1
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Zhang Z, Zhu Q. WD Repeat and HMG Box DNA Binding Protein 1: An Oncoprotein at the Hub of Tumorigenesis and a Novel Therapeutic Target. Int J Mol Sci 2023; 24:12494. [PMID: 37569867 PMCID: PMC10420296 DOI: 10.3390/ijms241512494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 08/01/2023] [Accepted: 08/04/2023] [Indexed: 08/13/2023] Open
Abstract
WD repeat and HMG-box DNA binding protein 1 (WDHD1) is a highly conserved gene from yeast to humans. It actively participates in DNA replication, playing a crucial role in DNA damage repair and the cell cycle, contributing to centromere formation and sister chromosome segregation. Notably, several studies have implicated WDHD1 in the development and progression of diverse tumor types, including esophageal carcinoma, pulmonary carcinoma, and breast carcinoma. Additionally, the inhibitor of WDHD1 has been found to enhance radiation sensitivity, improve drug resistance, and significantly decrease tumor cell proliferation. This comprehensive review aims to provide an overview of the molecular structure, biological functions, and regulatory mechanisms of WDHD1 in tumors, thereby establishing a foundation for future investigations and potential clinical applications of WDHD1.
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Affiliation(s)
| | - Qing Zhu
- Division of Abdominal Tumor Multimodality Treatment, Cancer Center, West China Hospital, Sichuan University, No. 37 Guoxue Alley, Chengdu 610041, China;
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2
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Ertay A, Liu H, Liu D, Peng P, Hill C, Xiong H, Hancock D, Yuan X, Przewloka MR, Coldwell M, Howell M, Skipp P, Ewing RM, Downward J, Wang Y. WDHD1 is essential for the survival of PTEN-inactive triple-negative breast cancer. Cell Death Dis 2020; 11:1001. [PMID: 33221821 PMCID: PMC7680459 DOI: 10.1038/s41419-020-03210-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 11/02/2020] [Accepted: 11/05/2020] [Indexed: 12/24/2022]
Abstract
Triple-negative breast cancer (TNBC) is the most aggressive type of breast cancer that lacks the oestrogen receptor, progesterone receptor and human epidermal growth factor receptor 2, making it difficult to target therapeutically. Targeting synthetic lethality is an alternative approach for cancer treatment. TNBC shows frequent loss of phosphatase and tensin homologue (PTEN) expression, which is associated with poor prognosis and treatment response. To identify PTEN synthetic lethal interactions, TCGA analysis coupled with a whole-genome siRNA screen in isogenic PTEN-negative and -positive cells were performed. Among the candidate genes essential for the survival of PTEN-inactive TNBC cells, WDHD1 (WD repeat and high-mobility group box DNA-binding protein 1) expression was increased in the low vs. high PTEN TNBC samples. It was also the top hit in the siRNA screen and its knockdown significantly inhibited cell viability in PTEN-negative cells, which was further validated in 2D and 3D cultures. Mechanistically, WDHD1 is important to mediate a high demand of protein translation in PTEN-inactive TNBC. Finally, the importance of WDHD1 in TNBC was confirmed in patient samples obtained from the TCGA and tissue microarrays with clinic-pathological information. Taken together, as an essential gene for the survival of PTEN-inactive TNBC cells, WDHD1 could be a potential biomarker or a therapeutic target for TNBC.
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Affiliation(s)
- Ayse Ertay
- Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Huiquan Liu
- Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430030, Wuhan, China
| | - Dian Liu
- Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430030, Wuhan, China
| | - Ping Peng
- Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430030, Wuhan, China
| | - Charlotte Hill
- Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Hua Xiong
- Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430030, Wuhan, China
| | - David Hancock
- Oncogene Biology, The Francis Crick Institute, London, NW1 1AT, UK
| | - Xianglin Yuan
- Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430030, Wuhan, China
| | - Marcin R Przewloka
- Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK
- Institute for Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Mark Coldwell
- Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK
- Institute for Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Michael Howell
- High-Throughput Screening, The Francis Crick Institute, London, NW1 1AT, UK
| | - Paul Skipp
- Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK
- Institute for Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK
- Centre for Proteomic Research, Institute for Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Rob M Ewing
- Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK
- Institute for Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Julian Downward
- Oncogene Biology, The Francis Crick Institute, London, NW1 1AT, UK.
| | - Yihua Wang
- Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
- Institute for Life Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, SO16 6YD, UK.
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3
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Fumasoni M, Murray AW. The evolutionary plasticity of chromosome metabolism allows adaptation to constitutive DNA replication stress. eLife 2020; 9:e51963. [PMID: 32043971 PMCID: PMC7069727 DOI: 10.7554/elife.51963] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 02/11/2020] [Indexed: 01/22/2023] Open
Abstract
Many biological features are conserved and thus considered to be resistant to evolutionary change. While rapid genetic adaptation following the removal of conserved genes has been observed, we often lack a mechanistic understanding of how adaptation happens. We used the budding yeast, Saccharomyces cerevisiae, to investigate the evolutionary plasticity of chromosome metabolism, a network of evolutionary conserved modules. We experimentally evolved cells constitutively experiencing DNA replication stress caused by the absence of Ctf4, a protein that coordinates the enzymatic activities at replication forks. Parallel populations adapted to replication stress, over 1000 generations, by acquiring multiple, concerted mutations. These mutations altered conserved features of two chromosome metabolism modules, DNA replication and sister chromatid cohesion, and inactivated a third, the DNA damage checkpoint. The selected mutations define a functionally reproducible evolutionary trajectory. We suggest that the evolutionary plasticity of chromosome metabolism has implications for genome evolution in natural populations and cancer.
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Affiliation(s)
- Marco Fumasoni
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
| | - Andrew W Murray
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
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4
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Yuan Z, Georgescu R, Santos RDLA, Zhang D, Bai L, Yao NY, Zhao G, O'Donnell ME, Li H. Ctf4 organizes sister replisomes and Pol α into a replication factory. eLife 2019; 8:47405. [PMID: 31589141 PMCID: PMC6800005 DOI: 10.7554/elife.47405] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 10/04/2019] [Indexed: 12/14/2022] Open
Abstract
The current view is that eukaryotic replisomes are independent. Here we show that Ctf4 tightly dimerizes CMG helicase, with an extensive interface involving Psf2, Cdc45, and Sld5. Interestingly, Ctf4 binds only one Pol α-primase. Thus, Ctf4 may have evolved as a trimer to organize two helicases and one Pol α-primase into a replication factory. In the 2CMG–Ctf43–1Pol α-primase factory model, the two CMGs nearly face each other, placing the two lagging strands toward the center and two leading strands out the sides. The single Pol α-primase is centrally located and may prime both sister replisomes. The Ctf4-coupled-sister replisome model is consistent with cellular microscopy studies revealing two sister forks of an origin remain attached and are pushed forward from a protein platform. The replication factory model may facilitate parental nucleosome transfer during replication.
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Affiliation(s)
- Zuanning Yuan
- Structural Biology Program, Van Andel Institute, Grand Rapids, United States
| | - Roxana Georgescu
- Howard Hughes Medical Institute, Chevy Chase, United States.,DNA Replication Laboratory, The Rockefeller University, New York, United States
| | | | - Daniel Zhang
- DNA Replication Laboratory, The Rockefeller University, New York, United States
| | - Lin Bai
- Structural Biology Program, Van Andel Institute, Grand Rapids, United States
| | - Nina Y Yao
- DNA Replication Laboratory, The Rockefeller University, New York, United States
| | - Gongpu Zhao
- David Van Andel Advanced Cryo-EM Suite, Van Andel Institute, Grand Rapids, United States
| | - Michael E O'Donnell
- Howard Hughes Medical Institute, Chevy Chase, United States.,DNA Replication Laboratory, The Rockefeller University, New York, United States
| | - Huilin Li
- Structural Biology Program, Van Andel Institute, Grand Rapids, United States
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5
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AND-1 fork protection function prevents fork resection and is essential for proliferation. Nat Commun 2018; 9:3091. [PMID: 30082684 PMCID: PMC6079002 DOI: 10.1038/s41467-018-05586-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 07/13/2018] [Indexed: 12/31/2022] Open
Abstract
AND-1/Ctf4 bridges the CMG helicase and DNA polymerase alpha, facilitating replication. Using an inducible degron system in avian cells, we find that AND-1 depletion is incompatible with proliferation, owing to cells accumulating in G2 with activated DNA damage checkpoint. Replication without AND-1 causes fork speed slow-down and accumulation of long single-stranded DNA (ssDNA) gaps at the replication fork junction, with these regions being converted to DNA double strand breaks (DSBs) in G2. Strikingly, resected forks and DNA damage accumulation in G2, but not fork slow-down, are reverted by treatment with mirin, an MRE11 nuclease inhibitor. Domain analysis of AND-1 further revealed that the HMG box is important for fast replication but not for proliferation, whereas conversely, the WD40 domain prevents fork resection and subsequent DSB-associated lethality. Thus, our findings uncover a fork protection function of AND-1/Ctf4 manifested via the WD40 domain that is essential for proliferation and averts genome instability. AND-1, the vertebrate orthologue of Ctf4, is a critical player during DNA replication and for maintenance of genome integrity. Here the authors use a conditional AND-1 depletion system in avian DT40 cells to reveal the consequences of the lack of AND-1 on cell proliferation and DNA replication.
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6
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Konada L, Aricthota S, Vadla R, Haldar D. Fission Yeast Sirtuin Hst4 Functions in Preserving Genomic Integrity by Regulating Replisome Component Mcl1. Sci Rep 2018; 8:8496. [PMID: 29855479 PMCID: PMC5981605 DOI: 10.1038/s41598-018-26476-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 04/19/2018] [Indexed: 11/09/2022] Open
Abstract
The Schizosaccharomyces pombe sirtuin Hst4, functions in the maintenance of genome stability by regulating histone H3 lysine56 acetylation (H3K56ac) and promoting cell survival during replicative stress. However, its molecular function in DNA damage survival is unclear. Here, we show that hst4 deficiency in the fission yeast causes S phase delay and DNA synthesis defects. We identified a novel functional link between hst4 and the replisome component mcl1 in a suppressor screen aimed to identify genes that could restore the slow growth and Methyl methanesulphonate (MMS) sensitivity phenotypes of the hst4Δ mutant. Expression of the replisome component Mcl1 rescues hst4Δ phenotypes. Interestingly, hst4 and mcl1 show an epistatic interaction and suppression of hst4Δ phenotypes by mcl1 is H3K56 acetylation dependent. Furthermore, Hst4 was found to regulate the expression of mcl1. Finally, we show that hSIRT2 depletion results in decreased levels of And-1 (human orthologue of Mcl1), establishing the conservation of this mechanism. Moreover, on induction of replication stress (MMS treatment), Mcl1 levels decrease upon Hst4 down regulation. Our results identify a novel function of Hst4 in regulation of DNA replication that is dependent on H3K56 acetylation. Both SIRT2 and And-1 are deregulated in cancers. Therefore, these findings could be of therapeutic importance in future.
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Affiliation(s)
- Lahiri Konada
- Centre for DNA Fingerprinting and Diagnostics, Survey Nos. 728, 729, 730 & 734, Opposite Uppal Water Tank, Beside BSNL T E Building, Uppal, Ranga Reddy District, Hyderabad, 500039, India.,Graduate Studies, Manipal University, Manipal, India
| | - Shalini Aricthota
- Centre for DNA Fingerprinting and Diagnostics, Survey Nos. 728, 729, 730 & 734, Opposite Uppal Water Tank, Beside BSNL T E Building, Uppal, Ranga Reddy District, Hyderabad, 500039, India.,Graduate Studies, Manipal University, Manipal, India
| | - Raghavendra Vadla
- Centre for DNA Fingerprinting and Diagnostics, Survey Nos. 728, 729, 730 & 734, Opposite Uppal Water Tank, Beside BSNL T E Building, Uppal, Ranga Reddy District, Hyderabad, 500039, India.,Graduate Studies, Manipal University, Manipal, India
| | - Devyani Haldar
- Centre for DNA Fingerprinting and Diagnostics, Survey Nos. 728, 729, 730 & 734, Opposite Uppal Water Tank, Beside BSNL T E Building, Uppal, Ranga Reddy District, Hyderabad, 500039, India.
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7
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Jahn LJ, Mason B, Brøgger P, Toteva T, Nielsen DK, Thon G. Dependency of Heterochromatin Domains on Replication Factors. G3 (BETHESDA, MD.) 2018; 8:477-489. [PMID: 29187422 PMCID: PMC5919735 DOI: 10.1534/g3.117.300341] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Accepted: 11/20/2017] [Indexed: 01/26/2023]
Abstract
Chromatin structure regulates both genome expression and dynamics in eukaryotes, where large heterochromatic regions are epigenetically silenced through the methylation of histone H3K9, histone deacetylation, and the assembly of repressive complexes. Previous genetic screens with the fission yeast Schizosaccharomyces pombe have led to the identification of key enzymatic activities and structural constituents of heterochromatin. We report here on additional factors discovered by screening a library of deletion mutants for silencing defects at the edge of a heterochromatic domain bound by its natural boundary-the IR-R+ element-or by ectopic boundaries. We found that several components of the DNA replication progression complex (RPC), including Mrc1/Claspin, Mcl1/Ctf4, Swi1/Timeless, Swi3/Tipin, and the FACT subunit Pob3, are essential for robust heterochromatic silencing, as are the ubiquitin ligase components Pof3 and Def1, which have been implicated in the removal of stalled DNA and RNA polymerases from chromatin. Moreover, the search identified the cohesin release factor Wpl1 and the forkhead protein Fkh2, both likely to function through genome organization, the Ssz1 chaperone, the Fkbp39 proline cis-trans isomerase, which acts on histone H3P30 and P38 in Saccharomyces cerevisiae, and the chromatin remodeler Fft3. In addition to their effects in the mating-type region, to varying extents, these factors take part in heterochromatic silencing in pericentromeric regions and telomeres, revealing for many a general effect in heterochromatin. This list of factors provides precious new clues with which to study the spatiotemporal organization and dynamics of heterochromatic regions in connection with DNA replication.
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Affiliation(s)
| | - Bethany Mason
- Department of Biology, University of Copenhagen, BioCenter, 2200, Denmark
| | - Peter Brøgger
- Department of Biology, University of Copenhagen, BioCenter, 2200, Denmark
| | - Tea Toteva
- Department of Biology, University of Copenhagen, BioCenter, 2200, Denmark
| | - Dennis Kim Nielsen
- Department of Biology, University of Copenhagen, BioCenter, 2200, Denmark
| | - Genevieve Thon
- Department of Biology, University of Copenhagen, BioCenter, 2200, Denmark
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8
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Kilkenny ML, Simon AC, Mainwaring J, Wirthensohn D, Holzer S, Pellegrini L. The human CTF4-orthologue AND-1 interacts with DNA polymerase α/primase via its unique C-terminal HMG box. Open Biol 2017; 7:170217. [PMID: 29167311 PMCID: PMC5717350 DOI: 10.1098/rsob.170217] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 10/30/2017] [Indexed: 11/12/2022] Open
Abstract
A dynamic multi-protein assembly known as the replisome is responsible for DNA synthesis in eukaryotic cells. In yeast, the hub protein Ctf4 bridges DNA helicase and DNA polymerase and recruits factors with roles in metabolic processes coupled to DNA replication. An important question in DNA replication is the extent to which the molecular architecture of the replisome is conserved between yeast and higher eukaryotes. Here, we describe the biochemical basis for the interaction of the human CTF4-orthologue AND-1 with DNA polymerase α (Pol α)/primase, the replicative polymerase that initiates DNA synthesis. AND-1 has maintained the trimeric structure of yeast Ctf4, driven by its conserved SepB domain. However, the primary interaction of AND-1 with Pol α/primase is mediated by its C-terminal HMG box, unique to mammalian AND-1, which binds the B subunit, at the same site targeted by the SV40 T-antigen for viral replication. In addition, we report a novel DNA-binding activity in AND-1, which might promote the correct positioning of Pol α/primase on the lagging-strand template at the replication fork. Our findings provide a biochemical basis for the specific interaction between two critical components of the human replisome, and indicate that important principles of replisome architecture have changed significantly in evolution.
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Affiliation(s)
- Mairi L Kilkenny
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Aline C Simon
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Jack Mainwaring
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - David Wirthensohn
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Sandro Holzer
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Luca Pellegrini
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
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9
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Sasaki M, Kobayashi T. Ctf4 Prevents Genome Rearrangements by Suppressing DNA Double-Strand Break Formation and Its End Resection at Arrested Replication Forks. Mol Cell 2017; 66:533-545.e5. [PMID: 28525744 DOI: 10.1016/j.molcel.2017.04.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 03/20/2017] [Accepted: 04/26/2017] [Indexed: 12/19/2022]
Abstract
Arrested replication forks lead to DNA double-strand breaks (DSBs), which are a major source of genome rearrangements. Yet DSB repair in the context of broken forks remains poorly understood. Here we demonstrate that DSBs that are formed at arrested forks in the budding yeast ribosomal RNA gene (rDNA) locus are normally repaired by pathways dependent on the Mre11-Rad50-Xrs2 complex but independent of HR. HR is also dispensable for DSB repair at stalled forks at tRNA genes. In contrast, in cells lacking the core replisome component Ctf4, DSBs are formed more frequently, and these DSBs undergo end resection and HR-mediated repair that is prone to rDNA hyper-amplification; this highlights Ctf4 as a key regulator of DSB end resection at arrested forks. End resection also occurs during physiological rDNA amplification even in the presence of Ctf4. Suppression of end resection is thus important for protecting DSBs at arrested forks from chromosome rearrangements.
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MESH Headings
- DNA Breaks, Double-Stranded
- DNA Repair
- DNA Replication
- DNA, Fungal/biosynthesis
- DNA, Fungal/chemistry
- DNA, Fungal/genetics
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Endodeoxyribonucleases/genetics
- Endodeoxyribonucleases/metabolism
- Exodeoxyribonucleases/genetics
- Exodeoxyribonucleases/metabolism
- Gene Rearrangement
- Microbial Viability
- Mutation
- Nucleic Acid Conformation
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Ribosomal/genetics
- RNA, Ribosomal/metabolism
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- Replication Origin
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Saccharomyces cerevisiae Proteins/genetics
- Saccharomyces cerevisiae Proteins/metabolism
- Time Factors
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Affiliation(s)
- Mariko Sasaki
- Laboratory of Genome Regeneration, Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Takehiko Kobayashi
- Laboratory of Genome Regeneration, Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
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10
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Li Y, Li Z, Wu R, Han Z, Zhu W. And-1 is required for homologous recombination repair by regulating DNA end resection. Nucleic Acids Res 2017; 45:2531-2545. [PMID: 27940557 PMCID: PMC5389477 DOI: 10.1093/nar/gkw1241] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 11/28/2016] [Indexed: 11/29/2022] Open
Abstract
Homologous recombination (HR) is a major mechanism to repair DNA double-strand breaks (DSBs). Although tumor suppressor CtIP is critical for DSB end resection, a key initial event of HR repair, the mechanism regulating the recruitment of CtIP to DSB sites remains largely unknown. Here, we show that acidic nucleoplasmic DNA‐binding protein 1 (And‐1) forms complexes with CtIP as well as other repair proteins, and is essential for HR repair by regulating DSB end resection. Furthermore, And-1 is recruited to DNA DSB sites in a manner dependent on MDC1, BRCA1 and ATM, down-regulation of And-1 impairs end resection by reducing the recruitment of CtIP to damage sites, and considerably reduces Chk1 activation and other damage response during HR repair. These findings collectively demonstrate a hitherto unknown role of MDC1→And-1→CtIP axis that regulates CtIP-mediated DNA end resection and cellular response to DSBs.
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Affiliation(s)
- Yongming Li
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Science, 2300 Eye Street, N.W., Washington, DC 20037, USA
| | - Zongzhu Li
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Science, 2300 Eye Street, N.W., Washington, DC 20037, USA
| | - Ruiqin Wu
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Science, 2300 Eye Street, N.W., Washington, DC 20037, USA
| | - Zhiyong Han
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Science, 2300 Eye Street, N.W., Washington, DC 20037, USA
| | - Wenge Zhu
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Science, 2300 Eye Street, N.W., Washington, DC 20037, USA
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11
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Abstract
This review focuses on the biogenesis and composition of the eukaryotic DNA replication fork, with an emphasis on the enzymes that synthesize DNA and repair discontinuities on the lagging strand of the replication fork. Physical and genetic methodologies aimed at understanding these processes are discussed. The preponderance of evidence supports a model in which DNA polymerase ε (Pol ε) carries out the bulk of leading strand DNA synthesis at an undisturbed replication fork. DNA polymerases α and δ carry out the initiation of Okazaki fragment synthesis and its elongation and maturation, respectively. This review also discusses alternative proposals, including cellular processes during which alternative forks may be utilized, and new biochemical studies with purified proteins that are aimed at reconstituting leading and lagging strand DNA synthesis separately and as an integrated replication fork.
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Affiliation(s)
- Peter M J Burgers
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110;
| | - Thomas A Kunkel
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709;
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12
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Forsburg SL, Shen KF. Centromere Stability: The Replication Connection. Genes (Basel) 2017; 8:genes8010037. [PMID: 28106789 PMCID: PMC5295031 DOI: 10.3390/genes8010037] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 01/10/2017] [Accepted: 01/12/2017] [Indexed: 11/16/2022] Open
Abstract
The fission yeast centromere, which is similar to metazoan centromeres, contains highly repetitive pericentromere sequences that are assembled into heterochromatin. This is required for the recruitment of cohesin and proper chromosome segregation. Surprisingly, the pericentromere replicates early in the S phase. Loss of heterochromatin causes this domain to become very sensitive to replication fork defects, leading to gross chromosome rearrangements. This review examines the interplay between components of DNA replication, heterochromatin assembly, and cohesin dynamics that ensures maintenance of genome stability and proper chromosome segregation.
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Affiliation(s)
- Susan L Forsburg
- Program in Molecular & Computational Biology, University of Southern California, Los Angeles, CA 90089-2910, USA.
| | - Kuo-Fang Shen
- Program in Molecular & Computational Biology, University of Southern California, Los Angeles, CA 90089-2910, USA.
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13
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Ranatunga NS, Forsburg SL. Characterization of a Novel MMS-Sensitive Allele of Schizosaccharomyces pombe mcm4. G3 (BETHESDA, MD.) 2016; 6:3049-3063. [PMID: 27473316 PMCID: PMC5068930 DOI: 10.1534/g3.116.033571] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 07/20/2016] [Indexed: 12/17/2022]
Abstract
The minichromosome maintenance (MCM) complex is the conserved helicase motor of the eukaryotic replication fork. Mutations in the Mcm4 subunit are associated with replication stress and double strand breaks in multiple systems. In this work, we characterize a new temperature-sensitive allele of Schizosaccharomyces pombe mcm4+ Uniquely among known mcm4 alleles, this mutation causes sensitivity to the alkylation damaging agent methyl methanesulfonate (MMS). Even in the absence of treatment or temperature shift, mcm4-c106 cells show increased repair foci of RPA and Rad52, and require the damage checkpoint for viability, indicating genome stress. The mcm4-c106 mutant is synthetically lethal with mutations disrupting fork protection complex (FPC) proteins Swi1 and Swi3. Surprisingly, we found that the deletion of rif1+ suppressed the MMS-sensitive phenotype without affecting temperature sensitivity. Together, these data suggest that mcm4-c106 destabilizes replisome structure.
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Affiliation(s)
- Nimna S Ranatunga
- Program in Molecular and Computational Biology, University of Southern California, Los Angeles, California 90089
| | - Susan L Forsburg
- Program in Molecular and Computational Biology, University of Southern California, Los Angeles, California 90089
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14
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Villa F, Simon AC, Ortiz Bazan MA, Kilkenny ML, Wirthensohn D, Wightman M, Matak-Vinkovíc D, Pellegrini L, Labib K. Ctf4 Is a Hub in the Eukaryotic Replisome that Links Multiple CIP-Box Proteins to the CMG Helicase. Mol Cell 2016; 63:385-96. [PMID: 27397685 PMCID: PMC4980431 DOI: 10.1016/j.molcel.2016.06.009] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 05/12/2016] [Accepted: 06/06/2016] [Indexed: 11/26/2022]
Abstract
Replisome assembly at eukaryotic replication forks connects the DNA helicase to DNA polymerases and many other factors. The helicase binds the leading-strand polymerase directly, but is connected to the Pol α lagging-strand polymerase by the trimeric adaptor Ctf4. Here, we identify new Ctf4 partners in addition to Pol α and helicase, all of which contain a “Ctf4-interacting-peptide” or CIP-box. Crystallographic analysis classifies CIP-boxes into two related groups that target different sites on Ctf4. Mutations in the CIP-box motifs of the Dna2 nuclease or the rDNA-associated protein Tof2 do not perturb DNA synthesis genome-wide, but instead lead to a dramatic shortening of chromosome 12 that contains the large array of rDNA repeats. Our data reveal unexpected complexity of Ctf4 function, as a hub that connects multiple accessory factors to the replisome. Most strikingly, Ctf4-dependent recruitment of CIP-box proteins couples other processes to DNA synthesis, including rDNA copy-number regulation. Ctf4 is a hub that links factors with diverse functions to the eukaryotic replisome Multiple Ctf4 partners bind via short sequences called “CIP-boxes” The CIP-boxes of Dna2 and Tof2 bind to distinct sites on Ctf4 Interaction of Dna2 and Tof2 with Ctf4 is important for rDNA copy number maintenance
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Affiliation(s)
- Fabrizio Villa
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Aline C Simon
- Department of Biochemistry, University of Cambridge, 80, Tennis Court Road, Cambridge CB2 1GA, UK
| | - Maria Angeles Ortiz Bazan
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Mairi L Kilkenny
- Department of Biochemistry, University of Cambridge, 80, Tennis Court Road, Cambridge CB2 1GA, UK
| | - David Wirthensohn
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Mel Wightman
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Dijana Matak-Vinkovíc
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Luca Pellegrini
- Department of Biochemistry, University of Cambridge, 80, Tennis Court Road, Cambridge CB2 1GA, UK.
| | - Karim Labib
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
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Hao J, de Renty C, Li Y, Xiao H, Kemp MG, Han Z, DePamphilis ML, Zhu W. And-1 coordinates with Claspin for efficient Chk1 activation in response to replication stress. EMBO J 2015; 34:2096-110. [PMID: 26082189 DOI: 10.15252/embj.201488016] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Accepted: 05/08/2015] [Indexed: 11/09/2022] Open
Abstract
The replisome is important for DNA replication checkpoint activation, but how specific components of the replisome coordinate with ATR to activate Chk1 in human cells remains largely unknown. Here, we demonstrate that And-1, a replisome component, acts together with ATR to activate Chk1. And-1 is phosphorylated at T826 by ATR following replication stress, and this phosphorylation is required for And-1 to accumulate at the damage sites, where And-1 promotes the interaction between Claspin and Chk1, thereby stimulating efficient Chk1 activation by ATR. Significantly, And-1 binds directly to ssDNA and facilitates the association of Claspin with ssDNA. Furthermore, And-1 associates with replication forks and is required for the recovery of stalled forks. These studies establish a novel ATR-And-1 axis as an important regulator for efficient Chk1 activation and reveal a novel mechanism of how the replisome regulates the replication checkpoint and genomic stability.
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Affiliation(s)
- Jing Hao
- Department of Biochemistry and Molecular Medicine, The George Washington University Medical School, Washington, DC, USA
| | | | - Yongming Li
- Department of Biochemistry and Molecular Medicine, The George Washington University Medical School, Washington, DC, USA
| | - Haijie Xiao
- Department of Biochemistry and Molecular Medicine, The George Washington University Medical School, Washington, DC, USA
| | - Michael G Kemp
- Department of Biological Sciences, Florida Institute of Technology, Melbourne, FL, USA
| | - Zhiyong Han
- Department of Biochemistry and Molecular Medicine, The George Washington University Medical School, Washington, DC, USA
| | | | - Wenge Zhu
- Department of Biochemistry and Molecular Medicine, The George Washington University Medical School, Washington, DC, USA
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16
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Fission yeast Drp1 is an essential protein required for recovery from DNA damage and chromosome segregation. DNA Repair (Amst) 2014; 24:98-106. [DOI: 10.1016/j.dnarep.2014.09.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 08/08/2014] [Accepted: 09/16/2014] [Indexed: 11/24/2022]
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Uzunova SD, Zarkov AS, Ivanova AM, Stoynov SS, Nedelcheva-Veleva MN. The subunits of the S-phase checkpoint complex Mrc1/Tof1/Csm3: dynamics and interdependence. Cell Div 2014; 9:4. [PMID: 25379053 PMCID: PMC4221646 DOI: 10.1186/1747-1028-9-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 10/17/2014] [Indexed: 01/22/2023] Open
Abstract
Background The S-phase checkpoint aims to prevent cells from generation of extensive single-stranded DNA that predisposes to genome instability. The S. cerevisiae complex Tof1/Csm3/Mrc1 acts to restrain the replicative MCM helicase when DNA synthesis is prohibited. Keeping the replication machinery intact allows restart of the replication fork when the block is relieved. Although the subunits of the Tof1/Csm3/Mrc1 complex are well studied, the impact of every single subunit on the triple complex formation and function needs to be established. Findings This work studies the cellular localization and the chromatin binding of GFP-tagged subunits when the complex is intact and when a subunit is missing. We demonstrate that the complex is formed in cell nucleus, not the cytoplasm, as Tof1, Csm3 and Mrc1 enter the nucleus independently from one another. Via in situ chromatin binding assay we show that a Tof1-Csm3 dimer formation and chromatin binding is required to ensure the attachment of Mrc1 to chromatin. Our study indicates that the translocation into the nucleus is not the process to regulate the timing of chromatin association of Mrc1. We also studied the nuclear behavior of Mrc1 subunit in the process of adaptation to the presence hydroxyurea. Our results indicate that after prolonged HU incubation, cells bypass the S-phase checkpoint and proceed throughout the cell cycle. This process is accompanied by Mrc1 chromatin detachment and Rad53 dephosphorylation. Conclusions In S. cerevisiae the subunits of the S-phase checkpoint complex Mrc1/Tof1/Csm3 independently enter the cell nucleus, where a Tof1-Csm3 dimer is formed to ensure the chromatin binding of Mrc1 and favor DNA replication and S-phase checkpoint fork arrest. In the process of adaptation to the presence of hydroxyurea Mrc1 is detached from chromatin and Rad53 checkpoint activity is diminished in order to allow S-phase checkpoint escape and completion of the cell cycle.
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Affiliation(s)
- Sonya Dimitrova Uzunova
- Institute of Molecular Biology "Roumen Tsanev", Bulgarian Academy of Sciences, 21 "Acad. George Bonchev" Str., 1113 Sofia, Bulgaria
| | - Alexander Stefanov Zarkov
- Institute of Molecular Biology "Roumen Tsanev", Bulgarian Academy of Sciences, 21 "Acad. George Bonchev" Str., 1113 Sofia, Bulgaria
| | - Anna Marianova Ivanova
- Institute of Molecular Biology "Roumen Tsanev", Bulgarian Academy of Sciences, 21 "Acad. George Bonchev" Str., 1113 Sofia, Bulgaria
| | - Stoyno Stefanov Stoynov
- Institute of Molecular Biology "Roumen Tsanev", Bulgarian Academy of Sciences, 21 "Acad. George Bonchev" Str., 1113 Sofia, Bulgaria
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18
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Simon AC, Zhou JC, Perera RL, van Deursen F, Evrin C, Ivanova ME, Kilkenny ML, Renault L, Kjaer S, Matak-Vinković D, Labib K, Costa A, Pellegrini L. A Ctf4 trimer couples the CMG helicase to DNA polymerase α in the eukaryotic replisome. Nature 2014; 510:293-297. [PMID: 24805245 PMCID: PMC4059944 DOI: 10.1038/nature13234] [Citation(s) in RCA: 169] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 03/06/2014] [Indexed: 11/30/2022]
Abstract
Efficient duplication of the genome requires the concerted action of helicase and DNA polymerases at replication forks to avoid stalling of the replication machinery and consequent genomic instability. In eukaryotes, the physical coupling between helicase and DNA polymerases remains poorly understood. Here we define the molecular mechanism by which the yeast Ctf4 protein links the Cdc45-MCM-GINS (CMG) DNA helicase to DNA polymerase α (Pol α) within the replisome. We use X-ray crystallography and electron microscopy to show that Ctf4 self-associates in a constitutive disk-shaped trimer. Trimerization depends on a β-propeller domain in the carboxy-terminal half of the protein, which is fused to a helical extension that protrudes from one face of the trimeric disk. Critically, Pol α and the CMG helicase share a common mechanism of interaction with Ctf4. We show that the amino-terminal tails of the catalytic subunit of Pol α and the Sld5 subunit of GINS contain a conserved Ctf4-binding motif that docks onto the exposed helical extension of a Ctf4 protomer within the trimer. Accordingly, we demonstrate that one Ctf4 trimer can support binding of up to three partner proteins, including the simultaneous association with both Pol α and GINS. Our findings indicate that Ctf4 can couple two molecules of Pol α to one CMG helicase within the replisome, providing a new model for lagging-strand synthesis in eukaryotes that resembles the emerging model for the simpler replisome of Escherichia coli. The ability of Ctf4 to act as a platform for multivalent interactions illustrates a mechanism for the concurrent recruitment of factors that act together at the fork.
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Affiliation(s)
- Aline C Simon
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Jin C Zhou
- Clare Hall Laboratories, Cancer Research U.K. London Research Institute, London EN6 3LD, UK
| | - Rajika L Perera
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Frederick van Deursen
- Cancer Research U.K. Manchester Institute, University of Manchester, Manchester M20 4BX, UK
| | - Cecile Evrin
- MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Dundee DD1 5EH, UK
| | - Marina E Ivanova
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Mairi L Kilkenny
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Ludovic Renault
- Clare Hall Laboratories, Cancer Research U.K. London Research Institute, London EN6 3LD, UK
| | - Svend Kjaer
- Protein purification, Cancer Research U.K. London Research Institute, London WC2A 3LY, UK
| | | | - Karim Labib
- MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Dundee DD1 5EH, UK
| | - Alessandro Costa
- Clare Hall Laboratories, Cancer Research U.K. London Research Institute, London EN6 3LD, UK
| | - Luca Pellegrini
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
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Interaction between human Ctf4 and the Cdc45/Mcm2-7/GINS (CMG) replicative helicase. Proc Natl Acad Sci U S A 2013; 110:19760-5. [PMID: 24255107 DOI: 10.1073/pnas.1320202110] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Chromosome transmission fidelity 4 (Ctf4) is a conserved protein required for DNA replication. In this report, interactions between human Ctf4 (hCtf4) and the replicative helicase containing the cell division cycle 45 (Cdc45)/minichromosome maintenance 2-7 (Mcm2-7)/Go, Ichi, Nii, and San (GINS) (CMG) proteins [human CMG (hCMG) complex] were examined. The hCtf4-CMG complex was isolated following in vitro interaction of purified proteins (hCtf4 plus the hCMG complex), coinfection of Spodoptera frugiperda (Sf9) insect cells with viruses expressing the hCMG complex and hCtf4, and from HeLa cell chromatin after benzonase and immunoprecipitation steps. The stability of the hCtf4-CMG complex depends upon interactions between hCtf4 and multiple components of the hCMG complex. The hCtf4-CMG complex, like the hCMG complex, contains DNA helicase activity that is more salt-resistant than the helicase activity of the hCMG complex. We demonstrate that the hCtf4-CMG complex contains a homodimeric hCtf4 and a monomeric hCMG complex and suggest that the homodimeric hCtf4 acts as a platform linking polymerase α to the hCMG complex. The role of the hCMG complex as the core of the replisome is also discussed.
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20
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Roseaulin LC, Noguchi C, Noguchi E. Proteasome-dependent degradation of replisome components regulates faithful DNA replication. Cell Cycle 2013; 12:2564-9. [PMID: 23907116 PMCID: PMC3865046 DOI: 10.4161/cc.25692] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The replication machinery, or the replisome, collides with a variety of obstacles during the normal process of DNA replication. In addition to damaged template DNA, numerous chromosome regions are considered to be difficult to replicate owing to the presence of DNA secondary structures and DNA-binding proteins. Under these conditions, the replication fork stalls, generating replication stress. Stalled forks are prone to collapse, posing serious threats to genomic integrity. It is generally thought that the replication checkpoint functions to stabilize the replisome and replication fork structure upon replication stress. This is important in order to allow DNA replication to resume once the problem is solved. However, our recent studies demonstrated that some replisome components undergo proteasome-dependent degradation during DNA replication in the fission yeast Schizosaccharomyces pombe. Our investigation has revealed the involvement of the SCFPof3 (Skp1-Cullin/Cdc53-F-box) ubiquitin ligase in replisome regulation. We also demonstrated that forced accumulation of the replisome components leads to abnormal DNA replication upon replication stress. Here we review these findings and present additional data indicating the importance of replisome degradation for DNA replication. Our studies suggest that cells activate an alternative pathway to degrade replisome components in order to preserve genomic integrity.
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Affiliation(s)
- Laura C Roseaulin
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA, USA
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21
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Roseaulin LC, Noguchi C, Martinez E, Ziegler MA, Toda T, Noguchi E. Coordinated degradation of replisome components ensures genome stability upon replication stress in the absence of the replication fork protection complex. PLoS Genet 2013; 9:e1003213. [PMID: 23349636 PMCID: PMC3547854 DOI: 10.1371/journal.pgen.1003213] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 11/15/2012] [Indexed: 11/18/2022] Open
Abstract
The stabilization of the replisome complex is essential in order to achieve highly processive DNA replication and preserve genomic integrity. Conversely, it would also be advantageous for the cell to abrogate replisome functions to prevent inappropriate replication when fork progression is adversely perturbed. However, such mechanisms remain elusive. Here we report that replicative DNA polymerases and helicases, the major components of the replisome, are degraded in concert in the absence of Swi1, a subunit of the replication fork protection complex. In sharp contrast, ORC and PCNA, which are also required for DNA replication, were stably maintained. We demonstrate that this degradation of DNA polymerases and helicases is dependent on the ubiquitin-proteasome system, in which the SCF(Pof3) ubiquitin ligase is involved. Consistently, we show that Pof3 interacts with DNA polymerase ε. Remarkably, forced accumulation of replisome components leads to abnormal DNA replication and mitotic catastrophes in the absence of Swi1. Swi1 is known to prevent fork collapse at natural replication block sites throughout the genome. Therefore, our results suggest that the cell elicits a program to degrade replisomes upon replication stress in the absence of Swi1. We also suggest that this program prevents inappropriate duplication of the genome, which in turn contributes to the preservation of genomic integrity.
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Affiliation(s)
- Laura C. Roseaulin
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Chiaki Noguchi
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Esteban Martinez
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Melissa A. Ziegler
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Takashi Toda
- Laboratory of Cell Regulation, Cancer Research UK, London Research Institute, Lincoln's Inn Field Laboratories, London, United Kingdom
| | - Eishi Noguchi
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
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22
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Abstract
During S phase, not only does DNA have to be replicated, but also newly synthesized DNA molecules have to be connected with each other. This sister chromatid cohesion is essential for the biorientation of chromosomes on the mitotic or meiotic spindle, and is thus an essential prerequisite for chromosome segregation. Cohesion is mediated by cohesin complexes that are thought to embrace sister chromatids as large rings. Cohesin binds to DNA dynamically before DNA replication and is converted into a stably DNA-bound form during replication. This conversion requires acetylation of cohesin, which in vertebrates leads to recruitment of sororin. Sororin antagonizes Wapl, a protein that is able to release cohesin from DNA, presumably by opening the cohesin ring. Inhibition of Wapl by sororin therefore "locks" cohesin rings on DNA and allows them to maintain cohesion for long periods of time in mammalian oocytes, possibly for months or even years.
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23
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Li Y, Xiao H, de Renty C, Jaramillo-Lambert A, Han Z, DePamphilis ML, Brown KJ, Zhu W. The involvement of acidic nucleoplasmic DNA-binding protein (And-1) in the regulation of prereplicative complex (pre-RC) assembly in human cells. J Biol Chem 2012; 287:42469-79. [PMID: 23093411 DOI: 10.1074/jbc.m112.404277] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DNA replication in all eukaryotes starts with the process of loading the replicative helicase MCM2-7 onto chromatin during late mitosis of the cell cycle. MCM2-7 is a key component of the prereplicative complex (pre-RC), which is loaded onto chromatin by the concerted action of origin recognition complex, Cdc6, and Cdt1. Here, we demonstrate that And-1 is assembled onto chromatin in late mitosis and early G(1) phase before the assembly of pre-RC in human cells. And-1 forms complexes with MCM2-7 to facilitate the assembly of MCM2-7 onto chromatin at replication origins in late mitosis and G(1) phase. We also present data to show that depletion of And-1 significantly reduces the interaction between Cdt1 and MCM7 in G(1) phase cells. Thus, human And-1 facilitates loading of the MCM2-7 helicase onto chromatin during the assembly of pre-RC.
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Affiliation(s)
- Yongming Li
- Department of Biochemistry and Molecular Biology, The George Washington University Medical School, Washington, D. C. 20037, USA
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24
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Errico A, Costanzo V. Mechanisms of replication fork protection: a safeguard for genome stability. Crit Rev Biochem Mol Biol 2012; 47:222-35. [DOI: 10.3109/10409238.2012.655374] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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25
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Abstract
Histone acetyltransferases (HATs) play a central role in the modification of chromatin as well as in pathogenesis of a broad set of diseases including cancers. Gcn5 is the first identified transcription-related histone acetyltransferase (HAT) that has been implicated in the regulation of diverse cellular functions. However, how Gcn5 proteins are regulated remains largely unknown. Here we show that And-1 (a HMG domain-containing protein) has remarkable capability to regulate the stability of Gcn5 proteins and thereby histone H3 acetylation. We find that And-1 forms a complex with both histone H3 and Gcn5. Downregulation of And-1 results in Gcn5 degradation, leading to the reduction of H3K9 and H3K56 acetylation. And-1 overexpression stabilizes Gcn5 through protein-protein interactions in vivo. Furthermore, And-1 expression is increased in cancer cells in a manner correlating with increased Gcn5 and H3K9Ac and H3K56Ac. Thus, our data reveal not only a functional link between Gcn5 and And-1 that is essential to regulate Gcn5 protein stability and histone H3 acetylation, but also a potential role of And-1 in cancer.
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26
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Hsieh CL, Lin CL, Liu H, Chang YJ, Shih CJ, Zhong CZ, Lee SC, Tan BCM. WDHD1 modulates the post-transcriptional step of the centromeric silencing pathway. Nucleic Acids Res 2011; 39:4048-62. [PMID: 21266480 PMCID: PMC3105424 DOI: 10.1093/nar/gkq1338] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The centromere is a highly specialized chromosomal element that is essential for chromosome segregation during mitosis. Centromere integrity must therefore be properly preserved and is strictly dependent upon the establishment and maintenance of surrounding chromatin structure. Here we identify WDHD1, a WD40-domain and HMG-domain containing protein, as a key regulator of centromere function. We show that WDHD1 associates with centromeres in a cell cycle-dependent manner, coinciding with mid-to-late S phase. WDHD1 down-regulation compromises HP1α localization to pericentric heterochromatin and leads to altered expression of epigenetic markers associated with this chromatin region. As a consequence, such reduced epigenetic silencing is manifested in disrupted heterochromatic state of the centromere and a defective mitosis. Moreover, we demonstrate that a possible underlying mechanism of WDHD1's involvement lies in the proper generation of the small non-coding RNAs encoded by the centromeric satellite repeats. This role is mediated at the post-transcriptional level and likely through stabilizing Dicer association with centromeric RNA. Collectively, these findings suggest that WDHD1 may be a critical component of the RNA-dependent epigenetic control mechanism that sustains centromere integrity and genomic stability.
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Affiliation(s)
- Chia-Ling Hsieh
- Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan
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27
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Rapp JB, Noguchi C, Das MM, Wong LK, Ansbach AB, Holmes AM, Arcangioli B, Noguchi E. Checkpoint-dependent and -independent roles of Swi3 in replication fork recovery and sister chromatid cohesion in fission yeast. PLoS One 2010; 5:e13379. [PMID: 20967229 PMCID: PMC2953522 DOI: 10.1371/journal.pone.0013379] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 09/21/2010] [Indexed: 12/19/2022] Open
Abstract
Multiple genome maintenance processes are coordinated at the replication fork to preserve genomic integrity. How eukaryotic cells accomplish such a coordination is unknown. Swi1 and Swi3 form the replication fork protection complex and are involved in various processes including stabilization of replication forks, activation of the Cds1 checkpoint kinase and establishment of sister chromatid cohesion in fission yeast. However, the mechanisms by which the Swi1–Swi3 complex achieves and coordinates these tasks are not well understood. Here, we describe the identification of separation-of-function mutants of Swi3, aimed at dissecting the molecular pathways that require Swi1–Swi3. Unlike swi3 deletion mutants, the separation-of-function mutants were not sensitive to agents that stall replication forks. However, they were highly sensitive to camptothecin that induces replication fork breakage. In addition, these mutants were defective in replication fork regeneration and sister chromatid cohesion. Interestingly, unlike swi3-deleted cell, the separation-of-functions mutants were proficient in the activation of the replication checkpoint, but their fork regeneration defects were more severe than those of checkpoint mutants including cds1Δ, chk1Δ and rad3Δ. These results suggest that, while Swi3 mediates full activation of the replication checkpoint in response to stalled replication forks, Swi3 activates a checkpoint-independent pathway to facilitate recovery of collapsed replication forks and the establishment of sister chromatid cohesion. Thus, our separation-of-function alleles provide new insight into understanding the multiple roles of Swi1-Swi3 in fork protection during DNA replication, and into understanding how replication forks are maintained in response to different genotoxic agents.
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Affiliation(s)
- Jordan B. Rapp
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Chiaki Noguchi
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Mukund M. Das
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Lisa K. Wong
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Alison B. Ansbach
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Allyson M. Holmes
- Unité de Dynamique du Génome, URA 1644 du CNRS, Departement de la Structure et Dynamique des Génomes, Institut Pasteur, Paris, France
| | - Benoit Arcangioli
- Unité de Dynamique du Génome, URA 1644 du CNRS, Departement de la Structure et Dynamique des Génomes, Institut Pasteur, Paris, France
| | - Eishi Noguchi
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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28
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Hsk1- and SCF(Pof3)-dependent proteolysis of S. pombe Ams2 ensures histone homeostasis and centromere function. Dev Cell 2010; 18:385-96. [PMID: 20230746 PMCID: PMC2880248 DOI: 10.1016/j.devcel.2009.12.024] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Revised: 11/03/2009] [Accepted: 12/22/2009] [Indexed: 12/18/2022]
Abstract
Schizosaccharomyces pombe GATA factor Ams2 is responsible for cell cycle-dependent transcriptional activation of all the core histone genes peaking at G1/S phase. Intriguingly, its own protein level also fluctuates concurrently. Here, we show that Ams2 is ubiquitylated and degraded through the SCF (Skp1-Cdc53/Cullin-1-F-box) ubiquitin ligase, in which F box protein Pof3 binds this protein. Ams2 is phosphorylated at multiple sites, which is required for SCFPof3-dependent proteolysis. Hsk1/Cdc7 kinase physically associates with and phosphorylates Ams2. Even mild overexpression of Ams2 induces constitutive histone expression and chromosome instability, and its toxicity is exaggerated when Hsk1 function is compromised. This is partly attributable to abnormal incorporation of canonical H3 into the central CENP-A/Cnp1-rich centromere, thereby reversing specific chromatin structures to apparently normal nucleosomes. We propose that Hsk1 plays a vital role during post S phase in genome stability via SCFPof3-mediated degradation of Ams2, thereby maintaining centromere integrity.
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Bermudez VP, Farina A, Tappin I, Hurwitz J. Influence of the human cohesion establishment factor Ctf4/AND-1 on DNA replication. J Biol Chem 2010; 285:9493-9505. [PMID: 20089864 DOI: 10.1074/jbc.m109.093609] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ctf4/AND-1 is a highly conserved gene product required for both DNA replication and the establishment of sister chromatid cohesion. In this report, we examined the mechanism of action of human Ctf4 (hCtf4) in DNA replication both in vitro and in vivo. Our findings show that the purified hCtf4 exists as a dimer and that the hCtf4 SepB domain likely plays a primary role determining the dimeric structure. hCtf4 binds preferentially to DNA template-primer structures, interacts directly with the replicative DNA polymerases (alpha, delta, and epsilon), and markedly stimulates the polymerase activities of DNA polymerases alpha and epsilon in vitro. Depletion of hCtf4 in HeLa cells by small interfering RNA resulted in G(1)/S phase arrest. DNA fiber analysis revealed that cells depleted of hCtf4 exhibited a rate of DNA replication slower than cells treated with control small interfering RNA. These findings suggest that in human cells, hCtf4 plays an essential role in DNA replication and its ability to stimulate the replicative DNA polymerases may contribute to this effect.
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Affiliation(s)
- Vladimir P Bermudez
- Program of Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, New York 10065
| | - Andrea Farina
- Program of Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, New York 10065
| | - Inger Tappin
- Program of Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, New York 10065
| | - Jerard Hurwitz
- Program of Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, New York 10065.
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Gambus A, van Deursen F, Polychronopoulos D, Foltman M, Jones RC, Edmondson RD, Calzada A, Labib K. A key role for Ctf4 in coupling the MCM2-7 helicase to DNA polymerase alpha within the eukaryotic replisome. EMBO J 2009; 28:2992-3004. [PMID: 19661920 DOI: 10.1038/emboj.2009.226] [Citation(s) in RCA: 210] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2009] [Accepted: 07/15/2009] [Indexed: 01/14/2023] Open
Abstract
The eukaryotic replisome is a crucial determinant of genome stability, but its structure is still poorly understood. We found previously that many regulatory proteins assemble around the MCM2-7 helicase at yeast replication forks to form the replisome progression complex (RPC), which might link MCM2-7 to other replisome components. Here, we show that the RPC associates with DNA polymerase alpha that primes each Okazaki fragment during lagging strand synthesis. Our data indicate that a complex of the GINS and Ctf4 components of the RPC is crucial to couple MCM2-7 to DNA polymerase alpha. Others have found recently that the Mrc1 subunit of RPCs binds DNA polymerase epsilon, which synthesises the leading strand at DNA replication forks. We show that cells lacking both Ctf4 and Mrc1 experience chronic activation of the DNA damage checkpoint during chromosome replication and do not complete the cell cycle. These findings indicate that coupling MCM2-7 to replicative polymerases is an important feature of the regulation of chromosome replication in eukaryotes, and highlight a key role for Ctf4 in this process.
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Affiliation(s)
- Agnieszka Gambus
- Cancer Research UK, Paterson Institute for Cancer Research, University of Manchester, Manchester, UK
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31
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Tanaka H, Kubota Y, Tsujimura T, Kumano M, Masai H, Takisawa H. Replisome progression complex links DNA replication to sister chromatid cohesion in Xenopus egg extracts. Genes Cells 2009; 14:949-63. [PMID: 19622120 DOI: 10.1111/j.1365-2443.2009.01322.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
Cohesin-mediated sister chromatid cohesion is established during the S-phase, and recent studies demonstrate that a cohesin protein ring concatenates sister DNA molecules. However, little is known about how DNA replication is linked to the establishment of sister chromatid cohesion. Here, we used Xenopus egg extracts to show that AND-1 and Tim1-Tipin, homologues of Saccharomyces cerevisiae Ctf4 and Tof1-Csm3, respectively, are associated with the replisome and are required for proper establishment of the cohesion observed in the M-phase extracts. Immunodepletion of both AND-1 and Tim1-Tipin from the extracts leads to aberrant sister chromatid cohesion, which is similarly induced by the depletion of cohesin. These results demonstrate that AND-1 and Tim1-Tipin are key factors linking DNA replication and establishment of sister chromatid cohesion. On the basis of the physical interactions between AND-1 and DNA polymerases, we discuss a model to describe how replisome progression complex establishes sister chromatid cohesion.
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Affiliation(s)
- Hiroshi Tanaka
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
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32
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Yoshizawa-Sugata N, Masai H. Roles of human AND-1 in chromosome transactions in S phase. J Biol Chem 2009; 284:20718-28. [PMID: 19439411 PMCID: PMC2742837 DOI: 10.1074/jbc.m806711200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 03/02/2009] [Indexed: 11/06/2022] Open
Abstract
Coordinated execution of DNA replication, checkpoint activation, and postreplicative chromatid cohesion is intimately related to the replication fork machinery. Human AND-1/chromosome transmission fidelity 4 is localized adjacent to replication foci and is required for efficient DNA synthesis. In S phase, AND-1 is phosphorylated in response to replication arrest in a manner dependent on checkpoint kinase, ataxia telangiectasia-mutated, ataxia telangiectasia-mutated and Rad3-related protein, and Cdc7 kinase but not on Chk1. Depletion of AND-1 increases DNA damage, delays progression of S phase, leads to accumulation of late S and/or G2 phase cells, and induces cell death in cancer cells. It also elevated UV-radioresistant DNA synthesis and caused premature recovery of replication after hydroxyurea arrest, indicating that lack of AND-1 compromises checkpoint activation. This may be partly due to the decreased levels of Chk1 protein in AND-1-depleted cells. Furthermore, AND-1 interacts with cohesin proteins Smc1, Smc3, and Rad21/Scc1, consistent with proposed roles of yeast counterparts of AND-1 in sister chromatid cohesion. Depletion of AND-1 leads to significant inhibition of homologous recombination repair of an I-SceI-driven double strand break. Based on these data, we propose that AND-1 coordinates multiple cellular events in S phase and G2 phase, such as DNA replication, checkpoint activation, sister chromatid cohesion, and DNA damage repair, thus playing a pivotal role in maintenance of genome integrity.
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Affiliation(s)
- Naoko Yoshizawa-Sugata
- From the Genome Dynamics Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Hisao Masai
- From the Genome Dynamics Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
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33
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Tanaka H, Katou Y, Yagura M, Saitoh K, Itoh T, Araki H, Bando M, Shirahige K. Ctf4 coordinates the progression of helicase and DNA polymerase alpha. Genes Cells 2009; 14:807-20. [PMID: 19496828 DOI: 10.1111/j.1365-2443.2009.01310.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Ctf4 is a protein conserved in eukaryotes and a constituent of the replisome progression complex. It also plays a role in the establishment of sister chromatid cohesion. In our current study, we demonstrate that the replication checkpoint is activated in the absence of Ctf4, and that the interaction between the MCM helicase-go ichi ni san (GINS) complex and DNA polymerase alpha (Pol alpha)-primase is destabilized specifically in a ctf4Delta mutant. An in vitro interaction between GINS and DNA Pol alpha was also found to be mediated by Ctf4. The same interaction was not affected in the absence of the replication checkpoint mediators Tof1 or Mrc1. In ctf4Delta cells, DNA pol alpha became significantly unstable and was barely detectable at the replication forks in HU. In contrast, the quantities of helicase and DNA pol epsilon bound to replication forks were almost unchanged but their localizations were widely and abnormally dispersed in the mutant cells compared with wild type. These results lead us to propose that Ctf4 is a key connector between DNA helicase and Pol alpha and is required for the coordinated progression of the replisome.
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Affiliation(s)
- Hirokazu Tanaka
- Laboratory of Chromosome Structure and Function, Department of Biological Science, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama City, Kanagawa, Japan
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34
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35
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Farina A, Shin JH, Kim DH, Bermudez VP, Kelman Z, Seo YS, Hurwitz J. Studies with the human cohesin establishment factor, ChlR1. Association of ChlR1 with Ctf18-RFC and Fen1. J Biol Chem 2008; 283:20925-36. [PMID: 18499658 PMCID: PMC2475708 DOI: 10.1074/jbc.m802696200] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Revised: 05/21/2008] [Indexed: 01/17/2023] Open
Abstract
Human ChlR1 (hChlR1), a member of the DEAD/DEAH subfamily of helicases, was shown to interact with components of the cohesin complex and play a role in sister chromatid cohesion. In order to study the biochemical and biological properties of hChlR1, we purified the protein from 293 cells and demonstrated that hChlR1 possesses DNA-dependent ATPase and helicase activities. This helicase translocates on single-stranded DNA in the 5' to 3' direction in the presence of ATP and, to a lesser extent, dATP. Its unwinding activity requires a 5'-singlestranded region for helicase loading, since flush-ended duplex structures do not support unwinding. The helicase activity of hChlR1 is capable of displacing duplex regions up to 100 bp, which can be extended to 500 bp by RPA or the cohesion establishment factor, the Ctf18-RFC (replication factor C) complex. We show that hChlR1 interacts with the hCtf18-RFC complex, human proliferating cell nuclear antigen, and hFen1. The interactions between Fen1 and hChlR1 stimulate the flap endonuclease activity of Fen1. Selective depletion of either hChlR1 or Fen1 by targeted small interfering RNA treatment results in the precocious separation of sister chromatids. These findings are consistent with a role of hChlR1 in the establishment of sister chromatid cohesion and suggest that its action may contribute to lagging strand processing events important in cohesion.
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Affiliation(s)
- Andrea Farina
- Program of Molecular Biology, Memorial
Sloan Kettering Cancer Center, New York, New York 10065, the
University of Maryland Biotechnology Institute,
Rockville, Maryland 20850, and the Department of
Biological Sciences, Korea Advanced Institute of Science and Technology,
Daejeon, 305-701, Korea
| | - Jae-Ho Shin
- Program of Molecular Biology, Memorial
Sloan Kettering Cancer Center, New York, New York 10065, the
University of Maryland Biotechnology Institute,
Rockville, Maryland 20850, and the Department of
Biological Sciences, Korea Advanced Institute of Science and Technology,
Daejeon, 305-701, Korea
| | - Do-Hyung Kim
- Program of Molecular Biology, Memorial
Sloan Kettering Cancer Center, New York, New York 10065, the
University of Maryland Biotechnology Institute,
Rockville, Maryland 20850, and the Department of
Biological Sciences, Korea Advanced Institute of Science and Technology,
Daejeon, 305-701, Korea
| | - Vladimir P. Bermudez
- Program of Molecular Biology, Memorial
Sloan Kettering Cancer Center, New York, New York 10065, the
University of Maryland Biotechnology Institute,
Rockville, Maryland 20850, and the Department of
Biological Sciences, Korea Advanced Institute of Science and Technology,
Daejeon, 305-701, Korea
| | - Zvi Kelman
- Program of Molecular Biology, Memorial
Sloan Kettering Cancer Center, New York, New York 10065, the
University of Maryland Biotechnology Institute,
Rockville, Maryland 20850, and the Department of
Biological Sciences, Korea Advanced Institute of Science and Technology,
Daejeon, 305-701, Korea
| | - Yeon-Soo Seo
- Program of Molecular Biology, Memorial
Sloan Kettering Cancer Center, New York, New York 10065, the
University of Maryland Biotechnology Institute,
Rockville, Maryland 20850, and the Department of
Biological Sciences, Korea Advanced Institute of Science and Technology,
Daejeon, 305-701, Korea
| | - Jerard Hurwitz
- Program of Molecular Biology, Memorial
Sloan Kettering Cancer Center, New York, New York 10065, the
University of Maryland Biotechnology Institute,
Rockville, Maryland 20850, and the Department of
Biological Sciences, Korea Advanced Institute of Science and Technology,
Daejeon, 305-701, Korea
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36
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A DNA polymerase alpha accessory protein, Mcl1, is required for propagation of centromere structures in fission yeast. PLoS One 2008; 3:e2221. [PMID: 18493607 PMCID: PMC2376062 DOI: 10.1371/journal.pone.0002221] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Accepted: 04/02/2008] [Indexed: 11/19/2022] Open
Abstract
Specialized chromatin exists at centromeres and must be precisely transmitted during DNA replication. The mechanisms involved in the propagation of these structures remain elusive. Fission yeast centromeres are composed of two chromatin domains: the central CENP-ACnp1 kinetochore domain and flanking heterochromatin domains. Here we show that fission yeast Mcl1, a DNA polymerase α (Polα) accessory protein, is critical for maintenance of centromeric chromatin. In a screen for mutants that alleviate both central domain and outer repeat silencing, we isolated several cos mutants, of which cos1 is allelic to mcl1. The mcl1-101 mutation causes reduced CENP-ACnp1 in the central domain and an aberrant increase in histone acetylation in both domains. These phenotypes are also observed in a mutant of swi7+, which encodes a catalytic subunit of Polα. Mcl1 forms S-phase-specific nuclear foci, which colocalize with those of PCNA and Polα. These results suggest that Mcl1 and Polα are required for propagation of centromere chromatin structures during DNA replication.
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37
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Ansbach AB, Noguchi C, Klansek IW, Heidlebaugh M, Nakamura TM, Noguchi E. RFCCtf18 and the Swi1-Swi3 complex function in separate and redundant pathways required for the stabilization of replication forks to facilitate sister chromatid cohesion in Schizosaccharomyces pombe. Mol Biol Cell 2007; 19:595-607. [PMID: 18045993 DOI: 10.1091/mbc.e07-06-0618] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Sister chromatid cohesion is established during S phase near the replication fork. However, how DNA replication is coordinated with chromosomal cohesion pathway is largely unknown. Here, we report studies of fission yeast Ctf18, a subunit of the RFC(Ctf18) replication factor C complex, and Chl1, a putative DNA helicase. We show that RFC(Ctf18) is essential in the absence of the Swi1-Swi3 replication fork protection complex required for the S phase stress response. Loss of Ctf18 leads to an increased sensitivity to S phase stressing agents, a decreased level of Cds1 kinase activity, and accumulation of DNA damage during S phase. Ctf18 associates with chromatin during S phase, and it is required for the proper resumption of replication after fork arrest. We also show that chl1Delta is synthetically lethal with ctf18Delta and that a dosage increase of chl1(+) rescues sensitivities of swi1Delta to S phase stressing agents, indicating that Chl1 is involved in the S phase stress response. Finally, we demonstrate that inactivation of Ctf18, Chl1, or Swi1-Swi3 leads to defective centromere cohesion, suggesting the role of these proteins in chromosome segregation. We propose that RFC(Ctf18) and the Swi1-Swi3 complex function in separate and redundant pathways essential for replication fork stabilization to facilitate sister chromatid cohesion in fission yeast.
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Affiliation(s)
- Alison B Ansbach
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
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38
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Zhu W, Ukomadu C, Jha S, Senga T, Dhar SK, Wohlschlegel JA, Nutt LK, Kornbluth S, Dutta A. Mcm10 and And-1/CTF4 recruit DNA polymerase alpha to chromatin for initiation of DNA replication. Genes Dev 2007; 21:2288-99. [PMID: 17761813 PMCID: PMC1973143 DOI: 10.1101/gad.1585607] [Citation(s) in RCA: 176] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The MCM2-7 helicase complex is loaded on DNA replication origins during the G1 phase of the cell cycle to license the origins for replication in S phase. How the initiator primase-polymerase complex, DNA polymerase alpha (pol alpha), is brought to the origins is still unclear. We show that And-1/Ctf4 (Chromosome transmission fidelity 4) interacts with Mcm10, which associates with MCM2-7, and with the p180 subunit of DNA pol alpha. And-1 is essential for DNA synthesis and the stability of p180 in mammalian cells. In Xenopus egg extracts And-1 is loaded on the chromatin after Mcm10, concurrently with DNA pol alpha, and is required for efficient DNA synthesis. Mcm10 is required for chromatin loading of And-1 and an antibody that disrupts the Mcm10-And-1 interaction interferes with the loading of And-1 and of pol alpha, inhibiting DNA synthesis. And-1/Ctf4 is therefore a new replication initiation factor that brings together the MCM2-7 helicase and the DNA pol alpha-primase complex, analogous to the linker between helicase and primase or helicase and polymerase that is seen in the bacterial replication machinery. The discovery also adds to the connection between replication initiation and sister chromatid cohesion.
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Affiliation(s)
- Wenge Zhu
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
| | - Chinweike Ukomadu
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
| | - Sudhakar Jha
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
| | - Takeshi Senga
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
| | - Suman K. Dhar
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
| | - James A. Wohlschlegel
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
| | - Leta K. Nutt
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | - Sally Kornbluth
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | - Anindya Dutta
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
- Corresponding author.E-MAIL ; FAX (434) 924-5069
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39
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Xu H, Boone C, Brown GW. Genetic dissection of parallel sister-chromatid cohesion pathways. Genetics 2007; 176:1417-29. [PMID: 17483413 PMCID: PMC1931553 DOI: 10.1534/genetics.107.072876] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2007] [Accepted: 04/25/2007] [Indexed: 11/18/2022] Open
Abstract
Sister-chromatid cohesion, the process of pairing replicated chromosomes during mitosis and meiosis, is mediated through the essential cohesin complex and a number of nonessential cohesion genes, but the specific roles of these nonessential genes in sister-chromatid cohesion remain to be clarified. We analyzed sister-chromatid cohesion in double mutants of mrc1Delta, tof1Delta, and csm3Delta and identified additive cohesion defects that indicated the existence of at least two pathways that contribute to sister-chromatid cohesion. To understand the relationship of other nonessential cohesion genes with respect to these two pathways, pairwise combinations of deletion and temperature-sensitive alleles were tested for cohesion defects. These data defined two cohesion pathways, one containing CSM3, TOF1, CTF4, and CHL1, and the second containing MRC1, CTF18, CTF8, and DCC1. Furthermore, we found that the nonessential genes are not important for the maintenance of cohesion at G(2)/M. Thus, our data suggest that nonessential cohesion genes make critical redundant contributions to the establishment of sister-chromatid cohesion and define two cohesion pathways, thereby establishing a framework for understanding the role of nonessential genes in sister-chromatid cohesion.
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Affiliation(s)
- Hong Xu
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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40
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Mamnun YM, Katayama S, Toda T. Fission yeast Mcl1 interacts with SCF(Pof3) and is required for centromere formation. Biochem Biophys Res Commun 2006; 350:125-30. [PMID: 16997270 DOI: 10.1016/j.bbrc.2006.09.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Accepted: 09/01/2006] [Indexed: 11/20/2022]
Abstract
The fission yeast S-phase regulator Mcl1, an orthologue of budding yeast Ctf4, is an interacting protein of DNA polymerase alpha and an important factor to ensure DNA replication and sister chromatid cohesion. Deletion of this protein results in severe cohesion defects, however, the function and cellular role of this protein remains elusive. In this study we isolate Mcl1 as an interaction partner of the F-box protein Pof3, which is a component of the ubiquitin ligase complex SCF(Pof3). Comparing the phenotypes of cells lacking pof3+ or mcl1+ we find a broad overlap including the accumulation of DNA damage and activation of the DNA damage pathway. Importantly, we identity a novel, specific role for Mcl1 in the transcriptional silencing and the localisation of CENP-A at the centromeres.
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Affiliation(s)
- Yasmine M Mamnun
- Laboratory of Cell Regulation, London Research Institute, Cancer Research UK, 44 Lincoln's Inn Fields, London WC2A 3PX, UK
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41
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Abstract
There has been remarkable progress in the last 20 years in defining the molecular mechanisms that regulate initiation of DNA synthesis in eukaryotic cells. Replication origins in the DNA nucleate the ordered assembly of protein factors to form a prereplication complex (preRC) that is poised for DNA synthesis. Transition of the preRC to an active initiation complex is regulated by cyclin-dependent kinases and other signaling molecules, which promote further protein assembly and activate the mini chromosome maintenance helicase. We will review these mechanisms and describe the state of knowledge about the proteins involved. However, we will also consider an additional layer of complexity. The DNA in the cell is packaged with histone proteins into chromatin. Chromatin structure provides an additional layer of heritable information with associated epigenetic modifications. Thus, we will begin by describing chromatin structure, and how the cell generally controls access to the DNA. Access to the DNA requires active chromatin remodeling, specific histone modifications, and regulated histone deposition. Studies in transcription have revealed a variety of mechanisms that regulate DNA access, and some of these are likely to be shared with DNA replication. We will briefly describe heterochromatin as a model for an epigenetically inherited chromatin state. Next, we will describe the mechanisms of replication initiation and how these are affected by constraints of chromatin. Finally, chromatin must be reassembled with appropriate modifications following passage of the replication fork, and our third major topic will be the reassembly of chromatin and its associated epigenetic marks. Thus, in this chapter, we seek to bring together the studies of replication initiation and the studies of chromatin into a single holistic narrative.
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Affiliation(s)
- Angel P Tabancay
- Molecular and Computational Biology Section University of Southern California Los Angeles, California 90089, USA
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42
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Tsutsui Y, Morishita T, Natsume T, Yamashita K, Iwasaki H, Yamao F, Shinagawa H. Genetic and physical interactions between Schizosaccharomyces pombe Mcl1 and Rad2, Dna2 and DNA polymerase alpha: evidence for a multifunctional role of Mcl1 in DNA replication and repair. Curr Genet 2005; 48:34-43. [PMID: 15915339 DOI: 10.1007/s00294-005-0584-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Revised: 04/20/2005] [Accepted: 04/24/2005] [Indexed: 12/01/2022]
Abstract
Schizosaccharomyces pombe rad2 is involved in Okazaki fragments processing during lagging-strand DNA replication. Previous studies identified several slr mutants that are co-lethal with rad2Delta and sensitive to methyl methanesulfonate as single mutants. One of these mutants, slr3-1, is characterized here. Complementation and sequence analyses show that slr3-1 (mcl1-101) is allelic to mcl1(+), which is required for chromosome replication, cohesion and segregation. mcl1-101 is temperature-sensitive for growth and is highly sensitive to DNA damage. mcl1 cells arrest with 2C DNA content and chromosomal DNA double-strand breaks accumulate at the restrictive temperature. Mcl1p, which belongs to the Ctf4p/SepBp family, interacts both genetically and physically with DNA polymerase alpha. Mutations in rhp51 and dna2 enhance the growth defect of the mcl1-101 mutant. These results strongly suggest that Mcl1p is a functional homologue of Saccharomyces cerevisiae Ctf4p and plays a role in lagging-strand synthesis and Okazaki fragment processing, in addition to DNA repair.
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Affiliation(s)
- Yasuhiro Tsutsui
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan.
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43
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Gygax SE, Semighini CP, Goldman GH, Harris SD. SepBCTF4 is required for the formation of DNA-damage-induced UvsCRAD51 foci in Aspergillus nidulans. Genetics 2005; 169:1391-402. [PMID: 15654119 PMCID: PMC1449558 DOI: 10.1534/genetics.104.030817] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
SepB is an essential, conserved protein required for chromosomal DNA metabolism in Aspergillus nidulans. Homologs of SepB include yeast Ctf4p and human hAnd-1. Molecular and bioinformatic characterization of these proteins suggests that they act as molecular scaffolds. Furthermore, recent observations implicate the yeast family members in lagging-strand replication and the establishment of sister-chromatid cohesion. Here, we demonstrate that SepB functions in the A. nidulans DNA damage response. In particular, analysis of double mutants reveals that SepB is a member of the UvsC(RAD51) epistasis group. In accord with this prediction, we show that UvsC(RAD51) forms DNA-damage-induced nuclear foci in a manner that requires SepB function. We also provide evidence that implicates SepB in sister-chromatid cohesion, thereby suggesting that cohesion may play a role in regulating the localization and/or assembly of UvsC(RAD51) complexes.
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Affiliation(s)
- Scott E Gygax
- Department of Microbiology, University of Connecticut Health Center, Farmington, 06030-3205, USA.
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44
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Williams DR, McIntosh JR. Mcl1p is a polymerase alpha replication accessory factor important for S-phase DNA damage survival. EUKARYOTIC CELL 2005; 4:166-77. [PMID: 15643072 PMCID: PMC544150 DOI: 10.1128/ec.4.1.166-177.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Accepted: 10/26/2004] [Indexed: 01/25/2023]
Abstract
Mcl1p is an essential fission yeast chromatin-binding protein that belongs to a family of highly conserved eukaryotic proteins important for sister chromatid cohesion. The essential function is believed to result from its role as a Pol1p (polymerase alpha) accessory protein, a conclusion based primarily on analogy to Ctf4p's interaction with Pol1p. In this study, we show that Mcl1p also binds to Pol1p with high affinity for the N terminus of Pol1p during S phase and DNA damage. Characterization of an inducible allele of mcl1+, (nmt41)mcl1-MH, shows that altered expression levels of Mcl1p lead to sensitivity to DNA-damaging agents and synthetic lethality with the replication checkpoint mutations rad3Delta, rqh1Delta, and hsk1-1312. Further, we find that the overexpression of the S-phase checkpoint kinase, Cds1, or the loss of Hsk1 kinase activity can disrupt Mcl1p's interaction with chromatin and Pol1p during replication arrest with hydroxyurea. We take these data to mean that Mcl1p is a dynamic component of the polymerase alpha complex during replication and is important for the replication stress response in fission yeast.
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Affiliation(s)
- Dewight R Williams
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, USA.
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Zhou Y, Wang TSF. A coordinated temporal interplay of nucleosome reorganization factor, sister chromatin cohesion factor, and DNA polymerase alpha facilitates DNA replication. Mol Cell Biol 2004; 24:9568-79. [PMID: 15485923 PMCID: PMC522230 DOI: 10.1128/mcb.24.21.9568-9579.2004] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
DNA replication depends critically upon chromatin structure. Little is known about how the replication complex overcomes the nucleosome packages in chromatin during DNA replication. To address this question, we investigate factors that interact in vivo with the principal initiation DNA polymerase, DNA polymerase alpha (Polalpha). The catalytic subunit of budding yeast Polalpha (Pol1p) has been shown to associate in vitro with the Spt16p-Pob3p complex, a component of the nucleosome reorganization system required for both replication and transcription, and with a sister chromatid cohesion factor, Ctf4p. Here, we show that an N-terminal region of Polalpha (Pol1p) that is evolutionarily conserved among different species interacts with Spt16p-Pob3p and Ctf4p in vivo. A mutation in a glycine residue in this N-terminal region of POL1 compromises the ability of Pol1p to associate with Spt16p and alters the temporal ordered association of Ctf4p with Pol1p. The compromised association between the chromatin-reorganizing factor Spt16p and the initiating DNA polymerase Pol1p delays the Pol1p assembling onto and disassembling from the late-replicating origins and causes a slowdown of S-phase progression. Our results thus suggest that a coordinated temporal and spatial interplay between the conserved N-terminal region of the Polalpha protein and factors that are involved in reorganization of nucleosomes and promoting establishment of sister chromatin cohesion is required to facilitate S-phase progression.
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Affiliation(s)
- Yanjiao Zhou
- Department of Pathology, Edwards Building, Room R270, Stanford University Medical Center, 300 Pasteur Dr., Stanford, CA 94305-5324, USA
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Petronczki M, Chwalla B, Siomos MF, Yokobayashi S, Helmhart W, Deutschbauer AM, Davis RW, Watanabe Y, Nasmyth K. Sister-chromatid cohesion mediated by the alternative RF-CCtf18/Dcc1/Ctf8, the helicase Chl1 and the polymerase-α-associated protein Ctf4 is essential for chromatid disjunction during meiosis II. J Cell Sci 2004; 117:3547-59. [PMID: 15226378 DOI: 10.1242/jcs.01231] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Cohesion between sister chromatids mediated by a multisubunit complex called cohesin is established during DNA replication and is essential for the orderly segregation of chromatids during anaphase. In budding yeast, a specialized replication factor C called RF-CCtf18/Dcc1/Ctf8 and the DNA-polymerase-α-associated protein Ctf4 are required to maintain sister-chromatid cohesion in cells arrested for long periods in mitosis. We show here that CTF8, CTF4 and a helicase encoded by CHL1 are required for efficient sister chromatid cohesion in unperturbed mitotic cells, and provide evidence that Chl1 functions during S-phase. We also show that, in contrast to mitosis, RF-CCtf18/Dcc1/Cft8, Ctf4 and Chl1 are essential for chromosome segregation during meiosis and for the viability of meiotic products. Our finding that cells deleted for CTF8, CTF4 or CHL1 undergo massive meiosis II non-disjunction suggests that the second meiotic division is particularly sensitive to cohesion defects. Using a functional as well as a cytological assay, we demonstrate that CTF8, CHL1 and CTF4 are essential for cohesion between sister centromeres during meiosis but dispensable for cohesin's association with centromeric DNA. Our finding that mutants in fission yeast ctf18 and dcc1 have similar defects suggests that the involvement of the alternative RF-CCtf18/Dcc1/Ctf8 complex in sister chromatid cohesion might be highly conserved.
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Affiliation(s)
- Mark Petronczki
- Research Institute of Molecular Pathology, Dr. Bohrgasse 7, A-1030 Vienna, Austria
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Bermudez VP, Maniwa Y, Tappin I, Ozato K, Yokomori K, Hurwitz J. The alternative Ctf18-Dcc1-Ctf8-replication factor C complex required for sister chromatid cohesion loads proliferating cell nuclear antigen onto DNA. Proc Natl Acad Sci U S A 2003; 100:10237-42. [PMID: 12930902 PMCID: PMC193545 DOI: 10.1073/pnas.1434308100] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The linkage of sister chromatids after DNA replication ensures the faithful inheritance of chromosomes by daughter cells. In budding yeast, the establishment of sister chromatid cohesion requires Ctf8, Dcc1, and Ctf18, a homologue of the p140 subunit of the replication factor C (RFC). In this report we demonstrate that in 293T cells, Flag-tagged Ctf18 forms a seven-subunit cohesion-RFC complex comprised of Ctf18, Dcc1, Ctf8, RFCp40, RFCp38, RFCp37, and RFCp36 (Ctf18-RFC). We demonstrate that a stoichiometric heteroheptameric Ctf18-RFC complex can be assembled by coexpressing the seven proteins in baculovirus-infected insect cells. In addition, the two other stable subcomplexes were formed, which include a pentameric complex comprised of Ctf18, RFCp40, RFCp38, RFCp37, and RFCp36 and a dimeric Dcc1-Ctf8. Both the five- and seven-subunit Ctf18-RFC complexes bind to single-stranded and primed DNAs and possess weak ATPase activity that is stimulated by the addition of primed DNA and proliferating cell nuclear antigen (PCNA). These complexes catalyzed the ATP-dependent loading of PCNA onto primed and gapped DNA but not onto double-stranded nicked or single-stranded circular DNAs. Consistent with these observations, both Ctf18-RFC complexes substituted for the replicative RFC in the PCNA-dependent DNA polymerase delta-catalyzed DNA replication reaction. These results support a model in which sister chromatid cohesion is linked to DNA replication.
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Affiliation(s)
- Vladimir P Bermudez
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA
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Stanlis KKH, McIntosh JR. Single-strand DNA aptamers as probes for protein localization in cells. J Histochem Cytochem 2003; 51:797-808. [PMID: 12754291 DOI: 10.1177/002215540305100611] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The accurate localization of proteins in fixed cells is important for many studies in cell biology, but good fixation is often antagonistic to good immunolabeling, given the density of well-preserved cells and the size of most labeled antibody probes. We therefore explored the use of single-stranded oligonucleotides (aptamers), which can bind to proteins with very high affinity and specificity but which are only approximately 10 kD. To evaluate these probes for general protein localization, we sought an aptamer that binds to a widely used protein tag, the green fluorescent protein (GFP). Although this quest was not successful, we were able to solve several practical problems that will confront any such labeling effort, e.g., the rates at which oligonucleotides enter fixed cells of different kinds and the extent of nonspecific oligonucleotide binding to both mammalian and yeast cell structures. Because such localization methods would be of particular value for electron microscopy of optimally fixed material, we also explored the solubility of aptamers under conditions suitable for freeze-substitution fixation. We found that aptamers are sufficiently soluble in cold organic solvents to encourage the view that this approach may be useful for the localization of specific proteins in context of cellular fine structure.
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Affiliation(s)
- Kristi K H Stanlis
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309-0347, USA
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Current awareness on yeast. Yeast 2003; 20:455-62. [PMID: 12728936 DOI: 10.1002/yea.943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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