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Sommers JA, Banerjee T, Hinds T, Wan B, Wold MS, Lei M, Brosh RM. Novel function of the Fanconi anemia group J or RECQ1 helicase to disrupt protein-DNA complexes in a replication protein A-stimulated manner. J Biol Chem 2014; 289:19928-41. [PMID: 24895130 DOI: 10.1074/jbc.m113.542456] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Understanding how cellular machinery deals with chromosomal genome complexity is an important question because protein bound to DNA may affect various cellular processes of nucleic acid metabolism. DNA helicases are at the forefront of such processes, yet there is only limited knowledge how they remodel protein-DNA complexes and how these mechanisms are regulated. We have determined that representative human RecQ and Fe-S cluster DNA helicases are potently blocked by a protein-DNA interaction. The Fanconi anemia group J (FANCJ) helicase partners with the single-stranded DNA-binding protein replication protein A (RPA) to displace BamHI-E111A bound to duplex DNA in a specific manner. Protein displacement was dependent on the ATPase-driven function of the helicase and unique properties of RPA. Further biochemical studies demonstrated that the shelterin proteins TRF1 and TRF2, which preferentially bind the telomeric repeat found at chromosome ends, effectively block FANCJ from unwinding the forked duplex telomeric substrate. RPA, but not the Escherichia coli single-stranded DNA-binding protein or shelterin factor Pot1, stimulated FANCJ ejection of TRF1 from the telomeric DNA substrate. FANCJ was also able to displace TRF2 from the telomeric substrate in an RPA-dependent manner. The stimulation of helicase-catalyzed protein displacement is also observed with the DNA helicase RECQ1, suggesting a conserved functional interaction of RPA-interacting helicases. These findings suggest that partnerships between RPA and interacting human DNA helicases may greatly enhance their ability to dislodge proteins bound to duplex DNA, an activity that is likely to be highly relevant to their biological roles in DNA metabolism.
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Affiliation(s)
- Joshua A Sommers
- From the Laboratory of Molecular Gerontology, Biomedical Research Center, NIA, National Institutes of Health, Baltimore, Maryland 21224
| | - Taraswi Banerjee
- From the Laboratory of Molecular Gerontology, Biomedical Research Center, NIA, National Institutes of Health, Baltimore, Maryland 21224
| | - Twila Hinds
- From the Laboratory of Molecular Gerontology, Biomedical Research Center, NIA, National Institutes of Health, Baltimore, Maryland 21224
| | - Bingbing Wan
- the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, and
| | - Marc S Wold
- the Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Ming Lei
- the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, and
| | - Robert M Brosh
- From the Laboratory of Molecular Gerontology, Biomedical Research Center, NIA, National Institutes of Health, Baltimore, Maryland 21224,
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52
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Guo M, Vidhyasagar V, Ding H, Wu Y. Insight into the roles of helicase motif Ia by characterizing Fanconi anemia group J protein (FANCJ) patient mutations. J Biol Chem 2014; 289:10551-10565. [PMID: 24573678 DOI: 10.1074/jbc.m113.538892] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Helicases are molecular motors that couple the energy of ATP hydrolysis to the unwinding and remodeling of structured DNA or RNA, which is coordinated by conserved helicase motifs. FANCJ is a DNA helicase that is genetically linked to Fanconi anemia, breast cancer, and ovarian cancer. Here, we characterized two Fanconi anemia patient mutations, R251C and Q255H, that are localized in helicase motif Ia. Our genetic complementation analysis revealed that both the R251C and Q255H alleles failed to rescue cisplatin sensitivity of a FANCJ null cell line as detected by cell survival or γ-H2AX foci formation. Furthermore, our biochemical assays demonstrated that both purified recombinant proteins abolished DNA helicase activity and failed to disrupt the DNA-protein complex. Intriguingly, R251C impaired DNA binding ability to single-strand DNA and double-strand DNA, whereas Q255H retained higher binding activity to these DNA substrates compared with wild-type FANCJ protein. Consequently, R251C abolished its DNA-dependent ATP hydrolysis activity, whereas Q255H retained normal ATPase activity. Physically, R251C had reduced ATP binding ability, whereas Q255H had normal ATP binding ability and could translocate on single-strand DNA. Although both proteins were recruited to damage sites in our laser-activated confocal assays, they lost their DNA repair function, which explains why they exerted a domain negative effect when expressed in a wild-type background. Taken together, our work not only reveals the structural function of helicase motif Ia but also provides the molecular pathology of FANCJ in related diseases.
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Affiliation(s)
- Manhong Guo
- Department of Biochemistry, University of Saskatchewan, Health Sciences Building, Saskatoon, Saskatchewan, S7N 5E5, Canada
| | - Venkatasubramanian Vidhyasagar
- Department of Biochemistry, University of Saskatchewan, Health Sciences Building, Saskatoon, Saskatchewan, S7N 5E5, Canada
| | - Hao Ding
- Department of Biochemistry, University of Saskatchewan, Health Sciences Building, Saskatoon, Saskatchewan, S7N 5E5, Canada
| | - Yuliang Wu
- Department of Biochemistry, University of Saskatchewan, Health Sciences Building, Saskatoon, Saskatchewan, S7N 5E5, Canada.
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Rudra S, Skibbens RV. Chl1 DNA helicase regulates Scc2 deposition specifically during DNA-replication in Saccharomyces cerevisiae. PLoS One 2013; 8:e75435. [PMID: 24086532 PMCID: PMC3784445 DOI: 10.1371/journal.pone.0075435] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 08/13/2013] [Indexed: 11/19/2022] Open
Abstract
The conserved family of cohesin proteins that mediate sister chromatid cohesion requires Scc2, Scc4 for chromatin-association and Eco1/Ctf7 for conversion to a tethering competent state. A popular model, based on the notion that cohesins form huge ring-like structures, is that Scc2, Scc4 function is essential only during G1 such that sister chromatid cohesion results simply from DNA replisome passage through pre-loaded cohesin rings. In such a scenario, cohesin deposition during G1 is temporally uncoupled from Eco1-dependent establishment reactions that occur during S-phase. Chl1 DNA helicase (homolog of human ChlR1/DDX11 and BACH1/BRIP1/FANCJ helicases implicated in Fanconi anemia, breast and ovarian cancer and Warsaw Breakage Syndrome) plays a critical role in sister chromatid cohesion, however, the mechanism through which Chl1 promotes cohesion remains poorly understood. Here, we report that Chl1 promotes Scc2 loading unto DNA such that both Scc2 and cohesin enrichment to chromatin are defective in chl1 mutant cells. The results further show that both Chl1 expression and chromatin-recruitment are tightly regulated through the cell cycle, peaking during S-phase. Importantly, kinetic ChIP studies reveals that Chl1 is required for Scc2 chromatin-association specifically during S-phase, but not during G1. Despite normal chromatin enrichment of both Scc2 and cohesin during G1, chl1 mutant cells exhibit severe chromosome segregation and cohesion defects--revealing that G1-loaded cohesins is insufficient to promote cohesion. Based on these findings, we propose a new model wherein S-phase cohesin loading occurs during DNA replication and in concert with both cohesion establishment and chromatin assembly reactions--challenging the notion that DNA replication fork navigates through or around pre-loaded cohesin rings.
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Affiliation(s)
- Soumya Rudra
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - Robert V. Skibbens
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
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54
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Bharti SK, Sommers JA, George F, Kuper J, Hamon F, Shin-ya K, Teulade-Fichou MP, Kisker C, Brosh RM. Specialization among iron-sulfur cluster helicases to resolve G-quadruplex DNA structures that threaten genomic stability. J Biol Chem 2013; 288:28217-29. [PMID: 23935105 DOI: 10.1074/jbc.m113.496463] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G-quadruplex (G4) DNA, an alternate structure formed by Hoogsteen hydrogen bonds between guanines in G-rich sequences, threatens genomic stability by perturbing normal DNA transactions including replication, repair, and transcription. A variety of G4 topologies (intra- and intermolecular) can form in vitro, but the molecular architecture and cellular factors influencing G4 landscape in vivo are not clear. Helicases that unwind structured DNA molecules are emerging as an important class of G4-resolving enzymes. The BRCA1-associated FANCJ helicase is among those helicases able to unwind G4 DNA in vitro, and FANCJ mutations are associated with breast cancer and linked to Fanconi anemia. FANCJ belongs to a conserved iron-sulfur (Fe S) cluster family of helicases important for genomic stability including XPD (nucleotide excision repair), DDX11 (sister chromatid cohesion), and RTEL (telomere metabolism), genetically linked to xeroderma pigmentosum/Cockayne syndrome, Warsaw breakage syndrome, and dyskeratosis congenita, respectively. To elucidate the role of FANCJ in genomic stability, its molecular functions in G4 metabolism were examined. FANCJ efficiently unwound in a kinetic and ATPase-dependent manner entropically favored unimolecular G4 DNA, whereas other Fe-S helicases tested did not. The G4-specific ligands Phen-DC3 or Phen-DC6 inhibited FANCJ helicase on unimolecular G4 ∼1000-fold better than bi- or tetramolecular G4 DNA. The G4 ligand telomestatin induced DNA damage in human cells deficient in FANCJ but not DDX11 or XPD. These findings suggest FANCJ is a specialized Fe-S cluster helicase that preserves chromosomal stability by unwinding unimolecular G4 DNA likely to form in transiently unwound single-stranded genomic regions.
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Affiliation(s)
- Sanjay Kumar Bharti
- From the Laboratory of Molecular Gerontology, NIA, National Institutes of Health, National Institutes of Health Biomedical Research Center, Baltimore, Maryland 21224
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Suhasini AN, Sommers JA, Muniandy PA, Coulombe Y, Cantor SB, Masson JY, Seidman MM, Brosh RM. Fanconi anemia group J helicase and MRE11 nuclease interact to facilitate the DNA damage response. Mol Cell Biol 2013; 33:2212-27. [PMID: 23530059 PMCID: PMC3648079 DOI: 10.1128/mcb.01256-12] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Accepted: 03/14/2013] [Indexed: 01/31/2023] Open
Abstract
FANCJ mutations are linked to Fanconi anemia (FA) and increase breast cancer risk. FANCJ encodes a DNA helicase implicated in homologous recombination (HR) repair of double-strand breaks (DSBs) and interstrand cross-links (ICLs), but its mechanism of action is not well understood. Here we show with live-cell imaging that FANCJ recruitment to laser-induced DSBs but not psoralen-induced ICLs is dependent on nuclease-active MRE11. FANCJ interacts directly with MRE11 and inhibits its exonuclease activity in a specific manner, suggesting that FANCJ regulates the MRE11 nuclease to facilitate DSB processing and appropriate end resection. Cells deficient in FANCJ and MRE11 show increased ionizing radiation (IR) resistance, reduced numbers of γH2AX and RAD51 foci, and elevated numbers of DNA-dependent protein kinase catalytic subunit foci, suggesting that HR is compromised and the nonhomologous end-joining (NHEJ) pathway is elicited to help cells cope with IR-induced strand breaks. Interplay between FANCJ and MRE11 ensures a normal response to IR-induced DSBs, whereas FANCJ involvement in ICL repair is regulated by MLH1 and the FA pathway. Our findings are discussed in light of the current model for HR repair.
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Affiliation(s)
- Avvaru N. Suhasini
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, Baltimore, Maryland, USA
| | - Joshua A. Sommers
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, Baltimore, Maryland, USA
| | - Parameswary A. Muniandy
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, Baltimore, Maryland, USA
| | - Yan Coulombe
- Genome Stability Laboratory, Laval University Cancer Research Center, Quebec, Canada
| | - Sharon B. Cantor
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Jean-Yves Masson
- Genome Stability Laboratory, Laval University Cancer Research Center, Quebec, Canada
| | - Michael M. Seidman
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, Baltimore, Maryland, USA
| | - Robert M. Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, Baltimore, Maryland, USA
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56
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Qi Z, Pugh RA, Spies M, Chemla YR. Sequence-dependent base pair stepping dynamics in XPD helicase unwinding. eLife 2013; 2:e00334. [PMID: 23741615 PMCID: PMC3668415 DOI: 10.7554/elife.00334] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 04/26/2013] [Indexed: 11/13/2022] Open
Abstract
Helicases couple the chemical energy of ATP hydrolysis to directional translocation along nucleic acids and transient duplex separation. Understanding helicase mechanism requires that the basic physicochemical process of base pair separation be understood. This necessitates monitoring helicase activity directly, at high spatio-temporal resolution. Using optical tweezers with single base pair (bp) resolution, we analyzed DNA unwinding by XPD helicase, a Superfamily 2 (SF2) DNA helicase involved in DNA repair and transcription initiation. We show that monomeric XPD unwinds duplex DNA in 1-bp steps, yet exhibits frequent backsteps and undergoes conformational transitions manifested in 5-bp backward and forward steps. Quantifying the sequence dependence of XPD stepping dynamics with near base pair resolution, we provide the strongest and most direct evidence thus far that forward, single-base pair stepping of a helicase utilizes the spontaneous opening of the duplex. The proposed unwinding mechanism may be a universal feature of DNA helicases that move along DNA phosphodiester backbones. DOI:http://dx.doi.org/10.7554/eLife.00334.001.
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Affiliation(s)
- Zhi Qi
- Center for Biophysics and Computational Biology , University of Illinois at Urbana-Champaign , Urbana , United States
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57
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Ashton NW, Bolderson E, Cubeddu L, O'Byrne KJ, Richard DJ. Human single-stranded DNA binding proteins are essential for maintaining genomic stability. BMC Mol Biol 2013; 14:9. [PMID: 23548139 PMCID: PMC3626794 DOI: 10.1186/1471-2199-14-9] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 03/20/2013] [Indexed: 12/25/2022] Open
Abstract
The double-stranded conformation of cellular DNA is a central aspect of DNA stabilisation and protection. The helix preserves the genetic code against chemical and enzymatic degradation, metabolic activation, and formation of secondary structures. However, there are various instances where single-stranded DNA is exposed, such as during replication or transcription, in the synthesis of chromosome ends, and following DNA damage. In these instances, single-stranded DNA binding proteins are essential for the sequestration and processing of single-stranded DNA. In order to bind single-stranded DNA, these proteins utilise a characteristic and evolutionary conserved single-stranded DNA-binding domain, the oligonucleotide/oligosaccharide-binding (OB)-fold. In the current review we discuss a subset of these proteins involved in the direct maintenance of genomic stability, an important cellular process in the conservation of cellular viability and prevention of malignant transformation. We discuss the central roles of single-stranded DNA binding proteins from the OB-fold domain family in DNA replication, the restart of stalled replication forks, DNA damage repair, cell cycle-checkpoint activation, and telomere maintenance.
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Affiliation(s)
- Nicholas W Ashton
- Genome Stability Laboratory, Cancer and Ageing Research Program, Institute of Health and Biomedical Innovation, Translational Research Institute, Queensland University of Technology, Woolloongabba, Queensland, 4102, Australia
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58
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Sakasai R, Sakai A, Iimori M, Kiyonari S, Matsuoka K, Kakeji Y, Kitao H, Maehara Y. CtIP- and ATR-dependent FANCJ phosphorylation in response to DNA strand breaks mediated by DNA replication. Genes Cells 2012; 17:962-70. [PMID: 23157317 DOI: 10.1111/gtc.12011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 09/25/2012] [Indexed: 11/30/2022]
Abstract
FANCJ, also called BACH1/BRIP1, is a 5'-3' DEAH helicase, whose mutations are known as a risk factor for Fanconi anemia and also breast and ovarian cancer. FANCJ is thought to contribute to DNA double-strand break (DSB) repair and S-phase checkpoint through binding to multiple partner proteins, such as BRCA1 and TopBP1, but its molecular regulation remains unclear. We focused on DNA damage-induced phosphorylation of FANCJ and found that reagents that cause DSB or replication fork stalling induce FANCJ hyperphosphorylation. In particular, camptothecin (CPT) induced rapid and efficient FANCJ hyperphosphorylation that was largely dependent on TopBP1 and ATM-Rad3 related (ATR) kinase. Furthermore, DNA end resection that exposes single-strand DNA at the DSB site was required for hyperphosphorylation. Interestingly, upon CPT treatment, a dramatic increase in the FANCJ-TopBP1 complex was observed, and this increase was not alleviated even when ATR-dependent hyperphosphorylation was suppressed. These results suggest that FANCJ function may be modulated by hyperphosphorylation in a DNA end resection- and ATR-dependent manner and by FANCJ-TopBP1 complex formation in response to replication-coupled DSBs.
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Affiliation(s)
- Ryo Sakasai
- Innovative Anticancer Strategy for Therapeutics and Diagnosis Group, Innovation Center for Medical Redox Navigation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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59
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Unwinding and rewinding: double faces of helicase? J Nucleic Acids 2012; 2012:140601. [PMID: 22888405 PMCID: PMC3409536 DOI: 10.1155/2012/140601] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 05/28/2012] [Indexed: 12/29/2022] Open
Abstract
Helicases are enzymes that use ATP-driven motor force to unwind double-stranded DNA or RNA. Recently, increasing evidence demonstrates that some helicases also possess rewinding activity—in other words, they can anneal two complementary single-stranded nucleic acids. All five members of the human RecQ helicase family, helicase PIF1, mitochondrial helicase TWINKLE, and helicase/nuclease Dna2 have been shown to possess strand-annealing activity. Moreover, two recently identified helicases—HARP and AH2 have only ATP-dependent rewinding activity. These findings not only enhance our understanding of helicase enzymes but also establish the presence of a new type of protein: annealing helicases. This paper discusses what is known about these helicases, focusing on their biochemical activity to zip and unzip double-stranded DNA and/or RNA, their possible regulation mechanisms, and biological functions.
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60
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Xie J, Peng M, Guillemette S, Quan S, Maniatis S, Wu Y, Venkatesh A, Shaffer SA, Brosh RM, Cantor SB. FANCJ/BACH1 acetylation at lysine 1249 regulates the DNA damage response. PLoS Genet 2012; 8:e1002786. [PMID: 22792074 PMCID: PMC3390368 DOI: 10.1371/journal.pgen.1002786] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Accepted: 05/10/2012] [Indexed: 01/08/2023] Open
Abstract
BRCA1 promotes DNA repair through interactions with multiple proteins, including CtIP and FANCJ (also known as BRIP1/BACH1). While CtIP facilitates DNA end resection when de-acetylated, the function of FANCJ in repair processing is less well defined. Here, we report that FANCJ is also acetylated. Preventing FANCJ acetylation at lysine 1249 does not interfere with the ability of cells to survive DNA interstrand crosslinks (ICLs). However, resistance is achieved with reduced reliance on recombination. Mechanistically, FANCJ acetylation facilitates DNA end processing required for repair and checkpoint signaling. This conclusion was based on the finding that FANCJ and its acetylation were required for robust RPA foci formation, RPA phosphorylation, and Rad51 foci formation in response to camptothecin (CPT). Furthermore, both preventing and mimicking FANCJ acetylation at lysine 1249 disrupts FANCJ function in checkpoint maintenance. Thus, we propose that the dynamic regulation of FANCJ acetylation is critical for robust DNA damage response, recombination-based processing, and ultimately checkpoint maintenance. The BRCA1–Fanconi anemia (FA) pathway is required for both tumor suppression and cell survival, particularly following treatment with DNA damaging agents that induce DNA interstrand crosslinks (ICLs). ICL processing by the BRCA–FA pathway includes promotion of homologous recombination (HR) and DNA damage tolerance through translesion synthesis. However, little is known about how the BRCA–FA pathway or these ICL processing mechanisms are regulated. Here, we identify acetylation as a DNA damage–dependent regulator of the BRCA–FA protein, FANCJ. FANCJ acetylation at lysine 1249 is enhanced by expression of the histone acetyltransferase CBP and reduced by expression of histone deacetylases HDAC3 or SIRT1. Furthermore, acetylation on endogenous FANCJ is induced upon treatment of cells with agents that generate DNA lesions. Consistent with this post-translation event regulating FANCJ function during cellular DNA repair, preventing FANCJ acetylation skews ICL processing. Cells have reduced reliance on HR factor Rad54 and greater reliance on translesion synthesis polymerase polη. Our data indicate that FANCJ acetylation contributes to DNA end processing that is required for HR. Furthermore, resection-dependent checkpoint maintenance relies on the dynamic regulation of FANCJ acetylation. The implication of these findings is that FANCJ acetylation contributes to DNA repair choice within the BRCA–FA pathway.
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Affiliation(s)
- Jenny Xie
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Min Peng
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Shawna Guillemette
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Steven Quan
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Stephanie Maniatis
- Proteomics and Mass Spectrometry Facility and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Yuliang Wu
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH Biomedical Research Center, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Aditya Venkatesh
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Scott A. Shaffer
- Proteomics and Mass Spectrometry Facility and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Robert M. Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH Biomedical Research Center, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Sharon B. Cantor
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail:
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61
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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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62
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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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63
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Marceau AH. Functions of single-strand DNA-binding proteins in DNA replication, recombination, and repair. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2012; 922:1-21. [PMID: 22976174 DOI: 10.1007/978-1-62703-032-8_1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Double-stranded (ds) DNA contains all of the necessary genetic information, although practical use of this information requires unwinding of the duplex DNA. DNA unwinding creates single-stranded (ss) DNA intermediates that serve as templates for myriad cellular functions. Exposure of ssDNA presents several problems to the cell. First, ssDNA is thermodynamically less stable than dsDNA, which leads to spontaneous formation of duplex secondary structures that impede genome maintenance processes. Second, relative to dsDNA, ssDNA is hypersensitive to chemical and nucleolytic attacks that can cause damage to the genome. Cells deal with these potential problems by encoding specialized ssDNA-binding proteins (SSBs) that bind to and stabilize ssDNA structures required for essential genomic processes. SSBs are essential proteins found in all domains of life. SSBs bind ssDNA with high affinity and in a sequence-independent manner and, in doing so, SSBs help to form the central nucleoprotein complex substrate for DNA replication, recombination, and repair processes. While SSBs are found in every organism, the proteins themselves share surprisingly little sequence similarity, subunit composition, and oligomerization states. All SSB proteins contain at least one DNA-binding oligonucleotide/oligosaccharide binding (OB) fold, which consists minimally of a five stranded beta-sheet arranged as a beta barrel capped by a single alpha helix. The OB fold is responsible for both ssDNA binding and oligomerization (for SSBs that operate as oligomers). The overall organization of OB folds varies between bacteria, eukaryotes, and archaea. As part of SSB/ssDNA cellular structures, SSBs play direct roles in the DNA replication, recombination, and repair. In many cases, SSBs have been found to form specific complexes with diverse genome maintenance proteins, often helping to recruit SSB/ssDNA-processing enzymes to the proper cellular sites of action. This clustering of genome maintenance factors can help to stimulate and coordinate the activities of individual enzymes and is also important for dislodging SSB from ssDNA. These features support a model in which DNA metabolic processes have evolved to work on ssDNA/SSB nucleoprotein filaments rather than on naked ssDNA. In this volume, methods are described to interrogate SSB-DNA and SSB-protein binding functions along with approaches that aim to understand the cellular functions of SSB. This introductory chapter offers a general overview of SSBs that focuses on their structures, DNA-binding mechanisms, and protein-binding partners.
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Affiliation(s)
- Aimee H Marceau
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
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Wang W, Corrigan-Cummins M, Hudson J, Maric I, Simakova O, Neelapu SS, Kwak LW, Janik JE, Gause B, Jaffe ES, Calvo KR. MicroRNA profiling of follicular lymphoma identifies microRNAs related to cell proliferation and tumor response. Haematologica 2011; 97:586-94. [PMID: 22102710 DOI: 10.3324/haematol.2011.048132] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND MicroRNAs can play an important role in tumorigenesis through post-transcriptional regulation of gene expression, and are not well characterized in follicular lymphoma. DESIGN AND METHODS MicroRNA profiles of enriched follicular lymphoma tumor cells from 16 patients were generated by assaying 851 human microRNAs. Tandem gene expression profiles were obtained for predicting microRNA targets. RESULTS The expression of 133 microRNAs was significantly different (> 2-fold; P<0.05) between follicular lymphoma and follicular hyperplasia. Forty-four microRNAs in three groups generated a unique follicular lymphoma signature. Of these, ten microRNAs were increased (miR-193a-5p, -193b*, -345, -513b, -574-3p, -584, -663, -1287, -1295, and -1471), 11 microRNAs were decreased (miR-17*, -30a, -33a, -106a*, -141, -202, -205, -222, -301b, -431*, and -570), and 23 microRNAs formed a group that was increased in most cases of follicular lymphoma but showed lower expression in a subset of cases (let-7a, let-7f, miR-7-1*, -9, -9*, -20a, -20b, -30b, -96, -98, -194, -195, -221*, -374a, -374b, -451, -454, -502-3p, -532-3p, -664*, -1274a, -1274b, and -1260). Higher expression of this last group was associated with improved response to chemotherapy. Gene expression analysis revealed increased expression of MAPK1, AKT1, PRKCE, IL4R and DROSHA and decreased expression of CDKN1A/p21, SOCS2, CHEK1, RAD51, KLF4, BLIMP1 and IRF4 in follicular lymphoma. Functional studies indicated that CDKN1A/p21 and SOCS2 expression is directly regulated by miR-20a/-20b and miR-194, respectively. CONCLUSIONS Follicular lymphoma is characterized by a unique microRNA signature, containing a subset of microRNAs whose expression correlate with response to chemotherapy. miR-20a/b and miR-194 target CDKN1A and SOCS2 in follicular lymphoma, potentially contributing to tumor cell proliferation and survival.
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Affiliation(s)
- Weixin Wang
- Department of Laboratory Medicine, Hematology Section NIH Clinical Center, 10 Center Dr, Bldg 10/2C306 Bethesda, 20892-1508, USA
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65
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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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66
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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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67
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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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68
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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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69
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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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70
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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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71
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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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72
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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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73
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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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74
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Suhasini AN, Brosh RM. Mechanistic and biological aspects of helicase action on damaged DNA. Cell Cycle 2010; 9:2317-29. [PMID: 20574162 DOI: 10.4161/cc.9.12.11902] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Helicases catalytically unwind structured nucleic acids in a nucleoside-triphosphate-dependent and directionally specific manner, and are essential for virtually all aspects of nucleic acid metabolism. ATPase-driven helicases which translocate along nucleic acids play a role in damage recognition or unwinding of a DNA tract containing the lesion. Although classical biochemical experiments provided evidence that bulky covalent adducts inhibit DNA unwinding catalyzed by certain DNA helicases in a strand-specific manner (i.e., block to DNA unwinding restricted to adduct residence in the strand the helicase translocates), recent studies suggest more complex arrangements that may depend on the helicase under study, its assembly in a protein complex, and the type of structural DNA perturbation. Moreover, base and sugar phosphate backbone modifications exert effects on DNA helicases that suggest specialized tracking mechanisms. As a component of the replication stress response, the single-stranded DNA binding protein Replication Protein A (RPA) may serve to enable eukaryotic DNA helicases to overcome certain base lesions. Helicases play important roles in DNA damage signaling which also involve their partnership with RPA. In this review, we will discuss our current understanding of mechanistic and biological aspects of helicase action on damaged DNA.
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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, Baltimore, MD, USA
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75
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Oakley GG, Patrick SM. Replication protein A: directing traffic at the intersection of replication and repair. FRONT BIOSCI-LANDMRK 2010; 15:883-900. [PMID: 20515732 DOI: 10.2741/3652] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Since the initial discovery of replication protein A (RPA) as a DNA replication factor, much progress has been made on elucidating critical roles for RPA in other DNA metabolic pathways. RPA has been shown to be required for DNA replication, DNA repair, DNA recombination, and the DNA damage response pathway with roles in checkpoint activation. This review summarizes the current understanding of RPA structure, phosphorylation and protein-protein interactions in mediating these DNA metabolic processes.
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Affiliation(s)
- Greg G Oakley
- College of Dentistry, University of Nebraska Medical Center, Lincoln, Nebraska 68583, USA
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76
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Richard DJ, Bolderson E, Khanna KK. Multiple human single-stranded DNA binding proteins function in genome maintenance: structural, biochemical and functional analysis. Crit Rev Biochem Mol Biol 2010; 44:98-116. [PMID: 19367476 DOI: 10.1080/10409230902849180] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
DNA exists predominantly in a duplex form that is preserved via specific base pairing. This base pairing affords a considerable degree of protection against chemical or physical damage and preserves coding potential. However, there are many situations, e.g. during DNA damage and programmed cellular processes such as DNA replication and transcription, in which the DNA duplex is separated into two single-stranded DNA (ssDNA) strands. This ssDNA is vulnerable to attack by nucleases, binding by inappropriate proteins and chemical attack. It is very important to control the generation of ssDNA and protect it when it forms, and for this reason all cellular organisms and many viruses encode a ssDNA binding protein (SSB). All known SSBs use an oligosaccharide/oligonucleotide binding (OB)-fold domain for DNA binding. SSBs have multiple roles in binding and sequestering ssDNA, detecting DNA damage, stimulating strand-exchange proteins and helicases, and mediation of protein-protein interactions. Recently two additional human SSBs have been identified that are more closely related to bacterial and archaeal SSBs. Prior to this it was believed that replication protein A, RPA, was the only human equivalent of bacterial SSB. RPA is thought to be required for most aspects of DNA metabolism including DNA replication, recombination and repair. This review will discuss in further detail the biological pathways in which human SSBs function.
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Affiliation(s)
- Derek J Richard
- Cancer and Cell Biology Division, The Queensland Institute of Medical Research, 300 Herston Road, Herston, QLD 4006, Australia
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77
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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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78
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Muniandy PA, Liu J, Majumdar A, Liu ST, Seidman MM. DNA interstrand crosslink repair in mammalian cells: step by step. Crit Rev Biochem Mol Biol 2010; 45:23-49. [PMID: 20039786 PMCID: PMC2824768 DOI: 10.3109/10409230903501819] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Interstrand DNA crosslinks (ICLs) are formed by natural products of metabolism and by chemotherapeutic reagents. Work in E. coli identified a two cycle repair scheme involving incisions on one strand on either side of the ICL (unhooking) producing a gapped intermediate with the incised oligonucleotide attached to the intact strand. The gap is filled by recombinational repair or lesion bypass synthesis. The remaining monoadduct is then removed by nucleotide excision repair (NER). Despite considerable effort, our understanding of each step in mammalian cells is still quite limited. In part this reflects the variety of crosslinking compounds, each with distinct structural features, used by different investigators. Also, multiple repair pathways are involved, variably operative during the cell cycle. G(1) phase repair requires functions from NER, although the mechanism of recognition has not been determined. Repair can be initiated by encounters with the transcriptional apparatus, or a replication fork. In the case of the latter, the reconstruction of a replication fork, stalled or broken by collision with an ICL, adds to the complexity of the repair process. The enzymology of unhooking, the identity of the lesion bypass polymerases required to fill the first repair gap, and the functions involved in the second repair cycle are all subjects of active inquiry. Here we will review current understanding of each step in ICL repair in mammalian cells.
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Affiliation(s)
- Parameswary A Muniandy
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
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79
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Abstract
Fanconi Anemia (FA) is an inherited genomic instability disorder, caused by mutations in genes regulating replication-dependent removal of interstrand DNA crosslinks. The Fanconi Anemia pathway is thought to coordinate a complex mechanism that enlists elements of three classic DNA repair pathways, namely homologous recombination, nucleotide excision repair, and mutagenic translesion synthesis, in response to genotoxic insults. To this end, the Fanconi Anemia pathway employs a unique nuclear protein complex that ubiquitinates FANCD2 and FANCI, leading to formation of DNA repair structures. Lack of obvious enzymatic activities among most FA members has made it challenging to unravel its precise modus operandi. Here we review the current understanding of how the Fanconi Anemia pathway components participate in DNA repair and discuss the mechanisms that regulate this pathway to ensure timely, efficient, and correct restoration of chromosomal integrity.
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Affiliation(s)
- George-Lucian Moldovan
- Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA
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80
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Single-molecule analysis reveals differential effect of ssDNA-binding proteins on DNA translocation by XPD helicase. Mol Cell 2009; 35:694-703. [PMID: 19748362 PMCID: PMC2776038 DOI: 10.1016/j.molcel.2009.07.003] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 05/06/2009] [Accepted: 07/08/2009] [Indexed: 01/30/2023]
Abstract
An encounter between a DNA-translocating enzyme and a DNA-bound protein must occur frequently in the cell, but little is known about its outcome. Here we developed a multicolor single-molecule fluorescence approach to simultaneously monitor single-stranded DNA (ssDNA) translocation by a helicase and the fate of another protein bound to the same DNA. Distance-dependent fluorescence quenching by the iron-sulfur cluster of the archaeal XPD (Rad3) helicase was used as a calibrated proximity signal. Despite the similar equilibrium DNA-binding properties, the two cognate ssDNA-binding proteins RPA1 and RPA2 differentially affected XPD translocation. RPA1 competed with XPD for ssDNA access. In contrast, RPA2 did not interfere with XPD-ssDNA binding but markedly slowed down XPD translocation. Mechanistic models of bypassing DNA-bound proteins by the Rad3 family helicases and their biological implications are discussed.
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81
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Ali AM, Singh TR, Meetei AR. FANCM-FAAP24 and FANCJ: FA proteins that metabolize DNA. Mutat Res 2009; 668:20-26. [PMID: 19379763 PMCID: PMC2714411 DOI: 10.1016/j.mrfmmm.2009.04.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Revised: 03/31/2009] [Accepted: 04/02/2009] [Indexed: 05/27/2023]
Abstract
Fanconi anemia (FA) is a rare autosomal recessive or X-linked disorder characterized by aplastic anemia, cancer susceptibility and cellular sensitivity to DNA-crosslinking agents. Eight FA proteins (FANCA, -B, -C, -E, -F, -G, -L and -M) and three non-FA proteins (FAAP100, FAAP24 and HES1) form the FA nuclear core complex that is required for monoubiquitination of the FANCD2-FANCI dimer upon DNA damage. The other three FA proteins, FANCD1/BRCA2, FANCJ/BACH1/BRIP1 and FANCN/PALB2, act in parallel or downstream of the FANCD2-FANCI dimer. Despite the isolation and characterization of several FA proteins, the mechanism by which these proteins protect cells from DNA interstrand crosslinking agents has been unclear. This is because a majority of the FA proteins lack any recognizable functional domains that can provide insight into their function. The recently discovered FANCM (Hef) and FANCJ (BRIP1/BACH1) proteins contain helicase domains, providing potential insight into the role of FA proteins in DNA repair. FANCM with its partner, FAAP24, and FANCJ bind and metabolize a variety of DNA substrates. In this review, we focus on the discovery, structure, and function of the FANCM-FAAP24 and FANCJ proteins.
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Affiliation(s)
- Abdullah Mahmood Ali
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children’s Research Foundation, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio 45229
| | - Thiyam Ramsing Singh
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children’s Research Foundation, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio 45229
| | - Amom Ruhikanta Meetei
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children’s Research Foundation, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio 45229
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio 45229
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82
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de Winter JP, Joenje H. The genetic and molecular basis of Fanconi anemia. Mutat Res 2009; 668:11-19. [PMID: 19061902 DOI: 10.1016/j.mrfmmm.2008.11.004] [Citation(s) in RCA: 143] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 10/28/2008] [Accepted: 11/06/2008] [Indexed: 05/27/2023]
Abstract
The capacity to maintain genomic integrity is shared by all living organisms. Multiple pathways are distinguished that safeguard genomic stability, most of which have originated in primitive life forms. In human individuals, defects in these pathways are typically associated with cancer proneness. The Fanconi anemia pathway, one of these pathways, has evolved relatively late during evolution and exists - in its fully developed form - only in vertebrates. This pathway, in which thus far 13 distinct proteins have been shown to participate, appears essential for error-free DNA replication. Inactivating mutations in the corresponding genes underlie the recessive disease Fanconi anemia (FA). In the last decade the genetic basis of this disorder has been uncovered by a variety of approaches, including complementation cloning, genetic linkage analysis and protein association studies. Here we review these approaches, introduce the encoded proteins, and discuss their possible role in ensuring genomic integrity.
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Affiliation(s)
- Johan P de Winter
- Department of Clinical Genetics, Section Oncogenetics, VU University Medical Center, Van der Boechorststraat 7, Amsterdam 1081 BT, The Netherlands.
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Suhasini AN, Sommers JA, Mason AC, Voloshin ON, Camerini-Otero RD, Wold MS, Brosh RM. FANCJ helicase uniquely senses oxidative base damage in either strand of duplex DNA and is stimulated by replication protein A to unwind the damaged DNA substrate in a strand-specific manner. J Biol Chem 2009; 284:18458-70. [PMID: 19419957 DOI: 10.1074/jbc.m109.012229] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
FANCJ mutations are genetically linked to the Fanconi anemia complementation group J and predispose individuals to breast cancer. Understanding the role of FANCJ in DNA metabolism and how FANCJ dysfunction leads to tumorigenesis requires mechanistic studies of FANCJ helicase and its protein partners. In this work, we have examined the ability of FANCJ to unwind DNA molecules with specific base damage that can be mutagenic or lethal. FANCJ was inhibited by a single thymine glycol, but not 8-oxoguanine, in either the translocating or nontranslocating strands of the helicase substrate. In contrast, the human RecQ helicases (BLM, RECQ1, and WRN) display strand-specific inhibition of unwinding by the thymine glycol damage, whereas other DNA helicases (DinG, DnaB, and UvrD) are not significantly inhibited by thymine glycol in either strand. In the presence of replication protein A (RPA), but not Escherichia coli single-stranded DNA-binding protein, FANCJ efficiently unwound the DNA substrate harboring the thymine glycol damage in the nontranslocating strand; however, inhibition of FANCJ helicase activity by the translocating strand thymine glycol was not relieved. Strand-specific stimulation of human RECQ1 helicase activity was also observed, and RPA bound with high affinity to single-stranded DNA containing a single thymine glycol. Based on the biochemical studies, we propose a model for the specific functional interaction between RPA and FANCJ on the thymine glycol substrates. These studies are relevant to the roles of RPA, FANCJ, and other DNA helicases in the metabolism of damaged DNA that can interfere with basic cellular processes of DNA metabolism.
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Affiliation(s)
- Avvaru N Suhasini
- Laboratory of Molecular Gerontology, Biomedical Research Center, NIA, National Institutes of Health, Baltimore, Maryland 21224, USA
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84
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Wu Y, Brosh RM. FANCJ helicase operates in the Fanconi Anemia DNA repair pathway and the response to replicational stress. Curr Mol Med 2009; 9:470-82. [PMID: 19519404 PMCID: PMC2763586 DOI: 10.2174/156652409788167159] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Fanconi anemia (FA) is an autosomal recessive disorder characterized by multiple congenital anomalies, progressive bone marrow failure, and high cancer risk. Cells from FA patients exhibit spontaneous chromosomal instability and hypersensitivity to DNA interstrand cross-linking (ICL) agents. Although the precise mechanistic details of the FA/BRCA pathway of ICL-repair are not well understood, progress has been made in the identification of the FA proteins that are required for the pathway. Among the 13 FA complementation groups from which all the FA genes have been cloned, only a few of the FA proteins are predicted to have direct roles in DNA metabolism. One of the more recently identified FA proteins, shown to be responsible for complementation of the FA complementation group J, is the BRCA1 Associated C-terminal Helicase (BACH1, designated FANCJ), originally identified as a protein associated with breast cancer. FANCJ has been proposed to function downstream of FANCD2 monoubiquitination, a critical event in the FA pathway. Evidence supports a role for FANCJ in a homologous recombination (HR) pathway of double strand break (DSB) repair. In this review, we will summarize the current knowledge in terms of FANCJ functions through its enzymatic activities and protein interactions. The molecular roles of FANCJ in DNA repair and the response to replicational stress will be discussed.
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Affiliation(s)
- Yuliang Wu
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
| | - Robert M. Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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85
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PALB2 is an integral component of the BRCA complex required for homologous recombination repair. Proc Natl Acad Sci U S A 2009; 106:7155-60. [PMID: 19369211 DOI: 10.1073/pnas.0811159106] [Citation(s) in RCA: 416] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Mutations in breast cancer susceptibility gene 1 and 2 (BRCA1 and BRCA2) predispose individuals to breast and ovarian cancer development. We previously reported an in vivo interaction between BRCA1 and BRCA2. However, the biological significance of their association is thus far undefined. Here, we report that PALB2, the partner and localizer of BRCA2, binds directly to BRCA1, and serves as the molecular scaffold in the formation of the BRCA1-PALB2-BRCA2 complex. The association between BRCA1 and PALB2 is primarily mediated via apolar bonding between their respective coiled-coil domains. More importantly, BRCA1 mutations identified in cancer patients disrupted the specific interaction between BRCA1 and PALB2. Consistent with the converging functions of the BRCA proteins in DNA repair, cells harboring mutations with abrogated BRCA1-PALB2 interaction resulted in defective homologous recombination (HR) repair. We propose that, via its direct interaction with PALB2, BRCA1 fine-tunes recombinational repair partly through its modulatory role in the PALB2-dependent loading of BRCA2-RAD51 repair machinery at DNA breaks. Our findings uncover PALB2 as the molecular adaptor between the BRCA proteins, and suggest that impaired HR repair is one of the fundamental causes for genomic instability and tumorigenesis observed in patients carrying BRCA1, BRCA2, or PALB2 mutations.
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86
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Wu Y, Suhasini AN, Brosh RM. Welcome the family of FANCJ-like helicases to the block of genome stability maintenance proteins. Cell Mol Life Sci 2009; 66:1209-22. [PMID: 19099189 PMCID: PMC2663010 DOI: 10.1007/s00018-008-8580-6] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The FANCJ family of DNA helicases is emerging as an important group of proteins for the prevention of human disease, cancer, and chromosomal instability. FANCJ was identified by its association with breast cancer, and is implicated in Fanconi Anemia. Proteins with sequence similarity to FANCJ are important for maintenance of genomic stability. Mutations in genes encoding proteins related to FANCJ, designated ChlR1 in human and Chl1p in yeast, result in sister chromatid cohesion defects. Nematodes mutated in dog-1 show germline as well as somatic deletions in genes containing guanine-rich DNA. Rtel knockout mice are embryonic lethal, and embryonic stem cells show telomere loss and chromosomal instability. FANCJ also shares sequence similarity with human XPD and yeast RAD3 helicases required for nucleotide excision repair. The recently solved structure of XPD has provided new insight to the helicase core and accessory domains of sequence related Superfamily 2 helicases. The functions and roles of members of the FANCJ-like helicase family will be discussed.
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Affiliation(s)
- Y. Wu
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, 251 Bayview Blvd, Baltimore, MD 21224 USA
| | - A. N. Suhasini
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, 251 Bayview Blvd, Baltimore, MD 21224 USA
| | - R. M. Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, 251 Bayview Blvd, Baltimore, MD 21224 USA
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87
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Sommers JA, Rawtani N, Gupta R, Bugreev DV, Mazin AV, Cantor SB, Brosh RM. FANCJ uses its motor ATPase to destabilize protein-DNA complexes, unwind triplexes, and inhibit RAD51 strand exchange. J Biol Chem 2009; 284:7505-17. [PMID: 19150983 DOI: 10.1074/jbc.m809019200] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Mutations in the FANCJ helicase predispose individuals to breast cancer and are genetically linked to the Fanconi anemia (FA) complementation group J. FA is a chromosomal instability disorder characterized by multiple congenital anomalies, progressive bone marrow failure, and high cancer risk. FANCJ has been proposed to function downstream of FANCD2 monoubiquitination, a critical event in the FA pathway. Evidence supports a role for FANCJ in a homologous recombination pathway of double strand break repair. In an effort to understand the molecular functions of FANCJ, we have investigated the ability of purified FANCJ recombinant protein to use its motor ATPase function for activities in addition to unwinding of conventional duplex DNA substrates. These efforts have led to the discovery that FANCJ ATP hydrolysis can be used to destabilize protein-DNA complexes and unwind triple helix alternate DNA structures. These novel catalytic functions of FANCJ may be important for its role in cellular DNA repair, recombination, or resolving DNA structural obstacles to replication. Consistent with this, we show that FANCJ can inhibit RAD51 strand exchange, an activity that is likely to be important for its role in controlling DNA repair through homologous recombination.
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Affiliation(s)
- Joshua A Sommers
- Laboratory of Molecular Gerontology, NIA, National Institutes of Health, National Institutes of Health Biomedical Research Center, Baltimore, Maryland 21224, USA
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88
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Frontini M, Vijayakumar M, Garvin A, Clarke N. A ChIP-chip approach reveals a novel role for transcription factor IRF1 in the DNA damage response. Nucleic Acids Res 2009; 37:1073-85. [PMID: 19129219 PMCID: PMC2651779 DOI: 10.1093/nar/gkn1051] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
IRF1 is a transcription factor that regulates key processes in the immune system and in tumour suppression. To gain further insight into IRF1's role in these processes, we searched for new target genes by performing chromatin immunoprecipitation coupled to a CpG island microarray (ChIP–chip). Using this approach we identified 202 new IRF1-binding sites with high confidence. Functional categorization of the target genes revealed a surprising cadre of new roles that can be linked to IRF1. One of the major functional categories was the DNA damage response pathway. In order to further validate our findings, we show that IRF1 can regulate the mRNA expression of a number of the DNA damage response genes in our list. In particular, we demonstrate that the mRNA and protein levels of the DNA repair protein BRIP1 [Fanconi anemia gene J (FANC J)] are upregulated after IRF1 over-expression. We also demonstrate that knockdown of IRF1 by siRNA results in loss of BRIP1 expression, abrogation of BRIP1 foci after DNA interstrand crosslink (ICL) damage and hypersensitivity to the DNA crosslinking agent, melphalan; a characteristic phenotype of FANC J cells. Taken together, our data provides a more complete understanding of the regulatory networks controlled by IRF1 and reveals a novel role for IRF1 in regulating the ICL DNA damage response.
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Affiliation(s)
- Mattia Frontini
- MRC Clinical Sciences Centre, Faculty of Medicine Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK
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89
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Wang LC, Stone S, Hoatlin ME, Gautier J. Fanconi anemia proteins stabilize replication forks. DNA Repair (Amst) 2008; 7:1973-81. [PMID: 18786657 DOI: 10.1016/j.dnarep.2008.08.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 08/08/2008] [Accepted: 08/15/2008] [Indexed: 10/21/2022]
Abstract
Fanconi anemia (FA) is a recessive genetic disorder characterized by hypersensitivity to crosslinking agents that has been attributed to defects in DNA repair and/or replication. FANCD2 and the FA core complex bind to chromatin during DNA replication; however, the role of FA proteins during replication is unknown. Using Xenopus cell-free extracts, we show that FANCL depletion results in defective DNA replication restart following treatment with camptothecin, a drug that results in DSBs during DNA replication. This defect is more pronounced following treatment with mitomycin C, presumably because of an additional role of the FA pathway in DNA crosslink repair. Moreover, we show that chromatin binding of FA core complex proteins during DNA replication follows origin assembly and origin firing and is dependent on the binding of RPA to ssDNA while FANCD2 additionally requires ATR, consistent with FA proteins acting at replication forks. Together, our data suggest that FA proteins play a role in replication restart at collapsed replication forks.
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Affiliation(s)
- Lily Chien Wang
- Institute for Cancer Genetics, Columbia University, New York, NY 10032, USA
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90
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Ferroplasma acidarmanus RPA2 facilitates efficient unwinding of forked DNA substrates by monomers of FacXPD helicase. J Mol Biol 2008; 383:982-98. [PMID: 18801373 DOI: 10.1016/j.jmb.2008.09.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 08/22/2008] [Accepted: 09/01/2008] [Indexed: 12/11/2022]
Abstract
The strand-separation activity that is important for many cellular DNA processing machineries is provided by DNA helicases. In order to understand the physiological properties of a helicase acting in the context of its macromolecular machinery, it is imperative to identify the proteins that interact with the enzyme and to analyze how these proteins affect its helicase activities. The archaeal Rad3 helicase XPD (xeroderma pigmentosum group D protein) from Ferroplasma acidarmanus (FacXPD) is a superfamily II 5'-->3' DNA helicase. Similar to its mammalian homolog working as an integral part of the transcription factor IIH complex, FacXPD may play an important role in nucleotide excision repair (NER) and transcription initiation. Interaction between FacXPD and other archaeal NER proteins likely modulates their respective activities. Replication protein A (RPA), a single-stranded DNA (ssDNA)-binding protein, is one of the NER proteins that functionally interact with the human transcription factor IIH complex. There are two RPA proteins in F. acidarmanus: FacRPA1, a homodimer of two monomers consisting of two oligonucleotide/oligosaccharide binding folds, and FacRPA2, a monomer containing a single oligonucleotide/oligosaccharide binding fold. In this study, we analyzed the effect of these ssDNA-binding proteins on FacXPD helicase activity. We found that FacRPA2 stimulates DNA unwinding by FacXPD helicase through a novel mechanism by providing a helix-destabilizing function. In contrast, FacRPA1 fails to stimulate helicase activity to the same extent as FacRPA2 and competes with FacXPD for binding to the ssDNA-double-stranded DNA junction. We conclude that the FacRPA2-coated fork is a preferred and likely physiological substrate that a monomer of FacXPD can unwind with a processivity sufficient for expansion of the NER or transcription bubble. We also suggest that duplex melting by a cognate ssDNA-binding protein coordinated with translocation by a helicase may represent a common strategy for duplex unwinding by the Rad3 family of helicases.
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91
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Maor-Shoshani A, Meira LB, Yang X, Samson LD. 3-Methyladenine DNA glycosylase is important for cellular resistance to psoralen interstrand cross-links. DNA Repair (Amst) 2008; 7:1399-406. [PMID: 18571479 DOI: 10.1016/j.dnarep.2008.04.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 04/18/2008] [Accepted: 04/25/2008] [Indexed: 11/29/2022]
Abstract
DNA interstrand cross-links (ICLs), widely used in chemotherapy, are cytotoxic lesions because they block replication and transcription. Repair of ICLs involves proteins from different repair pathways however the precise mechanism is still not completely understood. Here, we report that the 3-methyladenine DNA glycosylase (Aag), an enzyme that initiates base excision repair at a variety of alkylated bases, is also involved in the repair of ICLs. Aag(-/-) mouse embryonic stem cells were shown to be more sensitive to the cross-linking agent 4,5',8-trimethylpsoralen than wild-type cells, but no more sensitive than wild-type to the psoralen derivative Angelicin that forms only monoadducts. We show that gamma-H2AX foci formation, a marker for double strand breaks that are formed during ICL repair, is impaired in psoralen treated Aag(-/-) cells in both quantity and kinetics. However, in our in vitro system, purified human AAG can neither bind to the ICL nor cleave it. Taken together, our results suggest that Aag is important for the resistance of mouse ES cells to psoralen-induced ICLs.
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Affiliation(s)
- Ayelet Maor-Shoshani
- Biological Engineering Department and Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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92
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FANCJ helicase defective in Fanconia anemia and breast cancer unwinds G-quadruplex DNA to defend genomic stability. Mol Cell Biol 2008; 28:4116-28. [PMID: 18426915 DOI: 10.1128/mcb.02210-07] [Citation(s) in RCA: 320] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
FANCJ mutations are associated with breast cancer and genetically linked to the bone marrow disease Fanconi anemia (FA). The genomic instability of FA-J mutant cells suggests that FANCJ helicase functions in the replicational stress response. A putative helicase with sequence similarity to FANCJ in Caenorhabditis elegans (DOG-1) and mouse (RTEL) is required for poly(G) tract maintenance, suggesting its involvement in the resolution of alternate DNA structures that impede replication. Under physiological conditions, guanine-rich sequences spontaneously assemble into four-stranded structures (G quadruplexes [G4]) that influence genomic stability. FANCJ unwound G4 DNA substrates in an ATPase-dependent manner. FANCJ G4 unwinding is specific since another superfamily 2 helicase, RECQ1, failed to unwind all G4 substrates tested under conditions in which the helicase unwound duplex DNA. Replication protein A stimulated FANCJ G4 unwinding, whereas the mismatch repair complex MSH2/MSH6 inhibited this activity. FANCJ-depleted cells treated with the G4-interactive compound telomestatin displayed impaired proliferation and elevated levels of apoptosis and DNA damage compared to small interfering RNA control cells, suggesting that G4 DNA is a physiological substrate of FANCJ. Although the FA pathway has been classically described in terms of interstrand cross-link (ICL) repair, the cellular defects associated with FANCJ mutation extend beyond the reduced ability to repair ICLs and involve other types of DNA structural roadblocks to replication.
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93
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Abstract
Far western blotting (WB) was derived from the standard WB method to detect protein-protein interactions in vitro. In Far WB, proteins in a cell lysate containing prey proteins are firstly separated by SDS or native PAGE, and transferred to a membrane, as in a standard WB. The proteins in the membrane are then denatured and renatured. The membrane is then blocked and probed, usually with purified bait protein(s). The bait proteins are detected on spots in the membrane where a prey protein is located if the bait proteins and the prey protein together form a complex. Compared with other biochemical binding assays, Far WB allows prey proteins to be endogenously expressed without purification. Unlike most methods using cell lysates (e.g., co-immunoprecipitation (co-IP)) or living cells (e.g., fluorescent resonance energy transfer (FRET)), Far WB determines whether two proteins bind to each other directly. Furthermore, in cases where they bind to each other indirectly, Far WB allows the examination of candidate protein(s) that form a complex between them. Typically, 2-3 d are required to carry out the experiment.
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94
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Sharma S, Brosh RM. Unique and important consequences of RECQ1 deficiency in mammalian cells. Cell Cycle 2008; 7:989-1000. [PMID: 18414032 DOI: 10.4161/cc.7.8.5707] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Five members of the RecQ subfamily of DEx-H-containing DNA helicases have been identified in both human and mouse, and mutations in BLM, WRN, and RECQ4 are associated with human diseases of premature aging, cancer, and chromosomal instability. Although a genetic disease has not been linked to RECQ1 mutations, RECQ1 helicase is the most highly expressed of the human RecQ helicases, suggesting an important role in cellular DNA metabolism. Recent advances have elucidated a unique role of RECQ1 to suppress genomic instability. Embryonic fibroblasts from RECQ1-deficient mice displayed aneuploidy, chromosomal instability, and increased load of DNA damage.(1) Acute depletion of human RECQ1 renders cells sensitive to DNA damage and results in spontaneous gamma-H2AX foci and elevated sister chromatid exchanges, indicating aberrant repair of DNA breaks.(2) Consistent with a role in DNA repair, RECQ1 relocalizes to irradiation-induced nuclear foci and associates with chromatin.(2) RECQ1 catalytic activities(3) and interactions with DNA repair proteins(2,4,5) are likely to be important for its molecular functions in genome homeostasis. Collectively, these studies provide the first evidence for an important role of RECQ1 to confer chromosomal stability that is unique from that of other RecQ helicases and suggest its potential involvement in tumorigenesis.
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Affiliation(s)
- Sudha Sharma
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland, USA
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95
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Abstract
Homologous recombination (HR) comprises a series of interrelated pathways that function in the repair of DNA double-stranded breaks (DSBs) and interstrand crosslinks (ICLs). In addition, recombination provides critical support for DNA replication in the recovery of stalled or broken replication forks, contributing to tolerance of DNA damage. A central core of proteins, most critically the RecA homolog Rad51, catalyzes the key reactions that typify HR: homology search and DNA strand invasion. The diverse functions of recombination are reflected in the need for context-specific factors that perform supplemental functions in conjunction with the core proteins. The inability to properly repair complex DNA damage and resolve DNA replication stress leads to genomic instability and contributes to cancer etiology. Mutations in the BRCA2 recombination gene cause predisposition to breast and ovarian cancer as well as Fanconi anemia, a cancer predisposition syndrome characterized by a defect in the repair of DNA interstrand crosslinks. The cellular functions of recombination are also germane to DNA-based treatment modalities of cancer, which target replicating cells by the direct or indirect induction of DNA lesions that are substrates for recombination pathways. This review focuses on mechanistic aspects of HR relating to DSB and ICL repair as well as replication fork support.
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Affiliation(s)
- Xuan Li
- Section of Microbiology University of California, Davis, Davis CA 95616-8665, USA
| | - Wolf-Dietrich Heyer
- Section of Microbiology University of California, Davis, Davis CA 95616-8665, USA
- Section of Molecular and Cellular Biology, University of California, Davis, Davis CA 95616-8665, USA
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