
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark.
| | - Kuniyoshi Iwabuchi
- Department of Biochemistry, Kanazawa Medical University, Ishikawa, Japan
| | - Olaf-Georg Issinger
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| |
Collapse
|
61
|
The Mre11 complex suppresses oncogene-driven breast tumorigenesis and metastasis. Mol Cell 2013; 52:353-65. [PMID: 24120666 DOI: 10.1016/j.molcel.2013.09.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 08/07/2013] [Accepted: 08/30/2013] [Indexed: 12/20/2022]
Abstract
The DNA damage response (DDR) is activated by oncogenic stress, but the mechanisms by which this occurs, and the particular DDR functions that constitute barriers to tumorigenesis, remain unclear. We established a mouse model of sporadic oncogene-driven breast tumorigenesis in a series of mutant mouse strains with specific DDR deficiencies to reveal a role for the Mre11 complex in the response to oncogene activation. We demonstrate that an Mre11-mediated DDR restrains mammary hyperplasia by effecting an oncogene-induced G2 arrest. Impairment of Mre11 complex functions promotes the progression of mammary hyperplasias into invasive and metastatic breast cancers, which are often associated with secondary inactivation of the Ink4a-Arf (CDKN2a) locus. These findings provide insight into the mechanism of DDR engagement by activated oncogenes and highlight genetic interactions between the DDR and Ink4a-Arf pathways in suppression of oncogene-driven tumorigenesis and metastasis.
Collapse
|
62
|
Goodarzi AA, Jeggo PA. The repair and signaling responses to DNA double-strand breaks. ADVANCES IN GENETICS 2013; 82:1-45. [PMID: 23721719 DOI: 10.1016/b978-0-12-407676-1.00001-9] [Citation(s) in RCA: 165] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A DNA double-strand break (DSB) has long been recognized as a severe cellular lesion, potentially representing an initiating event for carcinogenesis or cell death. The evolution of DSB repair pathways as well as additional processes, such as cell cycle checkpoint arrest, to minimize the cellular impact of DSB formation was, therefore, not surprising. However, the depth and complexity of the DNA damage responses being revealed by current studies were unexpected. Perhaps the most surprising finding to emerge is the dramatic changes to chromatin architecture that arise in the DSB vicinity. In this review, we overview the cellular response to DSBs focusing on DNA repair pathways and the interface between them. We consider additional events which impact upon these DSB repair pathways, including regulated arrest of cell cycle progression and chromatin architecture alterations. Finally, we discuss the impact of defects in these processes to human disease.
Collapse
Affiliation(s)
- Aaron A Goodarzi
- Department of Biochemistry & Molecular Biology, Southern Alberta Cancer Research Institute, University of Calgary, Calgary, Alberta, Canada
| | | |
Collapse
|
63
|
Stanley FKT, Moore S, Goodarzi AA. CHD chromatin remodelling enzymes and the DNA damage response. Mutat Res 2013; 750:31-44. [PMID: 23954449 DOI: 10.1016/j.mrfmmm.2013.07.008] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 07/22/2013] [Accepted: 07/26/2013] [Indexed: 01/08/2023]
Abstract
The protein and DNA complex known as chromatin is a dynamic structure, adapting to alter the spatial arrangement of genetic information within the nucleus to meet the ever changing demands of life. Following decades of research, a dizzying array of regulatory factors is now known to control the architecture of chromatin at nearly every level. Amongst these, ATP-dependent chromatin remodelling enzymes play a key role, required for the establishment, maintenance and re-organization of chromatin through their ability to adjust the contact points between DNA and histones, the spacing between individual nucleosomes and the over-arching chromatin superstructure. Utilizing energy from ATP hydrolysis, these enzymes serve as the gatekeepers of genomic access and are essential for transcriptional regulation, DNA replication and cell division. In recent years, a vital role in DNA Double Strand Break (DSB) repair has emerged, particularly within complex chromatin environments such as heterochromatin, or regions undergoing energetic transactions such as transcription or DNA replication. Here, we will provide an overview of what is understood about ATP-dependent chromatin remodelling enzymes in the context of the DNA damage response. We will first touch upon all four major chromatin remodelling enzyme families and then focus chiefly on the nine members of the Chromodomain, Helicase, DNA-binding (CHD) family, particularly CHD3, CHD4, CHD5 and CHD6. These four proteins have established and emerging roles in DNA repair, the oxidative stress response, the maintenance of genomic stability and/or cancer prevention.
Collapse
Affiliation(s)
- Fintan K T Stanley
- Southern Alberta Cancer Research Institute, Department of Biochemistry and Molecular Biology and Department of Oncology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | | | | |
Collapse
|
64
|
Visualisation of γH2AX foci caused by heavy ion particle traversal; distinction between core track versus non-track damage. PLoS One 2013; 8:e70107. [PMID: 23967070 PMCID: PMC3743843 DOI: 10.1371/journal.pone.0070107] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Accepted: 06/18/2013] [Indexed: 11/19/2022] Open
Abstract
Heavy particle irradiation produces complex DNA double strand breaks (DSBs) which can arise from primary ionisation events within the particle trajectory. Additionally, secondary electrons, termed delta-electrons, which have a range of distributions can create low linear energy transfer (LET) damage within but also distant from the track. DNA damage by delta-electrons distant from the track has not previously been carefully characterised. Using imaging with deconvolution, we show that at 8 hours after exposure to Fe (∼200 keV/µm) ions, γH2AX foci forming at DSBs within the particle track are large and encompass multiple smaller and closely localised foci, which we designate as clustered γH2AX foci. These foci are repaired with slow kinetics by DNA non-homologous end-joining (NHEJ) in G1 phase with the magnitude of complexity diminishing with time. These clustered foci (containing 10 or more individual foci) represent a signature of DSBs caused by high LET heavy particle radiation. We also identified simple γH2AX foci distant from the track, which resemble those arising after X-ray exposure, which we attribute to low LET delta-electron induced DSBs. They are rapidly repaired by NHEJ. Clustered γH2AX foci induced by heavy particle radiation cause prolonged checkpoint arrest compared to simple γH2AX foci following X-irradiation. However, mitotic entry was observed when ∼10 clustered foci remain. Thus, cells can progress into mitosis with multiple clusters of DSBs following the traversal of a heavy particle.
Collapse
|
65
|
Ryu JS, Kang SJ, Koo HS. The 53BP1 homolog in C. elegans influences DNA repair and promotes apoptosis in response to ionizing radiation. PLoS One 2013; 8:e64028. [PMID: 23667696 PMCID: PMC3648578 DOI: 10.1371/journal.pone.0064028] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2012] [Accepted: 04/10/2013] [Indexed: 11/18/2022] Open
Abstract
53BP1 contributes to activation of the G2/M checkpoint downstream of ATM and MDC1 in response to ionizing radiation and promotes nonhomologous end-joining (NHEJ) in mammalian cells. In order to determine whether the cellular activities of 53BP1 are conserved in the model organism C. elegans, we analyzed the function of its homolog, HSR-9 in response to DNA damage. Deletion or Mos1-insertion in hsr-9 did not affect the sensitivity of worms to double strand DNA breaks (DSBs), as reflected in embryonic survival and larval development. Nevertheless, the hsr-9 mutations, as well as a lig-4 deletion, reversed the hypersensitivity of rad-54-deficient worms to DSBs. In addition, oocyte chromosomal aberrations, which were increased by rad-54 knockdown in response to DSBs, were also reduced by the hsr-9 mutations. The hsr-9 mutations did not prevent the cell cycle arrest induced by DSBs in mitotically proliferating germ cells. However, they attenuated apoptosis induced by DSBs, but not when CEP-1 (a p53 ortholog) was absent, suggesting that HSR-9 functions in the same pathway as CEP-1. We concluded that the 53BP1 homolog in C. elegans is not directly involved in cell cycle arrest in response to DSBs, but that it promotes apoptosis and also a form of NHEJ that occurs only when rad-54 is deficient.
Collapse
Affiliation(s)
- Jin-Sun Ryu
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea
| | - Sang Jo Kang
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea
| | - Hyeon-Sook Koo
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea
- * E-mail:
| |
Collapse
|
66
|
Zimmerman KM, Jones RM, Petermann E, Jeggo PA. Diminished origin-licensing capacity specifically sensitizes tumor cells to replication stress. Mol Cancer Res 2013; 11:370-80. [PMID: 23364533 PMCID: PMC3797919 DOI: 10.1158/1541-7786.mcr-12-0491] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Previous studies have shown that dormant licensed replication origins can be exploited to enhance recovery from replication stress. Since tumor cells express high levels of origin-licensing proteins, we examined whether depletion of such factors might specifically sensitize tumor versus nontumor cells. Consistent with previous findings, we observed that three tumor-derived cell lines overexpress ORC1, a licensing component, compared with four nontumor cell lines and that a greater level of ORC1 was required to maintain viability in the tumor cells. We determined siRNA-mediated knockdown conditions for each line that maximally reduced ORC1 but did not impact upon viability, which we considered would optimally deplete dormant origins. ORC1 depletion hypersensitized the tumor-derived cells to hydroxyurea and H202 but did not affect the sensitivity of the nontumor lines. Similar results were observed following depletion of ORC6 or CDC6. Furthermore, codepletion of p53 and ORC1 modestly impaired viability of 1BR3hTERT nontumor fibroblasts and more dramatically caused hypersensitivity to hydroxyurea. Finally, overexpression of the c-Myc oncogene combined with ORC1 depletion in nontumor BJhTERT cells diminished viability. Collectively, these findings suggest that tumor cells may have a reliance on origin-licensing capacity, suggesting that licensing factors could represent a target for drug-based cancer therapy.
Collapse
Affiliation(s)
| | - Rebecca M. Jones
- School of Cancer Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Eva Petermann
- School of Cancer Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Penelope A. Jeggo
- Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK
| |
Collapse
|
67
|
Furia L, Pelicci PG, Faretta M. A computational platform for robotized fluorescence microscopy (II): DNA damage, replication, checkpoint activation, and cell cycle progression by high-content high-resolution multiparameter image-cytometry. Cytometry A 2013; 83:344-55. [PMID: 23463591 DOI: 10.1002/cyto.a.22265] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 01/09/2013] [Accepted: 01/22/2013] [Indexed: 12/12/2022]
Abstract
Dissection of complex molecular-networks in rare cell populations is limited by current technologies that do not allow simultaneous quantification, high-resolution localization, and statistically robust analysis of multiple parameters. We have developed a novel computational platform (Automated Microscopy for Image CytOmetry, A.M.I.CO) for quantitative image-analysis of data from confocal or widefield robotized microscopes. We have applied this image-cytometry technology to the study of checkpoint activation in response to spontaneous DNA damage in nontransformed mammary cells. Cell-cycle profile and active DNA-replication were correlated to (i) Ki67, to monitor proliferation; (ii) phosphorylated histone H2AX (γH2AX) and 53BP1, as markers of DNA-damage response (DDR); and (iii) p53 and p21, as checkpoint-activation markers. Our data suggest the existence of cell-cycle modulated mechanisms involving different functions of γH2AX and 53BP1 in DDR, and of p53 and p21 in checkpoint activation and quiescence regulation during the cell-cycle. Quantitative analysis, event selection, and physical relocalization have been then employed to correlate protein expression at the population level with interactions between molecules, measured with Proximity Ligation Analysis, with unprecedented statistical relevance.
Collapse
Affiliation(s)
- Laura Furia
- Department of Experimental Oncology, European Institute of Oncology, IFOM-IEO Campus for Oncogenomics, Milan 20139, Italy
| | | | | |
Collapse
|
68
|
Wakasaya T, Yoshino H, Fukushi Y, Yoshizawa A, Kashiwakura I. A liquid crystal-related compound induces cell cycle arrest at the G2/M phase and apoptosis in the A549 human non-small cell lung cancer cell line. Int J Oncol 2013; 42:1205-11. [PMID: 23381730 DOI: 10.3892/ijo.2013.1804] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 08/20/2012] [Indexed: 11/05/2022] Open
Abstract
Liquid crystals are the state of matter existing between liquid and crystalline phases, and recently there has been increasing interest in their biological effects. Following our recently reported work, we investigated the cell suppressive effects of liquid crystal-related compounds (LCRCs), which are precursors of liquid crystals, in the human non-small lung cancer cell line A549. We found that 2-(4-butoxyphenyl)-5-(4-hydroxyphenyl)pyrimidine (LCRC-1) dramatically suppressed cell growth. Treatment with 12 µM LCRC-1 for 12 h induced cell cycle arrest at the G2/M phase. Furthermore, LCRC-1 increased the sub-G1 fraction and Annexin V-positive cells and activated caspase-3 in A549 cells, which showed that it can induce apoptosis in these cells. Furthermore, because the induction of apoptosis by LCRC-1 was partly inhibited by treatment with pan-caspase inhibitor, it appeared that LCRC-1 induced apoptosis by a caspase-dependent pathway. The ability of LCRC-1 to cause DNA damage was assessed, but LCRC-1 did not induce expression of γ-H2AX, which is a marker of DNA damage. Treatment with LCRC-1 did not inhibit the proliferation of WI-38 normal fibroblast cells, which makes the tumor-specific suppressive effect of LCRC-1 attractive for its application as a new antitumor drug.
Collapse
Affiliation(s)
- Takuya Wakasaya
- Department of Radiological Life Sciences, Division of Medical Life Sciences, Hirosaki University Graduate School of Health Sciences, Hirosaki, Aomori 036-8564, Japan
| | | | | | | | | |
Collapse
|
69
|
Pathways for genome integrity in G2 phase of the cell cycle. Biomolecules 2012; 2:579-607. [PMID: 24970150 PMCID: PMC4030857 DOI: 10.3390/biom2040579] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 11/17/2012] [Accepted: 11/23/2012] [Indexed: 12/31/2022] Open
Abstract
The maintenance of genome integrity is important for normal cellular functions, organism development and the prevention of diseases, such as cancer. Cellular pathways respond immediately to DNA breaks leading to the initiation of a multi-facetted DNA damage response, which leads to DNA repair and cell cycle arrest. Cell cycle checkpoints provide the cell time to complete replication and repair the DNA damage before it can continue to the next cell cycle phase. The G2/M checkpoint plays an especially important role in ensuring the propagation of error-free copies of the genome to each daughter cell. Here, we review recent progress in our understanding of DNA repair and checkpoint pathways in late S and G2 phases. This review will first describe the current understanding of normal cell cycle progression through G2 phase to mitosis. It will also discuss the DNA damage response including cell cycle checkpoint control and DNA double-strand break repair. Finally, we discuss the emerging concept that DNA repair pathways play a major role in the G2/M checkpoint pathway thereby blocking cell division as long as DNA lesions are present.
Collapse
|
70
|
Puthiyaveetil AG, Reilly CM, Pardee TS, Caudell DL. Non-homologous end joining mediated DNA repair is impaired in the NUP98-HOXD13 mouse model for myelodysplastic syndrome. Leuk Res 2012; 37:112-6. [PMID: 23131583 DOI: 10.1016/j.leukres.2012.10.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 10/07/2012] [Accepted: 10/16/2012] [Indexed: 11/17/2022]
Abstract
Chromosomal translocations typically impair cell differentiation and often require secondary mutations for malignant transformation. However, the role of a primary translocation in the development of collaborating mutations is debatable. To delineate the role of leukemic translocation NUP98-HOXD13 (NHD13) in secondary mutagenesis, DNA break and repair mechanisms in stimulated mouse B lymphocytes expressing NHD13 were analyzed. Our results showed significantly reduced expression of non-homologous end joining (NHEJ)-mediated DNA repair genes, DNA Pkcs, DNA ligase4, and Xrcc4 leading to cell cycle arrest at G2/M phase. Our results showed that expression of NHD13 fusion gene resulted in impaired NHEJ-mediated DNA break repair.
Collapse
Affiliation(s)
- Abdul Gafoor Puthiyaveetil
- Laboratory of Molecular Pathology, Center for Molecular Medicine & Infectious Diseases, Virginia Tech, Blacksburg, VA 24061, USA
| | | | | | | |
Collapse
|
71
|
The histone variant macroH2A1.1 is recruited to DSBs through a mechanism involving PARP1. FEBS Lett 2012; 586:3920-5. [PMID: 23031826 DOI: 10.1016/j.febslet.2012.09.030] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 08/13/2012] [Accepted: 09/20/2012] [Indexed: 01/06/2023]
Abstract
The repair of DNA double-strand breaks (DSBs) requires remodeling of the local chromatin architecture to allow the repair machinery to access sites of damage. Here, we report that the histone variant macroH2A1.1 is recruited to DSBs. Cells lacking macroH2A1 have defective recruitment of 53BP1, defective activation of chk2 kinase and increased radiosensitivity. Importantly, macroH2A1.1 is not incorporated into nucleosomes at DSBs, but instead associates with the chromatin through a mechanism which requires PARP1 activity. These results reveal an unusual mechanism involving a direct association of macroH2A1.1 with PARylated chromatin which is critical for retaining 53BP1 at sites of damage.
Collapse
|
72
|
Thompson LH. Recognition, signaling, and repair of DNA double-strand breaks produced by ionizing radiation in mammalian cells: the molecular choreography. Mutat Res 2012; 751:158-246. [PMID: 22743550 DOI: 10.1016/j.mrrev.2012.06.002] [Citation(s) in RCA: 261] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Revised: 06/09/2012] [Accepted: 06/16/2012] [Indexed: 12/15/2022]
Abstract
The faithful maintenance of chromosome continuity in human cells during DNA replication and repair is critical for preventing the conversion of normal diploid cells to an oncogenic state. The evolution of higher eukaryotic cells endowed them with a large genetic investment in the molecular machinery that ensures chromosome stability. In mammalian and other vertebrate cells, the elimination of double-strand breaks with minimal nucleotide sequence change involves the spatiotemporal orchestration of a seemingly endless number of proteins ranging in their action from the nucleotide level to nucleosome organization and chromosome architecture. DNA DSBs trigger a myriad of post-translational modifications that alter catalytic activities and the specificity of protein interactions: phosphorylation, acetylation, methylation, ubiquitylation, and SUMOylation, followed by the reversal of these changes as repair is completed. "Superfluous" protein recruitment to damage sites, functional redundancy, and alternative pathways ensure that DSB repair is extremely efficient, both quantitatively and qualitatively. This review strives to integrate the information about the molecular mechanisms of DSB repair that has emerged over the last two decades with a focus on DSBs produced by the prototype agent ionizing radiation (IR). The exponential growth of molecular studies, heavily driven by RNA knockdown technology, now reveals an outline of how many key protein players in genome stability and cancer biology perform their interwoven tasks, e.g. ATM, ATR, DNA-PK, Chk1, Chk2, PARP1/2/3, 53BP1, BRCA1, BRCA2, BLM, RAD51, and the MRE11-RAD50-NBS1 complex. Thus, the nature of the intricate coordination of repair processes with cell cycle progression is becoming apparent. This review also links molecular abnormalities to cellular pathology as much a possible and provides a framework of temporal relationships.
Collapse
Affiliation(s)
- Larry H Thompson
- Biology & Biotechnology Division, L452, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551-0808, United States.
| |
Collapse
|
73
|
Köcher S, Rieckmann T, Rohaly G, Mansour WY, Dikomey E, Dornreiter I, Dahm-Daphi J. Radiation-induced double-strand breaks require ATM but not Artemis for homologous recombination during S-phase. Nucleic Acids Res 2012; 40:8336-47. [PMID: 22730303 PMCID: PMC3458552 DOI: 10.1093/nar/gks604] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Double-strand breaks (DSBs) are repaired by two distinct pathways, non-homologous end joining (NHEJ) and homologous recombination (HR). The endonuclease Artemis and the PIK kinase Ataxia-Telangiectasia Mutated (ATM), mutated in prominent human radiosensitivity syndromes, are essential for repairing a subset of DSBs via NHEJ in G1 and HR in G2. Both proteins have been implicated in DNA end resection, a mandatory step preceding homology search and strand pairing in HR. Here, we show that during S-phase Artemis but not ATM is dispensable for HR of radiation-induced DSBs. In replicating AT cells, numerous Rad51 foci form gradually, indicating a Rad51 recruitment process that is independent of ATM-mediated end resection. Those DSBs decorated with Rad51 persisted through S- and G2-phase indicating incomplete HR resulting in unrepaired DSBs and a pronounced G2 arrest. We demonstrate that in AT cells loading of Rad51 depends on functional ATR/Chk1. The ATR-dependent checkpoint response is most likely activated when the replication fork encounters radiation-induced single-strand breaks leading to generation of long stretches of single-stranded DNA. Together, these results provide new insight into the role of ATM for initiation and completion of HR during S- and G2-phase. The DSB repair defect during S-phase significantly contributes to the radiosensitivity of AT cells.
Collapse
Affiliation(s)
- Sabrina Köcher
- Institute of Radiobiology and Molecular Radiation Oncology, Philipps-University of Marburg, Baldingerstr. 35032 Marburg, Germany
| | | | | | | | | | | | | |
Collapse
|
74
|
Phosphoproteomic analysis reveals that PP4 dephosphorylates KAP-1 impacting the DNA damage response. EMBO J 2012; 31:2403-15. [PMID: 22491012 DOI: 10.1038/emboj.2012.86] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Accepted: 03/15/2012] [Indexed: 02/08/2023] Open
Abstract
Protein phosphatase PP4C has been implicated in the DNA damage response (DDR), but its substrates in DDR remain largely unknown. We devised a novel proteomic strategy for systematic identification of proteins dephosphorylated by PP4C and identified KRAB-domain-associated protein 1 (KAP-1) as a substrate. Ionizing radiation leads to phosphorylation of KAP-1 at S824 (via ATM) and at S473 (via CHK2). A PP4C/R3β complex interacts with KAP-1 and silencing this complex leads to persistence of phospho-S824 and phospho-S473. We identify a new role for KAP-1 in DDR by showing that phosphorylation of S473 impacts the G2/M checkpoint. Depletion of PP4R3β or expression of the phosphomimetic KAP-1 S473 mutant (S473D) leads to a prolonged G2/M checkpoint. Phosphorylation of S824 is necessary for repair of heterochromatic DNA lesions and similar to cells expressing phosphomimetic KAP-1 S824 mutant (S824D), or PP4R3β-silenced cells, display prolonged relaxation of chromatin with release of chromatin remodelling protein CHD3. Our results define a new role for PP4-mediated dephosphorylation in the DDR, including the regulation of a previously undescribed function of KAP-1 in checkpoint response.
Collapse
|
75
|
Harding SM, Bristow RG. Discordance between phosphorylation and recruitment of 53BP1 in response to DNA double-strand breaks. Cell Cycle 2012; 11:1432-44. [PMID: 22421153 DOI: 10.4161/cc.19824] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
During the DNA damage response (DDR), chromatin modifications contribute to localization of 53BP1 to sites of DNA double-strand breaks (DSBs). 53BP1 is phosphorylated during the DDR, but it is unclear whether phosphorylation is directly coupled to chromatin binding. In this study, we used human diploid fibroblasts and HCT116 tumor cells to study 53BP1 phosphorylation at Serine-25 and Serine-1778 during endogenous and exogenous DSBs (DNA replication and whole-cell or sub-nuclear microbeam irradiation, respectively). In non-stressed conditions, endogenous DSBs in S-phase cells led to accumulation of 53BP1 and γH2AX into discrete nuclear foci. Only the frank collapse of DNA replication forks following hydroxyurea treatment initiated 53BP1(Ser25) and 53BP1(Ser1778) phosphorylation. In response to exogenous DSBs, 53BP1(Ser25) and 53BP1(Ser1778) phosphoforms localized to sites of initial DSBs in a cell cycle-independent manner. 53BP1 phosphoforms also localized to late residual foci and associated with PML-NBs during IR-induced senescence. Using isogenic cell lines and small-molecule inhibitors, we observed that DDR-induced 53BP1 phosphorylation was dependent on ATM and DNA-PKcs kinase activity but independent of MRE11 sensing or RNF168 chromatin remodeling. However, loss of RNF168 blocked recruitment of phosphorylated 53BP1 to sites of DNA damage. Our results uncouple 53BP1 phosphorylation from DSB localization and support parallel pathways for 53BP1 biology during the DDR. As relative 53BP1 expression may be a biomarker of DNA repair capacity in solid tumors, the tracking of 53BP1 phosphoforms in situ may give unique information regarding different cancer phenotypes or response to cancer treatment.
Collapse
Affiliation(s)
- Shane M Harding
- Department of Medical Biophysics, University of Toronto, Toronto, Canada
| | | |
Collapse
|
76
|
Tomimatsu N, Mukherjee B, Deland K, Kurimasa A, Bolderson E, Khanna KK, Burma S. Exo1 plays a major role in DNA end resection in humans and influences double-strand break repair and damage signaling decisions. DNA Repair (Amst) 2012; 11:441-8. [PMID: 22326273 DOI: 10.1016/j.dnarep.2012.01.006] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Revised: 12/28/2011] [Accepted: 01/09/2012] [Indexed: 02/03/2023]
Abstract
The resection of DNA double-strand breaks (DSBs) to generate ssDNA tails is a pivotal event in the cellular response to these breaks. In the two-step model of resection, primarily elucidated in yeast, initial resection by Mre11-CtIP is followed by extensive resection by two distinct pathways involving Exo1 or BLM/WRN-Dna2. However, resection pathways and their exact contributions in humans in vivo are not as clearly worked out as in yeast. Here, we examined the contribution of Exo1 to DNA end resection in humans in vivo in response to ionizing radiation (IR) and its relationship with other resection pathways (Mre11-CtIP or BLM/WRN). We find that Exo1 plays a predominant role in resection in human cells along with an alternate pathway dependent on WRN. While Mre11 and CtIP stimulate resection in human cells, they are not absolutely required for this process and Exo1 can function in resection even in the absence of Mre11-CtIP. Interestingly, the recruitment of Exo1 to DNA breaks appears to be inhibited by the NHEJ protein Ku80, and the higher level of resection that occurs upon siRNA-mediated depletion of Ku80 is dependent on Exo1. In addition, Exo1 may be regulated by 53BP1 and Brca1, and the restoration of resection in BRCA1-deficient cells upon depletion of 53BP1 is dependent on Exo1. Finally, we find that Exo1-mediated resection facilitates a transition from ATM- to ATR-mediated cell cycle checkpoint signaling. Our results identify Exo1 as a key mediator of DNA end resection and DSB repair and damage signaling decisions in human cells.
Collapse
Affiliation(s)
- Nozomi Tomimatsu
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, USA
| | | | | | | | | | | | | |
Collapse
|
77
|
Fink LS, Roell M, Caiazza E, Lerner C, Stamato T, Hrelia S, Lorenzini A, Sell C. 53BP1 contributes to a robust genomic stability in human fibroblasts. Aging (Albany NY) 2012; 3:836-45. [PMID: 21931182 PMCID: PMC3227449 DOI: 10.18632/aging.100381] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Faithful repair of damaged DNA is a crucial process in maintaining cell viability and function. A multitude of factors and pathways guides this process and includes repair proteins and cell cycle checkpoint factors. Differences in the maintenance of genomic processes are one feature that may contribute to species-specific differences in lifespan. We predicted that 53BP1, a key transducer of the DNA damage response and cell cycle checkpoint control, is highly involved in maintaining genomic stability and may function differently in cells from different species. We demonstrate a difference in the levels and recruitment of 53BP1 in mouse and human cells following DNA damage. In addition, we show that unresolved DNA damage persists more in mouse cells than in human cells, as evidenced by increased numbers of micronuclei. The difference in micronuclei seems to be related to the levels of 53BP1 present in cells. Finally, we present evidence that unresolved DNA damage correlates with species lifespan. Taken together, these studies suggest a link between recruitment of 53BP1, resolution of DNA damage, and increased species lifespan.
Collapse
Affiliation(s)
- Lauren S Fink
- Department of Pathology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | | | | | | | | | | | | | | |
Collapse
|
78
|
Abstract
DNA-damaging therapies represent the most frequently used non-surgical anticancer strategies in the treatment of human tumors. These therapies can kill tumor cells, but at the same time they can be particularly damaging and mutagenic to healthy tissues. The efficacy of DNA-damaging treatments can be improved if tumor cell death is selectively enhanced, and the recent application of poly-(ADP-ribose) polymerase inhibitors in BRCA1/2-deficient tumors is a successful example of this. DNA damage is known to trigger cell-cycle arrest through activation of DNA-damage checkpoints. This arrest can be reversed once the damage has been repaired, but irreparable damage can promote apoptosis or senescence. Alternatively, cells can reenter the cell cycle before repair has been completed, giving rise to mutations. In this review we discuss the mechanisms involved in the activation and inactivation of DNA-damage checkpoints, and how the transition from arrest and cell-cycle re-entry is controlled. In addition, we discuss recent attempts to target the checkpoint in anticancer strategies.
Collapse
|
79
|
Brunton H, Goodarzi AA, Noon AT, Shrikhande A, Hansen RS, Jeggo PA, Shibata A. Analysis of human syndromes with disordered chromatin reveals the impact of heterochromatin on the efficacy of ATM-dependent G2/M checkpoint arrest. Mol Cell Biol 2011; 31:4022-35. [PMID: 21791604 PMCID: PMC3187363 DOI: 10.1128/mcb.05289-11] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 07/12/2011] [Indexed: 11/20/2022] Open
Abstract
Heterochromatin (HC) poses a barrier to γH2AX focus expansion and DNA double-strand break (DSB) repair, the latter being relieved by ATM-dependent KAP-1 phosphorylation. Using high-resolution imaging, we show here that the HC superstructure markedly restricts ATM signaling to cell cycle checkpoint proteins. The impact of HC is greater than anticipated from the percentage of HC-DNA and, in distinction to DSB repair, ATM only partly overcomes the constraints posed by HC. Importantly, we examine ATM signaling in human syndromes with disordered HC. After depletion of MeCP2 and DNMT3B, proteins defective in the Rett and immunodeficiency with centromere instability and facial anomalies (ICF) syndromes, respectively, we demonstrate enhanced γH2AX signal expansion at HC-chromocenters in mouse NIH 3T3 cells, which have visible HC-chromocenters. Previous studies have shown that the G(2)/M checkpoint is inefficient requiring multiple DSBs to initiate arrest. MeCP2 and DNMT3B depletion leads to hypersensitive radiation-induced G(2)/M checkpoint arrest despite normal DSB repair. Cell lines from Rett, ICF, and Hutchinson-Guildford progeria syndrome patients similarly showed hyperactivated ATM signaling and hypersensitive and prolonged G(2)/M checkpoint arrest. Collectively, these findings reveal that heterochromatin contributes to the previously described inefficient G(2)/M checkpoint arrest and demonstrate how the signaling response can be uncoupled from DSB repair.
Collapse
Affiliation(s)
- Holly Brunton
- Genome Damage and Stability Centre, University of Sussex, East Sussex BN1 9RQ, United Kingdom
| | - Aaron A. Goodarzi
- Genome Damage and Stability Centre, University of Sussex, East Sussex BN1 9RQ, United Kingdom
| | - Angela T. Noon
- Genome Damage and Stability Centre, University of Sussex, East Sussex BN1 9RQ, United Kingdom
| | - Amruta Shrikhande
- Genome Damage and Stability Centre, University of Sussex, East Sussex BN1 9RQ, United Kingdom
| | - R. Scott Hansen
- Departments of Medicine and Genome Sciences, University of Washington, Seattle, Washington 98195
| | - Penny A. Jeggo
- Genome Damage and Stability Centre, University of Sussex, East Sussex BN1 9RQ, United Kingdom
| | - Atsushi Shibata
- Genome Damage and Stability Centre, University of Sussex, East Sussex BN1 9RQ, United Kingdom
| |
Collapse
|
80
|
Abstract
The embryonic ventricular and subventricular zones (VZ/SVZ) contain the neuronal stem and progenitor cells and undergo rapid proliferation. The intermediate zone (IZ) contains nonreplicating, differentiated cells. The VZ/SVZ is hypersensitive to radiation-induced apoptosis. Ablation of DNA non-homologous end-joining (NHEJ) proteins, XRCC4 or DNA ligase IV (LigIV), confers ataxia telangiectasia mutated (ATM)-dependent apoptosis predominantly in the IZ. We examine the mechanistic basis underlying these distinct sensitivities using a viable LigIV (Lig4(Y288C)) mouse, which permits an examination of the DNA damage responses in the embryonic and adult brain. Via combined analysis of DNA breakage, apoptosis, and cell-cycle checkpoint control in tissues, we show that apoptosis in the VZ/SVZ and IZ is activated by low numbers of DNA double-strand breaks (DSBs). Unexpectedly, high sensitivity in the VZ/SVZ arises from sensitive activation of ATM-dependent apoptosis plus an ATM-independent process. In contrast, the IZ appears to be hypersensitive to persistent DSBs. NHEJ functions efficiently in both compartments. The VZ/SVZ and IZ regions incur high endogenous DNA breakage, which correlates with VZ proliferation. We demonstrate a functional G(2)/M checkpoint in VZ/SVZ cells and show that it is not activated by low numbers of DSBs, allowing damaged VZ/SVZ cells to transit into the IZ. We propose a novel model in which microcephaly in LIG4 syndrome arises from sensitive apoptotic induction from persisting DSBs in the IZ, which arise from high endogenous breakage in the VZ/SVZ and transit of damaged cells to the IZ. The VZ/SVZ, in contrast, is highly sensitive to acute radiation-induced DSB formation.
Collapse
|
81
|
Huo Q, Yang Q. P53-Binding protein 1: A new player for tumorigenesis and a new target for breast cancer treatment. Med Hypotheses 2011; 77:359-63. [DOI: 10.1016/j.mehy.2011.05.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 04/16/2011] [Accepted: 05/11/2011] [Indexed: 12/21/2022]
|
82
|
Noon AT, Goodarzi AA. 53BP1-mediated DNA double strand break repair: insert bad pun here. DNA Repair (Amst) 2011; 10:1071-6. [PMID: 21868291 DOI: 10.1016/j.dnarep.2011.07.012] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 07/26/2011] [Indexed: 02/09/2023]
Abstract
53BP1 is an established player in the cellular response to DNA damage and is a canonical component of ionizing-radiation induced foci--that cadre of proteins which assemble at DNA double strand breaks following radiation exposure and which are readily visualized by immunofluorescence microscopy. While its roles in p53 regulation and cell cycle checkpoint activation have been studied for some time, the impact of 53BP1 on DNA double strand break rejoining has only come to light in the past few years. Convincing evidence now exists for 53BP1 significantly affecting the outcome of DNA double strand break repair in several contexts, many of which hint to an important role in modulating chromatin structure surrounding the break site. Here, we highlight the known and emerging roles of 53BP1 in DNA double strand break repair, including the repair of lesions induced within heterochromatin, following telomere uncapping, in long-range V(D)J recombination, during immunoglobulin class switch recombination and its much debated role in regulating resection during homologous recombination.
Collapse
Affiliation(s)
- Angela T Noon
- Southern Alberta Cancer Research Institute, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada T2N4N1
| | | |
Collapse
|
83
|
Abstract
Mutation rates vary significantly within the genome and across species. Recent studies revealed a long suspected replication-timing effect on mutation rate, but the mechanisms that regulate the increase in mutation rate as the genome is replicated remain unclear. Evidence is emerging, however, that DNA repair systems, in general, are less efficient in late replicating heterochromatic regions compared to early replicating euchromatic regions of the genome. At the same time, mutation rates in both vertebrates and invertebrates have been shown to vary with generation time (GT). GT is correlated with genome size, which suggests a possible nucleotypic effect on species-specific mutation rates. These and other observations all converge on a role for DNA replication checkpoints in modulating generation times and mutation rates during the DNA synthetic phase (S phase) of the cell cycle. The following will examine the potential role of the intra-S checkpoint in regulating cell cycle times (GT) and mutation rates in eukaryotes. This article was published online on August 5, 2011. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected October 4, 2011.
Collapse
Affiliation(s)
- John Herrick
- Department of Physics, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada.
| |
Collapse
|
84
|
The role of homologous recombination in radiation-induced double-strand break repair. Radiother Oncol 2011; 101:7-12. [PMID: 21737170 DOI: 10.1016/j.radonc.2011.06.019] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 06/08/2011] [Accepted: 06/08/2011] [Indexed: 11/23/2022]
Abstract
DNA double-strand breaks (DSBs) represent the most biologically significant lesions induced by ionizing radiation (IR). HR is the predominant pathway for repairing one-ended DSBs arising in S-phase when the replication fork encounters single-stranded breaks or base damages. Here, we discuss recent findings that two-ended DSBs directly induced by X- or γ-rays in late S- or G2-phase are repaired predominantly by NHEJ, with HR only repairing a sub-fraction of such DSBs. This sub-fraction represents DSBs which localize to heterochromatic DNA regions and, which in control cells, are repaired with slow kinetics over many hours post irradiation. The observation that defined DSB populations are repaired by either NHEJ or HR suggests an assignment of specific tasks for each of the two processes. Furthermore, heavy ion induced complex DSBs, which are in general more slowly repaired than X- or γ-ray induced breaks, are nearly always repaired by HR independent of chromatin localization suggesting that the speed of repair is an important factor determining the DSB repair pathway usage. Finally, NHEJ and HR can, under certain conditions, also compensate for each other such that DSBs normally repaired by one pathway can undergo repair by the other if genetic failures necessitate the pathway switch.
Collapse
|
85
|
p53 transactivation and the impact of mutations, cofactors and small molecules using a simplified yeast-based screening system. PLoS One 2011; 6:e20643. [PMID: 21674059 PMCID: PMC3107237 DOI: 10.1371/journal.pone.0020643] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Accepted: 05/06/2011] [Indexed: 11/19/2022] Open
Abstract
Background The p53 tumor suppressor, which is altered in most cancers, is a sequence-specific transcription factor that is able to modulate the expression of many target genes and influence a variety of cellular pathways. Inactivation of the p53 pathway in cancer frequently occurs through the expression of mutant p53 protein. In tumors that retain wild type p53, the pathway can be altered by upstream modulators, particularly the p53 negative regulators MDM2 and MDM4. Methodology/Principal Findings Given the many factors that might influence p53 function, including expression levels, mutations, cofactor proteins and small molecules, we expanded our previously described yeast-based system to provide the opportunity for efficient investigation of their individual and combined impacts in a miniaturized format. The system integrates i) variable expression of p53 proteins under the finely tunable GAL1,10 promoter, ii) single copy, chromosomally located p53-responsive and control luminescence reporters, iii) enhanced chemical uptake using modified ABC-transporters, iv) small-volume formats for treatment and dual-luciferase assays, and v) opportunities to co-express p53 with other cofactor proteins. This robust system can distinguish different levels of expression of WT and mutant p53 as well as interactions with MDM2 or 53BP1. Conclusions/Significance We found that the small molecules Nutlin and RITA could both relieve the MDM2-dependent inhibition of WT p53 transactivation function, while only RITA could impact p53/53BP1 functional interactions. PRIMA-1 was ineffective in modifying the transactivation capacity of WT p53 and missense p53 mutations. This dual-luciferase assay can, therefore, provide a high-throughput assessment tool for investigating a matrix of factors that can influence the p53 network, including the effectiveness of newly developed small molecules, on WT and tumor-associated p53 mutants as well as interacting proteins.
Collapse
|
86
|
Lossaint G, Besnard E, Fisher D, Piette J, Dulić V. Chk1 is dispensable for G2 arrest in response to sustained DNA damage when the ATM/p53/p21 pathway is functional. Oncogene 2011; 30:4261-74. [DOI: 10.1038/onc.2011.135] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
|
87
|
Deckbar D, Jeggo PA, Löbrich M. Understanding the limitations of radiation-induced cell cycle checkpoints. Crit Rev Biochem Mol Biol 2011; 46:271-83. [PMID: 21524151 PMCID: PMC3171706 DOI: 10.3109/10409238.2011.575764] [Citation(s) in RCA: 151] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The DNA damage response pathways involve processes of double-strand break (DSB) repair and cell cycle checkpoint control to prevent or limit entry into S phase or mitosis in the presence of unrepaired damage. Checkpoints can function to permanently remove damaged cells from the actively proliferating population but can also halt the cell cycle temporarily to provide time for the repair of DSBs. Although efficient in their ability to limit genomic instability, checkpoints are not foolproof but carry inherent limitations. Recent work has demonstrated that the G1/S checkpoint is slowly activated and allows cells to enter S phase in the presence of unrepaired DSBs for about 4–6 h post irradiation. During this time, only a slowing but not abolition of S-phase entry is observed. The G2/M checkpoint, in contrast, is quickly activated but only responds to a level of 10–20 DSBs such that cells with a low number of DSBs do not initiate the checkpoint or terminate arrest before repair is complete. Here, we discuss the limitations of these checkpoints in the context of the current knowledge of the factors involved. We suggest that the time needed to fully activate G1/S arrest reflects the existence of a restriction point in G1-phase progression. This point has previously been defined as the point when mitogen starvation fails to prevent cells from entering S phase. However, cells that passed the restriction point can respond to DSBs, albeit with reduced efficiency.
Collapse
Affiliation(s)
- Dorothee Deckbar
- Darmstadt University of Technology, Radiation Biology and DNA Repair, Darmstadt, Germany
| | | | | |
Collapse
|
88
|
Inhibition of checkpoint kinase 1 sensitizes lung cancer brain metastases to radiotherapy. Biochem Biophys Res Commun 2011; 406:53-8. [DOI: 10.1016/j.bbrc.2011.01.106] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Accepted: 01/27/2011] [Indexed: 11/20/2022]
|
89
|
Quennet V, Beucher A, Barton O, Takeda S, Löbrich M. CtIP and MRN promote non-homologous end-joining of etoposide-induced DNA double-strand breaks in G1. Nucleic Acids Res 2010; 39:2144-52. [PMID: 21087997 PMCID: PMC3064790 DOI: 10.1093/nar/gkq1175] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Topoisomerases class II (topoII) cleave and re-ligate the DNA double helix to allow the passage of an intact DNA strand through it. Chemotherapeutic drugs such as etoposide target topoII, interfere with the normal enzymatic cleavage/re-ligation reaction and create a DNA double-strand break (DSB) with the enzyme covalently bound to the 5'-end of the DNA. Such DSBs are repaired by one of the two major DSB repair pathways, non-homologous end-joining (NHEJ) or homologous recombination. However, prior to repair, the covalently bound topoII needs to be removed from the DNA end, a process requiring the MRX complex and ctp1 in fission yeast. CtIP, the mammalian ortholog of ctp1, is known to promote homologous recombination by resecting DSB ends. Here, we show that human cells arrested in G0/G1 repair etoposide-induced DSBs by NHEJ and, surprisingly, require the MRN complex (the ortholog of MRX) and CtIP. CtIP's function for repairing etoposide-induced DSBs by NHEJ in G0/G1 requires the Thr-847 but not the Ser-327 phosphorylation site, both of which are needed for resection during HR. This finding establishes that CtIP promotes NHEJ of etoposide-induced DSBs during G0/G1 phase with an end-processing function that is distinct to its resection function.
Collapse
Affiliation(s)
- Verena Quennet
- Radiation Biology and DNA Repair, Darmstadt University of Technology, 64287 Darmstadt, Germany
| | | | | | | | | |
Collapse
|
90
|
Goodarzi AA, Jeggo P, Lobrich M. The influence of heterochromatin on DNA double strand break repair: Getting the strong, silent type to relax. DNA Repair (Amst) 2010; 9:1273-82. [PMID: 21036673 DOI: 10.1016/j.dnarep.2010.09.013] [Citation(s) in RCA: 229] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/09/2010] [Indexed: 01/11/2023]
Abstract
DNA non-homologous end-joining (NHEJ) and homologous recombination (HR) represent the major DNA double strand break (DSB) pathways in mammalian cells, whilst ataxia telangiectasia mutated (ATM) lies at the core of the DSB signalling response. ATM signalling plays a major role in modifying chromatin structure in the vicinity of the DSB and increasing evidence suggests that this function influences the DSB rejoining process. DSBs have long been known to be repaired with two (or more) component kinetics. The majority (∼85%) of DSBs are repaired with fast kinetics in a predominantly ATM-independent manner. In contrast, ∼15% of radiation-induced DSBs are repaired with markedly slower kinetics via a process that requires ATM and those mediator proteins, such as MDC1 or 53BP1, that accumulate at ionising radiation induced foci (IRIF). DSBs repaired with slow kinetics predominantly localise to the periphery of genomic heterochromatin (HC). Indeed, there is mounting evidence that chromatin complexity and not damage complexity confers slow DSB repair kinetics. ATM's role in HC-DSB repair involves the direct phosphorylation of KAP-1, a key HC formation factor. KAP-1 phosphorylation (pKAP-1) arises in both a pan-nuclear and a focal manner after radiation and ATM-dependent pKAP-1 is essential for DSB repair within HC regions. Mediator proteins such as 53BP1, which are also essential for HC-DSB repair, are expendable for pan-nuclear pKAP-1 whilst being essential for pKAP-1 formation at IRIF. Data suggests that the essential function of the mediator proteins is to promote the retention of activated ATM at DSBs, concentrating the phosphorylation of KAP-1 at HC DSBs. DSBs arising in G2 phase are also repaired with fast and slow kinetics but, in contrast to G0/G1 where they all DSBs are repaired by NHEJ, the slow component of DSB repair in G2 phase represents an HR process involving the Artemis endonuclease. Results suggest that whilst NHEJ repairs the majority of DSBs in G2 phase, Artemis-dependent HR uniquely repairs HC DSBs. Collectively, these recent studies highlight not only how chromatin complexity influences the factors required for DSB repair but also the pathway choice.
Collapse
Affiliation(s)
- Aaron A Goodarzi
- Genome Damage and Stability Centre, University of Sussex, East Sussex BN1 9RQ, United Kingdom
| | | | | |
Collapse
|
91
|
The interplay between BRCA1 and 53BP1 influences death, aging, senescence and cancer. DNA Repair (Amst) 2010; 9:1112-6. [PMID: 20724228 DOI: 10.1016/j.dnarep.2010.07.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Accepted: 07/21/2010] [Indexed: 02/02/2023]
Abstract
In proliferating cells DNA double strand breaks (DSBs) are a common occurrence during DNA replication. DSB repair using homologous recombination is essential for the error-free repair of such breaks and proliferating cells require some level of HR activity for their viability. The BRCA1 tumour suppressor has an important role in this process and is believed to channel the DSBs into the HR pathway. The related 53BP1 gene is known to positively regulate repair of DSBs outside of S phase, but via the NHEJ pathway. Two new studies suggest a new role for 53BP1 as an inhibitor of HR [1,2]. These genetic studies establish that 53BP1, but not other components of the NHEJ machinery, can inhibit the early resection step of HR. In cells defective for BRCA1, which is required for efficient HR, the balance between promoting and inhibiting HR is thrown towards inhibition. Simultaneous loss of 53BP1 can rescue the HR defect of BRCA1-defective cells and restore cellular viability. Here, I provide an overview of these studies and discuss their implications for tumourigenesis.
Collapse
|