1
|
Jeong E, Lee SG, Kim HS, Yang J, Shin J, Kim Y, Kim J, Schärer OD, Kim Y, Yeo JE, Kim HM, Cho Y. Structural basis of the fanconi anemia-associated mutations within the FANCA and FANCG complex. Nucleic Acids Res 2020; 48:3328-3342. [PMID: 32002546 PMCID: PMC7102982 DOI: 10.1093/nar/gkaa062] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 01/17/2020] [Accepted: 01/21/2020] [Indexed: 12/13/2022] Open
Abstract
Monoubiquitination of the Fanconi anemia complementation group D2 (FANCD2) protein by the FA core ubiquitin ligase complex is the central event in the FA pathway. FANCA and FANCG play major roles in the nuclear localization of the FA core complex. Mutations of these two genes are the most frequently observed genetic alterations in FA patients, and most point mutations in FANCA are clustered in the C-terminal domain (CTD). To understand the basis of the FA-associated FANCA mutations, we determined the cryo-electron microscopy (EM) structures of Xenopus laevis FANCA alone at 3.35 Å and 3.46 Å resolution and two distinct FANCA–FANCG complexes at 4.59 and 4.84 Å resolution, respectively. The FANCA CTD adopts an arc-shaped solenoid structure that forms a pseudo-symmetric dimer through its outer surface. FA- and cancer-associated point mutations are widely distributed over the CTD. The two different complex structures capture independent interactions of FANCG with either FANCA C-terminal HEAT repeats, or the N-terminal region. We show that mutations that disturb either of these two interactions prevent the nuclear localization of FANCA, thereby leading to an FA pathway defect. The structure provides insights into the function of FANCA CTD, and provides a framework for understanding FA- and cancer-associated mutations.
Collapse
Affiliation(s)
- Eunyoung Jeong
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Seong-Gyu Lee
- Center for Biomolecular and Cellular Structure, Institute for Basic Science (IBS), Daejeon, 34141, Republic of Korea.,Graduate School of Medical Science & Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
| | - Hyun-Suk Kim
- Center for Genomic Integrity, Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Jihyeon Yang
- Center for Genomic Integrity, Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Jinwoo Shin
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Youngran Kim
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Jihan Kim
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Orlando D Schärer
- Center for Genomic Integrity, Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea.,Department of Biological Sciences, School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Youngjin Kim
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Jung-Eun Yeo
- Center for Genomic Integrity, Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Ho Min Kim
- Center for Biomolecular and Cellular Structure, Institute for Basic Science (IBS), Daejeon, 34141, Republic of Korea.,Graduate School of Medical Science & Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
| | - Yunje Cho
- Department of Life Science, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| |
Collapse
|
2
|
Benitez A, Liu W, Palovcak A, Wang G, Moon J, An K, Kim A, Zheng K, Zhang Y, Bai F, Mazin AV, Pei XH, Yuan F, Zhang Y. FANCA Promotes DNA Double-Strand Break Repair by Catalyzing Single-Strand Annealing and Strand Exchange. Mol Cell 2018; 71:621-628.e4. [PMID: 30057198 PMCID: PMC6097932 DOI: 10.1016/j.molcel.2018.06.030] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 02/04/2018] [Accepted: 06/20/2018] [Indexed: 01/24/2023]
Abstract
FANCA is a component of the Fanconi anemia (FA) core complex that activates DNA interstrand crosslink repair by monoubiquitination of FANCD2. Here, we report that purified FANCA protein catalyzes bidirectional single-strand annealing (SA) and strand exchange (SE) at a level comparable to RAD52, while a disease-causing FANCA mutant, F1263Δ, is defective in both activities. FANCG, which directly interacts with FANCA, dramatically stimulates its SA and SE activities. Alternatively, FANCB, which does not directly interact with FANCA, does not stimulate this activity. Importantly, five other patient-derived FANCA mutants also exhibit deficient SA and SE, suggesting that the biochemical activities of FANCA are relevant to the etiology of FA. A cell-based DNA double-strand break (DSB) repair assay demonstrates that FANCA plays a direct role in the single-strand annealing sub-pathway (SSA) of DSB repair by catalyzing SA, and this role is independent of the canonical FA pathway and RAD52.
Collapse
Affiliation(s)
- Anaid Benitez
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Wenjun Liu
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Anna Palovcak
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Guanying Wang
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Jaewon Moon
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Kevin An
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Anna Kim
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Kevin Zheng
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Yu Zhang
- Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Feng Bai
- Department of Surgery, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Alexander V Mazin
- Department of Biochemistry & Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Xin-Hai Pei
- Department of Surgery, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Fenghua Yuan
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Yanbin Zhang
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
| |
Collapse
|
3
|
Takahashi D, Sato K, Hirayama E, Takata M, Kurumizaka H. Human FAN1 promotes strand incision in 5'-flapped DNA complexed with RPA. J Biochem 2015; 158:263-70. [PMID: 25922199 DOI: 10.1093/jb/mvv043] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Accepted: 04/09/2015] [Indexed: 12/21/2022] Open
Abstract
Fanconi anaemia (FA) is a human infantile recessive disorder. Seventeen FA causal proteins cooperatively function in the DNA interstrand crosslink (ICL) repair pathway. Dual DNA strand incisions around the crosslink are critical steps in ICL repair. FA-associated nuclease 1 (FAN1) is a DNA structure-specific endonuclease that is considered to be involved in DNA incision at the stalled replication fork. Replication protein A (RPA) rapidly assembles on the single-stranded DNA region of the stalled fork. However, the effect of RPA on the FAN1-mediated DNA incision has not been determined. In this study, we purified human FAN1, as a bacterially expressed recombinant protein. FAN1 exhibited robust endonuclease activity with 5'-flapped DNA, which is formed at the stalled replication fork. We found that FAN1 efficiently promoted DNA incision at the proper site of RPA-coated 5'-flapped DNA. Therefore, FAN1 possesses the ability to promote the ICL repair of 5'-flapped DNA covered by RPA.
Collapse
Affiliation(s)
- Daisuke Takahashi
- Laboratory of Structural Biology, Graduate School of Advanced Science & Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan and
| | - Koichi Sato
- Laboratory of Structural Biology, Graduate School of Advanced Science & Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan and
| | - Emiko Hirayama
- Laboratory of Structural Biology, Graduate School of Advanced Science & Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan and
| | - Minoru Takata
- Laboratory of DNA Damage Signaling, Department of Late Effects Studies, Radiation Biology Center, Kyoto University, Yoshida-konoe, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hitoshi Kurumizaka
- Laboratory of Structural Biology, Graduate School of Advanced Science & Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan and
| |
Collapse
|
4
|
Sato K, Ishiai M, Takata M, Kurumizaka H. Defective FANCI binding by a fanconi anemia-related FANCD2 mutant. PLoS One 2014; 9:e114752. [PMID: 25489943 PMCID: PMC4260917 DOI: 10.1371/journal.pone.0114752] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 11/13/2014] [Indexed: 12/24/2022] Open
Abstract
FANCD2 is a product of one of the genes associated with Fanconi anemia (FA), a rare recessive disease characterized by bone marrow failure, skeletal malformations, developmental defects, and cancer predisposition. FANCD2 forms a complex with FANCI (ID complex) and is monoubiquitinated, which facilitates the downstream interstrand crosslink (ICL) repair steps, such as ICL unhooking and nucleolytic end resection. In the present study, we focused on the chicken FANCD2 (cFANCD2) mutant harboring the Leu234 to Arg (L234R) substitution. cFANCD2 L234R corresponds to the human FANCD2 L231R mutation identified in an FA patient. We found that cFANCD2 L234R did not complement the defective ICL repair in FANCD2−/− DT40 cells. Purified cFANCD2 L234R did not bind to chicken FANCI, and its monoubiquitination was significantly deficient, probably due to the abnormal ID complex formation. In addition, the histone chaperone activity of cFANCD2 L234R was also defective. These findings may explain some aspects of Fanconi anemia pathogenesis by a FANCD2 missense mutation.
Collapse
Affiliation(s)
- Koichi Sato
- Laboratory of Structural Biology, Graduate School of Advanced Science & Engineering, Waseda University, Tokyo, Japan
| | - Masamichi Ishiai
- Laboratory of DNA Damage Signaling, Department of Late Effects Studies, Radiation Biology Center, Kyoto University, Kyoto, Japan
| | - Minoru Takata
- Laboratory of DNA Damage Signaling, Department of Late Effects Studies, Radiation Biology Center, Kyoto University, Kyoto, Japan
| | - Hitoshi Kurumizaka
- Laboratory of Structural Biology, Graduate School of Advanced Science & Engineering, Waseda University, Tokyo, Japan
- * E-mail:
| |
Collapse
|
5
|
Huang Y, Leung JWC, Lowery M, Matsushita N, Wang Y, Shen X, Huong D, Takata M, Chen J, Li L. Modularized functions of the Fanconi anemia core complex. Cell Rep 2014; 7:1849-57. [PMID: 24910428 DOI: 10.1016/j.celrep.2014.04.029] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 03/04/2014] [Accepted: 04/15/2014] [Indexed: 10/25/2022] Open
Abstract
The Fanconi anemia (FA) core complex provides the essential E3 ligase function for spatially defined FANCD2 ubiquitination and FA pathway activation. Of the seven FA gene products forming the core complex, FANCL possesses a RING domain with demonstrated E3 ligase activity. The other six components do not have clearly defined roles. Through epistasis analyses, we identify three functional modules in the FA core complex: a catalytic module consisting of FANCL, FANCB, and FAAP100 is absolutely required for the E3 ligase function, and the FANCA-FANCG-FAAP20 and the FANCC-FANCE-FANCF modules provide nonredundant and ancillary functions that help the catalytic module bind chromatin or sites of DNA damage. Disruption of the catalytic module causes complete loss of the core complex function, whereas loss of any ancillary module component does not. Our work reveals the roles of several FA gene products with previously undefined functions and a modularized assembly of the FA core complex.
Collapse
Affiliation(s)
- Yaling Huang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Justin W C Leung
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Megan Lowery
- Department of Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Nobuko Matsushita
- Laboratory of Molecular Biochemistry, School of Life Science, Tokyo University of Pharmacy and Life Science, Tokyo 192-0392, Japan
| | - Yucai Wang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Xi Shen
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Do Huong
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Minoru Takata
- Laboratory of DNA Damage Signaling, Department of Late Effect Studies, Radiation Biology Center, Kyoto University, Kyoto 606-8501, Japan
| | - Junjie Chen
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Lei Li
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA; Department of Genetics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
| |
Collapse
|
6
|
Towards a molecular understanding of the fanconi anemia core complex. Anemia 2012; 2012:926787. [PMID: 22675617 PMCID: PMC3364535 DOI: 10.1155/2012/926787] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 03/21/2012] [Indexed: 11/17/2022] Open
Abstract
Fanconi Anemia (FA) is a genetic disorder characterized by the inability of patient cells to repair DNA damage caused by interstrand crosslinking agents. There are currently 14 verified FA genes, where mutation of any single gene prevents repair of DNA interstrand crosslinks (ICLs). The accumulation of ICL damage results in genome instability and patients having a high predisposition to cancers. The key event of the FA pathway is dependent on an eight-protein core complex (CC), required for the monoubiquitination of each member of the FANCD2-FANCI complex. Interestingly, the majority of patient mutations reside in the CC. The molecular mechanisms underlying the requirement for such a large complex to carry out a monoubiquitination event remain a mystery. This paper documents the extensive efforts of researchers so far to understand the molecular roles of the CC proteins with regard to its main function in the FA pathway, the monoubiquitination of FANCD2 and FANCI.
Collapse
|
7
|
Fanconi anemia proteins and their interacting partners: a molecular puzzle. Anemia 2012; 2012:425814. [PMID: 22737580 PMCID: PMC3378961 DOI: 10.1155/2012/425814] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Accepted: 03/13/2012] [Indexed: 11/17/2022] Open
Abstract
In recent years, Fanconi anemia (FA) has been the subject of intense investigations, primarily in the DNA repair research field. Many discoveries have led to the notion of a canonical pathway, termed the FA pathway, where all FA proteins function sequentially in different protein complexes to repair DNA cross-link damages. Although a detailed architecture of this DNA cross-link repair pathway is emerging, the question of how a defective DNA cross-link repair process translates into the disease phenotype is unresolved. Other areas of research including oxidative metabolism, cell cycle progression, apoptosis, and transcriptional regulation have been studied in the context of FA, and some of these areas were investigated before the fervent enthusiasm in the DNA repair field. These other molecular mechanisms may also play an important role in the pathogenesis of this disease. In addition, several FA-interacting proteins have been identified with roles in these “other” nonrepair molecular functions. Thus, the goal of this paper is to revisit old ideas and to discuss protein-protein interactions related to other FA-related molecular functions to try to give the reader a wider perspective of the FA molecular puzzle.
Collapse
|
8
|
Gari K, Constantinou A. The role of the Fanconi anemia network in the response to DNA replication stress. Crit Rev Biochem Mol Biol 2009; 44:292-325. [PMID: 19728769 DOI: 10.1080/10409230903154150] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Fanconi anemia is a genetically heterogeneous disorder associated with chromosome instability and a highly elevated risk for developing cancer. The mutated genes encode proteins involved in the cellular response to DNA replication stress. Fanconi anemia proteins are extensively connected with DNA caretaker proteins, and appear to function as a hub for the coordination of DNA repair with DNA replication and cell cycle progression. At a molecular level, however, the raison d'être of Fanconi anemia proteins still remains largely elusive. The thirteen Fanconi anemia proteins identified to date have not been embraced into a single and defined biological process. To help put the Fanconi anemia puzzle into perspective, we begin this review with a summary of the strategies employed by prokaryotes and eukaryotes to tolerate obstacles to the progression of replication forks. We then summarize what we know about Fanconi anemia with an emphasis on biochemical aspects, and discuss how the Fanconi anemia network, a late acquisition in evolution, may function to permit the faithful and complete duplication of our very large vertebrate chromosomes.
Collapse
Affiliation(s)
- Kerstin Gari
- DNA Damage Response Laboratory, Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, UK
| | | |
Collapse
|
9
|
Tremblay CS, Huard CC, Huang FF, Habi O, Bourdages V, Lévesque G, Carreau M. The fanconi anemia core complex acts as a transcriptional co-regulator in hairy enhancer of split 1 signaling. J Biol Chem 2009; 284:13384-13395. [PMID: 19321451 DOI: 10.1074/jbc.m807921200] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Mutations in one of the 13 Fanconi anemia (FA) genes cause a progressive bone marrow failure disorder associated with developmental abnormalities and a predisposition to cancer. Although FA has been defined as a DNA repair disease based on the hypersensitivity of patient cells to DNA cross-linking agents, FA patients develop various developmental defects such as skeletal abnormalities, microphthalmia, and endocrine abnormalities that may be linked to transcriptional defects. Recently, we reported that the FA core complex interacts with the transcriptional repressor Hairy Enhancer of Split 1 (HES1) suggesting that the core complex plays a role in transcription. Here we show that the FA core complex contributes to transcriptional regulation of HES1-responsive genes, including HES1 and the cyclin-dependent kinase inhibitor p21(cip1/waf1). Chromatin immunoprecipitation studies show that the FA core complex interacts with the HES1 promoter but not the p21(cip1/waf1) promoter. Furthermore, we show that the FA core complex interferes with HES1 binding to the co-repressor transducin-like-Enhancer of Split, suggesting that the core complex affects transcription both directly and indirectly. Taken together these data suggest a novel function of the FA core complex in transcriptional regulation.
Collapse
Affiliation(s)
- Cédric S Tremblay
- Centre Hospitalier de l'Université Laval, Université Laval, Québec GIV 4G2, Canada
| | - Caroline C Huard
- Centre Hospitalier de l'Université Laval, Université Laval, Québec GIV 4G2, Canada
| | - Feng-Fei Huang
- Centre Hospitalier de l'Université Laval, Université Laval, Québec GIV 4G2, Canada
| | - Ouassila Habi
- Centre Hospitalier de l'Université Laval, Université Laval, Québec GIV 4G2, Canada
| | - Valérie Bourdages
- Centre Hospitalier de l'Université Laval, Université Laval, Québec GIV 4G2, Canada
| | - Georges Lévesque
- Centre Hospitalier de l'Université Laval, Université Laval, Québec GIV 4G2, Canada; Medical Biology and Université Laval, Québec GIV 4G2, Canada
| | - Madeleine Carreau
- Medical Biology and Université Laval, Québec GIV 4G2, Canada; Departments of Pediatrics Université Laval, Québec GIV 4G2, Canada.
| |
Collapse
|
10
|
Xie Y, De Winter JP, Waisfisz Q, Nieuwint AWM, Scheper RJ, Arwert F, Hoatlin ME, Ossenkoppele GJ, Schuurhuis GJ, Joenje H. Aberrant Fanconi anaemia protein profiles in acute myeloid leukaemia cells. Br J Haematol 2008. [DOI: 10.1111/j.1365-2141.2000.02450.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
11
|
Oda T, Hayano T, Miyaso H, Takahashi N, Yamashita T. Hsp90 regulates the Fanconi anemia DNA damage response pathway. Blood 2007; 109:5016-26. [PMID: 17327415 DOI: 10.1182/blood-2006-08-038638] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Heat shock protein 90 (Hsp90) regulates diverse signaling pathways. Emerging evidence suggests that Hsp90 inhibitors, such as 17-allylamino-17-demethoxygeldanamycin (17-AAG), enhance DNA damage-induced cell death, suggesting that Hsp90 may regulate cellular responses to genotoxic stress. However, the underlying mechanisms are poorly understood. Here, we show that the Fanconi anemia (FA) pathway is involved in the Hsp90-mediated regulation of genotoxic stress response. In the FA pathway, assembly of 8 FA proteins including FANCA into a nuclear multiprotein complex, and the complex-dependent activation of FANCD2 are critical events for cellular tolerance against DNA cross-linkers. Hsp90 associates with FANCA, in vivo and in vitro, in a 17-AAG-sensitive manner. Disruption of the FANCA/Hsp90 association by cellular treatment with 17-AAG induces rapid proteasomal degradation and cytoplasmic relocalization of FANCA, leading to impaired activation of FANCD2. Furthermore, 17-AAG promotes DNA cross-linker-induced cytotoxicity, but this effect is much less pronounced in FA pathway-defective cells. Notably, 17-AAG enhances DNA cross-linker-induced chromosome aberrations. In conclusion, our results identify FANCA as a novel client of Hsp90, suggesting that Hsp90 promotes activation of the FA pathway through regulation of intracellular turnover and trafficking of FANCA, which is critical for cellular tolerance against genotoxic stress.
Collapse
Affiliation(s)
- Tsukasa Oda
- Laboratory of Molecular Genetics, Department of Molecular and Cellular Biology, Institute of Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi, Gunma 371-8512, Japan
| | | | | | | | | |
Collapse
|
12
|
Checinska A, Giaccone G, Hoogeland BSJ, Ferreira CG, Rodriguez JA, Kruyt FAE. TUCAN/CARDINAL/CARD8 and apoptosis resistance in non-small cell lung cancer cells. BMC Cancer 2006; 6:166. [PMID: 16796750 PMCID: PMC1538619 DOI: 10.1186/1471-2407-6-166] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2006] [Accepted: 06/23/2006] [Indexed: 11/10/2022] Open
Abstract
Background Activation of caspase-9 in response to treatment with cytotoxic drugs is inhibited in NSCLC cells, which may contribute to the clinical resistance to chemotherapy shown in this type of tumor. The aim of the present study was to investigate the mechanism of caspase-9 inhibition, with a focus on a possible role of TUCAN as caspase-9 inhibitor and a determinant of chemosensitivity in NSCLC cells. Methods Caspase-9 processing and activation were investigated by Western blot and by measuring the cleavage of the fluorogenic substrate LEHD-AFC. Proteins interaction assays, and RNA interference in combination with cell viability and apoptosis assays were used to investigate the involvement of TUCAN in inhibition of caspase-9 and chemosensitivity NSCLC. Results Analysis of the components of the caspase-9 activation pathway in a panel of NSCLC and SCLC cells revealed no intrinsic defects. In fact, exogenously added cytochrome c and dATP triggered procaspase-9 cleavage and activation in lung cancer cell lysates, suggesting the presence of an inhibitor. The reported inhibitor of caspase-9, TUCAN, was exclusively expressed in NSCLC cells. However, interactions between TUCAN and procaspase-9 could not be demonstrated by any of the assays used. Furthermore, RNA interference-mediated down-regulation of TUCAN did not restore cisplatin-induced caspase-9 activation or affect cisplatin sensitivity in NSCLC cells. Conclusion These results indicate that procaspase-9 is functional and can undergo activation and full processing in lung cancer cell extracts in the presence of additional cytochrome c/dATP. However, the inhibitory protein TUCAN does not play a role in inhibition of procaspase-9 and in determining the sensitivity to cisplatin in NSCLC.
Collapse
Affiliation(s)
- Agnieszka Checinska
- Department of Medical Oncology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Giuseppe Giaccone
- Department of Medical Oncology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Bas SJ Hoogeland
- Department of Medical Oncology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Carlos G Ferreira
- Department of Medical Oncology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands
- Department of Clinical and Translational Research, Instituto Nacional de Cancer, 20230-092 Rio De Janeiro, Brazil
| | - Jose A Rodriguez
- Department of Medical Oncology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Frank AE Kruyt
- Department of Medical Oncology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands
| |
Collapse
|
13
|
Medhurst AL, Laghmani EH, Steltenpool J, Ferrer M, Fontaine C, de Groot J, Rooimans MA, Scheper RJ, Meetei AR, Wang W, Joenje H, de Winter JP. Evidence for subcomplexes in the Fanconi anemia pathway. Blood 2006; 108:2072-80. [PMID: 16720839 PMCID: PMC1895538 DOI: 10.1182/blood-2005-11-008151] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fanconi anemia (FA) is a genomic instability disorder, clinically characterized by congenital abnormalities, progressive bone marrow failure, and predisposition to malignancy. Cells derived from patients with FA display a marked sensitivity to DNA cross-linking agents, such as mitomycin C (MMC). This observation has led to the hypothesis that the proteins defective in FA are involved in the sensing or repair of interstrand cross-link lesions of the DNA. A nuclear complex consisting of a majority of the FA proteins plays a crucial role in this process and is required for the monoubiquitination of a downstream target, FANCD2. Two new FA genes, FANCB and FANCL, have recently been identified, and their discovery has allowed a more detailed study into the molecular architecture of the FA pathway. We demonstrate a direct interaction between FANCB and FANCL and that a complex of these proteins binds FANCA. The interaction between FANCA and FANCL is dependent on FANCB, FANCG, and FANCM, but independent of FANCC, FANCE, and FANCF. These findings provide a framework for the protein interactions that occur "upstream" in the FA pathway and suggest that besides the FA core complex different subcomplexes exist that may have specific functions other than the monoubiquitination of FANCD2.
Collapse
Affiliation(s)
- Annette L Medhurst
- Department of Clinical Genetics and Human Genetics, Vrije Universiteit University Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Levran O, Diotti R, Pujara K, Batish SD, Hanenberg H, Auerbach AD. Spectrum of sequence variations in the FANCA gene: an International Fanconi Anemia Registry (IFAR) study. Hum Mutat 2006; 25:142-9. [PMID: 15643609 DOI: 10.1002/humu.20125] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Fanconi anemia (FA) is an autosomal recessive disorder that is defined by cellular hypersensitivity to DNA cross-linking agents, and is characterized clinically by developmental abnormalities, progressive bone-marrow failure, and predisposition to leukemia and solid tumors. There is extensive genetic heterogeneity, with at least 11 different FA complementation groups. FA-A is the most common group, accounting for approximately 65% of all affected individuals. The mutation spectrum of the FANCA gene, located on chromosome 16q24.3, is highly heterogeneous. Here we summarize all sequence variations (mutations and polymorphisms) in FANCA described in the literature and listed in the Fanconi Anemia Mutation Database as of March 2004, and report 61 novel FANCA mutations identified in FA patients registered in the International Fanconi Anemia Registry (IFAR). Thirty-eight novel SNPs, previously unreported in the literature or in dbSNP, were also identified. We studied the segregation of common FANCA SNPs in FA families to generate haplotypes. We found that FANCA SNP data are highly useful for carrier testing, prenatal diagnosis, and preimplantation genetic diagnosis, particularly when the disease-causing mutations are unknown. Twenty-two large genomic deletions were identified by detection of apparent homozygosity for rare SNPs. In addition, a conserved SNP haplotype block spanning at least 60 kb of the FANCA gene was identified in individuals from various ethnic groups.
Collapse
Affiliation(s)
- Orna Levran
- Laboratory of Human Genetics and Hematology, Rockefeller University, New York, New York 10021-6399, USA
| | | | | | | | | | | |
Collapse
|
15
|
Titus TA, Selvig DR, Qin B, Wilson C, Starks AM, Roe BA, Postlethwait JH. The Fanconi anemia gene network is conserved from zebrafish to human. Gene 2006; 371:211-23. [PMID: 16515849 DOI: 10.1016/j.gene.2005.11.038] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2005] [Revised: 10/24/2005] [Accepted: 11/30/2005] [Indexed: 11/28/2022]
Abstract
Fanconi anemia (FA) is a complex disease involving nine identified and two unidentified loci that define a network essential for maintaining genomic stability. To test the hypothesis that the FA network is conserved in vertebrate genomes, we cloned and sequenced zebrafish (Danio rerio) cDNAs and/or genomic BAC clones orthologous to all nine cloned FA genes (FANCA, FANCB, FANCC, FANCD1, FANCD2, FANCE, FANCF, FANCG, and FANCL), and identified orthologs in the genome database for the pufferfish Tetraodon nigroviridis. Genomic organization of exons and introns was nearly identical between zebrafish and human for all genes examined. Hydrophobicity plots revealed conservation of FA protein structure. Evolutionarily conserved regions identified functionally important domains, since many amino acid residues mutated in human disease alleles or shown to be critical in targeted mutagenesis studies are identical in zebrafish and human. Comparative genomic analysis demonstrated conserved syntenies for all FA genes. We conclude that the FA gene network has remained intact since the last common ancestor of zebrafish and human lineages. The application of powerful genetic, cellular, and embryological methodologies make zebrafish a useful model for discovering FA gene functions, identifying new genes in the network, and identifying therapeutic compounds.
Collapse
Affiliation(s)
- Tom A Titus
- Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403, USA
| | | | | | | | | | | | | |
Collapse
|
16
|
Dequen F, St-Laurent JF, Gagnon SN, Carreau M, Desnoyers S. The Caenorhabditis elegans FancD2 ortholog is required for survival following DNA damage. Comp Biochem Physiol B Biochem Mol Biol 2005; 141:453-60. [PMID: 15979372 DOI: 10.1016/j.cbpc.2005.05.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2004] [Revised: 05/10/2005] [Accepted: 05/11/2005] [Indexed: 01/04/2023]
Abstract
Fanconi anemia (FA) is an autosomal recessive disease characterized by bone-marrow failure, congenital abnormalities, and cancer susceptibility. There are 11 FA complementation groups in human where 8 genes have been identified. We found that FancD2 is conserved in evolution and present in the genome of the nematode Caenorhabditis elegans. The gene Y41E3.9 (CeFancD2) encodes a structural ortholog of human FANCD2 and is composed of 10 predicted exons. Our analysis showed that exons 6 and 7 were absent from a CeFancD2 EST suggesting the presence of a splice variant. In an attempt to characterize its role in DNA damage, we depleted worms of CeFANCD2 using RNAi. When the CeFANCD2(RNAi) worms were treated with a crosslinking agent, a significant drop in the progeny survival was noted. These worms were also sensitive, although to a lesser extent, to ionizing radiation (IR). Therefore, these data support an important role for CeFANCD2 in DNA damage response as for its human counterpart. The data also support the usefulness of C. elegans to study the Fanconi anemia pathway, and emphasize the biological importance of FANCD2 in DNA damage response throughout evolution.
Collapse
Affiliation(s)
- Florence Dequen
- CHUL Research Centre, Pediatrics Research Unit and Laval University, Department of Pediatrics, Canada
| | | | | | | | | |
Collapse
|
17
|
Macé G, Bogliolo M, Guervilly JH, Dugas du Villard JA, Rosselli F. 3R coordination by Fanconi anemia proteins. Biochimie 2005; 87:647-58. [PMID: 15935541 DOI: 10.1016/j.biochi.2005.05.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Fanconi anemia (FA) is a recessive cancer prone syndrome featuring bone marrow failure and hypersensitivity to DNA crosslinks. Nine FA genes have been isolated so far. The biochemical function(s) of the FA proteins remain(s) poorly determined. However, a large consensus exists on the evidence that, to cope with DNA cross-links, a cell needs a functional FA pathway. In this review, we resume current understanding of how the FA pathway works in response to DNA damage and how it is integrated in a complex network of proteins involved in the maintenance of the genetic stability.
Collapse
Affiliation(s)
- Gaëtane Macé
- Institut Gustave-Roussy PR2, UPR2169 du CNRS, 39, rue Camille-Desmoulins, 94805 Villejuif cedex, France
| | | | | | | | | |
Collapse
|
18
|
Ferrer M, Rodríguez JA, Spierings EA, de Winter JP, Giaccone G, Kruyt FAE. Identification of multiple nuclear export sequences in Fanconi anemia group A protein that contribute to CRM1-dependent nuclear export. Hum Mol Genet 2005; 14:1271-81. [PMID: 15790592 DOI: 10.1093/hmg/ddi138] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The Fanconi anemia (FA) pathway plays an important role in maintaining genomic stability, and defects in this pathway cause cancer susceptibility. The FA proteins have been found to function primarily in a nuclear complex, although a cytoplasmic localization and function for several FA proteins has also been reported. In this study, we investigated the possibility that FANCA, FANCC and FANCG are subjected to active export out of the nucleus. After treatment with leptomycin B, a specific inhibitor of CRM1-mediated nuclear export, the accumulation of epitope-tagged FANCA in the nucleus increased, whereas FANCC was affected to a lesser extent and FANCG showed no response. CRM1-mediated export of FANCA was further confirmed using CRM1 cotransfection, which led to a dramatic relocalization of FANCA to the cytoplasm. Five functional leucine-rich nuclear export sequences (NESs) distributed throughout the FANCA sequence were identified and characterized using an in vivo export assay. Simultaneous inactivation of three of these NESs resulted in a discrete but reproducible increase of FANCA nuclear accumulation. However, these NES mutations did not affect the ability of FANCA to complement the mitomycin C or cisplatin sensitivity of FA-A lymphoblasts. Surprisingly, mutations in the other two NESs resulted in an almost complete relocation of the protein to cytoplasm, suggesting that these motifs overlap with domains that are crucial for nuclear import. Taken together, these findings indicate that FANCA can be actively exported out of the nucleus by CRM1, revealing a new mechanism to regulate the function of the FA protein complex.
Collapse
Affiliation(s)
- Miriam Ferrer
- Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands
| | | | | | | | | | | |
Collapse
|
19
|
Ferrer M, de Winter JP, Mastenbroek DCJ, Curiel DT, Gerritsen WR, Giaccone G, Kruyt FAE. Chemosensitizing tumor cells by targeting the Fanconi anemia pathway with an adenovirus overexpressing dominant-negative FANCA. Cancer Gene Ther 2005; 11:539-46. [PMID: 15192709 DOI: 10.1038/sj.cgt.7700734] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Fanconi anemia (FA) is a rare genetic disorder characterized by bone-marrow failure and cellular hypersensitivity to crosslinking agents, including cisplatin. Here, we studied the use of the FA pathway as a possible target for cancer gene therapy with the aim to sensitize tumor cells for cisplatin by interfering with the FA pathway. As proof-of-principle, FA and non-FA lymphoblast-derived tumors were grown subcutaneously in scid mice and treated with two different concentrations of cisplatin. As predicted, the antitumor response was considerably improved in FA tumors. An adenoviral vector encoding a dominant-negative form of FANCA, FANCA600DN, was generated that interfered with endogenous FANCA-FANCG interaction resulting in the disruption of the FA pathway as illustrated by disturbed FANCD2 monoubiquitination. A panel of cell lines, including non-small-cell lung cancer cells, could be sensitized approximately two- to three-fold for cisplatin after Ad.CMV.FANCA600DN infection that may increase upon enhanced infection efficiency. In conclusion, targeting the FA pathway may provide a novel strategy for the sensitization of solid tumors for cisplatin and, in addition, provides a tool for examining the role of the FA pathway in determining chemoresistance in different tumor types.
Collapse
Affiliation(s)
- Miriam Ferrer
- Department of Medical Oncology, Division of Gene Therapy, VU University Medical Center, Amsterdam, The Netherlands
| | | | | | | | | | | | | |
Collapse
|
20
|
Park SJ, Ciccone SLM, Beck BD, Hwang B, Freie B, Clapp DW, Lee SH. Oxidative stress/damage induces multimerization and interaction of Fanconi anemia proteins. J Biol Chem 2004; 279:30053-9. [PMID: 15138265 DOI: 10.1074/jbc.m403527200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Fanconi anemia (FANC) is a heterogeneous genetic disorder characterized by a hypersensitivity to DNA-damaging agents, chromosomal instability, and defective DNA repair. Eight FANC genes have been identified so far, and five of them (FANCA, -C, -E, -F, and -G) assemble in a multinuclear complex and function at least in part in a complex to activate FANCD2 by monoubiquitination. Here we show that FANCA and FANCG are redox-sensitive proteins that are multimerized and/or form a nuclear complex in response to oxidative stress/damage. Both FANCA and FANCG proteins exist as monomers under non-oxidizing conditions, whereas they become multimers following H2O2 treatment. Treatment of cells with oxidizing agent not only triggers the multimeric complex of FANCA and FANCG in vivo but also induces the interaction between FANCA and FANCG. N-Ethylmaleimide treatment abolishes multimerization and interaction of FANCA and FANCG in vitro. Taken together, our results lead us to conclude that FANCA and FANCG uniquely respond to oxidative damage by forming complex(es) via intermolecular disulfide linkage(s), which may be crucial in forming such complexes and in determining their function.
Collapse
Affiliation(s)
- Su-Jung Park
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202, USA
| | | | | | | | | | | | | |
Collapse
|
21
|
Brodeur I, Goulet I, Tremblay CS, Charbonneau C, Delisle MC, Godin C, Huard C, Khandjian EW, Buchwald M, Lévesque G, Carreau M. Regulation of the Fanconi Anemia Group C Protein through Proteolytic Modification. J Biol Chem 2004; 279:4713-20. [PMID: 14625294 DOI: 10.1074/jbc.m301291200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The function of the Fanconi anemia group C protein (FANCC) is still unknown, though many studies point to a role in damage response signaling. Unlike other known FA proteins, FANCC is mainly localized to the cytoplasm and is thought to act as a messenger of cellular damage rather than an effector of repair. FANCC has been shown to interact with several cytoplasmic and nuclear proteins and to delay the onset of apoptosis through redox regulation of GSTP1. We investigated the fate and function of FANCC during apoptosis. Here we show that FANCC undergoes proteolytic modification by a caspase into a predominant 47-kDa ubiquitinated protein fragment. Lack of proteolytic modification at the putative cleavage site delays apoptosis but does not affect MMC complementation. These results suggest that FANCC function is regulated through proteolytic processing.
Collapse
Affiliation(s)
- Isabelle Brodeur
- Unité de Génétique Humaine et Moléculaire, CHUQ-Pavillon St-François d'Assise, Quebec, Quebec G1L 3L5, Canada
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Blom E, van de Vrugt HJ, de Vries Y, de Winter JP, Arwert F, Joenje H. Multiple TPR motifs characterize the Fanconi anemia FANCG protein. DNA Repair (Amst) 2004; 3:77-84. [PMID: 14697762 DOI: 10.1016/j.dnarep.2003.09.007] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The genome protection pathway that is defective in patients with Fanconi anemia (FA) is controlled by at least eight genes, including BRCA2. A key step in the pathway involves the monoubiquitylation of FANCD2, which critically depends on a multi-subunit nuclear 'core complex' of at least six FANC proteins (FANCA, -C, -E, -F, -G, and -L). Except for FANCL, which has WD40 repeats and a RING finger domain, no significant domain structure has so far been recognized in any of the core complex proteins. By using a homology search strategy comparing the human FANCG protein sequence with its ortholog sequences in Oryzias latipes (Japanese rice fish) and Danio rerio (zebrafish) we identified at least seven tetratricopeptide repeat motifs (TPRs) covering a major part of this protein. TPRs are degenerate 34-amino acid repeat motifs which function as scaffolds mediating protein-protein interactions, often found in multiprotein complexes. In four out of five TPR motifs tested (TPR1, -2, -5, and -6), targeted missense mutagenesis disrupting the motifs at the critical position 8 of each TPR caused complete or partial loss of FANCG function. Loss of function was evident from failure of the mutant proteins to complement the cellular FA phenotype in FA-G lymphoblasts, which was correlated with loss of binding to FANCA. Although the TPR4 mutant fully complemented the cells, it showed a reduced interaction with FANCA, suggesting that this TPR may also be of functional importance. The recognition of FANCG as a typical TPR protein predicts this protein to play a key role in the assembly and/or stabilization of the nuclear FA protein core complex.
Collapse
Affiliation(s)
- Eric Blom
- Department of Clinical Genetics and Human Genetics, VU University Medical Center, Van der Boechorststraat 7, NL-1081 BT, Amsterdam, The Netherlands
| | | | | | | | | | | |
Collapse
|
23
|
Gordon SM, Buchwald M. Fanconi anemia protein complex: mapping protein interactions in the yeast 2- and 3-hybrid systems. Blood 2003; 102:136-41. [PMID: 12649160 DOI: 10.1182/blood-2002-11-3517] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Fanconi anemia (FA) is an autosomal recessive syndrome characterized by progressive bone marrow failure and cancer predisposition. Eight FA complementation groups have been identified. The FANCA, FANCC, FANCE, FANCF, and FANCG proteins form a nuclear complex required for the monoubiquination of the FANCD2 protein. To investigate the architecture of the FA protein complex, the yeast 2-hybrid system was used to map contact points of the FANCA/FANCG, FANCC/FANCE, and FANCF/FANCG interactions. FANCG was shown to interact with both the amino-terminus of FANCA and the carboxyl-terminal region of FANCF. A FANCG mutant truncated at the carboxyl-terminus retained the ability to interact with FANCA. The interaction between FANCG and FANCF was ablated by a Leu71Pro mutant of FANCG. A central region of FANCE was sufficient for FANCC binding. A Leu554Pro mutant of FANCC failed to interact with FANCE. To further examine complex assembly, the yeast 3-hybrid system was used to investigate the ability of FANCG to act as a molecular bridge in mediating interaction between other FA proteins. FANCG was able to mediate interaction between FANCA and FANCF, as well as between monomers of FANCA. Direct interaction between FANCE and FANCD2 was also demonstrated in the yeast 2-hybrid system. This interaction involving an amino-terminal region of FANCD2 may provide a link between the FA protein complex and its downstream targets.
Collapse
Affiliation(s)
- Susan M Gordon
- Program in Genetics and Genomic Biology, Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada.
| | | |
Collapse
|
24
|
Abstract
Fanconi anemia is a rare autosomal recessive disease characterized by bone marrow failure, developmental anomalies, a high incidence of myelodysplasia and acute nonlymphocytic leukemia, and cellular hypersensitivity to cross linking agents. Five of the seven known Fanconi anemia proteins bind together in a complex and influence the function of a sixth, FANCD2, which colocalizes with BRCA1 in nuclear foci after genotoxic stress. Carboxy-terminal truncating mutations of the seventh Fanconi anemia gene, BRCA2, are hypomorphic and lead to FA-D1 and possibly FA-B. Because the Fanconi anemia alleles of BRCA2 fail to bind to Rad51 in response to genotoxic stress and Rad51 therefore fails to localize to nuclear damage foci, many investigators in the field suspect that the Fanconi anemia pathway supports the integrity of the Rad51 and BRCA1 and BRCA2 pathways as they function in homologous recombination repair. Because these abnormalities are common to all somatic cells, it is unlikely that dysfunction of this particular pathway results in tissue-specific apoptosis of hematopoietic cells. Indeed, at least one of the Fanconi anemia proteins, FANCC, exhibits functions in hematopoietic cells in addition to its role in the complex. Because FANCC protects hematopoietic cells from apoptotic cues in ways that do not require an intact heteromeric Fanconi anemia complex, it is reasonable to expect that the other Fanconi anemia gene products will have independent cytoplasmic and nuclear functions, particularly in hematopoietic and germ cells that seem to rely so substantially on an intact portfolio of Fanconi anemia proteins.
Collapse
Affiliation(s)
- Grover C Bagby
- Oregon Health and Science University Cancer Institute, Department of Medicine, Oregon Health and Science University, Portland 97201, USA.
| |
Collapse
|
25
|
Yagasaki H, Adachi D, Oda T, Garcia-Higuera I, Tetteh N, D'Andrea AD, Futaki M, Asano S, Yamashita T. A cytoplasmic serine protein kinase binds and may regulate the Fanconi anemia protein FANCA. Blood 2001; 98:3650-7. [PMID: 11739169 DOI: 10.1182/blood.v98.13.3650] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Fanconi anemia (FA) is an autosomal recessive disease with congenital anomalies, bone marrow failure, and susceptibility to leukemia. Patient cells show chromosome instability and hypersensitivity to DNA cross-linking agents. At least 8 complementation groups (A-G) have been identified and 6 FA genes (for subtypes A, C, D2, E, F, and G) have been cloned. Increasing evidence indicates that a protein complex assembly of multiple FA proteins, including FANCA and FANCG, plays a crucial role in the FA pathway. Previously, it was reported that FANCA was phosphorylated in lymphoblasts from normal controls, whereas the phosphorylation was defective in those derived from patients with FA of multiple complementation groups. The present study examined phosphorylation of FANCA ectopically expressed in FANCA(-) cells. Several patient-derived mutations abrogated in vivo phosphorylation of FANCA in this system, suggesting that FANCA phosphorylation is associated with its function. In vitro phosphorylation studies indicated that a physiologic protein kinase for FANCA (FANCA-PK) forms a complex with the substrate. Furthermore, at least a part of FANCA-PK as well as phosphorylated FANCA were included in the FANCA/FANCG complex. Thus, FANCA-PK appears to be another component of the FA protein complex and may regulate function of FANCA. FANCA-PK was characterized as a cytoplasmic serine kinase sensitive to wortmannin. Identification of the protein kinase is expected to elucidate regulatory mechanisms that control the FA pathway.
Collapse
Affiliation(s)
- H Yagasaki
- Division of Genetic Diagnosis, Institute of Medical Science, University of Tokyo, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Fagerlie S, Lensch MW, Pang Q, Bagby GC. The Fanconi anemia group C gene product: signaling functions in hematopoietic cells. Exp Hematol 2001; 29:1371-81. [PMID: 11750095 DOI: 10.1016/s0301-472x(01)00755-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- S Fagerlie
- OHSU Cancer Institute, Department of Medicine, Oregon Health and Science University, Portland, Ore. 97201-3098, USA
| | | | | | | |
Collapse
|
27
|
Abstract
DNA interstrand cross-links (ICLs) are very toxic to dividing cells, because they induce mutations, chromosomal rearrangements and cell death. Inducers of ICLs are important drugs in cancer treatment. We discuss the main properties of several classes of ICL agents and the types of damage they induce. The current insights in ICL repair in bacteria, yeast and mammalian cells are reviewed. An intriguing aspect of ICLs is that a number of multi-step DNA repair pathways including nucleotide excision repair, homologous recombination and post-replication/translesion repair all impinge on their repair. Furthermore, the breast cancer-associated proteins Brca1 and Brca2, the Fanconi anemia-associated FANC proteins, and cell cycle checkpoint proteins are involved in regulating the cellular response to ICLs. We depict several models that describe possible pathways for the repair or replicational bypass of ICLs.
Collapse
Affiliation(s)
- M L Dronkert
- Department of Cell Biology and Genetics, Erasmus University Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
| | | |
Collapse
|
28
|
Yamashita T, Nakahata T. Current knowledge on the pathophysiology of Fanconi anemia: from genes to phenotypes. Int J Hematol 2001; 74:33-41. [PMID: 11530803 DOI: 10.1007/bf02982547] [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] [Indexed: 11/29/2022]
Abstract
Fanconi anemia (FA) is an autosomal recessive disease characterized by congenital anomalies, bone marrow failure, and leukemia susceptibility. FA cells show chromosome instability and hypersensitivity to DNA cross-linking agents such as mitomycin C. Recent studies indicate that there are at least 8 genetically distinct FA groups (A, B, C, D1, D2, E, F, G). To date, 6 genes (for A, C, D2, E, F, and G) have been cloned. In this review, we describe the structures and functions of FA proteins. Increasing evidence indicates that the multiple FA proteins cooperate in a biochemical pathway and/or a multimer complex. FANCD2, a downstream component of the FA pathway, has recently been shown to be ubiquitinated in response to DNA damage and to translocate to nuclear foci containing BRCA1, a breast cancer susceptibility gene product, suggesting a role for this protein in DNA repair functions. We also describe 2 emerging issues: genotype-phenotype relationships and mosaicism. The FA pathway is likely to play a critical role as a caretaker of genomic integrity in hematopoietic stem cells. Clarifying the molecular basis of this disease may provide new insights into the pathogenesis of bone marrow failure syndromes and myeloid malignancies.
Collapse
Affiliation(s)
- T Yamashita
- Division of Genetic Diagnosis, Institute of Medical Science, University of Tokyo, Japan.
| | | |
Collapse
|
29
|
Abstract
The past few years have witnessed a considerable expansion in our understanding of the pathways that maintain chromosome stability in dividing cells through the identification of genes that are mutated in certain human chromosome instability disorders. Cells that are derived from patients with Fanconi anaemia (FA) show spontaneous chromosomal instability and mutagen hypersensitivity, but FA poses a unique challenge as the nature of the DNA-damage-response pathway thought to be affected by the disease has long been a mystery. However, the recent cloning of most of the FA-associated genes, and the characterization of their protein products, has provided tantalizing clues as to the molecular basis of this disease.
Collapse
Affiliation(s)
- H Joenje
- Department of Clinical Genetics and Human Genetics, and Oncology Research Institute, Free University Medical Centre, Van der Boechorststraat 7, NL-1081 BT, Amsterdam, The Netherlands.
| | | |
Collapse
|
30
|
Ren J, Youssoufian H. Functional analysis of the putative peroxidase domain of FANCA, the Fanconi anemia complementation group A protein. Mol Genet Metab 2001; 72:54-60. [PMID: 11161829 DOI: 10.1006/mgme.2000.3109] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fanconi anemia (FA) is an autosomal recessive disorder manifested by chromosomal breakage, birth defects, and susceptibility to bone marrow failure and cancer. At least seven complementation groups have been identified, and the genes defective in four groups have been cloned. The most common subtype is complementation group A. Although the normal functions of the gene products defective in FA cells are not completely understood, a clue to the function of the FA group A gene product (FANCA) was provided by the detection of limited homology in the amino terminal region to a class of heme peroxidases. We evaluated this hypothesis by mutagenesis and functional complementation studies. We substituted alanine residues for the most conserved FANCA residues in the putative peroxidase domain and tested their effects on known biochemical and cellular functions of FANCA. While the substitution mutants were comparable to wild-type FANCA with regard to their stability, subcellular localization, and interaction with FANCG, only the Trp(183)-to-Ala substitution (W183A) abolished the ability of FANCA to complement the sensitivity of FA group A cells to mitomycin C. By contrast, TUNEL assays for apoptosis after exposure to H2O2 showed no differences between parental FA group A cells, cells complemented with wild-type FANCA, and cells complemented with the W183A of FANCA. Moreover, semiquantitative RT-PCR analysis for the expression of the peroxide-sensitive heme oxygenase gene showed appropriate induction after H2O2 exposure. Thus, W183A appears to be essential for the in vivo activity of FANCA in a manner independent of its interaction with FANCG. Moreover, neither wild-type FANCA nor the W183A mutation appears to alter the peroxide-induced apoptosisor peroxide-sensing ability of FA group A cells.
Collapse
Affiliation(s)
- J Ren
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | | |
Collapse
|
31
|
The Fanconi anemia proteins FANCA and FANCG stabilize each other and promote the nuclear accumulation of the Fanconi anemia complex. Blood 2000. [DOI: 10.1182/blood.v96.9.3224.h8003224_3224_3230] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Fanconi anemia (FA) is an autosomal recessive cancer susceptibility syndrome with 8 complementation groups. Four of the FA genes have been cloned, and at least 3 of the encoded proteins, FANCA, FANCC, and FANCG/XRCC9, interact in a multisubunit protein complex. The FANCG protein binds directly to the amino terminal nuclear localization sequence (NLS) of FANCA, suggesting that FANCG plays a role in regulating FANCA nuclear accumulation. In the current study the functional consequences of FANCG/FANCA binding were examined. Correction of an FA-G cell line with the FANCG complementary DNA (cDNA) resulted in FANCA/FANCG binding, prolongation of the cellular half-life of FANCA, and an increase in the nuclear accumulation of the FA protein complex. Similar results were obtained upon correction of an FA-A cell line, with a reciprocal increase in the half-life of FANCG. Patient-derived mutant forms of FANCA, containing an intact NLS sequence but point mutations in the carboxy-terminal leucine zipper region, bound FANCG in the cytoplasm. The mutant forms failed to translocate to the nucleus of transduced cells, thereby suggesting a model of coordinated binding and nuclear translocation. These results demonstrate that the FANCA/FANCG interaction is required to maintain the cellular levels of both proteins. Moreover, at least one function of FANCG and FANCA is to regulate the nuclear accumulation of the FA protein complex. Failure to accumulate the nuclear FA protein complex results in the characteristic spectrum of clinical and cellular abnormalities observed in FA.
Collapse
|
32
|
The Fanconi anemia proteins FANCA and FANCG stabilize each other and promote the nuclear accumulation of the Fanconi anemia complex. Blood 2000. [DOI: 10.1182/blood.v96.9.3224] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Fanconi anemia (FA) is an autosomal recessive cancer susceptibility syndrome with 8 complementation groups. Four of the FA genes have been cloned, and at least 3 of the encoded proteins, FANCA, FANCC, and FANCG/XRCC9, interact in a multisubunit protein complex. The FANCG protein binds directly to the amino terminal nuclear localization sequence (NLS) of FANCA, suggesting that FANCG plays a role in regulating FANCA nuclear accumulation. In the current study the functional consequences of FANCG/FANCA binding were examined. Correction of an FA-G cell line with the FANCG complementary DNA (cDNA) resulted in FANCA/FANCG binding, prolongation of the cellular half-life of FANCA, and an increase in the nuclear accumulation of the FA protein complex. Similar results were obtained upon correction of an FA-A cell line, with a reciprocal increase in the half-life of FANCG. Patient-derived mutant forms of FANCA, containing an intact NLS sequence but point mutations in the carboxy-terminal leucine zipper region, bound FANCG in the cytoplasm. The mutant forms failed to translocate to the nucleus of transduced cells, thereby suggesting a model of coordinated binding and nuclear translocation. These results demonstrate that the FANCA/FANCG interaction is required to maintain the cellular levels of both proteins. Moreover, at least one function of FANCG and FANCA is to regulate the nuclear accumulation of the FA protein complex. Failure to accumulate the nuclear FA protein complex results in the characteristic spectrum of clinical and cellular abnormalities observed in FA.
Collapse
|
33
|
Baudoux L, Defechereux P, Rentier B, Piette J. Gene activation by Varicella-zoster virus IE4 protein requires its dimerization and involves both the arginine-rich sequence, the central part, and the carboxyl-terminal cysteine-rich region. J Biol Chem 2000; 275:32822-31. [PMID: 10889190 DOI: 10.1074/jbc.m001444200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Varicella-zoster virus (VZV) open reading frame 4-encoded protein (IE4) possesses transactivating properties for VZV genes as well as for those of heterologous viruses. Since most transcription factors act as dimers, IE4 dimerization was studied using the mammalian two-hybrid system. Introduction of mutations in the IE4 open reading frame demonstrated that both the central region and the carboxyl-terminal cysteine-rich domain were important for efficient dimerization. Within the carboxyl-terminal domain, substitution of amino acids encompassing residues 443-447 totally abolished dimerization. Gene activation by IE4 was studied by transient transfection with an IE4 expression plasmid and a reporter gene under the control of either the human immunodeficiency virus, type 1, long terminal repeat or the VZV thymidine kinase promoter. Regions of IE4 important for dimerization were also shown to be crucial for transactivation. In addition, the arginine-rich domains Rb and Rc of the amino-terminal region were also demonstrated to be important for transactivation, whereas the Ra domain as well as an acidic and bZIP-containing regions were shown to be dispensable for gene transactivation. A nucleocytoplasmic shuttling of IE4 has also been characterized, involving a nuclear localization signal identified within the Rb domain and a nuclear export mechanism partially depending on Crm-1.
Collapse
Affiliation(s)
- L Baudoux
- Laboratory of Fundamental Virology and Immunology, Institute of Pathology B23, University of Liege, B-4000 Liege, Belgium
| | | | | | | |
Collapse
|
34
|
Carboxy terminal region of the Fanconi anemia protein, FANCG/XRCC9, is required for functional activity. Blood 2000. [DOI: 10.1182/blood.v96.5.1625.h8001625a_1625_1632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fanconi anemia (FA) is an autosomal recessive cancer susceptibility syndrome with eight complementation groups. Four of the FA genes have been cloned, and at least three of the encoded proteins, FANCA, FANCC, and FANCG/XRCC9, interact in a nuclear complex, required for the maintenance of normal chromosome stability. In the current study, mutant forms of the FANCA and FANCG proteins have been generated and analyzed with respect to protein complex formation, nuclear translocation, and functional activity. The results demonstrate that the amino terminal two-thirds of FANCG (FANCG amino acids 1-428) binds to the amino terminal nuclear localization signal (NLS) of the FANCA protein. On the basis of 2-hybrid analysis, the FANCA/FANCG binding is a direct protein-protein interaction. Interestingly, a truncated mutant form of the FANCG protein, lacking the carboxy terminus, binds in a complex with FANCA and translocates to the nucleus; however, this mutant protein fails to bind to FANCC and fails to correct the mitomycin C sensitivity of an FA-G cell line. Taken together, these results demonstrate that binding of FANCG to the amino terminal FANCA NLS sequence is necessary but not sufficient for the functional activity of FANCG. Additional amino acid sequences at the carboxy terminus of FANCG are required for the binding of FANCC in the complex.
Collapse
|
35
|
Carboxy terminal region of the Fanconi anemia protein, FANCG/XRCC9, is required for functional activity. Blood 2000. [DOI: 10.1182/blood.v96.5.1625] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Fanconi anemia (FA) is an autosomal recessive cancer susceptibility syndrome with eight complementation groups. Four of the FA genes have been cloned, and at least three of the encoded proteins, FANCA, FANCC, and FANCG/XRCC9, interact in a nuclear complex, required for the maintenance of normal chromosome stability. In the current study, mutant forms of the FANCA and FANCG proteins have been generated and analyzed with respect to protein complex formation, nuclear translocation, and functional activity. The results demonstrate that the amino terminal two-thirds of FANCG (FANCG amino acids 1-428) binds to the amino terminal nuclear localization signal (NLS) of the FANCA protein. On the basis of 2-hybrid analysis, the FANCA/FANCG binding is a direct protein-protein interaction. Interestingly, a truncated mutant form of the FANCG protein, lacking the carboxy terminus, binds in a complex with FANCA and translocates to the nucleus; however, this mutant protein fails to bind to FANCC and fails to correct the mitomycin C sensitivity of an FA-G cell line. Taken together, these results demonstrate that binding of FANCG to the amino terminal FANCA NLS sequence is necessary but not sufficient for the functional activity of FANCG. Additional amino acid sequences at the carboxy terminus of FANCG are required for the binding of FANCC in the complex.
Collapse
|
36
|
Wong JC, Alon N, Norga K, Kruyt FA, Youssoufian H, Buchwald M. Cloning and analysis of the mouse Fanconi anemia group A cDNA and an overlapping penta zinc finger cDNA. Genomics 2000; 67:273-83. [PMID: 10936049 DOI: 10.1006/geno.2000.6252] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Despite the cloning of four disease-associated genes for Fanconi anemia (FA), the molecular pathogenesis of FA remains largely unknown. To study FA complementation group A using the mouse as a model system, we cloned and characterized the mouse homolog of the human FANCA cDNA. The mouse cDNA (Fanca) encodes a 161-kDa protein that shares 65% amino acid sequence identity with human FANCA. Fanca is located at the distal region of mouse chromosome 8 and has a ubiquitous pattern of expression in embryonic and adult tissues. Expression of the mouse cDNA in human FA-A cells restores the cellular drug sensitivity to normal levels. Thus, the expression pattern, protein structure, chromosomal location, and function of FANCA are conserved in the mouse. We also isolated a novel zinc finger protein, Zfp276, which has five C(2)H(2) domains. Interestingly, Zfp276 is situated in the Fanca locus, and the 3'UTR of its cDNA overlaps with the last four exons of Fanca in a tail-to-tail manner. Zfp276 is expressed in the same tissues as Fanca, but does not complement the mitomycin C (MMC)-sensitive phenotype of FA-A cells. The overlapping genomic organization between Zfp276 and Fanca may have relevance to the disease phenotype of FA.
Collapse
Affiliation(s)
- J C Wong
- Program in Genetics and Genomics Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | | | | | | | | | | |
Collapse
|
37
|
Kruyt FAE, Youssoufian H. Do Fanconi anemia genes control cell response to cross-linking agents by modulating cytochrome P-450 reductase activity? Drug Resist Updat 2000; 3:211-215. [PMID: 11498388 DOI: 10.1054/drup.2000.0159] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Fanconi anemia (FA) genes play an important role in maintaining chromosomal stability and the defense of mammalian cells against cross-linking agents, such as cisplatin and mitomycin C (MMC). Cells derived from FA patients display a characteristic hypersensitivity toward cross-linking agents. Despite great progression in our understanding of the mechanisms that protect cells against these potent anti-cancer drugs, the specific roles of FA gene products in these processes have not been delineated. Recent studies have shown that the FA group C gene product, FANCC, can bind to and regulate the activity of cytochrome P450-reductase (P450R), an enzyme involved in the bioactivation of MMC. In this mini-review, this finding is placed in the context of complex mechanisms involved in the bioreductive activation of MMC and the hypersensitivity of FA cells to MMC. Although it would be premature to attribute the FA phenotype wholly to an abnormal activation of MMC, the regulation of P450R by FANCC suggests a novel link between one or more FA gene products, the cellular oxidative state, and the response to chemotherapeutic agents. Copyright 2000 Harcourt Publishers Ltd.
Collapse
Affiliation(s)
- Frank A. E. Kruyt
- Department of Medical Oncology, University Hospital Vrije Universiteit, Amsterdam, The Netherlands
| | | |
Collapse
|
38
|
Huber PA, Medhurst AL, Youssoufian H, Mathew CG. Investigation of Fanconi anemia protein interactions by yeast two-hybrid analysis. Biochem Biophys Res Commun 2000; 268:73-7. [PMID: 10652215 DOI: 10.1006/bbrc.1999.2055] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fanconi anemia is a chromosomal breakage disorder with eight complementation groups (A-H), and three genes (FANCA, FANCC, and FANCG) have been identified. Initial investigations of the interaction between FANCA and FANCC, principally by co-immunoprecipitation, have proved controversial. We used the yeast two-hybrid assay to test for interactions of the FANCA, FANCC, and FANCG proteins. No activation of the reporter gene was observed in yeast co-expressing FANCA and FANCC as hybrid proteins, suggesting that FANCA does not directly interact with FANCC. However, a high level of activation was found when FANCA was co-expressed with FANCG, indicating strong, direct interaction between these proteins. Both FANCA and FANCG show weak but consistent interaction with themselves, suggesting that their function may involve dimerisation. The site of interaction of FANCG with FANCA was investigated by analysis of 12 mutant fragments of FANCG. Although both N- and C-terminal fragments did interact, binding to FANCA was drastically reduced, suggesting that more than one region of the FANCG protein is required for proper interaction with FANCA.
Collapse
Affiliation(s)
- P A Huber
- Division of Medical Genetics, Guy's, King's and St. Thomas' School of Medicine, Guy's Hospital, 7th Floor, Guy's Tower, London, SE1 9RT, United Kingdom.
| | | | | | | |
Collapse
|