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Fulneček J, Klimentová E, Cairo A, Bukovcakova SV, Alexiou P, Prokop Z, Riha K. The SAP domain of Ku facilitates its efficient loading onto DNA ends. Nucleic Acids Res 2023; 51:11706-11716. [PMID: 37850645 PMCID: PMC10681742 DOI: 10.1093/nar/gkad850] [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: 06/26/2023] [Revised: 09/11/2023] [Accepted: 09/29/2023] [Indexed: 10/19/2023] Open
Abstract
The evolutionarily conserved DNA repair complex Ku serves as the primary sensor of free DNA ends in eukaryotic cells. Its rapid association with DNA ends is crucial for several cellular processes, including non-homologous end joining (NHEJ) DNA repair and telomere protection. In this study, we conducted a transient kinetic analysis to investigate the impact of the SAP domain on individual phases of the Ku-DNA interaction. Specifically, we examined the initial binding, the subsequent docking of Ku onto DNA, and sliding of Ku along DNA. Our findings revealed that the C-terminal SAP domain of Ku70 facilitates the initial phases of the Ku-DNA interaction but does not affect the sliding process. This suggests that the SAP domain may either establish the first interactions with DNA, or stabilize these initial interactions during loading. To assess the biological role of the SAP domain, we generated Arabidopsis plants expressing Ku lacking the SAP domain. Intriguingly, despite the decreased efficiency of the ΔSAP Ku complex in loading onto DNA, the mutant plants exhibited full proficiency in classical NHEJ and telomere maintenance. This indicates that the speed with which Ku loads onto telomeres or DNA double-strand breaks is not the decisive factor in stabilizing these DNA structures.
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Affiliation(s)
| | | | | | | | | | - Zbynek Prokop
- Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Masaryk University, Brno, Czech Republic
- International Clinical Research Center, St Anne's University Hospital, Brno, Czech Republic
| | - Karel Riha
- CEITEC Masaryk University, Brno, Czech Republic
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2
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Tsai CW, Shih LC, Chang WS, Hsu CL, He JL, Hsia TC, Wang YC, Gu J, Bau DT. Non-Homologous End-Joining Pathway Genotypes Significantly Associated with Nasopharyngeal Carcinoma Susceptibility. Biomedicines 2023; 11:1648. [PMID: 37371742 DOI: 10.3390/biomedicines11061648] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 05/29/2023] [Accepted: 05/30/2023] [Indexed: 06/29/2023] Open
Abstract
Defects in the non-homologous end-joining (NHEJ) DNA repair pathway lead to genomic instability and carcinogenesis. However, the roles of individual NHEJ genes in nasopharyngeal carcinoma (NPC) etiology are not well-understood. The aim of this study was to assess the contribution of NHEJ genotypes, including XRCC4 (rs6869366, rs3734091, rs28360071, rs28360317, rs1805377), XRCC5 (rs828907, rs11685387, rs9288518), XRCC6 (rs5751129, rs2267437, rs132770, rs132774), XRCC7 rs7003908, and Ligase4 rs1805388, to NPC risk, with 208 NPC patients and 416 controls. Genotype-phenotype correlations were also investigated by measuring mRNA and protein expression in adjacent normal tissues and assessing the NHEJ repair capacity in blood lymphocytes from 43 NPC patients. The results showed significant differences in the distributions of variant genotypes at XRCC4 rs3734091, rs28360071, and XRCC6 rs2267437 between the cases and controls. The variant genotypes of these three polymorphisms were associated with significantly increased NPC risks. NPC patients with the risk genotypes at XRCC6 rs2267437 had significantly reduced expression levels of both mRNA and protein, as well as a lower NHEJ repair capacity, than those with the wild-type genotype. In conclusion, XRCC4 rs3734091, rs28360071, and XRCC6 rs2267437 in the NHEJ pathway were associated with NPC susceptibility. XRCC6 rs2267437 can modulate mRNA and protein expression and the NHEJ repair capacity.
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Affiliation(s)
- Chia-Wen Tsai
- Graduate Institute of Biomedical Sciences, China Medical University, Taichung 404333, Taiwan
- Terry Fox Cancer Research Laboratory, Department of Medical Research, China Medical University Hospital, Taichung 404332, Taiwan
| | - Liang-Chun Shih
- Graduate Institute of Biomedical Sciences, China Medical University, Taichung 404333, Taiwan
- Terry Fox Cancer Research Laboratory, Department of Medical Research, China Medical University Hospital, Taichung 404332, Taiwan
- Department of Otorhinolaryngology, China Medical University Hospital, Taichung 404332, Taiwan
| | - Wen-Shin Chang
- Graduate Institute of Biomedical Sciences, China Medical University, Taichung 404333, Taiwan
- Terry Fox Cancer Research Laboratory, Department of Medical Research, China Medical University Hospital, Taichung 404332, Taiwan
| | - Che-Lun Hsu
- Department of Otorhinolaryngology, China Medical University Hospital, Taichung 404332, Taiwan
| | - Jie-Long He
- Department of Post-Baccalaureate Veterinary Medicine, Asia University, Taichung 413305, Taiwan
| | - Te-Chun Hsia
- Terry Fox Cancer Research Laboratory, Department of Medical Research, China Medical University Hospital, Taichung 404332, Taiwan
| | - Yun-Chi Wang
- Graduate Institute of Biomedical Sciences, China Medical University, Taichung 404333, Taiwan
- Terry Fox Cancer Research Laboratory, Department of Medical Research, China Medical University Hospital, Taichung 404332, Taiwan
| | - Jian Gu
- Department of Epidemiology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Da-Tian Bau
- Graduate Institute of Biomedical Sciences, China Medical University, Taichung 404333, Taiwan
- Terry Fox Cancer Research Laboratory, Department of Medical Research, China Medical University Hospital, Taichung 404332, Taiwan
- Department of Bioinformatics and Medical Engineering, Asia University, Taichung 413305, Taiwan
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3
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Tadi SK, Tellier-Lebègue C, Nemoz C, Drevet P, Audebert S, Roy S, Meek K, Charbonnier JB, Modesti M. PAXX Is an Accessory c-NHEJ Factor that Associates with Ku70 and Has Overlapping Functions with XLF. Cell Rep 2017; 17:541-555. [PMID: 27705800 DOI: 10.1016/j.celrep.2016.09.026] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 08/31/2016] [Accepted: 09/09/2016] [Indexed: 01/19/2023] Open
Abstract
In mammalian cells, classical non-homologous end joining (c-NHEJ) is critical for DNA double-strand break repair induced by ionizing radiation and during V(D)J recombination in developing B and T lymphocytes. Recently, PAXX was identified as a c-NHEJ core component. We report here that PAXX-deficient cells exhibit a cellular phenotype uncharacteristic of a deficiency in c-NHEJ core components. PAXX-deficient cells display normal sensitivity to radiomimetic drugs, are proficient in transient V(D)J recombination assays, and do not shift toward higher micro-homology usage in plasmid repair assays. Although PAXX-deficient cells lack c-NHEJ phenotypes, PAXX forms a stable ternary complex with Ku bound to DNA. Formation of this complex involves an interaction with Ku70 and requires a bare DNA extension for stability. Moreover, the relatively weak Ku-dependent stimulation of LIG4/XRCC4 activity by PAXX is unmasked by XLF ablation. Thus, PAXX plays an accessory role during c-NHEJ that is largely overlapped by XLF's function.
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Affiliation(s)
- Satish K Tadi
- Cancer Research Center of Marseille, CNRS UMR7258, INSERM U1068, Institut Paoli-Calmettes, Aix-Marseille Université UM105, 13273 Marseille, France
| | - Carine Tellier-Lebègue
- Institute for Integrative Biology of the Cell (I2BC), IBITECS, CEA, CNRS, University Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Clément Nemoz
- Institute for Integrative Biology of the Cell (I2BC), IBITECS, CEA, CNRS, University Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Pascal Drevet
- Institute for Integrative Biology of the Cell (I2BC), IBITECS, CEA, CNRS, University Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Stéphane Audebert
- Cancer Research Center of Marseille, CNRS UMR7258, INSERM U1068, Institut Paoli-Calmettes, Aix-Marseille Université UM105, 13273 Marseille, France
| | - Sunetra Roy
- Department of Microbiology & Molecular Genetics, and Department of Pathobiology & Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA
| | - 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
| | - Jean-Baptiste Charbonnier
- Institute for Integrative Biology of the Cell (I2BC), IBITECS, CEA, CNRS, University Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Mauro Modesti
- Cancer Research Center of Marseille, CNRS UMR7258, INSERM U1068, Institut Paoli-Calmettes, Aix-Marseille Université UM105, 13273 Marseille, France.
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4
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Anisenko AN, Knyazhanskaya ES, Zatsepin TS, Gottikh MB. Human Ku70 protein binds hairpin RNA and double stranded DNA through two different sites. Biochimie 2016; 132:85-93. [PMID: 27825805 DOI: 10.1016/j.biochi.2016.11.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2016] [Accepted: 11/02/2016] [Indexed: 02/07/2023]
Abstract
Human protein Ku usually functions in the cell as a complex of two subunits, Ku70 and Ku80. The Ku heterodimer plays a key role in the non-homologous end joining DNA repair pathway by specifically recognizing the DNA ends at the site of the lesion. The binding of the Ku heterodimer to DNA has been well-studied, and its interactions with RNA have been also described. However, Ku70 subunit is known to have independent DNA binding capability, which is less characterized. RNA binding properties of Ku70 have not been yet specially studied. We have prepared recombinant full-length Ku70 and a set of its truncated mutants in E. coli, and studied their interactions with nucleic acids of various structures: linear single- and double-stranded DNA and RNA, as well as closed circular DNA and hairpin RNA. Ku70 has demonstrated a high affinity binding to double stranded DNA and hairpin RNA with a certain structure only. Interestingly, in contrast to the Ku heterodimer, Ku70 is found to interact with closed circular DNA. We also show for the first time that Ku70 employs two different sites for DNA and RNA binding. The double-stranded DNA is recognized by the C-terminal part of Ku70 including SAP domain as it has been earlier demonstrated, whereas hairpin RNA binding is provided by amino acids 251-438.
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Affiliation(s)
- Andrey N Anisenko
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia.
| | | | - Timofey S Zatsepin
- Chemistry Department, Lomonosov Moscow State University, Moscow, Russia; Skolkovo Institute of Science and Technology, Skolkovo, Russia.
| | - Marina B Gottikh
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.
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5
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Knyazhanskaya ES, Shadrina OA, Anisenko AN, Gottikh MB. Role of DNA-dependent protein kinase in the HIV-1 replication cycle. Mol Biol 2016. [DOI: 10.1134/s0026893316040075] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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6
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Huang CY, Tsai CW, Hsu CM, Shih LC, Chang WS, Shui HA, Bau DT. The role of XRCC6/Ku70 in nasopharyngeal carcinoma. Int J Oral Maxillofac Surg 2015; 44:1480-5. [PMID: 26149939 DOI: 10.1016/j.ijom.2015.06.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 06/08/2015] [Accepted: 06/09/2015] [Indexed: 12/09/2022]
Abstract
The association between XRCC6/Ku70, an upstream player in the DNA double-strand break repair system, and the risk of nasopharyngeal carcinoma (NPC) was examined. In this case-control study, 176 NPC patients and 352 cancer-free controls were genotyped, and the associations of XRCC6 promoter T-991C (rs5751129), promoter G-57C (rs2267437), promoter G-31A (rs132770), and intron 3 (rs132774) polymorphisms with NPC risk were evaluated. NPC tissue samples were also assessed for their XRCC6 mRNA and protein expression by real-time quantitative reverse transcription PCR and Western blotting, respectively. With regard to the XRCC6 promoter T-991C, the TC and CC genotypes were associated with a significantly increased risk of NPC compared with wild-type TT genotype (adjusted odds ratio 2.02 and 3.42, 95% confidence interval 1.21-3.32 and 1.28-8.94, P=0.0072 and 0.0165, respectively). The mRNA and protein expression levels for NPC tissues revealed significantly lower XRCC6 mRNA and protein expression in the NPC samples with TC/CC genotypes compared to those with the TT genotype (P=0.0210 and 0.0164, respectively). These findings suggest that XRCC6 may play an important role in the carcinogenesis of NPC and could serve as a chemotherapeutic target for personalized medicine and therapy.
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Affiliation(s)
- C-Y Huang
- Graduate Institute of Medical Sciences, National Defence Medical Centre, Taipei, Taiwan, ROC; Taichung Armed Forces General Hospital, Taichung, Taiwan, ROC
| | - C-W Tsai
- Graduate Institute of Basic Medical Science, China Medical University, Taichung, Taiwan, ROC; Terry Fox Cancer Research Laboratory, China Medical University Hospital, Taichung, Taiwan, ROC
| | - C-M Hsu
- Terry Fox Cancer Research Laboratory, China Medical University Hospital, Taichung, Taiwan, ROC
| | - L-C Shih
- Terry Fox Cancer Research Laboratory, China Medical University Hospital, Taichung, Taiwan, ROC
| | - W-S Chang
- Terry Fox Cancer Research Laboratory, China Medical University Hospital, Taichung, Taiwan, ROC; Graduate Institute of Clinical Medical Science, China Medical University, Taichung, Taiwan, ROC
| | - H-A Shui
- Graduate Institute of Medical Sciences, National Defence Medical Centre, Taipei, Taiwan, ROC
| | - D-T Bau
- Graduate Institute of Basic Medical Science, China Medical University, Taichung, Taiwan, ROC; Terry Fox Cancer Research Laboratory, China Medical University Hospital, Taichung, Taiwan, ROC; Graduate Institute of Clinical Medical Science, China Medical University, Taichung, Taiwan, ROC.
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7
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Kosova AA, Lavrik OI, Khodyreva SN. Role of Ku antigen in the repair of apurinic/apyrimidinic sites in DNA. Mol Biol 2015. [DOI: 10.1134/s0026893315010070] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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8
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Shamanna RA, Singh DK, Lu H, Mirey G, Keijzers G, Salles B, Croteau DL, Bohr VA. RECQ helicase RECQL4 participates in non-homologous end joining and interacts with the Ku complex. Carcinogenesis 2014; 35:2415-24. [PMID: 24942867 DOI: 10.1093/carcin/bgu137] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
RECQL4, a member of the RecQ helicase family, is a multifunctional participant in DNA metabolism. RECQL4 protein participates in several functions both in the nucleus and in the cytoplasm of the cell, and mutations in human RECQL4 are associated with three genetic disorders: Rothmund-Thomson, RAPADILINO and Baller-Gerold syndromes. We previously reported that RECQL4 is recruited to laser-induced DNA double-strand breaks (DSB). Here, we have characterized the functional roles of RECQL4 in the non-homologous end joining (NHEJ) pathway of DSB repair. In an in vitro NHEJ assay that depends on the activity of DNA-dependent protein kinase (DNA-PK), extracts from RECQL4 knockdown cells display reduced end-joining activity on DNA substrates with cohesive and non-cohesive ends. Depletion of RECQL4 also reduced the end joining activity on a GFP reporter plasmid in vivo. Knockdown of RECQL4 increased the sensitivity of cells to γ-irradiation and resulted in accumulation of 53BP1 foci after irradiation, indicating defects in the processing of DSB. We find that RECQL4 interacts with the Ku70/Ku80 heterodimer, part of the DNA-PK complex, via its N-terminal domain. Further, RECQL4 stimulates higher order DNA binding of Ku70/Ku80 to a blunt end DNA substrate. Taken together, these results implicate that RECQL4 participates in the NHEJ pathway of DSB repair via a functional interaction with the Ku70/Ku80 complex. This is the first study to provide both in vitro and in vivo evidence for a role of a RecQ helicase in NHEJ.
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Affiliation(s)
- Raghavendra A Shamanna
- Laboratory of Molecular Gerontology, Biomedical Research Center, National Institute on Aging, NIH, 251 Bayview Boulevard, Baltimore, MD 21224, USA, INRA, Université de Toulouse, UMR1331, Toxalim, Research Centre in Food Toxicology, F-31027 Toulouse, France and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Dharmendra Kumar Singh
- Laboratory of Molecular Gerontology, Biomedical Research Center, National Institute on Aging, NIH, 251 Bayview Boulevard, Baltimore, MD 21224, USA, INRA, Université de Toulouse, UMR1331, Toxalim, Research Centre in Food Toxicology, F-31027 Toulouse, France and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Huiming Lu
- Laboratory of Molecular Gerontology, Biomedical Research Center, National Institute on Aging, NIH, 251 Bayview Boulevard, Baltimore, MD 21224, USA, INRA, Université de Toulouse, UMR1331, Toxalim, Research Centre in Food Toxicology, F-31027 Toulouse, France and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Gladys Mirey
- INRA, Université de Toulouse, UMR1331, Toxalim, Research Centre in Food Toxicology, F-31027 Toulouse, France and
| | - Guido Keijzers
- Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Bernard Salles
- INRA, Université de Toulouse, UMR1331, Toxalim, Research Centre in Food Toxicology, F-31027 Toulouse, France and
| | - Deborah L Croteau
- Laboratory of Molecular Gerontology, Biomedical Research Center, National Institute on Aging, NIH, 251 Bayview Boulevard, Baltimore, MD 21224, USA, INRA, Université de Toulouse, UMR1331, Toxalim, Research Centre in Food Toxicology, F-31027 Toulouse, France and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Vilhelm A Bohr
- Laboratory of Molecular Gerontology, Biomedical Research Center, National Institute on Aging, NIH, 251 Bayview Boulevard, Baltimore, MD 21224, USA, INRA, Université de Toulouse, UMR1331, Toxalim, Research Centre in Food Toxicology, F-31027 Toulouse, France and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
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9
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Wang B, Xie M, Li R, Owonikoko TK, Ramalingam SS, Khuri FR, Curran WJ, Wang Y, Deng X. Role of Ku70 in deubiquitination of Mcl-1 and suppression of apoptosis. Cell Death Differ 2014; 21:1160-9. [PMID: 24769731 DOI: 10.1038/cdd.2014.42] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 02/17/2014] [Accepted: 03/06/2014] [Indexed: 01/12/2023] Open
Abstract
Mcl-1 is a unique antiapoptotic Bcl2 family member with a short half-life due to its rapid turnover through ubiquitination. We discovered that Ku70, a DNA double-strand break repair protein, functions as a deubiquitinase to stabilize Mcl-1. Ku70 knockout in mouse embryonic fibroblast (MEF) cells or depletion from human lung cancer H1299 cells leads to the accumulation of polyubiquitinated Mcl-1 and a reduction in its half-life and protein expression. Conversely, expression of exogenous Ku70 in Ku70(-/-) MEF cells restores Mcl-1 expression. Subcellular fractionation indicates that Ku70 extensively colocalizes with Mcl-1 in mitochondria, endoplasmic reticulum and nucleus in H1299 cells. Ku70 directly interacts with Mcl-1 via its C terminus (that is, aa 536-609), which is required and sufficient for deubiquitination and stabilization of Mcl-1, leading to suppression of apoptosis. Purified Ku70 protein directly deubiquitinates Mcl-1 by removing K48-linked polyubiquitin chains. Ku70 knockdown not only promotes Mcl-1 turnover but also enhances antitumor efficacy of the BH3-mimetic ABT-737 in human lung cancer xenografts. These findings identify Ku70 as a novel Mcl-1 deubiquitinase that could be a potential target for cancer therapy by manipulating Mcl-1 deubiquitination.
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Affiliation(s)
- B Wang
- Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - M Xie
- Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - R Li
- Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - T K Owonikoko
- Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - S S Ramalingam
- Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - F R Khuri
- Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - W J Curran
- Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - Y Wang
- Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - X Deng
- Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
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10
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Hang LE, Lopez CR, Liu X, Williams JM, Chung I, Wei L, Bertuch AA, Zhao X. Regulation of Ku-DNA association by Yku70 C-terminal tail and SUMO modification. J Biol Chem 2014; 289:10308-10317. [PMID: 24567323 DOI: 10.1074/jbc.m113.526178] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Ku70-Ku80 ring complex encloses DNA ends to facilitate telomere maintenance and DNA break repair. Many studies focus on the ring-forming regions of subunits Ku70 and Ku80. Less is known about the Ku70 C-terminal tail, which lies outside the ring. Our results suggest that this region is responsible for dynamic sumoylation of Yku70 upon DNA association in budding yeast. Mutating a cluster of five lysines in this region largely eliminates Yku70 sumoylation. Chromatin immunoprecipitation analyses show that yku70 mutants with these lysines replaced by arginines exhibit reduced Ku-DNA association at both telomeres and internal DNA breaks. Consistent with this physical evidence, Yku70 sumoylation deficiency is associated with impaired ability to block DNA end resection and suppression of multiple defects caused by inefficient resection. Correlating with these, yku70 mutants with reduced sumoylation levels exhibit shorter telomeres, increased G overhang levels, and altered levels of non-homologous end joining. We also show that diminution of sumoylation does not affect Yku70 protein levels or its interactions with protein and RNA partners. These results suggest a model whereby Yku70 sumoylation upon DNA association strengthens Ku-DNA interaction to promote multiple functions of Ku.
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Affiliation(s)
- Lisa E Hang
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065; Programs in Biochemistry, Cell, and Molecular Biology, Weill Graduate School of Medical Sciences of Cornell University, New York, New York 10065
| | | | - Xianpeng Liu
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065
| | - Jaime M Williams
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
| | - Inn Chung
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065
| | - Lei Wei
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065; Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, New York 10065
| | - Alison A Bertuch
- Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
| | - Xiaolan Zhao
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065; Programs in Biochemistry, Cell, and Molecular Biology, Weill Graduate School of Medical Sciences of Cornell University, New York, New York 10065; Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, New York 10065.
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11
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Deletion of individual Ku subunits in mice causes an NHEJ-independent phenotype potentially by altering apurinic/apyrimidinic site repair. PLoS One 2014; 9:e86358. [PMID: 24466051 PMCID: PMC3900520 DOI: 10.1371/journal.pone.0086358] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 12/07/2013] [Indexed: 01/25/2023] Open
Abstract
Ku70 and Ku80 form a heterodimer called Ku that forms a holoenzyme with DNA dependent-protein kinase catalytic subunit (DNA-PKCS) to repair DNA double strand breaks (DSBs) through the nonhomologous end joining (NHEJ) pathway. As expected mutating these genes in mice caused a similar DSB repair-defective phenotype. However, ku70-/- cells and ku80-/- cells also appeared to have a defect in base excision repair (BER). BER corrects base lesions, apurinic/apyrimidinic (AP) sites and single stand breaks (SSBs) utilizing a variety of proteins including glycosylases, AP endonuclease 1 (APE1) and DNA Polymerase β (Pol β). In addition, deleting Ku70 was not equivalent to deleting Ku80 in cells and mice. Therefore, we hypothesized that free Ku70 (not bound to Ku80) and/or free Ku80 (not bound to Ku70) possessed activity that influenced BER. To further test this hypothesis we performed two general sets of experiments. The first set showed that deleting either Ku70 or Ku80 caused an NHEJ-independent defect. We found ku80-/- mice had a shorter life span than dna-pkcs-/- mice demonstrating a phenotype that was greater than deleting the holoenzyme. We also found Ku70-deletion induced a p53 response that reduced the level of small mutations in the brain suggesting defective BER. We further confirmed that Ku80-deletion impaired BER via a mechanism that was not epistatic to Pol β. The second set of experiments showed that free Ku70 and free Ku80 could influence BER. We observed that deletion of either Ku70 or Ku80, but not both, increased sensitivity of cells to CRT0044876 (CRT), an agent that interferes with APE1. In addition, free Ku70 and free Ku80 bound to AP sites and in the case of Ku70 inhibited APE1 activity. These observations support a novel role for free Ku70 and free Ku80 in altering BER.
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12
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Li H, Marple T, Hasty P. Ku80-deleted cells are defective at base excision repair. Mutat Res 2013; 745-746:16-25. [PMID: 23567907 DOI: 10.1016/j.mrfmmm.2013.03.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 03/18/2013] [Accepted: 03/29/2013] [Indexed: 11/27/2022]
Abstract
Ku80 forms a heterodimer with Ku70, called Ku, that repairs DNA double-strand breaks (DSBs) via the nonhomologous end joining (NHEJ) pathway. As a consequence of deleting NHEJ, Ku80-mutant cells are hypersensitive to agents that cause DNA DSBs like ionizing radiation. Here we show that Ku80 deletion also decreased resistance to ROS and alkylating agents that typically cause base lesions and single-strand breaks (SSBs). This is unusual since base excision repair (BER), not NHEJ, typically repairs these types of lesions. However, we show that deletion of another NHEJ protein, DNA ligase IV (Lig4), did not cause hypersensitivity to these agents. In addition, the ROS and alkylating agents did not induce γ-H2AX foci that are diagnostic of DSBs. Furthermore, deletion of Ku80, but not Lig4 or Ku70, reduced BER capacity. Ku80 deletion also impaired BER at the initial lesion recognition/strand scission step; thus, involvement of a DSB is unlikely. Therefore, our data suggests that Ku80 deletion impairs BER via a mechanism that does not repair DSBs.
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Affiliation(s)
- Han Li
- The Department of Molecular Medicine, The University of Texas Health Science Center, San Antonio, TX 78245-3207, USA
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13
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Li JJ, Gu QH, Li M, Yang HP, Cao LM, Hu CP. Role of Ku70 and Bax in epigallocatechin-3-gallate-induced apoptosis of A549 cells in vivo. Oncol Lett 2012; 5:101-106. [PMID: 23255902 DOI: 10.3892/ol.2012.972] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 08/15/2012] [Indexed: 11/06/2022] Open
Abstract
EGCG (epigallocatechin-3-gallate), the major catechin found in green tea, has been demonstrated to inhibit proliferation and induce apoptosis in a number of types of tumors. Recent studies reveal that EGCG has various anticancer effects. This study investigated a further possible molecular mechanism of the anticancer effects of EGCG in murine lung cancer xenografts. In the study, A549 human lung cancer cells were injected into nude mice. Tumor volume was used to measure cancer cell growth. The weight of the animals was used to assess the toxicity of the drugs. The expression of protein and mRNA was assayed by western blot analysis and RT-PCR, respectively. The interaction between Bax and Ku70 was determined by immunoprecipitation. Our results suggest that EGCG induced A549 lung cancer cell apoptosis in vivo, and had less toxic effects compared to classical anticancer drugs. EGCG may inhibit the surrogate markers of proliferation and apoptosis (caspase 3) in A549 tumor xenografts in vivo. In addition, EGCG downregulated the expression of Bcl-xl and upregulated the expression of Bax mRNA and protein. Further experiments indicated that EGCG downregulated the protein expression of Ku70 and interrupted the binding of Ku70 and Bax. This is the first study demonstrating that the induction of apoptosis by EGCG may be caused by the downregulation of Ku70 and that EGCG disrupts the interaction between Ku70 and Bax in lung cancer.
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Affiliation(s)
- Jing-Jing Li
- Department of Respiratory Medicine, Xiangya Hospital, Central South University, Changsha, Hunan 410008, P.R. China
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14
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Kerr E, Holohan C, McLaughlin KM, Majkut J, Dolan S, Redmond K, Riley J, McLaughlin K, Stasik I, Crudden M, Van Schaeybroeck S, Fenning C, O'Connor R, Kiely P, Sgobba M, Haigh D, Johnston PG, Longley DB. Identification of an acetylation-dependant Ku70/FLIP complex that regulates FLIP expression and HDAC inhibitor-induced apoptosis. Cell Death Differ 2012; 19:1317-27. [PMID: 22322857 PMCID: PMC3392639 DOI: 10.1038/cdd.2012.8] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Revised: 12/21/2011] [Accepted: 12/21/2011] [Indexed: 12/31/2022] Open
Abstract
FLIP is a potential anti-cancer therapeutic target that inhibits apoptosis by blocking caspase 8 activation by death receptors. We report a novel interaction between FLIP and the DNA repair protein Ku70 that regulates FLIP protein stability by inhibiting its polyubiquitination. Furthermore, we found that the histone deacetylase (HDAC) inhibitor Vorinostat (SAHA) enhances the acetylation of Ku70, thereby disrupting the FLIP/Ku70 complex and triggering FLIP polyubiquitination and degradation by the proteasome. Using in vitro and in vivo colorectal cancer models, we further demonstrated that SAHA-induced apoptosis is dependant on FLIP downregulation and caspase 8 activation. In addition, an HDAC6-specific inhibitor Tubacin recapitulated the effects of SAHA, suggesting that HDAC6 is a key regulator of Ku70 acetylation and FLIP protein stability. Thus, HDAC inhibitors with anti-HDAC6 activity act as efficient post-transcriptional suppressors of FLIP expression and may, therefore, effectively act as 'FLIP inhibitors'.
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Affiliation(s)
- E Kerr
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - C Holohan
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - K M McLaughlin
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - J Majkut
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - S Dolan
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - K Redmond
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - J Riley
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - K McLaughlin
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - I Stasik
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - M Crudden
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - S Van Schaeybroeck
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - C Fenning
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - R O'Connor
- Cell Biology Laboratory, Department of Biochemistry, University College Cork, Cork, Republic of Ireland
| | - P Kiely
- Cell Biology Laboratory, Department of Biochemistry, University College Cork, Cork, Republic of Ireland
| | - M Sgobba
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - D Haigh
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - P G Johnston
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
| | - D B Longley
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK
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15
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Wang W, Gao Y, Yan F, Wang M, Hu F, Wang D, Cao Q, Qin C, Yin C, Zhang Z, Pan X. Association of Ku70 A-31G polymorphism and risk of renal cell carcinoma in a Chinese population. DNA Cell Biol 2012; 31:1314-20. [PMID: 22455395 DOI: 10.1089/dna.2011.1540] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The DNA repair gene Ku70 plays a key role in the DNA double-strand breaks (DSBs) repair system. Defects in DSBs repair capacity can lead to genomic instability. We hypothesized that the Ku70 A-31G polymorphism (rs132770) was associated with the risk of renal cell carcinoma (RCC). In a hospital-based case-control study of 620 RCC patients and 623 cancer-free controls frequency matched by age and sex, we genotyped the functional polymorphism Ku70 A-31G (rs132770). Thirty-eight normal renal tissue samples with different genotypes were tested to estimate the Ku70 mRNA expression by real-time quantitative reverse transcription. Compared with the GG genotype, the GA and GA/AA genotypes had a significantly decreased risk of RCC [adjusted odds ratio (OR) = 0.62, 95% confidence interval (CI) = 0.44-0.87 for GA, and OR = 0.62, 95% CI = 0.45-0.86 for GA/AA]. The in vivo experiments with normal renal tissues revealed that a statistically significantly higher Ku70 mRNA expression was identified in samples with GA/AA genotypes compared with those with GG genotypes (p = 0.001). These results suggested that the Ku70 A-31G polymorphism is involved in the etiology of RCC and, thus, may be a marker for genetic susceptibility to RCC in the Chinese populations.
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Affiliation(s)
- Wei Wang
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
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16
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Accumulation of Ku70 at DNA double-strand breaks in living epithelial cells. Exp Cell Res 2011; 317:2429-37. [PMID: 21820429 DOI: 10.1016/j.yexcr.2011.07.018] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 07/13/2011] [Accepted: 07/18/2011] [Indexed: 12/18/2022]
Abstract
Ku70 and Ku80 play an essential role in the DNA double-strand break (DSB) repair pathway, i.e., nonhomologous DNA-end-joining (NHEJ). No accumulation mechanisms of Ku70 at DSBs have been clarified in detail, although the accumulation mechanism of Ku70 at DSBs plays key roles in regulating the NHEJ activity. Here, we show the essential domains for the accumulation and function of Ku70 at DSBs in living lung epithelial cells. Our results showed that EGFP-Ku70 accumulation at DSBs began immediately after irradiation. Our findings demonstrate that three domains of Ku70, i.e., the α/β, DNA-binding, and Ku80-binding domains, but not the SAP domain, are necessary for the accumulation at or recognition of DSBs in the early stage after irradiation. Moreover, our findings demonstrate that the leucine at amino acid 385 of Ku70 in the Ku80-binding domain, but not the three target amino acids for acetylation in the DNA-binding domain, is involved in the localization and accumulation of Ku70 at DSBs. Furthermore, accumulations of XRCC4 and XLF, but not that of Artemis, at DSBs are dependent on the presence of Ku70. These findings suggest that Artemis can work in not only the Ku-dependent repair process, but also the Ku-independent process at DSBs in living epithelial cells.
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17
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Zheng Y, Ao Z, Wang B, Jayappa KD, Yao X. Host protein Ku70 binds and protects HIV-1 integrase from proteasomal degradation and is required for HIV replication. J Biol Chem 2011; 286:17722-35. [PMID: 21454661 DOI: 10.1074/jbc.m110.184739] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
HIV-1 integrase (IN) is a key viral enzymatic protein acting in several viral replication steps, including integration. IN has been shown to be an unstable protein degraded by the N-end rule pathway through the host ubiquitin-proteasome machinery. However, it is still not fully understood how this viral protein is protected from the host ubiquitin-proteasome system within cells during HIV replication. In the present study, we provide evidence that the host protein Ku70 interacts with HIV-1 IN and protects it from the Lys(48)-linked polyubiquitination proteasomal pathway. Moreover, Ku70 is able to down-regulate the overall protein polyubiquitination level within the host cells and to specifically deubiquitinate IN through their interaction. Mutagenic studies revealed that the C terminus of IN (residues 230-288) is required for IN binding to the N-terminal part of Ku70 (Ku70(1-430)), and their interaction is independent of Ku70/80 heterodimerization. Finally, knockdown of Ku70 expression in both virus-producing and target CD4(+) T cells significantly disrupted HIV-1 replication and rendered two-long terminal repeat circles and integration undetectable, indicating that Ku70 is required for both the early and the late stages of the HIV-1 life cycle. Interestingly, Ku70 was incorporated into the progeny virus in an IN-dependent way. We proposed that Ku70 may interact with IN during viral assembly and accompany HIV-1 IN upon entry into the new target cells, acting to 1) protect IN from the host defense system and 2) assist IN integration activity. Overall, this report provides another example of how HIV-1 hijacks host cellular machinery to protect the virus itself and to facilitate its replication.
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Affiliation(s)
- Yingfeng Zheng
- Laboratory of Molecular Human Retrovirology, Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
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18
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Urano M, He F, Minami A, Ling CC, Li GC. Response to multiple radiation doses of human colorectal carcinoma cells infected with recombinant adenovirus containing dominant-negative Ku70 fragment. Int J Radiat Oncol Biol Phys 2010; 77:877-85. [PMID: 20510198 DOI: 10.1016/j.ijrobp.2009.12.062] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Revised: 12/23/2009] [Accepted: 12/28/2009] [Indexed: 11/30/2022]
Abstract
PURPOSE To investigate the effect of recombinant replication-defective adenovirus containing dominant-negative Ku70 fragment on the response of tumor cells to multiple small radiation doses. Our ultimate goal is to demonstrate the feasibility of using this virus in gene-radiotherapy to enhance the radiation response of tumor cells. METHODS AND MATERIALS Human colorectal HCT8 and HT29 carcinoma cells were plated in glass tubes, infected with virus (25 multiplicity of infection), and irradiated with a single dose or zero to five doses of 3 Gy each at 6-h intervals. Hypoxia was induced by flushing with 100% nitrogen gas. The cells were trypsinized 0 or 6 h after the final irradiation, and cell survival was determined by colony formation. The survival data were fitted to linear-quadratic model or exponential line. RESULTS Virus infection enhanced the radiation response of the HCT8 and HT29 cells. The virus enhancement ratio for single-dose irradiation at a surviving fraction of 0.1 was approximately 1.3 for oxic and hypoxic HCT8 and 1.4 and 1.1 for oxic and hypoxic HT29, respectively. A similar virus enhancement ratio of 1.2-1.3 was observed for both oxic and hypoxic cells irradiated with multiple doses; however, these values were smaller than the values found for dominant-negative Ku70-transfected Rat-1 cells. This difference has been discussed. The oxygen enhancement ratio for HCT8 and HT29 receiving fractionated doses was 1.2 and 2.0, respectively, and virus infection altered them slightly. CONCLUSION Infection of recombinant replication-defective adenovirus containing dominant-negative Ku70 fragment enhanced the response of human colorectal cancer cells to single and multiple radiation doses.
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Affiliation(s)
- Muneyasu Urano
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
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19
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Li H, Choi YJ, Hanes MA, Marple T, Vogel H, Hasty P. Deleting Ku70 is milder than deleting Ku80 in p53-mutant mice and cells. Oncogene 2009; 28:1875-8. [DOI: 10.1038/onc.2009.57] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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20
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Urano M, Huang Y, He F, Minami A, Ling CC, Li GC. Response to multiple radiation doses of fibroblasts over-expressing dominant negative Ku70. Int J Radiat Oncol Biol Phys 2008; 71:533-41. [PMID: 18374502 DOI: 10.1016/j.ijrobp.2007.12.061] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2006] [Revised: 11/21/2007] [Accepted: 12/22/2007] [Indexed: 11/30/2022]
Abstract
PURPOSE To evaluate the response of cells over-expressing dominant negative (DN) Ku70 to single and multiple small radiation doses. METHODS AND MATERIALS Clones of fibroblasts over-expressing DNKu70, DNKu70-7, DNKu70-11, and parental Rat-1 cells were irradiated under oxic or hypoxic conditions with single or multiple doses. Cells were trypsinized 0 or 6 h after irradiation to determine surviving fraction (SF). RESULTS Oxic DNKu70-7 or -11 cells trypsinized 6 h after irradiation were 1.52 or 1.25 and 1.28 or 1.15 times more sensitive than oxic Rat-1 at SF of 0.5 and 0.1, respectively. Hypoxic DNKu70-7 or -11 cells trypsinized 6 h after irradiation were 1.44 or 1.70 and 1.33 or 1.51 times more sensitive than hypoxic Rat-1 at SF of 0.5 and 0.1, respectively. To the multiple doses, oxic and hypoxic DNKu70-7 or -11 cells were 1.35 or 1.37 and 2.23 or 4.61 times more sensitive than oxic and hypoxic Rat-1, respectively, resulting in very small oxygen enhancement ratios. Namely, enhancement caused by DNKu70 under hypoxia after multiple doses was greater than that under oxic conditions and greater than that after single dose. CONCLUSIONS Over-expression of DNKu70 enhances cells' response to radiation given as a single dose and as multiple small doses. The enhancement after multiple doses was stronger under hypoxic than under oxic conditions. These results encourage the use of DNKu70 fragment in a gene-radiotherapy.
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Affiliation(s)
- Muneyasu Urano
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
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21
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Wang SY, Peng L, Li CP, Li AP, Zhou JW, Zhang ZD, Liu QZ. Genetic variants of the XRCC7 gene involved in DNA repair and risk of human bladder cancer. Int J Urol 2008; 15:534-9. [PMID: 18422577 DOI: 10.1111/j.1442-2042.2008.02049.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To investigate the association between the polymorphisms of the KU70 and X-ray repair cross complementing group 7 (XRCC7) genes and the risk of bladder cancer. METHODS This hospital-based case-control study included 213 patients with newly diagnosed bladder transitional cell carcinoma and 235 cancer-free controls frequency-matched by age and sex. Two polymorphisms, KU70 and XRCC7, using a method involving polymerase chain reaction-restriction fragment length polymorphism were genotyped. RESULTS The risk of bladder cancer decreased in a dose-response manner as the number of XRCC76721G alleles increased (adjusted odds ratio [OR] = 0.70, 95% confident interval [CI] = 0.47-1.03 for 6721GT and OR = 0.31, 95% CI = 0.10-0.99 for 6721GG; P(trend) = 0.013). However, when we used 6721 (GT + GG) as the reference, we found a statistically significant increased risk of bladder cancer associated with the 6721TT genotype (OR = 1.53, 95% CI = 1.04-2.25). In the stratification analysis, this increased risk was more pronounced among subgroups of patients aged >65 years (OR = 2.27; 95% CI = 1.25-4.10) and ever smokers (OR = 2.06, 95% CI = 1.15-3.68). Furthermore, we observed a 3.24-fold increased risk (95% CI = 1.35-7.78) for smokers aged >65 years carrying 6721TT genotype compared with those carrying the 6721 (GG + GT) genotype. However, the KU70-61C > G polymorphism was not associated with a significantly increased risk of bladder cancer. CONCLUSIONS The XRCC7 but not the KU70 polymorphism appears to be involved in the etiology of human bladder cancer. Larger studies with more detailed data on environmental exposure are needed to verify these initial findings.
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Affiliation(s)
- Shou-Yu Wang
- Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China
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22
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Koike M, Koike A. Accumulation of Ku80 proteins at DNA double-strand breaks in living cells. Exp Cell Res 2007; 314:1061-70. [PMID: 18164703 DOI: 10.1016/j.yexcr.2007.11.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2007] [Revised: 11/15/2007] [Accepted: 11/15/2007] [Indexed: 01/14/2023]
Abstract
Ku plays a key role in multiple nuclear processes, e.g., DNA double-strand break (DSB) repair. The regulation mechanism of the localizations of Ku70 and Ku80 plays a key role in regulating the multiple functions of Ku. Although numerous biochemical studies in vitro have elucidated the DNA binding mechanism of Ku, no accumulation mechanisms of Ku70 and Ku80 at DSBs have been clarified in detail in vivo. In this study, we examined the accumulation mechanism of Ku80 at DSBs in living cells. EGFP-Ku80 accumulation at DSBs began immediately after irradiation. On the other hand, our data show that Ku70 alone, which has DNA binding activity independent of Ku80, cannot accumulate at the DSBs, whereas Ku70 bound to Ku80 can. The deletion of the C-terminal DNA-PKcs-binding domain and the mutation at the SUMOylation site of Ku80 had no effect on Ku80 accumulation. Unexpectedly, N-terminal deletion mutants of Ku80 fully lost their accumulation activity, although the mutants retained their Ku70 binding activity. Altogether, these data demonstrate that Ku80 is essential for Ku70 accumulation at DSBs. Furthermore, three domains of Ku80, i.e., the N-terminal alpha/beta, the DNA-binding, and Ku70-binding domains, seem to necessary for the accumulation at or recognition of DSBs in the early stage after irradiation.
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Affiliation(s)
- Manabu Koike
- DNA Repair Gene Res., National Institute of Radiological Sciences, Chiba, Japan.
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23
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Chen CS, Wang YC, Yang HC, Huang PH, Kulp SK, Yang CC, Lu YS, Matsuyama S, Chen CY, Chen CS. Histone deacetylase inhibitors sensitize prostate cancer cells to agents that produce DNA double-strand breaks by targeting Ku70 acetylation. Cancer Res 2007; 67:5318-27. [PMID: 17545612 DOI: 10.1158/0008-5472.can-06-3996] [Citation(s) in RCA: 159] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This study reports a histone deacetylation-independent mechanism whereby histone deacetylase (HDAC) inhibitors sensitize prostate cancer cells to DNA-damaging agents by targeting Ku70 acetylation. Ku70 represents a crucial component of the nonhomologous end joining repair machinery for DNA double-strand breaks (DSB). Our data indicate that pretreatment of prostate cancer cells with HDAC inhibitors (trichostatin A, suberoylanilide hydroxamic acid, MS-275, and OSU-HDAC42) led to increased Ku70 acetylation accompanied by reduced DNA-binding affinity without disrupting the Ku70/Ku80 heterodimer formation. As evidenced by increased Ser(139)-phosphorylated histone H2AX (gammaH2AX), impaired Ku70 function diminished cellular capability to repair DNA DSBs induced by bleomycin, doxorubicin, and etoposide, thereby enhancing their cell-killing effect. This sensitizing effect was most prominent when cells were treated with HDAC inhibitors and DNA-damaging agents sequentially. Mimicking acetylation was done by replacing K282, K317, K331, K338, K539, or K542 with glutamine via site-directed mutagenesis, which combined with computer docking analysis was used to analyze the role of these lysine residues in the interactions of Ku70 with DNA broken ends. Mutagenesis of K282, K338, K539, or K542 suppressed the activity of Ku70 to bind DNA, whereas mutagenesis of K317 or K331 with glutamine had no significant effect. Moreover, overexpression of K282Q or K338Q rendered DU-145 cells more susceptible to the effect of DNA-damaging agents on gammaH2AX formation and cell killing. Overall, the ability of HDAC inhibitors to regulate cellular ability to repair DNA damage by targeting Ku70 acetylation underlies the viability of their combination with DNA-damaging agents as a therapeutic strategy for prostate cancer.
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Affiliation(s)
- Chang-Shi Chen
- Division of Medicinal Chemistry, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210, USA
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24
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Bladen CL, Navarre S, Dynan WS, Kozlowski DJ. Expression of the Ku70 subunit (XRCC6) and protection from low dose ionizing radiation during zebrafish embryogenesis. Neurosci Lett 2007; 422:97-102. [PMID: 17630212 PMCID: PMC2075087 DOI: 10.1016/j.neulet.2007.05.045] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 04/20/2007] [Accepted: 05/11/2007] [Indexed: 10/23/2022]
Abstract
The Ku70 protein, a product of the XRCC6 gene, is a component of the nonhomologous end-joining (NHEJ) pathway of DNA repair, which protects cells from the effects of radiation-induced DNA damage. Although the spatial expression of Ku70 during vertebrate embryogenesis has not been described, DNA repair proteins are generally considered to be "housekeeping" genes, which are required for radioprotection in all cells. Here, we report the cloning and characterization of the zebrafish Ku70 ortholog. In situ hybridization and RT-PCR analyses demonstrate that Ku70 mRNA is maternally provided and expressed uniformly among embryonic blastomeres. Later during embryogenesis, zygotically transcribed Ku70 mRNA specifically accumulates in neural tissue, including the retina and proliferative regions of the developing brain. In the absence of genotoxic stress, morpholino-mediated knockdown of Ku70 expression does not affect zebrafish embryogenesis. However, exposure of Ku70 morpholino-injected embryos to low doses of ionizing radiation leads to marked cell death throughout the developing brain, spinal cord, and tail. These results suggest that Ku70 protein plays a crucial role in protecting the developing nervous system from radiation-induced DNA damage during embryogenesis.
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MESH Headings
- Animals
- Antigens, Nuclear/genetics
- Antigens, Nuclear/isolation & purification
- Antigens, Nuclear/metabolism
- Cell Death/genetics
- Cell Death/radiation effects
- Cell Differentiation/genetics
- Cell Differentiation/radiation effects
- Cytoprotection/genetics
- Cytoprotection/radiation effects
- DNA Damage/genetics
- DNA Damage/radiation effects
- DNA Repair/genetics
- DNA Repair/radiation effects
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/isolation & purification
- DNA-Binding Proteins/metabolism
- Embryo, Nonmammalian/embryology
- Embryo, Nonmammalian/metabolism
- Embryo, Nonmammalian/radiation effects
- Embryonic Development/genetics
- Embryonic Development/radiation effects
- Gene Expression Regulation, Developmental/genetics
- Gene Expression Regulation, Developmental/radiation effects
- Ku Autoantigen
- Molecular Sequence Data
- RNA, Messenger/antagonists & inhibitors
- RNA, Messenger/metabolism
- Radiation Dosage
- Radiation, Ionizing
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
- Species Specificity
- Zebrafish/embryology
- Zebrafish/genetics
- Zebrafish/metabolism
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Affiliation(s)
- Catherine L. Bladen
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA, 30912, USA
| | - Sammy Navarre
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA, 30912, USA
| | - William S. Dynan
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA, 30912, USA
| | - David J. Kozlowski
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA, 30912, USA
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA, 30912, USA
- Corresponding author: IMMAG, CB-2803, Medical College of Georgia,1120 15th Street, Augusta, GA 30912. Phone: (706) 721-8760. Fax: (706) 721-8752. E-mail:
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He F, Li L, Kim D, Wen B, Deng X, Gutin PH, Ling CC, Li GC. Adenovirus-mediated expression of a dominant negative Ku70 fragment radiosensitizes human tumor cells under aerobic and hypoxic conditions. Cancer Res 2007; 67:634-42. [PMID: 17234773 DOI: 10.1158/0008-5472.can-06-1860] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Ku70 is one component of a protein complex, the Ku70/Ku80 heterodimer, which binds to DNA double-strand breaks and activates DNA-dependent protein kinase (DNA-PK), leading to DNA damage repair. Our previous work has confirmed that Ku70 is important for DNA damage repair in that Ku70 deficiency compromises the ability of cells to repair DNA double-strand breaks, increases the radiosensitivity of cells, and enhances radiation-induced apoptosis. Because of the radioresistance of some human cancers, particularly glioblastoma, we examined the use of a radio-gene therapy paradigm to sensitize cells to ionizing radiation. Based on the analysis of the structure-function of Ku70 and the crystal structure of Ku70/Ku80 heterodimer, we designed and identified a candidate dominant negative fragment involving an NH(2)-terminal deletion, and designated it as DNKu70. We generated this mutant construct, stably overexpressed it in Rat-1 cells, and showed that it has a dominant negative effect (i.e., DNKu70 overexpression results in decreased Ku-DNA end-binding activity, and increases radiosensitivity). We then constructed and generated recombinant replication-defective adenovirus, with DNKu70 controlled by the cytomegalovirus promoter, and infected human glioma U-87 MG cells and human colorectal tumor HCT-8 cells. We show that the infected cells significantly express DNKu70 and are greatly radiosensitized under both aerobic and hypoxic conditions. The functional ramification of DNKu70 was further shown in vivo: expression of DNKu70 inhibits radiation-induced DNA-PK catalytic subunit autophosphorylation and prolongs the persistence of gamma-H2AX foci. If radiation-resistant tumor cells could be sensitized by down-regulating the cellular level/activity of Ku/DNA-PK, this approach could be evaluated as an adjuvant to radiation therapy.
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Affiliation(s)
- Fuqiu He
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA
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26
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Koike M, Koike A. The Ku70-binding site of Ku80 is required for the stabilization of Ku70 in the cytoplasm, for the nuclear translocation of Ku80, and for Ku80-dependent DNA repair. Exp Cell Res 2005; 305:266-76. [PMID: 15817152 DOI: 10.1016/j.yexcr.2004.12.027] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2004] [Revised: 11/24/2004] [Accepted: 12/13/2004] [Indexed: 10/25/2022]
Abstract
Ku plays a key role in multiple nuclear processes, e.g., DNA repair, transcription regulation, and replication. It is believed that heterodimerization between Ku70 and Ku80 is essential for Ku-dependent DNA repair, although its role is poorly understood. We previously identified the Ku70-binding site of Ku80. In this study, to understand the role of heterodimerization in the function of Ku, we generated and/or analyzed cell lines stably expressing the EGFP-tagged-wild-type human Ku80, its Ku70-binding mutant, its NLS-dysfunctional mutant, or its double mutant in Ku80-deficient cells. Our results show that the Ku70-binding site of Ku80 is required for the stabilization of Ku70 in the cytoplasm and for the nuclear translocation of Ku80 through its heterodimerization with Ku70. In addition, our results suggest that the nuclear translocation of Ku80 through the Ku70-binding site as well as through the NLS of Ku80 play, at least in part, a role in Ku80-dependent DNA repair. Furthermore, our results suggest the possibility that Ku80 has a DNA DSB repair function independent of Ku70 in the nuclei, in addition to that dependent on Ku70.
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Affiliation(s)
- Manabu Koike
- Radiation Hazards Research Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
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27
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Dudásová Z, Dudás A, Chovanec M. Non-homologous end-joining factors of Saccharomyces cerevisiae. FEMS Microbiol Rev 2005; 28:581-601. [PMID: 15539075 DOI: 10.1016/j.femsre.2004.06.001] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2004] [Revised: 06/02/2004] [Accepted: 06/02/2004] [Indexed: 01/09/2023] Open
Abstract
DNA double-strand breaks (DSB) are considered to be a severe form of DNA damage, because if left unrepaired, they can cause a cell death and, if misrepaired, they can lead to genomic instability and, ultimately, the development of cancer in multicellular organisms. The budding yeast Saccharomyces cerevisiae repairs DSB primarily by homologous recombination (HR), despite the presence of the KU70, KU80, DNA ligase IV and XRCC4 homologues, essential factors of the mammalian non-homologous end-joining (NHEJ) machinery. S. cerevisiae, however, lacks clear DNA-PKcs and ARTEMIS homologues, two important additional components of mammalian NHEJ. On the other hand, S. cerevisiae is endowed with a regulatory NHEJ component, Nej1, which has not yet been found in other organisms. Furthermore, there is evidence in budding yeast for a requirement for the Mre11/Rad50/Xrs2 complex for NHEJ, which does not appear to be the case either in Schizosaccharomyces pombe or in mammals. Here, we comprehensively describe the functions of all the S. cerevisiae NHEJ components identified so far and present current knowledge about the NHEJ process in this organism. In addition, this review depicts S. cerevisiae as a powerful model system for investigating the utilization of either NHEJ or HR in DSB repair.
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Affiliation(s)
- Zuzana Dudásová
- Laboratory of Molecular Genetics, Cancer Research Institute, Slovak Academy of Sciences, Vlárska 7, 833 91 Bratislava 37, Slovak Republic
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28
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Koike M, Koike A. The establishment and characterization of cell lines stably expressing human Ku80 tagged with enhanced green fluorescent protein. JOURNAL OF RADIATION RESEARCH 2004; 45:119-125. [PMID: 15133299 DOI: 10.1269/jrr.45.119] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The Ku protein is a complex of two subunits, Ku70 and Ku80, and it plays a role in multiple nuclear processes, e.g., nonhomologous DNA-end-joining (NHEJ), chromosome maintenance, and transcription regulation. On the other hand, several studies have reported a cytoplasmic or cell surface localization of Ku in various cell types. The mechanism underlying the regulation of all the diverse functions of Ku is still unclear, though the mechanism that regulates the nuclear localization of Ku70 and Ku80 appears to play, at least in part, a key role in regulating the physiological function of Ku. In this study, we generated cell lines expressing the human Ku80 tagged with the green fluorescent protein (GFP) color variants in Ku80-deficient cells, i.e., xrs-6 derived from CHO-K1. Although Ku70, as well as Ku80, was undetectable in xrs-6 cells, it was seen in these transformants at a level similar to the level of CHO-K1. Furthermore, etoposide- and radiosensitive phenotype of xrs-6 cells were corrected by an introduction of the tagged Ku80. Moreover, the tagged Ku80 suppressed apoptosis triggered by DNA damage. These results demonstrate that fusion to the GFP color variants does not interfere with the functions of the Ku80 in the Ku-dependent DSB repair. Therefore, these transformants might be useful not only in the analysis of Ku80 behavior, but also in an analysis of the dynamics of the NHEJ repair process.
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Affiliation(s)
- Manabu Koike
- Radiation Hazards Research Group, National Institute of Radiological Sciences, Chiba, Japan.
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29
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Roy R, Meier B, McAinsh AD, Feldmann HM, Jackson SP. Separation-of-function mutants of yeast Ku80 reveal a Yku80p-Sir4p interaction involved in telomeric silencing. J Biol Chem 2003; 279:86-94. [PMID: 14551211 DOI: 10.1074/jbc.m306841200] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Saccharomyces cerevisiae Ku heterodimer comprising Yku70p and Yku80p is involved in telomere maintenance and DNA repair by the pathway of non-homologous end joining. It is also a key regulator of transcriptional silencing of genes placed in close proximity to telomeres. Here, we describe the identification of separation-of-function mutants of Yku80p that exhibit defects in silencing but not DNA repair and show that these mutations map to an evolutionarily conserved domain within Yku80p. Furthermore, we reveal that Yku80p interacts with the silent information regulator protein Sir4p and that this interaction is mediated by the N-terminal 200 amino acid residues of Sir4p. Notably, this interaction also requires the region of Yku80p that contains the sites of the silencing defective mutations. Finally, we show that these mutations impair the Yku80p-Sir4p interaction and recruitment of Sir3p to telomeric regions in vivo. Taken together with other data, these findings indicate that the Yku80p-Sir4p interaction plays a vital role in the assembly of telomeric heterochromatin.
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Affiliation(s)
- Rajat Roy
- Wellcome Trust/Cancer Research UK Institute of Cancer and Developmental Biology, and Deparment of Zoology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
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30
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Sawada M, Sun W, Hayes P, Leskov K, Boothman DA, Matsuyama S. Ku70 suppresses the apoptotic translocation of Bax to mitochondria. Nat Cell Biol 2003; 5:320-9. [PMID: 12652308 DOI: 10.1038/ncb950] [Citation(s) in RCA: 294] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2002] [Revised: 12/02/2002] [Accepted: 02/21/2003] [Indexed: 01/28/2023]
Abstract
Bax induces mitochondrial-dependent cell death signals in mammalian cells. However, the mechanism of how Bax is kept inactive has remained unclear. Yeast-based functional screening of Bax inhibitors from mammalian cDNA libraries identified Ku70 as a new Bax suppressor. Bax-mediated apoptosis was suppressed by overexpression of Ku70 in mammalian cells, but enhanced by downregulation of Ku70. We found that Ku70 interacts with Bax, and that the carboxyl terminus of Ku70 and the amino terminus of Bax are required for this interaction. Bax is known to translocate from the cytosol to mitochondria when cells receive apoptotic stimuli. We found that Ku70 blocks the mitochondrial translocation of Bax. These results suggest that in addition to its previously recognized DNA repair activity in the nucleus, Ku70 has a cytoprotective function in the cytosol that controls the localization of Bax.
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Affiliation(s)
- Motoshi Sawada
- Blood Research Institute, The Blood Center of South Eastern Wisconsin, 8727 Watertown Plank Rd, Milwaukee, WI 53226, USA
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31
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Bertinato J, Tomlinson JJ, Schild-Poulter C, Haché RJG. Evidence implicating Ku antigen as a structural factor in RNA polymerase II-mediated transcription. Gene 2003; 302:53-64. [PMID: 12527196 DOI: 10.1016/s0378111902010892] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Ku antigen is an abundant nuclear protein with multiple functions that depend mainly on Ku's prolific and highly verstatile interactions with DNA. We have shown previously that the direct binding of Ku in vitro to negative regulatory element 1 (NRE1), a transcriptional regulatory element in the long terminal repeat of mouse mammary tumour virus, correlates with the regulation of viral transcription by Ku. In this study, we have sought to explore the interaction of Ku with NRE1 in vivo in yeast one-hybrid experiments. Unexpectedly, we observed that human Ku70 carrying a transcriptional activation domain from the yeast Gal4 protein induced transcription of yeast reporter genes pleiotrophically, independent of NRE1, promoter, reporter gene and chromosomal location. Ku80 with the same activation domain had no effect on transcription when expressed alone, but reconstituted activation when co-expressed with native human Ku70. The requirements for transcriptional activation by Ku-Gal4 activation domain proteins correlated with previous descriptions of the requirements for DNA sequence-independent DNA binding by Ku, but were distinct from determinants for DNA-end binding by a truncated Ku heterodimer determined recently by crystallography. These results suggest a preferential targeting of Ku to transcriptionally active chromatin that indicate a possible function for Ku within the RNA polymerase II holoenzyme.
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Affiliation(s)
- Jesse Bertinato
- Graduate Program in Biochemistry, University of Ottawa, The Ottawa Health Research Institute, 725 Parkdale Avenue, Ottawa, Ont. K1Y 4E9, Canada
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32
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Lim JW, Kim H, Kim KH. Expression of Ku70 and Ku80 mediated by NF-kappa B and cyclooxygenase-2 is related to proliferation of human gastric cancer cells. J Biol Chem 2002; 277:46093-100. [PMID: 12324457 DOI: 10.1074/jbc.m206603200] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Cyclooxygenase-2 (COX-2) expression is mediated by constitutive NF-kappaB and regulates human gastric cancer cell growth and proliferation. Inactivating Ku70 or Ku80 suppresses cell growth and induces apoptosis. It has been hypothesized that Ku70 and Ku80 expression may be associated with NF-kappaB activation and COX-2 expression and is involved in cell proliferation. In this study, we found that inhibition of constitutive NF-kappaB (by transfecting a mutated IkappaBalpha gene) and of COX-2 (by treatment with indomethacin and NS-398) suppressed Ku70 and Ku80 expression in cells. Treatment with prostaglandin E(2) adenocarcinoma gastric (AGS) increased expression of these Ku proteins in cells with low constitutive NF-kappaB levels. Inhibition of the Ku DNA end-binding activity by transfection with the C-terminal Ku80 expression gene suppressed cell proliferation. Ku70 or Ku80 overexpression by transfection with the Ku70 or Ku80 expression gene, respectively, enhanced proliferation of cells with low NF-kappaB levels. These results demonstrate that Ku70 and Ku80 expression is mediated by constitutively activated NF-kappaB and constitutively expressed COX-2 in gastric cancer cells and that the high Ku DNA end-binding activity contributes to cell proliferation. Ku70 and Ku80 expression may be related to gastric cell proliferation and carcinogenesis.
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Affiliation(s)
- Joo Weon Lim
- Department of Pharmacology and the Institute of Gastroenterology, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, Korea
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33
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Koike M. Dimerization, translocation and localization of Ku70 and Ku80 proteins. JOURNAL OF RADIATION RESEARCH 2002; 43:223-236. [PMID: 12518983 DOI: 10.1269/jrr.43.223] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The Ku protein is a complex of two subunits, Ku70 and Ku80, and was originally identified as an autoantigen recognized by the sera of patients with autoimmune diseases. The Ku protein plays a key role in multiple nuclear processes, e.g., DNA repair, chromosome maintenance, transcription regulation, and V(D)J recombination. The mechanism underlying the regulation of all the diverse functions of Ku is still unclear, although it seems that Ku is a multifunctional protein that works in nuclei. On the other hand, several studies have reported cytoplasmic or cell surface localization of Ku in various cell types. To clarify the fundamental characteristics of Ku, we have examined the expression, heterodimerization, subcellular localization, chromosome location, and molecular mechanisms of the nuclear transport of Ku70 and Ku80. The mechanism that regulates for nuclear localization of Ku70 and Ku80 appears to play, at least in part, a key role in regulating the physiological function of Ku in vivo.
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Affiliation(s)
- Manabu Koike
- Radiation Hazards Research Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
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34
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Karmakar P, Snowden CM, Ramsden DA, Bohr VA. Ku heterodimer binds to both ends of the Werner protein and functional interaction occurs at the Werner N-terminus. Nucleic Acids Res 2002; 30:3583-91. [PMID: 12177300 PMCID: PMC134248 DOI: 10.1093/nar/gkf482] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The human Werner syndrome protein, WRN, is a member of the RecQ helicase family and contains 3'-->5' helicase and 3'-->5' exonuclease activities. Recently, we showed that the exonuclease activity of WRN is greatly stimulated by the human Ku heterodimer protein. We have now mapped this interaction physically and functionally. The Ku70 subunit specifically interacts with the N-terminus (amino acids 1-368) of WRN, while the Ku80 subunit interacts with its C-terminus (amino acids 940- 1432). Binding between Ku70 and the N-terminus of WRN (amino acids 1-368) is sufficient for stimulation of WRN exonuclease activity. A mutant Ku heterodimer of full-length Ku80 and truncated Ku70 (amino acids 430-542) interacts with C-WRN but not with N-WRN and cannot stimulate WRN exonuclease activity. This emphasizes the functional significance of the interaction between the N-terminus of WRN and Ku70. The interaction between Ku80 and the C-terminus of WRN may modulate some other, as yet unknown, function. The strong interaction between Ku and WRN suggests that these two proteins function together in one or more pathways of DNA metabolism.
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Affiliation(s)
- Parimal Karmakar
- Laboratory of Molecular Gerontology, Box 1, National Institute on Aging, IRP, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224-6825, USA
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35
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Abstract
The recently determined crystal structure of the Ku heterodimer, in both DNA-bound and unbound forms, has shed new light on the mechanism by which this protein fulfills its key role in the repair of DNA double-strand breaks.
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Affiliation(s)
- A J Doherty
- Cambridge Institute for Medical Research, Department of Haematology, University of Cambridge, Hills Road, Cambridge CB2 2XY, UK.
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36
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Zhang Z, Zhu L, Lin D, Chen F, Chen DJ, Chen Y. The three-dimensional structure of the C-terminal DNA-binding domain of human Ku70. J Biol Chem 2001; 276:38231-6. [PMID: 11457852 DOI: 10.1074/jbc.m105238200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The proteins Ku70 (69.8 kDa) and Ku80 (82.7 kDa) form a heterodimeric complex that is an essential component of the nonhomologous end joining DNA double-strand break repair pathway in mammalian cells. Interaction of Ku with DNA is central for the functions of Ku. Ku70, which is mainly responsible for the DNA binding activity of the Ku heterodimer, contains two DNA-binding domains. We have solved the solution structure of the Ku80-independent DNA-binding domain of Ku70 encompassing residues 536-609 using nuclear magnetic resonance spectroscopy. Residues 536-560 are highly flexible and have a random structure but form specific interactions with DNA. Residues 561-609 of Ku70 form a well defined structure with 3 alpha-helices and also interact with DNA. The three-dimensional structure indicates that all conserved hydrophobic residues are in the hydrophobic core and therefore may be important for structural integrity. Most of the conserved positively charged residues are likely to be critical for DNA recognition. The C-terminal DNA-binding domain of Ku70 contains a helix-extended strand-helix motif, which occurs in other nucleic acid-binding proteins and may represent a common nucleic acid binding motif.
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Affiliation(s)
- Z Zhang
- Division of Immunology, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA
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37
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Aravind L, Koonin EV. Prokaryotic homologs of the eukaryotic DNA-end-binding protein Ku, novel domains in the Ku protein and prediction of a prokaryotic double-strand break repair system. Genome Res 2001; 11:1365-74. [PMID: 11483577 PMCID: PMC311082 DOI: 10.1101/gr.181001] [Citation(s) in RCA: 224] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Homologs of the eukaryotic DNA-end-binding protein Ku were identified in several bacterial and one archeal genome using iterative database searches with sequence profiles. Identification of prokaryotic Ku homologs allowed the dissection of the Ku protein sequences into three distinct domains, the Ku core that is conserved in eukaryotes and prokaryotes, a derived von Willebrand A domain that is fused to the amino terminus of the core in eukaryotic Ku proteins, and the newly recognized helix-extension-helix (HEH) domain that is fused to the carboxyl terminus of the core in eukaryotes and in one of the Ku homologs from the Actinomycete Streptomyces coelicolor. The version of the HEH domain present in eukaryotic Ku proteins represents the previously described DNA-binding domain called SAP. The Ku homolog from S. coelicolor contains a distinct version of the HEH domain that belongs to a previously unnoticed family of nucleic-acid-binding domains, which also includes HEH domains from the bacterial transcription termination factor Rho, bacterial and eukaryotic lysyl-tRNA synthetases, bacteriophage T4 endonuclease VII, and several uncharacterized proteins. The distribution of the Ku homologs in bacteria coincides with that of the archeal-eukaryotic-type DNA primase and genes for prokaryotic Ku homologs form predicted operons with genes coding for an ATP-dependent DNA ligase and/or archeal-eukaryotic-type DNA primase. Some of these operons additionally encode an uncharacterized protein that may function as nuclease or an Slx1p-like predicted nuclease containing a URI domain. A hypothesis is proposed that the Ku homolog, together with the associated gene products, comprise a previously unrecognized prokaryotic system for repair of double-strand breaks in DNA.
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Affiliation(s)
- L Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20894, USA.
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38
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Muller C, Monferran S, Gamp AC, Calsou P, Salles B. Inhibition of Ku heterodimer DNA end binding activity during granulocytic differentiation of human promyelocytic cell lines. Oncogene 2001; 20:4373-82. [PMID: 11466618 DOI: 10.1038/sj.onc.1204571] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2001] [Revised: 04/17/2001] [Accepted: 04/30/2001] [Indexed: 11/09/2022]
Abstract
The heterodimeric Ku protein (composed of the Ku 86 and Ku 70 sub-units) is a nuclear protein which binds to DNA termini without sequence specificity. Ku is the DNA-targeting component of the large catalytic sub-unit of the DNA-dependent protein kinase complex that is required for the repair of DNA double-strand breaks in mammalian cells. We studied the expression and function of Ku/DNA-PK during granulocytic differentiation of two human promyelocytic cell lines, HL60 and NB4, a process associated to decreased radiation resistance. After 3 days exposure to differentiating agents (either all-trans-retinoic acid or DMSO), Ku binding to double stranded (ds)-DNA ends declined dramatically whereas Ku protein levels remain unchanged. The nuclear, but not cytoplasmic, fraction of differentiated HL60 cells extracts exhibited a heat-sensitive inhibitory activity towards DNA binding of recombinant Ku heterodimer. We further demonstrate that immunoprecipitation of Ku is impaired in extracts from differentiated cells by using two antibodies that recognize epitopes within the C-terminus DNA binding domains of Ku 70 and Ku 86 proteins. These results favor the hypothesis of a protein interacting with Ku that would prevent DNA binding of heterodimerized Ku protein by steric hindrance.
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Affiliation(s)
- C Muller
- Institut de Pharmacologie et de Biologie Structurale (CNRS, UPR 9062) 205 route de Narbonne, 31077 Toulouse cedex, France
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39
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Abstract
Ku, a heterodimer of Ku70 and Ku80, plays a key role in multiple nuclear processes, e.g. DNA repair, chromosome maintenance, and transcription regulation. Heterodimerization is essential for Ku-dependent DNA repair in vivo, although its role is poorly understood. Some lines of evidence suggest that heterodimerization is required for the stabilization of Ku70 and Ku80. Here we show that the heterodimerization of these Ku subunits is important for their nuclear entry. When transfected into Ku-deficient xrs-6 cells, exogenous Ku70 and Ku80 tagged with green fluorescent protein accumulated into the nucleus, whereas each nuclear localization signal (NLS)-dysfunctional mutant was undetectable in the nucleus, supporting the idea that each Ku can translocate to the nucleus through its own NLS. On the other hand, the nuclear accumulation of each NLS-dysfunctional mutant was markedly enhanced by the presence of an exogenous wild-type counterpart. In Ku-expressing HeLa cells, each NLS-dysfunctional mutant, as well as wild-type Ku70 and Ku80, was still detectable in the nucleus, whereas the double mutant of each Ku subunit with decreased functions of both nuclear targeting and dimerization was undetectable in the nucleus. Our results indicate that each Ku subunit can translocate to the nucleus not only through its own NLS but also through heterodimerization with each other.
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Affiliation(s)
- M Koike
- Genome Research Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
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40
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Abstract
Ku is involved in the metabolism of DNA ends, DNA repair, and the maintenance of telomeres. It consists of a heterodimer of 70- and 80-kDa subunits. Recently we have demonstrated that Ku70 interacted with TRF2, a mammalian telomere-binding protein. Using the same yeast two-hybrid screening system, we now show that Ku70 also interacts with heterochromatin protein 1alpha (HP1alpha), a protein known to be associated with telomeres as well as heterochromatin. HP1 is a suppressor of the position effect variegation in Drosophila and acts as a transcriptional suppressor in mammalian cells. The interaction with Ku70 in the two-hybrid system was confirmed by a glutathione S-transferase pull-down study using bacterial recombinant proteins in vitro. The interaction was also reproduced in vivo in HeLa cells, where endogenous Ku70 coimmunoprecipitated with HP1alpha. This interaction was more effective in acidic pH and weakened considerably as the pH of the reaction buffer was elevated up to 7.5. Ku80 did not interact with HP1alpha directly. The interaction domains of Ku70 and HP1alpha included the Leu-Ser repeat (amino acids 200-385) and the chromo shadow domain, respectively. Ku70 was largely colocalized with transfected HP1alpha but not with a C-terminal deletion mutant, HP1alpha(Delta)C. In contrast to HP1alpha, Ku70 did not repress transcriptional activity of the reporter gene when tethered to DNA after transfection to mammalian cells. The implication of this interaction is discussed.
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Affiliation(s)
- K Song
- Department of Biochemistry, University of Ulsan College of Medicine, Seoul 138-736, Korea
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41
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Bertinato J, Schild-Poulter C, Haché RJ. Nuclear localization of Ku antigen is promoted independently by basic motifs in the Ku70 and Ku80 subunits. J Cell Sci 2001; 114:89-99. [PMID: 11112693 DOI: 10.1242/jcs.114.1.89] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The Ku antigen is a heteromeric (Ku70/Ku80), mostly nuclear protein. Ku participates in multiple nuclear processes from DNA repair to V(D)J recombination to telomere maintenance to transcriptional regulation and serves as a DNA binding subunit and allosteric regulator of DNA-dependent protein kinase. While some evidence suggests that subcellular localization of Ku may be subject to regulation, how Ku gains access to the nucleus is poorly understood. In this work, using a combination of indirect immunofluorescence and direct fluorescence, we have demonstrated that transfer of the Ku heterodimer to the nucleus is determined by basic nuclear localization signals in each of the Ku subunits that function independently. A bipartite basic nuclear localization signal between amino acids 539–556 of Ku70 was observed to be required for nuclear import of full-length Ku70 monomer, while a short Ku80 motif of four amino acids from 565–568 containing three lysines was required for the nuclear import of full-length Ku80. Ku heterodimers containing only one nuclear localization signal accumulated in the nucleus as efficiently as wild-type Ku, while site directed mutagenesis inactivating the basic motifs in each subunit, resulted in a Ku heterodimer that was completely localized to the cytoplasm. Lastly, our results indicate that mutations in Ku previously proposed to abrogate Ku70/Ku80 heterodimerization, markedly reduced the accumulation of Ku70 without affecting heterodimer formation in mammalian cells.
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Affiliation(s)
- J Bertinato
- Graduate Program in Biochemistry, Department of Medicine, University of Ottawa, Ontario, Canada, K1Y 4K9
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42
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Koike M, Shiomi T, Koike A. Ku70 can translocate to the nucleus independent of Ku80 translocation and DNA-PK autophosphorylation. Biochem Biophys Res Commun 2000; 276:1105-11. [PMID: 11027597 DOI: 10.1006/bbrc.2000.3567] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ku plays an important role in multiple nuclear processes, e.g., DNA repair, chromosome maintenance, and transcriptional regulation. Although some evidence suggests that the nuclear translocation of Ku plays a key role in regulating the function of Ku, the mechanism is poorly understood. Using the site-directed mutagenesis technique, we demonstrate here that Ku70 can translocate to the nucleus without heterodimerization with Ku80. The nuclear accumulation of Ku70 mutants of the nuclear localization signal, which retained their binding ability with Ku80, was diminished. On the other hand, Ku70 mutants which lacked the ability to bind with Ku80 could translocate to the nuclei. Human Ku70, when transfected, accumulated within the nuclei of hamster xrs-6 cells which had undetectable DNA-PK activity and Ku80. Ku70 and Ku80 mutants of DNA-PK phosphorylation sites showed normal heterodimerization and nuclear translocation. These findings also support the idea that Ku70 can translocate to the nucleus independent of DNA-PK autophosphorylation.
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Affiliation(s)
- M Koike
- Genome Research Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.
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Abstract
Ku, a heterodimer of 70- and 80-kDa subunits, plays a general role in the metabolism of DNA ends in eukaryotic cells, including double-strand DNA break repair, V(D)J recombination, and maintenance of telomeres. We have utilized the yeast two-hybrid system to identify Ku70-interacting proteins other than Ku80. Two reactive clones were found to encode the dimerization domain of TRF2, a mammalian telomeric protein that binds to duplex TTAGGG repeats at chromosome ends. This interaction was confirmed using bacterial fusion proteins and co-immunoprecipitations from eukaryotic cells overexpressing TRF2. The transfected TFR2 colocalized with Ku70.
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Affiliation(s)
- K Song
- Department of Biochemistry, University of Ulsan College of Medicine, Seoul, South Korea
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Driller L, Wellinger RJ, Larrivee M, Kremmer E, Jaklin S, Feldmann HM. A short C-terminal domain of Yku70p is essential for telomere maintenance. J Biol Chem 2000; 275:24921-7. [PMID: 10818099 DOI: 10.1074/jbc.m002588200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Yku heterodimer from Saccharomyces cerevisiae, comprising Yku70p and Yku80p, is involved in the maintenance of a normal telomeric DNA end structure and is an essential component of nonhomologous end joining (NHEJ). To investigate the role of the Yku70p subunit in these two different pathways, we generated C-terminal deletions of the Yku70 protein and examined their ability to complement the phenotypes of a yku70(-) strain. Deleting only the 30 C-terminal amino acids of Yku70p abolishes Yku DNA binding activity and causes a yku(-) phenotype; telomeres are shortened, and NHEJ is impaired. Using conditions in which at least as much mutant protein as full-length protein is normally detectable in cell extracts, deleting only 25 C-terminal amino acids of Yku70p results in no measurable effect on DNA binding of the Yku protein, and the cells are fully proficient for NHEJ. Nevertheless, these cells display considerably shortened telomeres, and significant amounts of single-stranded overhangs of the telomeric guanosine-rich strands are observed. Co-overexpression of this protein with Yku80p could rescue some but not all of the telomere-related phenotypes. Therefore, the C-terminal domain in Yku70p defines at least one domain that is especially involved in telomere maintenance but not in NHEJ.
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Affiliation(s)
- L Driller
- Institute for Biochemistry, University of Munich (LMU), Feodor-Lynen-Str. 25, D-81377 Munich, Germany
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45
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Ponting CP, Schultz J, Copley RR, Andrade MA, Bork P. Evolution of domain families. ADVANCES IN PROTEIN CHEMISTRY 2000; 54:185-244. [PMID: 10829229 DOI: 10.1016/s0065-3233(00)54007-8] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- C P Ponting
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
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46
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Abstract
Ku is a heterodimeric protein composed of approximately 70- and approximately 80-kDa subunits (Ku70 and Ku80) originally identified as an autoantigen recognized by the sera of patients with autoimmune diseases. Ku has high binding affinity for DNA ends and that is why originally it was known as a DNA end binding protein, but now it is known to also bind the DNA structure at nicks, gaps, hairpins, as well as the ends of telomeres. It has been reported also to bind with sequence specificity to DNA and with weak affinity to RNA. Ku is an abundant nuclear protein and is present in vertebrates, insects, yeast, and worms. Ku contains ssDNA-dependent ATPase and ATP-dependent DNA helicase activities. It is the regulatory subunit of the DNA-dependent protein kinase that phosphorylates many proteins, including SV-40 large T antigen, p53, RNA-polymerase II, RP-A, topoisomerases, hsp90, and many transcription factors such as c-Jun, c-Fos, oct-1, sp-1, c-Myc, TFIID, and many more. It seems to be a multifunctional protein that has been implicated to be involved directly or indirectly in many important cellular metabolic processes such as DNA double-strand break repair, V(D)J recombination of immunoglobulins and T-cell receptor genes, immunoglobulin isotype switching, DNA replication, transcription regulation, regulation of heat shock-induced responses, regulation of the precise structure of telomeric termini, and it also plays a novel role in G2 and M phases of the cell cycle. The mechanism underlying the regulation of all the diverse functions of Ku is still obscure.
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Affiliation(s)
- R Tuteja
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi.
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47
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Dong X, Wang J, Kabir FN, Shaw M, Reed AM, Stein L, Andrade LE, Trevisani VF, Miller ML, Fujii T, Akizuki M, Pachman LM, Satoh M, Reeves WH. Autoantibodies to DEK oncoprotein in human inflammatory disease. ARTHRITIS AND RHEUMATISM 2000; 43:85-93. [PMID: 10643703 DOI: 10.1002/1529-0131(200001)43:1<85::aid-anr11>3.0.co;2-d] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE To evaluate the specificity of anti-DEK antibodies for juvenile rheumatoid arthritis (JRA). METHODS Anti-DEK autoantibodies were measured by enzyme-linked immunosorbent assay (ELISA) using affinity-purified his6-DEK fusion protein. Sera from 639 subjects (417 patients with systemic autoimmune disease, 13 with sarcoidosis, 44 with pulmonary tuberculosis, 125 with uveitis, and 6 with scleritis, and 34 healthy control subjects) were screened. Reactivity was verified by immunoblotting and immunoprecipitation studies using baculovirus-expressed human DEK. RESULTS Anti-DEK activity was found at the following frequencies: JRA 39.4% (n = 71), systemic lupus erythematosus (SLE) 25.1% (n = 216), sarcoidosis 46.2% (n = 13), rheumatoid arthritis 15.5% (n = 71), systemic sclerosis 36.0% (n = 22), polymyositis 6.2% (n = 16), and adult Still's disease 0% (n = 21). Autoantibodies also were detected in 9.1% of tuberculosis sera (n = 44), but were undetectable in sera from the 34 healthy controls. Western blot and immunoprecipitation assay results correlated well with the ELISA findings. In general, levels of anti-DEK autoantibodies were higher in SLE than in other patient subsets, including JRA. CONCLUSION Anti-DEK autoantibodies are less specific for JRA than previously believed. They are produced in association with a variety of inflammatory conditions, many of which are associated with granuloma formation and/or predominant Thl cytokine production. Anti-DEK antibodies may be a marker for a subset of autoimmunity associated with interferon-gamma production rather than a particular disease subset.
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Affiliation(s)
- X Dong
- Thurston Arthritis Research Center and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, USA
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Koike M, Ikuta T, Miyasaka T, Shiomi T. Ku80 can translocate to the nucleus independent of the translocation of Ku70 using its own nuclear localization signal. Oncogene 1999; 18:7495-505. [PMID: 10602508 DOI: 10.1038/sj.onc.1203247] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ku antigen is a complex of Ku70 and Ku80 subunits and plays an important role in not only DNA double-strand breaks (DSB) repair and V(D)J recombination, but also in growth regulation. Ku is generally believed to always form and function as heterodimers on the basis of in vitro observations. Here we demonstrate that the localization of Ku80 does not completely coincide with that of Ku70. Ku70 and Ku80 were colocalized in the nucleus in the interphase but not in the late telophase/early G1 phase of the cell cycle. Since the in vivo function of Ku might be partially regulated by the control of its transport, we attempted to investigate the molecular mechanisms underlying the nuclear translocation of Ku. The nuclear translocation of Ku80 started during the late telophase/early G1 phase after the nuclear envelope was formed and this was preceded by the nuclear translocation of Ku70. Furthermore, we found that the Ku80 protein was transported to the nucleus without heterodimerization with Ku70. To understand in detail the mechanism of transport of Ku80, we attempted to identify the nuclear localization signal (NLS) of Ku80 and defined to a region spanning nine amino acid residues (positions 561 - 569). The Ku80 NLS was demonstrated to be mediated to the nuclear rim by two components of PTAC58 and PTAC97. All these findings support the idea that Ku80 can translocate to the nucleus using its own NLS independent of the translocation of Ku70.
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Affiliation(s)
- M Koike
- Genome Research Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
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49
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Mahajan KN, Gangi-Peterson L, Sorscher DH, Wang J, Gathy KN, Mahajan NP, Reeves WH, Mitchell BS. Association of terminal deoxynucleotidyl transferase with Ku. Proc Natl Acad Sci U S A 1999; 96:13926-31. [PMID: 10570175 PMCID: PMC24167 DOI: 10.1073/pnas.96.24.13926] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Terminal deoxynucleotidyl transferase (TdT) catalyzes the addition of nucleotides at the junctions of rearranging Ig and T cell receptor gene segments, thereby generating antigen receptor diversity. Ku is a heterodimeric protein composed of 70- and 86-kDa subunits that binds DNA ends and is required for V(D)J recombination and DNA double-strand break (DSB) repair. We provide evidence for a direct interaction between TdT and Ku proteins. Studies with a baculovirus expression system show that TdT can interact specifically with each of the Ku subunits and with the heterodimer. The interaction between Ku and TdT is also observed in pre-T cells with endogenously expressed proteins. The protein-protein interaction is DNA independent and occurs at physiological salt concentrations. Deletion mutagenesis experiments reveal that the N-terminal region of TdT (131 amino acids) is essential for interaction with the Ku heterodimer. This region, although not important for TdT polymerization activity, contains a BRCA1 C-terminal domain that has been shown to mediate interactions of proteins involved in DNA repair. The induction of DSBs in Cos-7 cells transfected with a human TdT expression construct resulted in the appearance of discrete nuclear foci in which TdT and Ku colocalize. The physical association of TdT with Ku suggests a possible mechanism by which TdT is recruited to the sites of DSBs such as V(D)J recombination intermediates.
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Affiliation(s)
- K N Mahajan
- University of North Carolina Lineberger Comprehensive Cancer Center, Chapel Hill, NC 27599, USA
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50
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Gell D, Jackson SP. Mapping of protein-protein interactions within the DNA-dependent protein kinase complex. Nucleic Acids Res 1999; 27:3494-502. [PMID: 10446239 PMCID: PMC148593 DOI: 10.1093/nar/27.17.3494] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In mammalian cells, the Ku and DNA-dependent protein kinase catalytic subunit (DNA-PKcs) proteins are required for the correct and efficient repair of DNA double-strand breaks. Ku comprises two tightly-associated subunits of approximately 69 and approximately 83 kDa, which are termed Ku70 and Ku80 (or Ku86), respectively. Previously, a number of regions of both Ku subunits have been demonstrated to be involved in their interaction, but the molecular mechanism of this interaction remains unknown. We have identified a region in Ku70 (amino acid residues 449-578) and a region in Ku80 (residues 439-592) that participate in Ku subunit interaction. Sequence analysis reveals that these interaction regions share sequence homology and suggests that the Ku subunits are structurally related. On binding to a DNA double-strand break, Ku is able to interact with DNA-PKcs, but how this interaction is mediated has not been defined. We show that the extreme C-terminus of Ku80, specifically the final 12 amino acid residues, mediates a highly specific interaction with DNA-PKcs. Strikingly, these residues appear to be conserved only in Ku80 sequences from vertebrate organisms. These data suggest that Ku has evolved to become part of the DNA-PK holo-enzyme by acquisition of a protein-protein interaction motif at the C-terminus of Ku80.
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Affiliation(s)
- D Gell
- Wellcome/CRC Institute, Tennis Court Road, Cambridge CB2 1QR, UK
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