151
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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.
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152
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Wu Y, Sommers JA, Loiland JA, Kitao H, Kuper J, Kisker C, Brosh RM. The Q motif of Fanconi anemia group J protein (FANCJ) DNA helicase regulates its dimerization, DNA binding, and DNA repair function. J Biol Chem 2012; 287:21699-716. [PMID: 22582397 DOI: 10.1074/jbc.m112.351338] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The Q motif, conserved in a number of RNA and DNA helicases, is proposed to be important for ATP binding based on structural data, but its precise biochemical functions are less certain. FANCJ encodes a Q motif DEAH box DNA helicase implicated in Fanconi anemia and breast cancer. A Q25A mutation of the invariant glutamine in the Q motif abolished its ability to complement cisplatin or telomestatin sensitivity of a fancj null cell line and exerted a dominant negative effect. Biochemical characterization of the purified recombinant FANCJ-Q25A protein showed that the mutation disabled FANCJ helicase activity and the ability to disrupt protein-DNA interactions. FANCJ-Q25A showed impaired DNA binding and ATPase activity but displayed ATP binding and temperature-induced unfolding transition similar to FANCJ-WT. Size exclusion chromatography and sedimentation velocity analyses revealed that FANCJ-WT existed as molecular weight species corresponding to a monomer and a dimer, and the dimeric form displayed a higher specific activity for ATPase and helicase, as well as greater DNA binding. In contrast, FANCJ-Q25A existed only as a monomer, devoid of helicase activity. Thus, the Q motif is essential for FANCJ enzymatic activity in vitro and DNA repair function in vivo.
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Affiliation(s)
- Yuliang Wu
- Laboratory of Molecular Gerontology, National Institutes of Health Biomedical Research Center, NIA, Baltimore, Maryland 21224, USA
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153
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BRCA1-mediated repression of mutagenic end-joining of DNA double-strand breaks requires complex formation with BACH1. Biochem J 2012; 441:919-26. [PMID: 22032289 DOI: 10.1042/bj20110314] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACH1 (BRCA1-associated C-terminal helicase 1), the product of the BRIP1 {BRCA1 [breast cancer 1, early onset]-interacting protein C-terminal helicase 1; also known as FANCJ [FA-J (Fanconi anaemia group J) protein]} gene mutated in Fanconi anaemia patients from complementation group J, has been implicated in DNA repair and damage signalling. BACH1 exerts DNA helicase activities and physically interacts with BRCA1 and MLH1 (mutL homologue 1), which differentially control DNA DSB (double-strand break) repair processes. The present study shows that BACH1 plays a role in both HR (homologous recombination) and MMEJ (microhomology-mediated non-homologous end-joining) and reveals discrete mechanisms underlying modulation of these pathways. Our results indicate that BACH1 stimulates HR, which depends on the integrity of the helicase domain. Disruption of the BRCA1-BACH1 complex through mutation of BACH1 compromised errorfree NHEJ (non-homologous end-joining) and accelerated error-prone MMEJ. Conversely, molecular changes in BACH1 abrogating MLH1 binding interfered neither with HR nor with MMEJ. Importantly, MMEJ is a mutagenic DSB repair pathway, which is derepressed in hereditary breast and ovarian carcinomas. Since BRCA1 and BACH1 mutations targeting the BRCA1-BACH1 interaction have been associated with breast cancer susceptibility, the results of the present study thus provide evidence for a novel role of BACH1 in tumour suppression.
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154
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Analysis of SLX4/FANCP in non-BRCA1/2-mutated breast cancer families. BMC Cancer 2012; 12:84. [PMID: 22401137 PMCID: PMC3315397 DOI: 10.1186/1471-2407-12-84] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Accepted: 03/08/2012] [Indexed: 12/04/2022] Open
Abstract
Background Genes that, when mutated, cause Fanconi anemia or greatly increase breast cancer risk encode for proteins that converge on a homology-directed DNA damage repair process. Mutations in the SLX4 gene, which encodes for a scaffold protein involved in the repair of interstrand cross-links, have recently been identified in unclassified Fanconi anemia patients. A mutation analysis of SLX4 in German or Byelorussian familial cases of breast cancer without detected mutations in BRCA1 or BRCA2 has been completed, with globally negative results. Methods The genomic region of SLX4, comprising all exons and exon-intron boundaries, was sequenced in 94 Spanish familial breast cancer cases that match a criterion indicating the potential presence of a highly-penetrant germline mutation, following exclusion of BRCA1 or BRCA2 mutations. Results This mutational analysis revealed extensive genetic variation of SLX4, with 21 novel single nucleotide variants; however, none could be linked to a clear alteration of the protein function. Nonetheless, genotyping 10 variants (nine novel, all missense amino acid changes) in a set of controls (138 women and 146 men) did not detect seven of them. Conclusions Overall, while the results of this study do not identify clearly pathogenic mutations of SLX4 contributing to breast cancer risk, further genetic analysis, combined with functional assays of the identified rare variants, may be warranted to conclusively assess the potential link with the disease.
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155
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Fanconi anemia (FA) binding protein FAAP20 stabilizes FA complementation group A (FANCA) and participates in interstrand cross-link repair. Proc Natl Acad Sci U S A 2012; 109:4491-6. [PMID: 22396592 DOI: 10.1073/pnas.1118720109] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Fanconi anemia (FA) pathway participates in interstrand cross-link (ICL) repair and the maintenance of genomic stability. The FA core complex consists of eight FA proteins and two Fanconi anemia-associated proteins (FAAP24 and FAAP100). The FA core complex has ubiquitin ligase activity responsible for monoubiquitination of the FANCI-FANCD2 (ID) complex, which in turn initiates a cascade of biochemical events that allow processing and removal of cross-linked DNA and thereby promotes cell survival following DNA damage. Here, we report the identification of a unique component of the FA core complex, namely, FAAP20, which contains a RAD18-like ubiquitin-binding zinc-finger domain. Our data suggest that FAAP20 promotes the functional integrity of the FA core complex via its direct interaction with the FA gene product, FANCA. Indeed, somatic knockout cells devoid of FAAP20 displayed the hallmarks of FA cells, including hypersensitivity to DNA cross-linking agents, chromosome aberrations, and reduced FANCD2 monoubiquitination. Taking these data together, our study indicates that FAAP20 is an important player involved in the FA pathway.
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156
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Wang B. BRCA1 tumor suppressor network: focusing on its tail. Cell Biosci 2012; 2:6. [PMID: 22369660 PMCID: PMC3315748 DOI: 10.1186/2045-3701-2-6] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 02/27/2012] [Indexed: 02/07/2023] Open
Abstract
Germline mutations of the BRCA1 tumor suppressor gene are a major cause of familial breast and ovarian cancer. BRCA1 plays critical roles in the DNA damage response that regulates activities of multiple repair and checkpoint pathways for maintaining genome stability. The BRCT domains of BRCA1 constitute a phospho-peptide binding domain recognizing a phospho-SPxF motif (S, serine; P, proline; × varies; F, phenylalanine). The BRCT domains are frequently targeted by clinically important mutations and most of these mutations disrupt the binding surface of the BRCT domains to phosphorylated peptides. The BRCT domain and its capability to bind phosphorylated protein is required for the tumor suppressor function of BRCA1. Through its BRCT phospho-binding ability BRCA1 forms at least three mutually exclusive complexes by binding to phosphorylated proteins Abraxas, Bach1 and CTIP. The A, B and C complexes, at lease partially undertake BRCA1's role in mechanisms of cell cycle checkpoint and DNA repair that maintain genome stability, thus may play important roles in BRCA1's tumor suppressor function.
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Affiliation(s)
- Bin Wang
- Department of Genetics, The University of Texas M,D, Anderson Cancer Center, 1515 Holcombe Blvd, Unit 1010, Houston, TX 77030, USA.
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157
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Wu Y, Brosh RM. DNA helicase and helicase-nuclease enzymes with a conserved iron-sulfur cluster. Nucleic Acids Res 2012; 40:4247-60. [PMID: 22287629 PMCID: PMC3378879 DOI: 10.1093/nar/gks039] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Conserved Iron-Sulfur (Fe-S) clusters are found in a growing family of metalloproteins that are implicated in prokaryotic and eukaryotic DNA replication and repair. Among these are DNA helicase and helicase-nuclease enzymes that preserve chromosomal stability and are genetically linked to diseases characterized by DNA repair defects and/or a poor response to replication stress. Insight to the structural and functional importance of the conserved Fe-S domain in DNA helicases has been gleaned from structural studies of the purified proteins and characterization of Fe-S cluster site-directed mutants. In this review, we will provide a current perspective of what is known about the Fe-S cluster helicases, with an emphasis on how the conserved redox active domain may facilitate mechanistic aspects of helicase function. We will discuss testable models for how the conserved Fe-S cluster might operate in helicase and helicase-nuclease enzymes to conduct their specialized functions that help to preserve the integrity of the genome.
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Affiliation(s)
- Yuliang Wu
- Department of Biochemistry, University of Saskatchewan, Health Sciences Building, Saskatoon, Saskatchewan, S7N 5E5, Canada.
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158
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Keimling M, Deniz M, Varga D, Stahl A, Schrezenmeier H, Kreienberg R, Hoffmann I, König J, Wiesmüller L. The power of DNA double-strand break (DSB) repair testing to predict breast cancer susceptibility. FASEB J 2012; 26:2094-104. [PMID: 22278937 DOI: 10.1096/fj.11-200790] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Most presently known breast cancer susceptibility genes have been linked to DSB repair. To identify novel markers that may serve as indicators for breast cancer risk, we performed DSB repair analyses using a case-control design. Thus, we examined 35 women with defined familial history of breast and/or ovarian cancer (first case group), 175 patients with breast cancer (second case group), and 245 healthy women without previous cancer or family history of breast cancer (control group). We analyzed DSB repair in peripheral blood lymphocytes (PBLs) by a GFP-based test system using 3 pathway-specific substrates. We found increases of microhomology-mediated nonhomologous end joining (mmNHEJ) and nonconservative single-strand annealing (SSA) in women with familial risk vs. controls (P=0.0001-0.0022) and patients with breast cancer vs. controls (P=0.0004-0.0042). Young age (<50) at initial diagnosis of breast cancer, which could be indicative of genetic predisposition, was associated with elevated SSA using two different substrates, amounting to similar odds ratios (ORs=2.54-4.46, P=0.0059-0.0095) as for familial risk (ORs=2.61-4.05, P=0.0007-0.0045). These findings and supporting validation data underscore the great potential of detecting distinct DSB repair activities in PBLs as method to estimate breast cancer susceptibility beyond limitations of genotyping and to predict responsiveness to therapeutics targeting DSB repair-dysfunctional tumors.
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Affiliation(s)
- Marlen Keimling
- Department of Obstetrics and Gynecology, Ulm University, Prittwitzstrasse 43, 89075 Ulm, Germany
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159
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Moldovan GL, Dejsuphong D, Petalcorin MIR, Hofmann K, Takeda S, Boulton SJ, D’Andrea AD. Inhibition of homologous recombination by the PCNA-interacting protein PARI. Mol Cell 2012; 45:75-86. [PMID: 22153967 PMCID: PMC3267324 DOI: 10.1016/j.molcel.2011.11.010] [Citation(s) in RCA: 173] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 08/12/2011] [Accepted: 11/04/2011] [Indexed: 12/23/2022]
Abstract
Inappropriate homologous recombination (HR) causes genomic instability and cancer. In yeast, the UvrD family helicase Srs2 is recruited to sites of DNA replication by SUMO-modified PCNA, where it acts to restrict HR by disassembling toxic RAD51 nucleofilaments. How human cells control recombination at replication forks is unknown. Here, we report that the protein PARI, containing a UvrD-like helicase domain, is a PCNA-interacting partner required for preservation of genome stability in human and DT40 chicken cells. Using cell-based and biochemical assays, we show that PARI restricts unscheduled recombination by interfering with the formation of RAD51-DNA HR structures. Finally, we show that PARI knockdown suppresses the genomic instability of Fanconi Anemia/BRCA pathway-deficient cells. Thus, we propose that PARI is a long sought-after factor that suppresses inappropriate recombination events at mammalian replication forks.
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Affiliation(s)
- George-Lucian Moldovan
- Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston MA 02215, USA
| | - Donniphat Dejsuphong
- Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston MA 02215, USA
| | - Mark I. R. Petalcorin
- DNA Damage Response Laboratory, Cancer Research UK, London Research Institute, Clare Hall, Blanche Lane, South Mimms EN6 3LD, UK
| | - Kay Hofmann
- Bioinformatics Group, Miltenyi Biotec GmbH, Friedrich-Ebert-Strasse 68, 51429 Bergisch-Gladbach, Germany
| | - Shunichi Takeda
- Department of Radiation Genetics, Kyoto University Graduate School of Medicine, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501, Japan
| | - Simon J. Boulton
- DNA Damage Response Laboratory, Cancer Research UK, London Research Institute, Clare Hall, Blanche Lane, South Mimms EN6 3LD, UK
| | - Alan D. D’Andrea
- Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston MA 02215, USA
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160
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The functions of MutL in mismatch repair: the power of multitasking. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 110:41-70. [PMID: 22749142 DOI: 10.1016/b978-0-12-387665-2.00003-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
DNA mismatch repair enhances genomic stability by correcting errors that have escaped polymerase proofreading. One of the critical steps in DNA mismatch repair is discriminating the new from the parental DNA strand as only the former needs repair. In Escherichia coli, the latent endonuclease MutH carries out this function. However, most prokaryotes and all eukaryotes lack a mutH gene. MutL is a key component of this system that mediates protein-protein interactions during mismatch recognition, strand discrimination, and strand removal. Hence, it had long been thought that the primary function of MutL was coordinating sequential mismatch repair steps. However, recent studies have revealed that most MutL homologs from organisms lacking MutH encode a conserved metal-binding motif associated with a weak endonuclease activity. As MutL homologs bearing this activity are found only in organisms relying on MutH-independent DNA mismatch repair, this finding unveils yet another crucial function of the MutL protein at the strand discrimination step. In this chapter, we review recent functional and structural work aimed at characterizing the multiple functions of MutL and discuss how the endonuclease activity of MutL is regulated by other repair factors.
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161
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Wu Y, Sommers JA, Khan I, de Winter JP, Brosh RM. Biochemical characterization of Warsaw breakage syndrome helicase. J Biol Chem 2011; 287:1007-21. [PMID: 22102414 DOI: 10.1074/jbc.m111.276022] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in the human ChlR1 gene are associated with a unique genetic disorder known as Warsaw breakage syndrome characterized by cellular defects in sister chromatid cohesion and hypersensitivity to agents that induce replication stress. A role of ChlR1 helicase in sister chromatid cohesion was first evidenced by studies of the yeast homolog Chl1p; however, its cellular functions in DNA metabolism are not well understood. We carefully examined the DNA substrate specificity of purified recombinant human ChlR1 protein and the biochemical effect of a patient-derived mutation, a deletion of a single lysine (K897del) in the extreme C terminus of ChlR1. The K897del clinical mutation abrogated ChlR1 helicase activity on forked duplex or D-loop DNA substrates by perturbing its DNA binding and DNA-dependent ATPase activity. Wild-type ChlR1 required a minimal 5' single-stranded DNA tail of 15 nucleotides to efficiently unwind a simple duplex DNA substrate. The additional presence of a 3' single-stranded DNA tail as short as five nucleotides dramatically increased ChlR1 helicase activity, demonstrating the preference of the enzyme for forked duplex structures. ChlR1 unwound G-quadruplex (G4) DNA with a strong preference for a two-stranded antiparallel G4 (G2') substrate and was only marginally active on a four-stranded parallel G4 structure. The marked difference in ChlR1 helicase activity on the G4 substrates, reflected by increased binding to the G2' substrate, distinguishes ChlR1 from the sequence-related FANCJ helicase mutated in Fanconi anemia. The biochemical results are discussed in light of the known cellular defects associated with ChlR1 deficiency.
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Affiliation(s)
- Yuliang Wu
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224, USA
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162
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Chung G, O'Neil NJ, Rose AM. CHL-1 provides an essential function affecting cell proliferation and chromosome stability in Caenorhabditis elegans. DNA Repair (Amst) 2011; 10:1174-82. [PMID: 21968058 DOI: 10.1016/j.dnarep.2011.09.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 08/24/2011] [Accepted: 09/09/2011] [Indexed: 01/05/2023]
Abstract
A family of helicases that are important in maintaining genome stability is the iron-sulfur group. Members of this family include DOG-1/FANCJ, RTEL1, XPD and Chl1p/DDX11. In Caenorhabitis elegans, the predicted gene M03C11.2 has orthology to the CHL1 (Chromosome loss 1) gene in Saccharomyces cerevisiae and DDX11 (DEAD/H box polypeptide 11) in humans. In this paper, we show that the chl-1 gene in C. elegans is required for normal development and fertility. Mutants have lineage-independent cell proliferation defects that result in a Stu (sterile uncoordinated) phenotype, characterized by gonadal abnormalities and a reduced number of D motor neurons and seam cells. A chromosome stability defect is present in the germ cells, where an abnormal number of DAPI-staining chromosomes appear in diakinesis. CHL-1 function is required for the integrity of poly-guanine/poly-cytosine DNA in the absence of DOG-1/FANCJ: the loss of CHL-1 alone does not result in the deletion of G-tracts, but it does increase the number of deletions observed in the dog-1; chl-1 double mutant, indicating a role for CHL-1 during replication and repair. In addition, we observed that cohesin defects increased the number of deletions in the absence of DOG-1/FANCJ. Our results demonstrate a role for CHL-1 in cell proliferation and maintaining normal chromosome numbers, and implicate CHL-1 in chromosome stability and repair of unresolved secondary structures during replication.
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Affiliation(s)
- George Chung
- Department of Medical Genetics, University of British Columbia, 419-2125 East Mall, Vancouver, BC, V6T 1Z4, Canada.
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163
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Constantinou A. Rescue of replication failure by Fanconi anaemia proteins. Chromosoma 2011; 121:21-36. [PMID: 22057367 PMCID: PMC3260432 DOI: 10.1007/s00412-011-0349-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 10/17/2011] [Accepted: 10/17/2011] [Indexed: 01/23/2023]
Abstract
Chromosomal aberrations are often associated with incomplete genome duplication, for instance at common fragile sites, or as a consequence of chemical alterations in the DNA template that block replication forks. Studies of the cancer-prone disease Fanconi anaemia (FA) have provided important insights into the resolution of replication problems. The repair of interstrand DNA crosslinks induced by chemotherapy drugs is coupled with DNA replication and controlled by FA proteins. We discuss here the recent discovery of new FA-associated proteins and the development of new tractable repair systems that have dramatically improved our understanding of crosslink repair. We focus also on how FA proteins protect against replication failure in the context of fragile sites and on the identification of reactive metabolites that account for the development of Fanconi anaemia symptoms.
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Affiliation(s)
- Angelos Constantinou
- Institute of Human Genetics, CNRS UPR 1142, 141 rue de la Cardonille, 34396 Montpellier Cedex 5, France.
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164
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Suhasini AN, Brosh RM. Fanconi anemia and Bloom's syndrome crosstalk through FANCJ-BLM helicase interaction. Trends Genet 2011; 28:7-13. [PMID: 22024395 DOI: 10.1016/j.tig.2011.09.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 09/14/2011] [Accepted: 09/14/2011] [Indexed: 12/01/2022]
Abstract
Fanconi anemia (FA) and Bloom's syndrome (BS) are rare hereditary chromosomal instability disorders. FA displays bone marrow failure, acute myeloid leukemia, and head and neck cancers, whereas BS is characterized by growth retardation, immunodeficiency, and a wide spectrum of cancers. The BLM gene mutated in BS encodes a DNA helicase that functions in a protein complex to suppress sister-chromatid exchange. Of the 15 FA genetic complementation groups implicated in interstrand crosslink repair, FANCJ encodes a DNA helicase involved in recombinational repair and replication stress response. Based on evidence that BLM and FANCJ interact we suggest that crosstalk between BLM and FA pathways is more complex than previously thought. We propose testable models for how FANCJ and BLM coordinate to help cells deal with stalled replication forks or double-strand breaks (DSB). Understanding how BLM and FANCJ cooperate will help to elucidate an important pathway for maintaining genomic stability.
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Affiliation(s)
- Avvaru N Suhasini
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health (NIH) Biomedical Research Center, 251 Bayview Boulevard, Baltimore, MD 21224, USA
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165
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Mutations in BRIP1 confer high risk of ovarian cancer. Nat Genet 2011; 43:1104-7. [PMID: 21964575 DOI: 10.1038/ng.955] [Citation(s) in RCA: 279] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 09/02/2011] [Indexed: 12/12/2022]
Abstract
Ovarian cancer causes more deaths than any other gynecologic malignancy in developed countries. Sixteen million sequence variants, identified through whole-genome sequencing of 457 Icelanders, were imputed to 41,675 Icelanders genotyped using SNP chips, as well as to their relatives. Sequence variants were tested for association with ovarian cancer (N of affected individuals = 656). We discovered a rare (0.41% allelic frequency) frameshift mutation, c.2040_2041insTT, in the BRIP1 (FANCJ) gene that confers an increase in ovarian cancer risk (odds ratio (OR) = 8.13, P = 2.8 × 10(-14)). The mutation was also associated with increased risk of cancer in general and reduced lifespan by 3.6 years. In a Spanish population, another frameshift mutation in BRIP1, c.1702_1703del, was seen in 2 out of 144 subjects with ovarian cancer and 1 out of 1,780 control subjects (P = 0.016). This allele was also associated with breast cancer (seen in 6/927 cases; P = 0.0079). Ovarian tumors from heterozygous carriers of the Icelandic mutation show loss of the wild-type allele, indicating that BRIP1 behaves like a classical tumor suppressor gene in ovarian cancer.
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166
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Dever SM, Golding SE, Rosenberg E, Adams BR, Idowu MO, Quillin JM, Valerie N, Xu B, Povirk LF, Valerie K. Mutations in the BRCT binding site of BRCA1 result in hyper-recombination. Aging (Albany NY) 2011; 3:515-32. [PMID: 21666281 PMCID: PMC3156602 DOI: 10.18632/aging.100325] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We introduced a K1702M mutation in the BRCA1 BRCT domain known to prevent the binding of proteins harboring pS-X-X-F motifs such as Abraxas-RAP80, BRIP1, and CtIP. Surprisingly, rather than impairing homologous recombination repair (HRR), expression of K1702M resulted in hyper-recombination coinciding with an accumulation of cells in S-G2 and no effect on nonhomologous end-joining. These cells also showed increased RAD51 and RPA nuclear staining. More pronounced effects were seen with a naturally occurring BRCT mutant (M1775R) that also produced elevated levels of ssDNA, in part co-localizing with RPA, in line with excessive DNA resection. M1775R induced unusual, thread-like promyelocytic leukemia (PML) nuclear bodies and clustered RPA foci rather than the typical juxtaposed RPA-PML foci seen with wild-type BRCA1. Interestingly, K1702M hyper-recombination diminished with a second mutation in the BRCA1 RING domain (I26A) known to reduce BRCA1 ubiquitin-ligase activity. Thesein vitro findings correlated with elevated nuclear RAD51 and RPA staining of breast cancer tissue from a patient with the M1775R mutation. Altogether, the disruption of BRCA1 (BRCT)-pS-X-X-F protein binding results in ubiquitination-dependent hyper-recombination via excessive DNA resection and the appearance of atypical PML-NBs. Thus, certain BRCA1 mutations that cause hyper-recombination instead of reduced DSB repair might lead to breast cancer.
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Affiliation(s)
- Seth M Dever
- Department of Radiation Oncology, Virginia Commonwealth University, Richmond, 23298, USA
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167
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Cantor SB, Guillemette S. Hereditary breast cancer and the BRCA1-associated FANCJ/BACH1/BRIP1. Future Oncol 2011; 7:253-61. [PMID: 21345144 DOI: 10.2217/fon.10.191] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
It is clear that FANCJ, also known as BACH1 or BRIP1, is an essential tumor suppressor gene based on the identification of clinically relevant mutations not only in breast cancer, but also the childhood cancer syndrome, Fanconi anemia. This conclusion is further supported by the direct and functional interaction between FANCJ and the hereditary breast cancer-associated gene product BRCA1. In the absence of the FANCJ DNA helicase or its interaction with BRCA1, cells have defects in several aspects of the DNA damage response. In particular, the BRCA1-FANCJ interaction is essential for promoting error-free repair, checkpoint control and for limiting DNA damage tolerance. As the number of FANCJ clinical mutations and affected patients accumulate, it will be critical to understand whether the associated tumors resemble BRCA-associated tumors. If so, FANCJ patients could also benefit from new therapies that selectively sensitize DNA repair-defective tumors and spare healthy cells. In this article, we summarize the breast cancer-associated FANCJ mutations and discuss functional outcomes for DNA repair and tumor suppression.
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Affiliation(s)
- Sharon B Cantor
- Department of Cancer Biology, University of Massachusetts Medical School, 364 Plantation St., Worcester, MA 01605, USA.
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168
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Kitao H, Nanda I, Sugino RP, Kinomura A, Yamazoe M, Arakawa H, Schmid M, Innan H, Hiom K, Takata M. FancJ/Brip1 helicase protects against genomic losses and gains in vertebrate cells. Genes Cells 2011; 16:714-27. [PMID: 21605288 DOI: 10.1111/j.1365-2443.2011.01523.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Defects in the FANCJ/BRIP1 helicase gene are associated with genome instability disorders such as familial breast cancer or Fanconi anemia (FA). Although FANCJ has an in vitro activity to resolve G-quadruplex (G4) structures, and FANCJ ortholog in C. elegans prevents G4-associated deletions during replication, how FANCJ loss affects genome integrity in higher organisms remains unclear. Here, we report that FANCJ, but not other FA genes FANCD2 or FANCC, protected against large-scale genomic deletion that occurred frequently at the rearranged immunoglobulin heavy chain (IgH) locus in chicken DT40 cell line, suggesting that FancJ protects the genome independently of the FA ubiquitination pathway. In a more unbiased approach using array-comparative genomic hybridization, we identified de novo deletions as well as amplifications in fancj cells kept in culture for 2 months. A cluster of G4 sequence motifs was found near the breakpoint of one amplified region, but G4 sequence motifs were not detected at the breakpoints of two deleted regions. These results collectively suggest that, unlike in C. elegans, actions of vertebrate FANCJ to promote genome stability may not be limited to protection against the G4-mediated gene deletions.
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Affiliation(s)
- Hiroyuki Kitao
- Laboratory of DNA Damage Signaling, Department of Late Effect Studies, Radiation Biology Center, Kyoto University, Kyoto, Japan
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169
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Cybulski KE, Howlett NG. FANCP/SLX4: a Swiss army knife of DNA interstrand crosslink repair. Cell Cycle 2011; 10:1757-63. [PMID: 21527828 PMCID: PMC3142459 DOI: 10.4161/cc.10.11.15818] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Accepted: 04/12/2011] [Indexed: 12/11/2022] Open
Abstract
Fanconi anemia (FA) is a rare genetic disease characterized by congenital abnormalities, bone marrow failure and heightened cancer susceptibility. The FA proteins are known to function in the cellular defense against DNA interstrand crosslinks (ICLs), a process that remains poorly understood. A recent spate of discoveries has led to the identification of one new FA gene, FANCP/SLX4, and two strong candidate FA genes, FAN1 and RAD51C. In this perspective we describe the discovery of FANCP/SLX4 and discuss how these new findings collectively refine our understanding of DNA ICL repair.
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170
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Garner E, Smogorzewska A. Ubiquitylation and the Fanconi anemia pathway. FEBS Lett 2011; 585:2853-60. [PMID: 21605559 DOI: 10.1016/j.febslet.2011.04.078] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 04/29/2011] [Accepted: 04/29/2011] [Indexed: 10/18/2022]
Abstract
The Fanconi anemia (FA) pathway maintains genome stability through co-ordination of DNA repair of interstrand crosslinks (ICLs). Disruption of the FA pathway yields hypersensitivity to interstrand crosslinking agents, bone marrow failure and cancer predisposition. Early steps in DNA damage dependent activation of the pathway are governed by monoubiquitylation of FANCD2 and FANCI by the intrinsic FA E3 ubiquitin ligase, FANCL. Downstream FA pathway components and associated factors such as FAN1 and SLX4 exhibit ubiquitin-binding motifs that are important for their DNA repair function, underscoring the importance of ubiquitylation in FA pathway mediated repair. Importantly, ubiquitylation provides the foundations for cross-talk between repair pathways, which in concert with the FA pathway, resolve interstrand crosslink damage and maintain genomic stability.
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Affiliation(s)
- Elizabeth Garner
- Laboratory of Genome Maintenance, The Rockefeller University, New York, NY 10065, USA
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171
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Martrat G, Maxwell CM, Tominaga E, Porta-de-la-Riva M, Bonifaci N, Gómez-Baldó L, Bogliolo M, Lázaro C, Blanco I, Brunet J, Aguilar H, Fernández-Rodríguez J, Seal S, Renwick A, Rahman N, Kühl J, Neveling K, Schindler D, Ramírez MJ, Castellà M, Hernández G, Easton DF, Peock S, Cook M, Oliver CT, Frost D, Platte R, Evans DG, Lalloo F, Eeles R, Izatt L, Chu C, Davidson R, Ong KR, Cook J, Douglas F, Hodgson S, Brewer C, Morrison PJ, Porteous M, Peterlongo P, Manoukian S, Peissel B, Zaffaroni D, Roversi G, Barile M, Viel A, Pasini B, Ottini L, Putignano AL, Savarese A, Bernard L, Radice P, Healey S, Spurdle A, Chen X, Beesley J, Rookus MA, Verhoef S, Tilanus-Linthorst MA, Vreeswijk MP, Asperen CJ, Bodmer D, Ausems MGEM, van Os TA, Blok MJ, Meijers-Heijboer HEJ, Hogervorst FBL, Goldgar DE, Buys S, John EM, Miron A, Southey M, Daly MB, Harbst K, Borg A, Rantala J, Barbany-Bustinza G, Ehrencrona H, Stenmark-Askmalm M, Kaufman B, Laitman Y, Milgrom R, Friedman E, Domchek SM, Nathanson KL, Rebbeck TR, Johannsson OT, Couch FJ, Wang X, Fredericksen Z, Cuadras D, Moreno V, Pientka FK, Depping R, Caldés T, Osorio A, Benítez J, Bueren J, Heikkinen T, Nevanlinna H, Hamann U, Torres D, Caligo MA, Godwin AK, Imyanitov EN, Janavicius R, Sinilnikova OM, Stoppa-Lyonnet D, Mazoyer S, Verny-Pierre C, Castera L, de Pauw A, Bignon YJ, Uhrhammer N, Peyrat JP, Vennin P, Ferrer SF, Collonge-Rame MA, Mortemousque I, McGuffog L, Chenevix-Trench G, Pereira-Smith OM, Antoniou AC, Cerón J, Tominaga K, Surrallés J, Pujana MA. Exploring the link between MORF4L1 and risk of breast cancer. Breast Cancer Res 2011; 13:R40. [PMID: 21466675 PMCID: PMC3219203 DOI: 10.1186/bcr2862] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2010] [Revised: 02/17/2011] [Accepted: 04/05/2011] [Indexed: 11/10/2022] Open
Abstract
INTRODUCTION Proteins encoded by Fanconi anemia (FA) and/or breast cancer (BrCa) susceptibility genes cooperate in a common DNA damage repair signaling pathway. To gain deeper insight into this pathway and its influence on cancer risk, we searched for novel components through protein physical interaction screens. METHODS Protein physical interactions were screened using the yeast two-hybrid system. Co-affinity purifications and endogenous co-immunoprecipitation assays were performed to corroborate interactions. Biochemical and functional assays in human, mouse and Caenorhabditis elegans models were carried out to characterize pathway components. Thirteen FANCD2-monoubiquitinylation-positive FA cell lines excluded for genetic defects in the downstream pathway components and 300 familial BrCa patients negative for BRCA1/2 mutations were analyzed for genetic mutations. Common genetic variants were genotyped in 9,573 BRCA1/2 mutation carriers for associations with BrCa risk. RESULTS A previously identified co-purifying protein with PALB2 was identified, MRG15 (MORF4L1 gene). Results in human, mouse and C. elegans models delineate molecular and functional relationships with BRCA2, PALB2, RAD51 and RPA1 that suggest a role for MRG15 in the repair of DNA double-strand breaks. Mrg15-deficient murine embryonic fibroblasts showed moderate sensitivity to γ-irradiation relative to controls and reduced formation of Rad51 nuclear foci. Examination of mutants of MRG15 and BRCA2 C. elegans orthologs revealed phenocopy by accumulation of RPA-1 (human RPA1) nuclear foci and aberrant chromosomal compactions in meiotic cells. However, no alterations or mutations were identified for MRG15/MORF4L1 in unclassified FA patients and BrCa familial cases. Finally, no significant associations between common MORF4L1 variants and BrCa risk for BRCA1 or BRCA2 mutation carriers were identified: rs7164529, Ptrend = 0.45 and 0.05, P2df = 0.51 and 0.14, respectively; and rs10519219, Ptrend = 0.92 and 0.72, P2df = 0.76 and 0.07, respectively. CONCLUSIONS While the present study expands on the role of MRG15 in the control of genomic stability, weak associations cannot be ruled out for potential low-penetrance variants at MORF4L1 and BrCa risk among BRCA2 mutation carriers.
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Affiliation(s)
- Griselda Martrat
- Translational Research Laboratory, Catalan Institute of Oncology, Bellvitge Institute for Biomedical Research (IDIBELL), Gran Via 199, L'Hospitalet del Llobregat 08908, Spain
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172
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Hu Y, Scully R, Sobhian B, Xie A, Shestakova E, Livingston DM. RAP80-directed tuning of BRCA1 homologous recombination function at ionizing radiation-induced nuclear foci. Genes Dev 2011; 25:685-700. [PMID: 21406551 PMCID: PMC3070932 DOI: 10.1101/gad.2011011] [Citation(s) in RCA: 187] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Accepted: 02/07/2011] [Indexed: 01/12/2023]
Abstract
In response to DNA double-strand breaks (DSBs), BRCA1 forms biochemically distinct complexes with certain other DNA damage response proteins. These structures, some of which are required for homologous recombination (HR)-type DSB repair, concentrate at distinct nuclear foci that demarcate sites of genome breakage. Polyubiquitin binding by one of these structures, the RAP80/BRCA1 complex, is required for efficient BRCA1 focal recruitment, but the relationship of this process to the execution of HR has been unclear. We found that this complex actively suppresses otherwise exaggerated, BRCA1-driven HR. By controlling the kinetics by which other BRCA1-interacting proteins that promote HR concentrate together with BRCA1 in nuclear foci, RAP80/BRCA1 complexes suppress excessive DSB end processing, HR-type DSB repair, and overt chromosomal instability. Since chromosomal instability emerges when BRCA1 HR function is either unbridled or absent, active tuning of BRCA1 activity, executed in nuclear foci, is important to genome integrity maintenance.
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Affiliation(s)
- Yiduo Hu
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
| | - Ralph Scully
- Department of Medicine, Harvard Medical School, Boston Massachusetts 02215, USA
- Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA
| | - Bijan Sobhian
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
| | - Anyong Xie
- Department of Medicine, Harvard Medical School, Boston Massachusetts 02215, USA
- Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA
| | - Elena Shestakova
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
| | - David M. Livingston
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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173
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Kim TM, Ko JH, Choi YJ, Hu L, Hasty P. The phenotype of FancB-mutant mouse embryonic stem cells. Mutat Res 2011; 712:20-7. [PMID: 21458466 DOI: 10.1016/j.mrfmmm.2011.03.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2010] [Revised: 03/11/2011] [Accepted: 03/23/2011] [Indexed: 12/20/2022]
Abstract
Fanconi anemia (FA) is a rare autosomal recessive disease characterized by bone marrow failure, developmental defects and cancer. There are multiple FA genes that enable the repair of interstrand crosslinks (ICLs) in coordination with a variety of other DNA repair pathways in a way that is poorly understood. Here we present the phenotype of mouse embryonic stem (ES) cells mutated for FancB. We found FancB-mutant cells exhibited reduced cellular proliferation, hypersensitivity to the crosslinking agent mitomycin C (MMC), increased spontaneous and MMC-induced chromosomal abnormalities, reduced spontaneous sister chromatid exchanges (SCEs), reduced gene targeting, reduced MMC-induced Rad51 foci and absent MMC-induced FancD2 foci. Since FancB is on the X chromosome and since ES cells are typically XY, FancB is an excellent target for an epistatic analysis to elucidate FA's role in ICL repair.
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Affiliation(s)
- Tae Moon Kim
- Department of Molecular Medicine and Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 15355 Lambda Drive, San Antonio, TX 78245, USA
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174
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EMSY overexpression disrupts the BRCA2/RAD51 pathway in the DNA-damage response: implications for chromosomal instability/recombination syndromes as checkpoint diseases. Mol Genet Genomics 2011; 285:325-40. [PMID: 21409565 PMCID: PMC3064890 DOI: 10.1007/s00438-011-0612-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 02/27/2011] [Indexed: 11/05/2022]
Abstract
EMSY links the BRCA2 pathway to sporadic breast/ovarian cancer. It encodes a nuclear protein that binds to the BRCA2 N-terminal domain implicated in chromatin/transcription regulation, but when sporadically amplified/overexpressed, increased EMSY level represses BRCA2 transactivation potential and induces chromosomal instability, mimicking the activity of BRCA2 mutations in the development of hereditary breast/ovarian cancer. In addition to chromatin/transcription regulation, EMSY may also play a role in the DNA-damage response, suggested by its ability to localize at chromatin sites of DNA damage/repair. This implies that EMSY overexpression may also repress BRCA2 in DNA-damage replication/checkpoint and recombination/repair, coordinated processes that also require its interacting proteins: PALB2, the partner and localizer of BRCA2; RPA, replication/checkpoint protein A; and RAD51, the inseparable recombination/repair enzyme. Here, using a well-characterized recombination/repair assay system, we demonstrate that a slight increase in EMSY level can indeed repress these two processes independently of transcriptional interference/repression. Since EMSY, RPA and PALB2 all bind to the same BRCA2 region, these findings further support a scenario wherein: (a) EMSY amplification may mimic BRCA2 deficiency, at least by overriding RPA and PALB2, crippling the BRCA2/RAD51 complex at DNA-damage and replication/transcription sites; and (b) BRCA2/RAD51 may coordinate these processes by employing at least EMSY, PALB2 and RPA. We extensively discuss the molecular details of how this can happen to ascertain its implications for a novel recombination mechanism apparently conceived as checkpoint rather than a DNA repair system for cell division, survival, death, and human diseases, including the tissue specificity of cancer predisposition, which may renew our thinking about targeted therapy and prevention.
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175
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Solyom S, Pylkäs K, Winqvist R. Screening for large genomic rearrangements of the BRIP1 and CHK1 genes in Finnish breast cancer families. Fam Cancer 2011; 9:537-40. [PMID: 20567916 DOI: 10.1007/s10689-010-9360-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In search for susceptibility genes that could explain an additional portion of familial breast cancer clustering in Finland, we set out to evaluate the presence of large genomic rearrangements in two candidate genes, BRIP1 and CHK1. BRIP1 is a BRCA1 associated protein that is mutated in a fraction of familial breast cancer and Fanconi anemia cases. To date, the role of large BRIP1 deletions in breast cancer susceptibility is not well-characterized. CHK1 is a critical maintainer of cell cycle checkpoints and genomic stability, and is also involved in the BRCA1 and FA protein signalling pathways. Although CHK1 is a very important protein for cell cycle and DNA integrity maintenance control, no mutations in this gene has yet been associated with predisposition to cancer. For the present study, blood DNA from affected index persons of 111 Northern Finnish breast cancer families was assessed for possible constitutional exonic deletions or amplifications in the BRIP1 and CHK1 genes by using the multiplex ligation-dependent probe amplification method. Our results showed that exonic deletions or amplifications affecting the BRIP1 and CHK1 genes seem not to contribute to hereditary breast cancer susceptibility in the Finnish population. To our knowledge, this is the first attempt to determine the existence of large CHK1 deletions in familial breast cancer or in any disease with a hereditary background.
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Affiliation(s)
- Szilvia Solyom
- Laboratory of Cancer Genetics, Department of Clinical Genetics and Biocenter Oulu, Oulu University Hospital, University of Oulu, PO Box 5000, 90014 Oulu, Finland
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176
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Wu Y, Brosh RM. Helicase-inactivating mutations as a basis for dominant negative phenotypes. Cell Cycle 2011; 9:4080-90. [PMID: 20980836 DOI: 10.4161/cc.9.20.13667] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
There is ample evidence from studies of both unicellular and multicellular organisms that helicase-inactivating mutations lead to cellular dysfunction and disease phenotypes. In this review, we will discuss the mechanisms underlying the basis for abnormal phenotypes linked to mutations in genes encoding DNA helicases. Recent evidence demonstrates that a clinically relevant patient missense mutation in Fanconi Anemia Complementation Group J exerts detrimental effects on the biochemical activities of the FANCJ helicase, and these molecular defects are responsible for aberrant genomic stability and a poor DNA damage response. The ability of FANCJ to use the energy from ATP hydrolysis to produce the force required to unwind duplex or G-quadruplex DNA structures or destabilize protein bound to DNA is required for its DNA repair functions in vivo. Strikingly, helicase-inactivating mutations can exert a spectrum of dominant negative phenotypes, indicating that expression of the mutant helicase protein potentially interferes with normal DNA metabolism and has an effect on basic cellular processes such as DNA replication, the DNA damage response and protein trafficking. This review emphasizes that future studies of clinically relevant mutations in helicase genes will be important to understand the molecular pathologies of the associated diseases and their impact on heterozygote carriers.
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Affiliation(s)
- Yuliang Wu
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, Baltimore, MD, USA
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177
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Coleman KA, Greenberg RA. The BRCA1-RAP80 complex regulates DNA repair mechanism utilization by restricting end resection. J Biol Chem 2011; 286:13669-80. [PMID: 21335604 DOI: 10.1074/jbc.m110.213728] [Citation(s) in RCA: 173] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The tumor suppressor protein BRCA1 is a constituent of several different protein complexes and is required for homology-directed repair (HDR) of DNA double strand breaks (DSBs). The most recently discovered BRCA1-RAP80 complex is recruited to ubiquitin structures on chromatin surrounding the break. Deficiency of any member of this complex confers hypersensitivity to DNA-damaging agents by undefined mechanisms. In striking contrast to other BRCA1-containing complexes that are known to promote HDR, we demonstrate that the BRCA1-RAP80 complex restricts end resection in S/G(2) phase of the cell cycle, thereby limiting HDR. RAP80 or BRCC36 deficiency resulted in elevated Mre11-CtIP-dependent 5' end resection with a concomitant increase in HDR mechanisms that rely on 3' single-stranded overhangs. We propose a model in which the BRCA1-RAP80 complex limits nuclease accessibility to DSBs, thus preventing excessive end resection and potentially deleterious homology-directed DSB repair mechanisms that can impair genome integrity.
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Affiliation(s)
- Kara A Coleman
- Department of Cancer Biology, Abramson Family Cancer Research Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6160, USA
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178
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Leung CCY, Gong Z, Chen J, Glover JNM. Molecular basis of BACH1/FANCJ recognition by TopBP1 in DNA replication checkpoint control. J Biol Chem 2011; 286:4292-301. [PMID: 21127055 PMCID: PMC3039391 DOI: 10.1074/jbc.m110.189555] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Revised: 11/10/2010] [Indexed: 01/26/2023] Open
Abstract
The diverse roles of TopBP1 in DNA replication and checkpoint signaling are associated with the scaffolding ability of TopBP1 to initiate various protein-protein interactions. The recognition of the BACH1/FANCJ helicase by TopBP1 is critical for the activation of the DNA replication checkpoint at stalled replication forks and is facilitated by the C-terminal tandem BRCT7/8 domains of TopBP1 and a phosphorylated Thr(1133) binding motif in BACH1. Here we provide the structural basis for this interaction through analysis of the x-ray crystal structures of TopBP1 BRCT7/8 both free and in complex with a BACH1 phospho-peptide. In contrast to canonical BRCT-phospho-peptide recognition, TopBP1 BRCT7/8 undergoes a dramatic conformational change upon BACH1 binding such that the two BRCT repeats pivot about the central BRCT-BRCT interface to provide an extensive and deep peptide-binding cleft. Additionally, we provide the first structural mechanism for Thr(P) recognition among BRCT domains. Together with systematic mutagenesis studies, we highlight the role of key contacts in governing the unique specificity of the TopBP1-BACH1 interaction.
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Affiliation(s)
- Charles Chung Yun Leung
- From the Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and
| | - Zihua Gong
- the Department of Experimental Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Junjie Chen
- the Department of Experimental Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - J. N. Mark Glover
- From the Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and
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179
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Suhasini AN, Rawtani NA, Wu Y, Sommers JA, Sharma S, Mosedale G, North PS, Cantor SB, Hickson ID, Brosh RM. Interaction between the helicases genetically linked to Fanconi anemia group J and Bloom's syndrome. EMBO J 2011; 30:692-705. [PMID: 21240188 DOI: 10.1038/emboj.2010.362] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Accepted: 12/22/2010] [Indexed: 11/09/2022] Open
Abstract
Bloom's syndrome (BS) and Fanconi anemia (FA) are autosomal recessive disorders characterized by cancer and chromosomal instability. BS and FA group J arise from mutations in the BLM and FANCJ genes, respectively, which encode DNA helicases. In this work, FANCJ and BLM were found to interact physically and functionally in human cells and co-localize to nuclear foci in response to replication stress. The cellular level of BLM is strongly dependent upon FANCJ, and BLM is degraded by a proteasome-mediated pathway when FANCJ is depleted. FANCJ-deficient cells display increased sister chromatid exchange and sensitivity to replication stress. Expression of a FANCJ C-terminal fragment that interacts with BLM exerted a dominant negative effect on hydroxyurea resistance by interfering with the FANCJ-BLM interaction. FANCJ and BLM synergistically unwound a DNA duplex substrate with sugar phosphate backbone discontinuity, but not an 'undamaged' duplex. Collectively, the results suggest that FANCJ catalytic activity and its effect on BLM protein stability contribute to preservation of genomic stability and a normal response to replication stress.
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Affiliation(s)
- Avvaru N Suhasini
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, Baltimore, MD 21224, USA
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180
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Uringa EJ, Youds JL, Lisaingo K, Lansdorp PM, Boulton SJ. RTEL1: an essential helicase for telomere maintenance and the regulation of homologous recombination. Nucleic Acids Res 2010; 39:1647-55. [PMID: 21097466 PMCID: PMC3061057 DOI: 10.1093/nar/gkq1045] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Telomere maintenance and DNA repair are crucial processes that protect the genome against instability. RTEL1, an essential iron–sulfur cluster-containing helicase, is a dominant factor that controls telomere length in mice and is required for telomere integrity. In addition, RTEL1 promotes synthesis-dependent strand annealing to direct DNA double-strand breaks into non-crossover outcomes during mitotic repair and in meiosis. Here, we review the role of RTEL1 in telomere maintenance and homologous recombination and discuss models linking RTEL1’s enzymatic activity to its function in telomere maintenance and DNA repair.
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Affiliation(s)
- Evert-Jan Uringa
- Terry Fox Laboratory, BC Cancer Agency, Avenue, Vancouver, BC, V5Z 1L3, Canada
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181
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Xie J, Guillemette S, Peng M, Gilbert C, Buermeyer A, Cantor SB. An MLH1 mutation links BACH1/FANCJ to colon cancer, signaling, and insight toward directed therapy. Cancer Prev Res (Phila) 2010; 3:1409-16. [PMID: 20978114 DOI: 10.1158/1940-6207.capr-10-0118] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Defects in MLH1, as with other mismatch repair (MMR) proteins, are the primary cause of hereditary nonpolyposis colon cancer (HNPCC). Mutations in MMR genes often disrupt mismatch repair and MMR signaling functions. However, some HNPCC-associated mutations have unknown pathogenicity. Here, we uncover an MLH1 clinical mutation with a leucine (L)-to-histidine (H) amino acid change at position 607 that ablates MLH1 binding to FANCJ. Given that a DNA helicase is not essential for mammalian MMR in vitro, we considered that loss of MLH1 binding to FANCJ could alter MMR signaling. Consistent with this hypothesis, FANCJ-deficient cells exhibit delayed MMR signaling and apoptotic responses that generate resistance to agents that induce O(6)-methylguanine lesions. Our data indicate that the delay in MMR signaling provides time for the methylguanine methyltransferase (MGMT) enzyme to reverse DNA methylation. In essence, FANCJ deficiency alters the competition between two pathways: MGMT-prosurvival versus MMR-prodeath. This outcome could explain the HNPCC familial cancers that present as microsatellite stable and with intact MMR, such as MLH(L607H). Importantly, the link between FANCJ and HNPCC provides insight toward directed therapies because loss of the FANCJ/MLH1 interaction also uniquely sensitizes cells to DNA cross-linking agents.
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Affiliation(s)
- Jenny Xie
- 1Department of Cancer Biology, University of Massachusetts Medical School, Women's Cancers Program, UMass Memorial Cancer Center, Worcester, Massachusetts 01605, USA
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182
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Kee Y, D'Andrea AD. Expanded roles of the Fanconi anemia pathway in preserving genomic stability. Genes Dev 2010; 24:1680-94. [PMID: 20713514 DOI: 10.1101/gad.1955310] [Citation(s) in RCA: 246] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Studying rare human genetic diseases often leads to a better understanding of normal cellular functions. Fanconi anemia (FA), for example, has elucidated a novel DNA repair mechanism required for maintaining genomic stability and preventing cancer. The FA pathway, an essential tumor-suppressive pathway, is required for protecting the human genome from a specific type of DNA damage; namely, DNA interstrand cross-links (ICLs). In this review, we discuss the recent progress in the study of the FA pathway, such as the identification of new FANCM-binding partners and the identification of RAD51C and FAN1 (Fanconi-associated nuclease 1) as new FA pathway-related proteins. We also focus on the role of the FA pathway as a potential regulator of DNA repair choices in response to double-strand breaks, and its novel functions during the mitotic phase of the cell cycle.
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Affiliation(s)
- Younghoon Kee
- Department of Radiation Oncology and Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
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183
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Zhang F, Fan Q, Ren K, Auerbach AD, Andreassen PR. FANCJ/BRIP1 recruitment and regulation of FANCD2 in DNA damage responses. Chromosoma 2010; 119:637-49. [PMID: 20676667 DOI: 10.1007/s00412-010-0285-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2010] [Revised: 06/07/2010] [Accepted: 06/29/2010] [Indexed: 01/28/2023]
Abstract
FANCJ/BRIP1 encodes a helicase that has been implicated in the maintenance of genomic stability. Here, to better understand FANCJ function in DNA damage responses, we have examined the regulation of its cellular localization. FANCJ nuclear foci assemble spontaneously during S phase and are induced by various stresses. FANCJ foci colocalize with the replication fork following treatment with hydroxyurea, but not spontaneously. Using FANCJ mutants, we find that FANCJ helicase activity and the capacity to bind BRCA1 are both involved in FANCJ recruitment. Given similarities to the recruitment of another Fanconi anemia protein, FANCD2, we tested for colocalization of FANCJ and FANCD2. Importantly, these proteins show substantial colocalization, and FANCJ promotes the assembly of FANCD2 nuclear foci. This process is linked to the proper localization of FANCJ itself since both FANCJ and FANCD2 nuclear foci are compromised by FANCJ mutants that abrogate its helicase activity or interaction with BRCA1. Our results suggest that FANCJ is recruited in response to replication stress and that FANCJ/BRIP1 may serve to link FANCD2 to BRCA1.
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Affiliation(s)
- Fan Zhang
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Research Foundation, 3333 Burnet Ave. ML S7.203, Cincinnati, OH 45229, USA
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184
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Abstract
Alternate DNA structures that deviate from B-form double-stranded DNA such as G-quadruplex (G4) DNA can be formed by sequences that are widely distributed throughout the human genome. G-quadruplex secondary structures, formed by the stacking of planar quartets composed of four guanines that interact by Hoogsteen hydrogen bonding, can affect cellular DNA replication and transcription, and influence genomic stability. The unique metabolism of G-rich chromosomal regions that potentially form quadruplexes may influence a number of biological processes including immunoglobulin gene rearrangements, promoter activation and telomere maintenance. A number of human diseases are characterized by telomere defects, and it is proposed that G-quadruplex structures which form at telomere ends play an important role in telomere stability. Evidence from cellular studies and model organisms suggests that diseases with known defects in G4 DNA helicases are likely to be perturbed in telomere maintenance and cellular DNA replication. In this minireview, we discuss the connections of G-quadruplex nucleic acids to human genetic diseases and cancer based on the recent literature.
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Affiliation(s)
- Yuliang Wu
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD, USA
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185
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Fanconi anemia group J mutation abolishes its DNA repair function by uncoupling DNA translocation from helicase activity or disruption of protein-DNA complexes. Blood 2010; 116:3780-91. [PMID: 20639400 DOI: 10.1182/blood-2009-11-256016] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Fanconi anemia (FA) is a genetic disease characterized by congenital abnormalities, bone marrow failure, and susceptibility to leukemia and other cancers. FANCJ, one of 13 genes linked to FA, encodes a DNA helicase proposed to operate in homologous recombination repair and replicational stress response. The pathogenic FANCJ-A349P amino acid substitution resides immediately adjacent to a highly conserved cysteine of the iron-sulfur domain. Given the genetic linkage of the FANCJ-A349P allele to FA, we investigated the effect of this particular mutation on the biochemical and cellular functions of the FANCJ protein. Purified recombinant FANCJ-A349P protein had reduced iron and was defective in coupling adenosine triphosphate (ATP) hydrolysis and translocase activity to unwinding forked duplex or G-quadruplex DNA substrates or disrupting protein-DNA complexes. The FANCJ-A349P allele failed to rescue cisplatin or telomestatin sensitivity of a FA-J null cell line as detected by cell survival or γ-H2AX foci formation. Furthermore, expression of FANCJ-A349P in a wild-type background exerted a dominant-negative effect, indicating that the mutant protein interferes with normal DNA metabolism. The ability of FANCJ to use the energy from ATP hydrolysis to produce the force required to unwind DNA or destabilize protein bound to DNA is required for its role in DNA repair.
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186
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Paeschke K, McDonald KR, Zakian VA. Telomeres: structures in need of unwinding. FEBS Lett 2010; 584:3760-72. [PMID: 20637196 DOI: 10.1016/j.febslet.2010.07.007] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 06/25/2010] [Accepted: 07/02/2010] [Indexed: 11/26/2022]
Abstract
Telomeres protect the ends of eukaryotic chromosomes from being recognized and processed as double strand breaks. In most organisms, telomeric DNA is highly repetitive with a high GC-content. Moreover, the G residues are concentrated in the strand running 3'-5' from the end of the chromosome towards its center. This G-rich strand is extended to form a 3' single-stranded tail that can form unusual secondary structures such as T-loops and G-quadruplex DNA. Both the duplex repeats and the single-stranded G-tail are assembled into stable protein-DNA complexes. The unique architecture, high GC content, and multi-protein association create particularly stable protein-DNA complexes that are a challenge for replication, recombination, and transcription. Helicases utilize the energy of nucleotide hydrolysis to unwind base paired nucleic acids and, in some cases, to displace proteins from them. The telomeric functions of helicases from the RecQ, Pifl, FANCJ, and DNA2 families are reviewed in this article. We summarize data showing that perturbation of their telomere activities can lead to telomere dysfunction and genome instability and in some cases human disease.
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Affiliation(s)
- Katrin Paeschke
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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187
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Evers B, Helleday T, Jonkers J. Targeting homologous recombination repair defects in cancer. Trends Pharmacol Sci 2010; 31:372-80. [PMID: 20598756 DOI: 10.1016/j.tips.2010.06.001] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Revised: 04/26/2010] [Accepted: 06/02/2010] [Indexed: 02/09/2023]
Abstract
DNA repair is essential for cells to maintain genome stability in an environment that constantly produces DNA damage. There is a growing appreciation that defects in homologous recombination repair underlie hereditary and sporadic tumourigenesis, and that deficiency in this pathway may dictate the sensitivity of tumours to certain DNA-damaging agents. Homologous recombination deficiency (HRD) may therefore prove to be a diagnostic criterion per se if appropriate biomarkers become available to identify these tumours. In addition, homologous recombination-deficient tumours are more sensitive to inhibition of other DNA repair pathways through so-called 'synthetic lethal interactions', a principle that is currently being tested in clinical trials. Finally, homologous recombination repair-deficient cells may have an increased dependency on certain cell-cycle checkpoints, which can be therapeutically exploited. Here we describe recent advances in strategies to identify and target HRD tumours, approaches to overcome resistance, and combinatory strategies to optimize treatment outcome.
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Affiliation(s)
- Bastiaan Evers
- Gray Institute for Radiation Oncology and Biology, University of Oxford, UK
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188
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Cantor SB, Xie J. Assessing the link between BACH1/FANCJ and MLH1 in DNA crosslink repair. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2010; 51:500-507. [PMID: 20658644 DOI: 10.1002/em.20568] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
FANCJ (also known as BRIP1 or BACH1) is a DNA helicase that was originally identified by its direct interaction with the hereditary breast cancer protein, BRCA1. Similar to BRCA1, FANCJ function is essential for DNA repair and breast cancer suppression. FANCJ is also mutated in the cancer prone syndrome Fanconi anemia, for which patient cells are characterized by extreme sensitivity to agents that generate DNA interstand crosslinks. Unexpectedly, correction of the interstrand crosslink sensitivity of FANCJ-null patient cells did not require the FANCJ/BRCA1 interaction. Instead, FANCJ binding to the mismatch repair protein, MLH1 was required. Given this finding, we address the role of FANCJ and MLH1 in DNA crosslink processing and how their functions could be linked in checkpoint and/or recombination pathways. We speculate that after DNA crosslink processing and repair, the FANCJ/MLH1 interaction is critical for recovery and restart of replication. These ideas are considered and summarized in this review.
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Affiliation(s)
- Sharon B Cantor
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
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189
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Hinz JM. Role of homologous recombination in DNA interstrand crosslink repair. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2010; 51:582-603. [PMID: 20658649 DOI: 10.1002/em.20577] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Homologous recombination repair (HRR) encompasses mechanisms that employ homologous DNA sequences as templates for repair or tolerance of a wide range of DNA lesions that inhibit DNA replication in S phase. Arguably the most imposing of these DNA lesions is that of the interstrand crosslink (ICL), consisting of a covalently attached chemical bridge between opposing DNA strands. ICL repair requires the coordinated activities of HRR and a number of proteins from other DNA repair and damage response systems, including nucleotide excision repair, base excision repair, mismatch repair, and translesion DNA synthesis (TLS). Interestingly, different organisms favor alternative methods of HRR in the ICL repair process. E. coli perform ICL repair using a homology-driven damage bypass mechanism analogous to daughter strand gap repair. Eukaryotes from yeast to humans initiate ICL repair primarily during DNA replication, relying on HRR activity to restart broken replication forks associated with double-strand break intermediates induced by nucleolytic activities of other excision repair factors. Higher eukaryotes also employ several additional factors, including members of the Fanconi anemia damage-response network, which further promote replication-associated ICL repair through the activation and coordination of various DNA excision repair, TLS, and HRR proteins. This review focuses on the proteins and general mechanisms of HRR associated with ICL repair in different model organisms.
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Affiliation(s)
- John M Hinz
- School of Molecular Biosciences, Washington State University, Pullman, Washington, USA.
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190
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Song L, Yuan F, Zhang Y. Does a helicase activity help mismatch repair in eukaryotes? IUBMB Life 2010; 62:548-53. [DOI: 10.1002/iub.349] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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191
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Abstract
The study of rare genetic diseases can lead to insights into the cause and treatment of common diseases. An example is the rare chromosomal instability disorder, Fanconi Anemia (FA). Studies of this disease have elucidated general mechanisms of bone marrow failure, cancer pathogenesis, and resistance to chemotherapy. The principal features of FA are aplastic anemia in childhood, susceptibility to cancer or leukemia, and hypersensitivity of FA cells to DNA cross-linking agents. There are thirteen FA genes, and one of these genes is identical to the well known breast cancer susceptibility gene, BRCA2. The corresponding FA proteins cooperate in the recognition and repair of damaged DNA. Inactivation of FA genes occurs not only in FA patients but also in a variety of cancers in the general population. These findings have broad implications for predicting the sensitivity and resistance of tumors to conventional anti-cancer agents, to inhibitors of poly-ADP ribose polymerase 1, an enzyme involved in DNA repair, and to other inhibitors of DNA repair.
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Affiliation(s)
- Alan D D'Andrea
- Department of Radiation Oncology, Dana-Farber Cancer Institute, Children's Hospital, and Harvard Medical School, Boston, MA 02115, USA.
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192
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Abstract
Germline mutations in the BRCA1 and BRCA2 genes are characterized by deficient repair of DNA double-strand breaks by homologous recombination. Defective DNA double-strand break repair has been not only implicated as a key contributor to tumorigenesis in mutation carriers but also represents a potential target for therapy. The transcriptional similarities between BRCA1-deficient tumors and sporadic tumors of the basal-like subtype have led to the investigation of homologous recombination repair-directed therapy in triple-negative tumors, which demonstrates overlap with the basal-like subtype. We broaden the scope of this topic by addressing a "repair-defective" rather than "BRCA1-like" phenotype. We discuss structural and functional aspects of key repair proteins including BRCA1, BRCA2, BRCA1 interacting protein C-terminal helicase 1, and partner and localizer of BRCA2 and describe the phenotypic consequences of their loss at the cellular, tissue, and organism level. We review potential mechanisms of repair pathway dysfunction in sporadic tumors and address how the identification of such defects may guide the application of repair-directed therapies.
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193
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Branzei D, Foiani M. Maintaining genome stability at the replication fork. Nat Rev Mol Cell Biol 2010; 11:208-19. [PMID: 20177396 DOI: 10.1038/nrm2852] [Citation(s) in RCA: 610] [Impact Index Per Article: 43.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Aberrant DNA replication is a major source of the mutations and chromosome rearrangements that are associated with pathological disorders. When replication is compromised, DNA becomes more prone to breakage. Secondary structures, highly transcribed DNA sequences and damaged DNA stall replication forks, which then require checkpoint factors and specialized enzymatic activities for their stabilization and subsequent advance. These mechanisms ensure that the local DNA damage response, which enables replication fork progression and DNA repair in S phase, is coupled with cell cycle transitions. The mechanisms that operate in eukaryotic cells to promote replication fork integrity and coordinate replication with other aspects of chromosome maintenance are becoming clear.
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Affiliation(s)
- Dana Branzei
- Fondazione IFOM, Istituto FIRC di Oncologia Molecolare, IFOM-IEO campus, Via Adamello 16, 20139 Milan, Italy.
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194
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Mitotic homologous recombination maintains genomic stability and suppresses tumorigenesis. Nat Rev Mol Cell Biol 2010; 11:196-207. [PMID: 20177395 DOI: 10.1038/nrm2851] [Citation(s) in RCA: 673] [Impact Index Per Article: 48.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Mitotic homologous recombination promotes genome stability through the precise repair of DNA double-strand breaks and other lesions that are encountered during normal cellular metabolism and from exogenous insults. As a result, homologous recombination repair is essential during proliferative stages in development and during somatic cell renewal in adults to protect against cell death and mutagenic outcomes from DNA damage. Mutations in mammalian genes encoding homologous recombination proteins, including BRCA1, BRCA2 and PALB2, are associated with developmental abnormalities and tumorigenesis. Recent advances have provided a clearer understanding of the connections between these proteins and of the key steps of homologous recombination and DNA strand exchange.
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195
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Zhang J, Zhao D, Park HK, Wang H, Dyer RB, Liu W, Klee GG, McNiven MA, Tindall DJ, Molina JR, Fei P. FAVL elevation in human tumors disrupts Fanconi anemia pathway signaling and promotes genomic instability and tumor growth. J Clin Invest 2010; 120:1524-34. [PMID: 20407210 DOI: 10.1172/jci40908] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Accepted: 02/17/2010] [Indexed: 12/22/2022] Open
Abstract
Fanconi anemia (FA) is a rare human genetic disease caused by mutations in any one of 13 known genes that encode proteins functioning in one common signaling pathway, the FA pathway, or in unknown genes. One characteristic of FA is an extremely high incidence of cancer, indicating the importance of the FA pathway in tumor suppression. However, the role of this pathway in the development and progression of human cancers in individuals who do not have FA has not been clearly determined. Here, we report that elevated expression of what we believe to be a novel splice variant of FA complementation group L (FANCL), which we identified and named FAVL, can impair the FA pathway in non-FA human tumor cells and act as a tumor promoting factor. FAVL expression was elevated in half of the human carcinoma cell lines and carcinoma tissue samples tested. Expression of FAVL resulted in decreased FANCL expression by sequestering FANCL to the cytoplasm and enhancing its degradation. Importantly, this impairment of the FA pathway by FAVL elevation provided human cancer cells with a growth advantage, caused chromosomal instability in vitro, and promoted tumor development in a xenograft mouse model. These data indicate that FAVL impairment of the FA pathway likely contributes to the development of non-FA human cancers and therefore add a challenging layer of complexity to the pathogenesis of human cancer. We further believe that these data will prove useful for developing additional tools for fighting human cancer.
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Affiliation(s)
- Jun Zhang
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota 55905, USA
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196
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Gong Z, Kim JE, Leung CCY, Glover JNM, Chen J. BACH1/FANCJ acts with TopBP1 and participates early in DNA replication checkpoint control. Mol Cell 2010; 37:438-46. [PMID: 20159562 DOI: 10.1016/j.molcel.2010.01.002] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Revised: 07/22/2009] [Accepted: 11/12/2009] [Indexed: 10/19/2022]
Abstract
Human TopBP1 plays a critical role in the control of DNA replication checkpoint. In this study, we report a specific interaction between TopBP1 and BACH1/FANCJ, a DNA helicase involved in the repair of DNA crosslinks. The TopBP1/BACH1 interaction is mediated by the very C-terminal tandem BRCT domains of TopBP1 and S phase-specific phosphorylation of BACH1 at Thr 1133 site. Interestingly, we demonstrate that depletion of TopBP1 or BACH1 attenuates the loading of RPA on chromatin. Moreover, both TopBP1 and BACH1 are required for ATR-dependent phosphorylation events in response to replication stress. Taken together, our data suggest that BACH1 has an unexpected early role in replication checkpoint control. A specific interaction between TopBP1 and BACH1 is likely to be required for the extension of single-stranded DNA regions and RPA loading following replication stress, which is a prerequisite for the subsequent activation of replication checkpoint.
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Affiliation(s)
- Zihua Gong
- Department of Experimental Radiation Oncology, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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197
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Targeting the FANCJ-BRCA1 interaction promotes a switch from recombination to poleta-dependent bypass. Oncogene 2010; 29:2499-508. [PMID: 20173781 DOI: 10.1038/onc.2010.18] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
BRCA1 and the DNA helicase FANCJ (also known as BACH1 or BRIP1) have common functions in breast cancer suppression and DNA repair. However, the functional significance of the direct interaction between BRCA1 and FANCJ remains unclear. Here, we have discovered that BRCA1 binding to FANCJ regulates DNA damage repair choice. Thus, when FANCJ binding to BRCA1 is ablated, the molecular mechanism chosen for the repair of damaged DNA is dramatically altered. Specifically, a FANCJ protein that cannot be phosphorylated at serine 990 or bind BRCA1 inhibits DNA repair via homologous recombination and promotes poleta-dependent bypass. Furthermore, the poleta-dependent bypass promoted by FANCJ requires the direct binding to the mismatch repair (MMR) protein, MLH1. Together, our findings implicate that in human cells BRCA1 binding to FANCJ is critical to regulate DNA repair choice and promote genomic stability. Moreover, unregulated FANCJ function could be associated with cancer and/or chemoresistance.
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198
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Abstract
The FANCJ protein (also known as BACH1 and BRIP1) is a DNA helicase that is required to preserve the genetic and structural integrity of the genome in complex eukaryotes. In humans, mutations in FANCJ are associated with the chromosome instability disorder Fanconi's anemia and also with the inherited predisposition early-onset breast cancer. Here I will discuss the contribution of FANCJ to human disease, its role in maintenance of genome stability and some current thoughts on the mechanisms through which this is achieved.
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Affiliation(s)
- Kevin Hiom
- Biomedical Research Institute, Ninewells Hospital & Medical School, University of Dundee, DD1 9SY, Scotland, UK.
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199
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Lee KY, Chung KY, Koo HS. The involvement of FANCM, FANCI, and checkpoint proteins in the interstrand DNA crosslink repair pathway is conserved in C. elegans. DNA Repair (Amst) 2010; 9:374-82. [PMID: 20075016 DOI: 10.1016/j.dnarep.2009.12.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Revised: 11/28/2009] [Accepted: 12/17/2009] [Indexed: 10/20/2022]
Abstract
Fanconi anemia (FA) patients are specifically defective in the repair of interstrand DNA crosslinks (ICLs), a complex process involving at least 13 FA proteins and other repair/checkpoint proteins. Of the 13 FA proteins, FANCD1/BRCA2, FANCD2, and FANCJ were previously found to be functionally conserved in C. elegans. We have also identified C. elegans homologs of FANCM and FANCI, and determined their epistatic relationships with homologs of FANCD2, checkpoint proteins, and RAD51 upon DNA crosslinking. The counterparts of FANCM, FANCI, and three checkpoint proteins (RPA, ATR and CHK1) are required for focus formation and ubiquitination associated with FANCD2 in C. elegans. However, C. elegans FANCM affects neither RPA focus formation nor CHK1 phosphorylation induced by ICLs, unlike the reported role of human FANCM, which influences ATR-CHK1 signaling at stalled replication forks. Although focus formation by both FANCD2 and RAD51 requires ATR-CHK1 signaling, FANCD2 and RAD51 acted independently in the formation of their respective foci. Thus, the FANCD2 activation pathway involving FANCM, FANCI, and the checkpoint proteins is conserved in C. elegans but with distinct differences.
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Affiliation(s)
- Kyong Yun Lee
- Department of Biochemistry, Yonsei University, Seodaemun-ku, Seoul, Republic of Korea
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200
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Bolderson E, Tomimatsu N, Richard DJ, Boucher D, Kumar R, Pandita TK, Burma S, Khanna KK. Phosphorylation of Exo1 modulates homologous recombination repair of DNA double-strand breaks. Nucleic Acids Res 2009; 38:1821-31. [PMID: 20019063 PMCID: PMC2847229 DOI: 10.1093/nar/gkp1164] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
DNA double-strand break (DSB) repair via the homologous recombination pathway is a multi-stage process, which results in repair of the DSB without loss of genetic information or fidelity. One essential step in this process is the generation of extended single-stranded DNA (ssDNA) regions at the break site. This ssDNA serves to induce cell cycle checkpoints and is required for Rad51 mediated strand invasion of the sister chromatid. Here, we show that human Exonuclease 1 (Exo1) is required for the normal repair of DSBs by HR. Cells depleted of Exo1 show chromosomal instability and hypersensitivity to ionising radiation (IR) exposure. We find that Exo1 accumulates rapidly at DSBs and is required for the recruitment of RPA and Rad51 to sites of DSBs, suggesting a role for Exo1 in ssDNA generation. Interestingly, the phosphorylation of Exo1 by ATM appears to regulate the activity of Exo1 following resection, allowing optimal Rad51 loading and the completion of HR repair. These data establish a role for Exo1 in resection of DSBs in human cells, highlighting the critical requirement of Exo1 for DSB repair via HR and thus the maintenance of genomic stability.
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Affiliation(s)
- Emma Bolderson
- Signal Transduction Laboratory, Queensland Institute of Medical Research, Brisbane, Queensland 4029, Australia
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