2
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Shastrula PK, Rice CT, Wang Z, Lieberman PM, Skordalakes E. Structural and functional analysis of an OB-fold in human Ctc1 implicated in telomere maintenance and bone marrow syndromes. Nucleic Acids Res 2019; 46:972-984. [PMID: 29228254 PMCID: PMC5778599 DOI: 10.1093/nar/gkx1213] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 11/23/2017] [Indexed: 12/18/2022] Open
Abstract
The human CST (Ctc1, Stn1 and Ten1) complex binds the telomeric overhang and regulates telomere length by promoting C-strand replication and inhibiting telomerase-dependent G-strand synthesis. Structural and biochemical studies on the human Stn1 and Ten1 complex revealed its mechanism of assembly and nucleic acid binding. However, little is known about the structural organization of the multi-domain Ctc1 protein and how each of these domains contribute to telomere length regulation. Here, we report the structure of a central domain of human Ctc1. The structure reveals a canonical OB-fold with the two identified disease mutations (R840W and V871M) contributing to the fold of the protein. In vitro assays suggest that although this domain is not contributing directly to Ctc1’s substrate binding properties, it affects full-length Ctc1 localization to telomeres and Stn1-Ten1 binding. Moreover, functional assays show that deletion of the entire OB-fold domain leads to significant increase in telomere length, frequency of internal single G-strands and fragile telomeres. Our findings demonstrate that a previously unknown OB-fold domain contributes to efficient Ctc1 telomere localization and chromosome end maintenance.
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Affiliation(s)
- Prashanth K Shastrula
- The Wistar Institute, Gene expression and regulation program, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Cory T Rice
- The Wistar Institute, Gene expression and regulation program, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Zhuo Wang
- The Wistar Institute, Gene expression and regulation program, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Paul M Lieberman
- The Wistar Institute, Gene expression and regulation program, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Emmanuel Skordalakes
- The Wistar Institute, Gene expression and regulation program, 3601 Spruce Street, Philadelphia, PA 19104, USA
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3
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Wang Y, Brady KS, Caiello BP, Ackerson SM, Stewart JA. Human CST suppresses origin licensing and promotes AND-1/Ctf4 chromatin association. Life Sci Alliance 2019; 2:2/2/e201800270. [PMID: 30979824 PMCID: PMC6464128 DOI: 10.26508/lsa.201800270] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 04/02/2019] [Accepted: 04/03/2019] [Indexed: 12/17/2022] Open
Abstract
Human CTC1-STN1-TEN1 (CST) is an RPA-like single-stranded DNA-binding protein that interacts with DNA polymerase α-primase (pol α) and functions in telomere replication. Previous studies suggest that CST also promotes replication restart after fork stalling. However, the precise role of CST in genome-wide replication remains unclear. In this study, we sought to understand whether CST alters origin licensing and activation. Replication origins are licensed by loading of the minichromosome maintenance 2-7 (MCM) complex in G1 followed by replisome assembly and origin firing in S-phase. We find that CST directly interacts with the MCM complex and disrupts binding of CDT1 to MCM, leading to decreased origin licensing. We also show that CST enhances replisome assembly by promoting AND-1/pol α chromatin association. Moreover, these interactions are not dependent on exogenous replication stress, suggesting that CST acts as a specialized replication factor during normal replication. Overall, our findings implicate CST as a novel regulator of origin licensing and replisome assembly/fork progression through interactions with MCM, AND-1, and pol α.
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Affiliation(s)
- Yilin Wang
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Kathryn S Brady
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Benjamin P Caiello
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Stephanie M Ackerson
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Jason A Stewart
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA .,Center for Colon Cancer Research, University of South Carolina, Columbia, SC, USA
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4
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Stewart JA, Wang Y, Ackerson SM, Schuck PL. Emerging roles of CST in maintaining genome stability and human disease. Front Biosci (Landmark Ed) 2018; 23:1564-1586. [PMID: 29293451 DOI: 10.2741/4661] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The human CTC1-STN1-TEN1 (CST) complex is a single-stranded DNA binding protein that shares homology with RPA and interacts with DNA polymerase alpha/primase. CST complexes are conserved from yeasts to humans and function in telomere maintenance. A common role of CST across species is in the regulation of telomere extension by telomerase and C-strand fill-in synthesis. However, recent studies also indicate that CST promotes telomere duplex replication as well the rescue of stalled DNA replication at non-telomeric sites. Furthermore, CST dysfunction and mutation is associated with several genetic diseases and cancers. In this review, we will summarize what is known about CST with a particular focus on the emerging roles of CST in DNA replication and human disease.
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Affiliation(s)
- Jason A Stewart
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA,
| | - Yilin Wang
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Stephanie M Ackerson
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Percy Logan Schuck
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
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6
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Bassett EA, Tokarew N, Allemano EA, Mazerolle C, Morin K, Mears AJ, McNeill B, Ringuette R, Campbell C, Smiley S, Pokrajac NT, Dubuc AM, Ramaswamy V, Northcott PA, Remke M, Monnier PP, Potter D, Paes K, Kirkpatrick LL, Coker KJ, Rice DS, Perez-Iratxeta C, Taylor MD, Wallace VA. Norrin/Frizzled4 signalling in the preneoplastic niche blocks medulloblastoma initiation. eLife 2016; 5. [PMID: 27823583 PMCID: PMC5100999 DOI: 10.7554/elife.16764] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 10/07/2016] [Indexed: 12/25/2022] Open
Abstract
The tumor microenvironment is a critical modulator of carcinogenesis; however, in many tumor types, the influence of the stroma during preneoplastic stages is unknown. Here we explored the relationship between pre-tumor cells and their surrounding stroma in malignant progression of the cerebellar tumor medulloblastoma (MB). We show that activation of the vascular regulatory signalling axis mediated by Norrin (an atypical Wnt)/Frizzled4 (Fzd4) inhibits MB initiation in the Ptch+/− mouse model. Loss of Norrin/Fzd4-mediated signalling in endothelial cells, either genetically or by short-term blockade, increases the frequency of pre-tumor lesions and creates a tumor-permissive microenvironment at the earliest, preneoplastic stages of MB. This pro-tumor stroma, characterized by angiogenic remodelling, is associated with an accelerated transition from preneoplasia to malignancy. These data expose a stromal component that regulates the earliest stages of tumorigenesis in the cerebellum, and a novel role for the Norrin/Fzd4 axis as an endogenous anti-tumor signal in the preneoplastic niche. DOI:http://dx.doi.org/10.7554/eLife.16764.001
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Affiliation(s)
- Erin A Bassett
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Nicholas Tokarew
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada.,Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - Ema A Allemano
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Chantal Mazerolle
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Katy Morin
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Alan J Mears
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Brian McNeill
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Randy Ringuette
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Canada
| | - Charles Campbell
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Canada
| | - Sheila Smiley
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Neno T Pokrajac
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Donald K. Johnson Eye Institute, Krembil Research Institute, University Health Network, Toronto, Canada
| | - Adrian M Dubuc
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Developmental and Stem Cell Biology Program, Arthur and Sonia Labatt Brain Tumor Research Centre, The Hospital for Sick Children, Toronto, Canada
| | - Vijay Ramaswamy
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Developmental and Stem Cell Biology Program, Arthur and Sonia Labatt Brain Tumor Research Centre, The Hospital for Sick Children, Toronto, Canada.,Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada.,Division of Haematology/Oncology, The Hospital for Sick Children, Toronto, Canada
| | - Paul A Northcott
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Developmental and Stem Cell Biology Program, Arthur and Sonia Labatt Brain Tumor Research Centre, The Hospital for Sick Children, Toronto, Canada
| | - Marc Remke
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Developmental and Stem Cell Biology Program, Arthur and Sonia Labatt Brain Tumor Research Centre, The Hospital for Sick Children, Toronto, Canada
| | - Philippe P Monnier
- Genetics and Development Division, Krembil Research Institute, University Health Network, Toronto, Canada.,Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Canada
| | - David Potter
- Department of Ophthalmology, Lexicon Pharmaceuticals Inc., The Woodlands, United States
| | - Kim Paes
- Department of Ophthalmology, Lexicon Pharmaceuticals Inc., The Woodlands, United States
| | - Laura L Kirkpatrick
- Department of Ophthalmology, Lexicon Pharmaceuticals Inc., The Woodlands, United States
| | - Kenneth J Coker
- Department of Ophthalmology, Lexicon Pharmaceuticals Inc., The Woodlands, United States
| | - Dennis S Rice
- Department of Ophthalmology, Lexicon Pharmaceuticals Inc., The Woodlands, United States
| | - Carol Perez-Iratxeta
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Canada
| | - Michael D Taylor
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Developmental and Stem Cell Biology Program, Arthur and Sonia Labatt Brain Tumor Research Centre, The Hospital for Sick Children, Toronto, Canada.,Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada
| | - Valerie A Wallace
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada.,Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada.,Donald K. Johnson Eye Institute, Krembil Research Institute, University Health Network, Toronto, Canada.,Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Canada
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7
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Lloyd NR, Dickey TH, Hom RA, Wuttke DS. Tying up the Ends: Plasticity in the Recognition of Single-Stranded DNA at Telomeres. Biochemistry 2016; 55:5326-40. [PMID: 27575340 PMCID: PMC5656232 DOI: 10.1021/acs.biochem.6b00496] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Telomeres terminate nearly exclusively in single-stranded DNA (ssDNA) overhangs comprised of the G-rich 3' end. This overhang varies widely in length from species to species, ranging from just a few bases to several hundred nucleotides. These overhangs are not merely a remnant of DNA replication but rather are the result of complex further processing. Proper management of the telomeric overhang is required both to deter the action of the DNA damage machinery and to present the ends properly to the replicative enzyme telomerase. This Current Topic addresses the biochemical and structural features used by the proteins that manage these variable telomeric overhangs. The Pot1 protein tightly binds the single-stranded overhang, preventing DNA damage sensors from binding. Pot1 also orchestrates the access of telomerase to that same substrate. The remarkable plasticity of the binding interface exhibited by the Schizosaccharomyces pombe Pot1 provides mechanistic insight into how these roles may be accomplished, and disease-associated mutations clustered around the DNA-binding interface in the hPOT1 highlight the importance of this function. The budding yeast Cdc13-Stn1-Ten1, a telomeric RPA complex closely associated with telomere function, also interacts with ssDNA in a fashion that allows degenerate sequences to be recognized. A related human complex composed of hCTC1, hSTN1, and hTEN1 has recently emerged with links to both telomere maintenance and general DNA replication and also exhibits mutations associated with telomere pathologies. Overall, these sequence-specific ssDNA binders exhibit a range of recognition properties that allow them to perform their unique biological functions.
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Affiliation(s)
- Neil R. Lloyd
- Department of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309-0596, USADepartment of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309, USA
| | | | - Robert A. Hom
- Department of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309-0596, USADepartment of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Deborah S. Wuttke
- Department of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309-0596, USADepartment of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309, USA
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