1
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Branzei D, Bene S, Gangwani L, Szakal B. The multifaceted roles of the Ctf4 replisome hub in the maintenance of genome integrity. DNA Repair (Amst) 2024; 142:103742. [PMID: 39137555 PMCID: PMC11425796 DOI: 10.1016/j.dnarep.2024.103742] [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: 04/06/2024] [Revised: 08/02/2024] [Accepted: 08/07/2024] [Indexed: 08/15/2024]
Abstract
At the core of cellular life lies a carefully orchestrated interplay of DNA replication, recombination, chromatin assembly, sister-chromatid cohesion and transcription. These fundamental processes, while seemingly discrete, are inextricably linked during genome replication. A set of replisome factors integrate various DNA transactions and contribute to the transient formation of sister chromatid junctions involving either the cohesin complex or DNA four-way junctions. The latter structures serve DNA damage bypass and may have additional roles in replication fork stabilization or in marking regions of replication fork blockage. Here, we will discuss these concepts based on the ability of one replisome component, Ctf4, to act as a hub and functionally link these processes during DNA replication to ensure genome maintenance.
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Affiliation(s)
- Dana Branzei
- The AIRC Institute of Molecular Oncology Foundation, IFOM ETS, Via Adamello 16, Milan 20139, Italy; Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche (IGM-CNR), Pavia 27100, Italy.
| | - Szabolcs Bene
- The AIRC Institute of Molecular Oncology Foundation, IFOM ETS, Via Adamello 16, Milan 20139, Italy
| | - Laxman Gangwani
- Bond Life Sciences Center and Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA
| | - Barnabas Szakal
- The AIRC Institute of Molecular Oncology Foundation, IFOM ETS, Via Adamello 16, Milan 20139, Italy
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2
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Yuan Z, Georgescu R, Yao NY, Yurieva O, O’Donnell ME, Li H. Mechanism of PCNA loading by Ctf18-RFC for leading-strand DNA synthesis. Science 2024; 385:eadk5901. [PMID: 39088616 PMCID: PMC11349045 DOI: 10.1126/science.adk5901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 02/10/2024] [Accepted: 05/31/2024] [Indexed: 08/03/2024]
Abstract
The proliferating cell nuclear antigen (PCNA) clamp encircles DNA to hold DNA polymerases (Pols) to DNA for processivity. The Ctf18-RFC PCNA loader, a replication factor C (RFC) variant, is specific to the leading-strand Pol (Polε). We reveal here the underlying mechanism of Ctf18-RFC specificity to Polε using cryo-electron microscopy and biochemical studies. We found that both Ctf18-RFC and Polε contain specific structural features that direct PCNA loading onto DNA. Unlike other clamp loaders, Ctf18-RFC has a disordered ATPase associated with a diverse cellular activities (AAA+) motor that requires Polε to bind and stabilize it for efficient PCNA loading. In addition, Ctf18-RFC can pry prebound Polε off of DNA, then load PCNA onto DNA and transfer the PCNA-DNA back to Polε. These elements in both Ctf18-RFC and Polε provide specificity in loading PCNA onto DNA for Polε.
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Affiliation(s)
- Zuanning Yuan
- Department of Structural Biology, Van Andel Institute, Grand Rapids, Michigan, USA
| | - Roxana Georgescu
- DNA Replication Laboratory, The Rockefeller University, New York, New York, USA
- Howard Hughes Medical Institute, New York, New York, USA
| | - Nina Y. Yao
- DNA Replication Laboratory, The Rockefeller University, New York, New York, USA
| | - Olga Yurieva
- DNA Replication Laboratory, The Rockefeller University, New York, New York, USA
- Howard Hughes Medical Institute, New York, New York, USA
| | - Michael E. O’Donnell
- DNA Replication Laboratory, The Rockefeller University, New York, New York, USA
- Howard Hughes Medical Institute, New York, New York, USA
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, Michigan, USA
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3
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Kang S, Yoo J, Myung K. PCNA cycling dynamics during DNA replication and repair in mammals. Trends Genet 2024; 40:526-539. [PMID: 38485608 DOI: 10.1016/j.tig.2024.02.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 02/18/2024] [Accepted: 02/20/2024] [Indexed: 06/06/2024]
Abstract
Proliferating cell nuclear antigen (PCNA) is a eukaryotic replicative DNA clamp. Furthermore, DNA-loaded PCNA functions as a molecular hub during DNA replication and repair. PCNA forms a closed homotrimeric ring that encircles the DNA, and association and dissociation of PCNA from DNA are mediated by clamp-loader complexes. PCNA must be actively released from DNA after completion of its function. If it is not released, abnormal accumulation of PCNA on chromatin will interfere with DNA metabolism. ATAD5 containing replication factor C-like complex (RLC) is a PCNA-unloading clamp-loader complex. ATAD5 deficiency causes various DNA replication and repair problems, leading to genome instability. Here, we review recent progress regarding the understanding of the action mechanisms of PCNA unloading complex in DNA replication/repair pathways.
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Affiliation(s)
- Sukhyun Kang
- Center for Genomic Integrity, Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea
| | - Juyeong Yoo
- Center for Genomic Integrity, Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea; Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Kyungjae Myung
- Center for Genomic Integrity, Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea; Department of Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea.
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4
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He Q, Wang F, O’Donnell ME, Li H. Cryo-EM reveals a nearly complete PCNA loading process and unique features of the human alternative clamp loader CTF18-RFC. Proc Natl Acad Sci U S A 2024; 121:e2319727121. [PMID: 38669181 PMCID: PMC11067034 DOI: 10.1073/pnas.2319727121] [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: 11/10/2023] [Accepted: 03/15/2024] [Indexed: 04/28/2024] Open
Abstract
The DNA sliding clamp PCNA is a multipurpose platform for DNA polymerases and many other proteins involved in DNA metabolism. The topologically closed PCNA ring needs to be cracked open and loaded onto DNA by a clamp loader, e.g., the well-studied pentameric ATPase complex RFC (RFC1-5). The CTF18-RFC complex is an alternative clamp loader found recently to bind the leading strand DNA polymerase ε and load PCNA onto leading strand DNA, but its structure and the loading mechanism have been unknown. By cryo-EM analysis of in vitro assembled human CTF18-RFC-DNA-PCNA complex, we have captured seven loading intermediates, revealing a detailed PCNA loading mechanism onto a 3'-ss/dsDNA junction by CTF18-RFC. Interestingly, the alternative loader has evolved a highly mobile CTF18 AAA+ module likely to lower the loading activity, perhaps to avoid competition with the RFC and to limit its role to leading strand clamp loading. To compensate for the lost stability due to the mobile AAA+ module, CTF18 has evolved a unique β-hairpin motif that reaches across RFC2 to interact with RFC5, thereby stabilizing the pentameric complex. Further, we found that CTF18 also contains a separation pin to locally melt DNA from the 3'-end of the primer; this ensures its ability to load PCNA to any 3'-ss/dsDNA junction, facilitated by the binding energy of the E-plug to the major groove. Our study reveals unique structural features of the human CTF18-RFC and contributes to a broader understanding of PCNA loading by the alternative clamp loaders.
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Affiliation(s)
- Qing He
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI49503
| | - Feng Wang
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI49503
| | - Michael E. O’Donnell
- DNA Replication Laboratory, The Rockefeller University, New York, NY10065
- HHMI, The Rockefeller University, New York, NY10065
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI49503
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5
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Kawasoe Y, Shimokawa S, Gillespie PJ, Blow JJ, Tsurimoto T, Takahashi TS. The Atad5 RFC-like complex is the major unloader of proliferating cell nuclear antigen in Xenopus egg extracts. J Biol Chem 2024; 300:105588. [PMID: 38141767 PMCID: PMC10827553 DOI: 10.1016/j.jbc.2023.105588] [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: 08/29/2023] [Revised: 12/04/2023] [Accepted: 12/11/2023] [Indexed: 12/25/2023] Open
Abstract
Proliferating cell nuclear antigen (PCNA) is a homo-trimeric clamp complex that serves as the molecular hub for various DNA transactions, including DNA synthesis and post-replicative mismatch repair. Its timely loading and unloading are critical for genome stability. PCNA loading is catalyzed by Replication factor C (RFC) and the Ctf18 RFC-like complex (Ctf18-RLC), and its unloading is catalyzed by Atad5/Elg1-RLC. However, RFC, Ctf18-RLC, and even some subcomplexes of their shared subunits are capable of unloading PCNA in vitro, leaving an ambiguity in the division of labor in eukaryotic clamp dynamics. By using a system that specifically detects PCNA unloading, we show here that Atad5-RLC, which accounts for only approximately 3% of RFC/RLCs, nevertheless provides the major PCNA unloading activity in Xenopus egg extracts. RFC and Ctf18-RLC each account for approximately 40% of RFC/RLCs, while immunodepletion of neither Rfc1 nor Ctf18 detectably affects the rate of PCNA unloading in our system. PCNA unloading is dependent on the ATP-binding motif of Atad5, independent of nicks on DNA and chromatin assembly, and inhibited effectively by PCNA-interacting peptides. These results support a model in which Atad5-RLC preferentially unloads DNA-bound PCNA molecules that are free from their interactors.
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Affiliation(s)
| | - Sakiko Shimokawa
- Graduate School of Systems Life Sciences, Kyushu University, Fukuoka, Japan
| | - Peter J Gillespie
- Division of Molecular, Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
| | - J Julian Blow
- Division of Molecular, Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
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6
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Williams SL, Casas‐Delucchi CS, Raguseo F, Guneri D, Li Y, Minamino M, Fletcher EE, Yeeles JTP, Keyser UF, Waller ZAE, Di Antonio M, Coster G. Replication-induced DNA secondary structures drive fork uncoupling and breakage. EMBO J 2023; 42:e114334. [PMID: 37781931 PMCID: PMC10646557 DOI: 10.15252/embj.2023114334] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 09/20/2023] [Accepted: 09/21/2023] [Indexed: 10/03/2023] Open
Abstract
Sequences that form DNA secondary structures, such as G-quadruplexes (G4s) and intercalated-Motifs (iMs), are abundant in the human genome and play various physiological roles. However, they can also interfere with replication and threaten genome stability. Multiple lines of evidence suggest G4s inhibit replication, but the underlying mechanism remains unclear. Moreover, evidence of how iMs affect the replisome is lacking. Here, we reconstitute replication of physiologically derived structure-forming sequences to find that a single G4 or iM arrest DNA replication. Direct single-molecule structure detection within solid-state nanopores reveals structures form as a consequence of replication. Combined genetic and biophysical characterisation establishes that structure stability and probability of structure formation are key determinants of replisome arrest. Mechanistically, replication arrest is caused by impaired synthesis, resulting in helicase-polymerase uncoupling. Significantly, iMs also induce breakage of nascent DNA. Finally, stalled forks are only rescued by a specialised helicase, Pif1, but not Rrm3, Sgs1, Chl1 or Hrq1. Altogether, we provide a mechanism for quadruplex structure formation and resolution during replication and highlight G4s and iMs as endogenous sources of replication stress.
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Affiliation(s)
- Sophie L Williams
- Genome Replication Lab, Division of Cancer Biology, Institute of Cancer ResearchChester Beatty LaboratoriesLondonUK
| | - Corella S Casas‐Delucchi
- Genome Replication Lab, Division of Cancer Biology, Institute of Cancer ResearchChester Beatty LaboratoriesLondonUK
| | - Federica Raguseo
- Chemistry DepartmentImperial College London, MSRHLondonUK
- Institute of Chemical Biology, MSRHLondonUK
| | | | - Yunxuan Li
- Cavendish LaboratoryUniversity of CambridgeCambridgeUK
| | | | | | | | | | | | - Marco Di Antonio
- Chemistry DepartmentImperial College London, MSRHLondonUK
- Institute of Chemical Biology, MSRHLondonUK
- Francis Crick InstituteLondonUK
| | - Gideon Coster
- Genome Replication Lab, Division of Cancer Biology, Institute of Cancer ResearchChester Beatty LaboratoriesLondonUK
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7
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Choudhry SK, Neal ML, Li S, Navare AT, Van Eeuwen T, Wozniak RW, Mast FD, Rout MP, Aitchison JD. Nuclear pore complexes mediate subtelomeric gene silencing by regulating PCNA levels on chromatin. J Cell Biol 2023; 222:e202207060. [PMID: 37358474 PMCID: PMC10292210 DOI: 10.1083/jcb.202207060] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 04/02/2023] [Accepted: 06/07/2023] [Indexed: 06/27/2023] Open
Abstract
The nuclear pore complex (NPC) physically interacts with chromatin and regulates gene expression. The Saccharomyces cerevisiae inner ring nucleoporin Nup170 has been implicated in chromatin organization and the maintenance of gene silencing in subtelomeric regions. To gain insight into how Nup170 regulates this process, we used protein-protein interactions, genetic interactions, and transcriptome correlation analyses to identify the Ctf18-RFC complex, an alternative proliferating cell nuclear antigen (PCNA) loader, as a facilitator of the gene regulatory functions of Nup170. The Ctf18-RFC complex is recruited to a subpopulation of NPCs that lack the nuclear basket proteins Mlp1 and Mlp2. In the absence of Nup170, PCNA levels on DNA are reduced, resulting in the loss of silencing of subtelomeric genes. Increasing PCNA levels on DNA by removing Elg1, which is required for PCNA unloading, rescues subtelomeric silencing defects in nup170Δ. The NPC, therefore, mediates subtelomeric gene silencing by regulating PCNA levels on DNA.
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Affiliation(s)
- Sanjeev Kumar Choudhry
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, WA, USA
| | - Maxwell L. Neal
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, WA, USA
| | - Song Li
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, WA, USA
| | - Arti T. Navare
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, WA, USA
| | - Trevor Van Eeuwen
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA
| | | | - Fred D. Mast
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, WA, USA
| | - Michael P. Rout
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA
| | - John D. Aitchison
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, WA, USA
- Departments of Pediatrics and Biochemistry, University of Washington, Seattle, WA, USA
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8
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Washif M, Ahmad T, Hosen MB, Rahman MR, Taniguchi T, Okubo H, Hirota K, Kawasumi R. CTF18-RFC contributes to cellular tolerance against chain-terminating nucleoside analogs (CTNAs) in cooperation with proofreading exonuclease activity of DNA polymerase ε. DNA Repair (Amst) 2023; 127:103503. [PMID: 37099849 DOI: 10.1016/j.dnarep.2023.103503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 04/10/2023] [Accepted: 04/18/2023] [Indexed: 04/28/2023]
Abstract
Chemotherapeutic nucleoside analogs, such as cytarabine (Ara-C), are incorporated into genomic DNA during replication. Incorporated Ara-CMP (Ara-cytidine monophosphate) serves as a chain terminator and inhibits DNA synthesis by replicative polymerase epsilon (Polε). The proofreading exonuclease activity of Polε removes the misincorporated Ara-CMP, thereby contributing to the cellular tolerance to Ara-C. Purified Polε performs proofreading, and it is generally believed that proofreading in vivo does not need additional factors. In this study, we demonstrated that the proofreading by Polε in vivo requires CTF18, a component of the leading-strand replisome. We found that loss of CTF18 in chicken DT40 cells and human TK6 cells results in hypersensitivity to Ara-C, indicating the conserved function of CTF18 in the cellular tolerance of Ara-C. Strikingly, we found that proofreading-deficient POLE1D269A/-, CTF18-/-, and POLE1D269A/-/CTF18-/- cells showed indistinguishable phenotypes, including the extent of hypersensitivity to Ara-C and decreased replication rate with Ara-C. This observed epistatic relationship between POLE1D269A/- and CTF18-/- suggests that they are interdependent in removing mis-incorporated Ara-CMP from the 3' end of primers. Mechanistically, we found that CTF18-/- cells have reduced levels of chromatin-bound Polε upon Ara-C treatment, suggesting that CTF18 contributes to the tethering of Polε on fork at the stalled end and thereby facilitating the removal of inserted Ara-C. Collectively, these data reveal the previously unappreciated role of CTF18 in Polε-exonuclease-mediated maintenance of the replication fork upon Ara-C incorporation.
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Affiliation(s)
- Mubasshir Washif
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Tasnim Ahmad
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Md Bayejid Hosen
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Md Ratul Rahman
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Tomoya Taniguchi
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Hiromori Okubo
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Kouji Hirota
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Ryotaro Kawasumi
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan.
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9
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Sharifnia T, Wawer MJ, Goodale A, Lee Y, Kazachkova M, Dempster JM, Muller S, Levy J, Freed DM, Sommer J, Kalfon J, Vazquez F, Hahn WC, Root DE, Clemons PA, Schreiber SL. Mapping the landscape of genetic dependencies in chordoma. Nat Commun 2023; 14:1933. [PMID: 37024492 PMCID: PMC10079670 DOI: 10.1038/s41467-023-37593-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 03/21/2023] [Indexed: 04/08/2023] Open
Abstract
Identifying the spectrum of genes required for cancer cell survival can reveal essential cancer circuitry and therapeutic targets, but such a map remains incomplete for many cancer types. We apply genome-scale CRISPR-Cas9 loss-of-function screens to map the landscape of selectively essential genes in chordoma, a bone cancer with few validated targets. This approach confirms a known chordoma dependency, TBXT (T; brachyury), and identifies a range of additional dependencies, including PTPN11, ADAR, PRKRA, LUC7L2, SRRM2, SLC2A1, SLC7A5, FANCM, and THAP1. CDK6, SOX9, and EGFR, genes previously implicated in chordoma biology, are also recovered. We find genomic and transcriptomic features that predict specific dependencies, including interferon-stimulated gene expression, which correlates with ADAR dependence and is elevated in chordoma. Validating the therapeutic relevance of dependencies, small-molecule inhibitors of SHP2, encoded by PTPN11, have potent preclinical efficacy against chordoma. Our results generate an emerging map of chordoma dependencies to enable biological and therapeutic hypotheses.
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Affiliation(s)
- Tanaz Sharifnia
- Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA.
| | - Mathias J Wawer
- Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
- Kojin Therapeutics, Boston, MA, 02210, USA
| | - Amy Goodale
- Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
| | - Yenarae Lee
- Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
| | - Mariya Kazachkova
- Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
- University of California San Diego, La Jolla, CA, 92093, USA
| | | | - Sandrine Muller
- Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
| | - Joan Levy
- Chordoma Foundation, Durham, NC, 27702, USA
- Melanoma Research Alliance, Washington, D.C., 20005, USA
| | | | | | - Jérémie Kalfon
- Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
| | | | - William C Hahn
- Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
- Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - David E Root
- Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
| | - Paul A Clemons
- Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA
| | - Stuart L Schreiber
- Broad Institute of Harvard and MIT, Cambridge, MA, 02142, USA.
- Harvard University, Cambridge, MA, 02138, USA.
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10
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Minamino M, Bouchoux C, Canal B, Diffley JFX, Uhlmann F. A replication fork determinant for the establishment of sister chromatid cohesion. Cell 2023; 186:837-849.e11. [PMID: 36693376 DOI: 10.1016/j.cell.2022.12.044] [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: 08/14/2022] [Revised: 11/08/2022] [Accepted: 12/22/2022] [Indexed: 01/24/2023]
Abstract
Concomitant with DNA replication, the chromosomal cohesin complex establishes cohesion between newly replicated sister chromatids. Cohesion establishment requires acetylation of conserved cohesin lysine residues by Eco1 acetyltransferase. Here, we explore how cohesin acetylation is linked to DNA replication. Biochemical reconstitution of replication-coupled cohesin acetylation reveals that transient DNA structures, which form during DNA replication, control the acetylation reaction. As polymerases complete lagging strand replication, strand displacement synthesis produces DNA flaps that are trimmed to result in nicked double-stranded DNA. Both flaps and nicks stimulate cohesin acetylation, while subsequent nick ligation to complete Okazaki fragment maturation terminates the acetylation reaction. A flapped or nicked DNA substrate constitutes a transient molecular clue that directs cohesin acetylation to a window behind the replication fork, next to where cohesin likely entraps both sister chromatids. Our results provide an explanation for how DNA replication is linked to sister chromatid cohesion establishment.
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Affiliation(s)
- Masashi Minamino
- Chromosome Segregation Laboratory, The Francis Crick Institute, London NW1 1AT, UK
| | - Céline Bouchoux
- Chromosome Segregation Laboratory, The Francis Crick Institute, London NW1 1AT, UK
| | - Berta Canal
- Chromosome Replication Laboratory, The Francis Crick Institute, London NW1 1AT, UK
| | - John F X Diffley
- Chromosome Replication Laboratory, The Francis Crick Institute, London NW1 1AT, UK
| | - Frank Uhlmann
- Chromosome Segregation Laboratory, The Francis Crick Institute, London NW1 1AT, UK.
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11
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van Schie JJ, de Lint K, Pai GM, Rooimans MA, Wolthuis RM, de Lange J. MMS22L-TONSL functions in sister chromatid cohesion in a pathway parallel to DSCC1-RFC. Life Sci Alliance 2023; 6:e202201596. [PMID: 36622344 PMCID: PMC9733570 DOI: 10.26508/lsa.202201596] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 11/30/2022] [Accepted: 11/30/2022] [Indexed: 12/14/2022] Open
Abstract
The leading strand-oriented alternative PCNA clamp loader DSCC1-RFC functions in DNA replication, repair, and sister chromatid cohesion (SCC), but how it facilitates these processes is incompletely understood. Here, we confirm that loss of human DSCC1 results in reduced fork speed, increased DNA damage, and defective SCC. Genome-wide CRISPR screens in DSCC1-KO cells reveal multiple synthetically lethal interactions, enriched for DNA replication and cell cycle regulation. We show that DSCC1-KO cells require POLE3 for survival. Co-depletion of DSCC1 and POLE3, which both interact with the catalytic polymerase ε subunit, additively impair DNA replication, suggesting that these factors contribute to leading-strand DNA replication in parallel ways. An additional hit is MMS22L, which in humans forms a heterodimer with TONSL. Synthetic lethality of DSCC1 and MMS22L-TONSL likely results from detrimental SCC loss. We show that MMS22L-TONSL, like DDX11, functions in a SCC establishment pathway parallel to DSCC1-RFC. Because both DSCC1-RFC and MMS22L facilitate ESCO2 recruitment to replication forks, we suggest that distinct ESCO2 recruitment pathways promote SCC establishment following either cohesin conversion or de novo cohesin loading.
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Affiliation(s)
- Janne Jm van Schie
- Department of Human Genetics, Section Oncogenetics, Amsterdam UMC Location Vrije Universiteit Amsterdam, Amsterdam, Netherlands
- Cancer Center Amsterdam, Cancer Biology and Immunology, Amsterdam, Netherlands
| | - Klaas de Lint
- Department of Human Genetics, Section Oncogenetics, Amsterdam UMC Location Vrije Universiteit Amsterdam, Amsterdam, Netherlands
- Cancer Center Amsterdam, Cancer Biology and Immunology, Amsterdam, Netherlands
| | - Govind M Pai
- Department of Human Genetics, Section Oncogenetics, Amsterdam UMC Location Vrije Universiteit Amsterdam, Amsterdam, Netherlands
- Cancer Center Amsterdam, Cancer Biology and Immunology, Amsterdam, Netherlands
| | - Martin A Rooimans
- Department of Human Genetics, Section Oncogenetics, Amsterdam UMC Location Vrije Universiteit Amsterdam, Amsterdam, Netherlands
- Cancer Center Amsterdam, Cancer Biology and Immunology, Amsterdam, Netherlands
| | - Rob Mf Wolthuis
- Department of Human Genetics, Section Oncogenetics, Amsterdam UMC Location Vrije Universiteit Amsterdam, Amsterdam, Netherlands
- Cancer Center Amsterdam, Cancer Biology and Immunology, Amsterdam, Netherlands
| | - Job de Lange
- Department of Human Genetics, Section Oncogenetics, Amsterdam UMC Location Vrije Universiteit Amsterdam, Amsterdam, Netherlands
- Cancer Center Amsterdam, Cancer Biology and Immunology, Amsterdam, Netherlands
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12
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Choudhary K, Kupiec M. The cohesin complex of yeasts: sister chromatid cohesion and beyond. FEMS Microbiol Rev 2023; 47:6825453. [PMID: 36370456 DOI: 10.1093/femsre/fuac045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 11/07/2022] [Accepted: 11/09/2022] [Indexed: 11/13/2022] Open
Abstract
Each time a cell divides, it needs to duplicate the genome and then separate the two copies. In eukaryotes, which usually have more than one linear chromosome, this entails tethering the two newly replicated DNA molecules, a phenomenon known as sister chromatid cohesion (SCC). Cohesion ensures proper chromosome segregation to separate poles during mitosis. SCC is achieved by the presence of the cohesin complex. Besides its canonical function, cohesin is essential for chromosome organization and DNA damage repair. Surprisingly, yeast cohesin is loaded in G1 before DNA replication starts but only acquires its binding activity during DNA replication. Work in microorganisms, such as Saccharomyces cerevisiae and Schizosaccharomyces pombe has greatly contributed to the understanding of cohesin composition and functions. In the last few years, much progress has been made in elucidating the role of cohesin in chromosome organization and compaction. Here, we discuss the different functions of cohesin to ensure faithful chromosome segregation and genome stability during the mitotic cell division in yeast. We describe what is known about its composition and how DNA replication is coupled with SCC establishment. We also discuss current models for the role of cohesin in chromatin loop extrusion and delineate unanswered questions about the activity of this important, conserved complex.
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Affiliation(s)
- Karan Choudhary
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Martin Kupiec
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
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13
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Li H, O'Donnell M, Kelch B. Unexpected new insights into DNA clamp loaders: Eukaryotic clamp loaders contain a second DNA site for recessed 5' ends that facilitates repair and signals DNA damage: Eukaryotic clamp loaders contain a second DNA site for recessed 5' ends that facilitates repair and signals DNA damage. Bioessays 2022; 44:e2200154. [PMID: 36116108 PMCID: PMC9927785 DOI: 10.1002/bies.202200154] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 09/02/2022] [Accepted: 09/06/2022] [Indexed: 12/15/2022]
Abstract
Clamp loaders are pentameric AAA+ assemblies that use ATP to open and close circular DNA sliding clamps around DNA. Clamp loaders show homology in all organisms, from bacteria to human. The eukaryotic PCNA clamp is loaded onto 3' primed DNA by the replication factor C (RFC) hetero-pentameric clamp loader. Eukaryotes also have three alternative RFC-like clamp loaders (RLCs) in which the Rfc1 subunit is substituted by another protein. One of these is the yeast Rad24-RFC (Rad17-RFC in human) that loads a 9-1-1 heterotrimer clamp onto a recessed 5' end of DNA. Recent structural studies of Rad24-RFC have discovered an unexpected 5' DNA binding site on the outside of the clamp loader and reveal how a 5' end can be utilized for loading the 9-1-1 clamp onto DNA. In light of these results, new studies reveal that RFC also contains a 5' DNA binding site, which functions in gap repair. These studies also reveal many new features of clamp loaders. As reviewed herein, these recent studies together have transformed our view of the clamp loader mechanism.
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Affiliation(s)
- Huilin Li
- Department of Structural BiologyVan Andel InstituteGrand RapidsMichiganUSA
| | - Mike O'Donnell
- DNA Replication LaboratoryThe Rockefeller UniversityNew YorkNew YorkUSA,Howard Hughes Medical InstituteThe Rockefeller UniversityNew YorkNew YorkUSA
| | - Brian Kelch
- Department of Biochemistry and Molecular BiotechnologyUniversity of Massachusetts Chan Medical SchoolWorcesterMassachusettsUSA
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14
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A DNA Replication Fork-centric View of the Budding Yeast DNA Damage Response. DNA Repair (Amst) 2022; 119:103393. [DOI: 10.1016/j.dnarep.2022.103393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 08/25/2022] [Accepted: 08/26/2022] [Indexed: 11/23/2022]
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15
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Baris Y, Taylor MRG, Aria V, Yeeles JTP. Fast and efficient DNA replication with purified human proteins. Nature 2022; 606:204-210. [PMID: 35585232 PMCID: PMC7613936 DOI: 10.1038/s41586-022-04759-1] [Citation(s) in RCA: 59] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 04/13/2022] [Indexed: 12/16/2022]
Abstract
Chromosome replication is performed by a complex and intricate ensemble of proteins termed the replisome, where the DNA polymerases Polδ and Polε, DNA polymerase α-primase (Polα) and accessory proteins including AND-1, CLASPIN and TIMELESS-TIPIN (respectively known as Ctf4, Mrc1 and Tof1-Csm3 in Saccharomyces cerevisiae) are organized around the CDC45-MCM-GINS (CMG) replicative helicase1-7. Because a functional human replisome has not been reconstituted from purified proteins, how these factors contribute to human DNA replication and whether additional proteins are required for optimal DNA synthesis are poorly understood. Here we report the biochemical reconstitution of human replisomes that perform fast and efficient DNA replication using 11 purified human replication factors made from 43 polypeptides. Polε, but not Polδ, is crucial for optimal leading-strand synthesis. Unexpectedly, Polε-mediated leading-strand replication is highly dependent on the sliding-clamp processivity factor PCNA and the alternative clamp loader complex CTF18-RFC. We show how CLASPIN and TIMELESS-TIPIN contribute to replisome progression and demonstrate that, in contrast to the budding yeast replisome8, AND-1 directly augments leading-strand replication. Moreover, although AND-1 binds to Polα9,10, the interaction is dispensable for lagging-strand replication, indicating that Polα is functionally recruited via an AND-1-independent mechanism for priming in the human replisome. Collectively, our work reveals how the human replisome achieves fast and efficient leading-strand and lagging-strand DNA replication, and provides a powerful system for future studies of the human replisome and its interactions with other DNA metabolic processes.
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16
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Multiple roles of Pol epsilon in eukaryotic chromosome replication. Biochem Soc Trans 2022; 50:309-320. [PMID: 35129614 PMCID: PMC9022971 DOI: 10.1042/bst20210082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 12/23/2021] [Accepted: 01/06/2022] [Indexed: 11/17/2022]
Abstract
Pol epsilon is a tetrameric assembly that plays distinct roles during eukaryotic chromosome replication. It catalyses leading strand DNA synthesis; yet this function is dispensable for viability. Its non-catalytic domains instead play an essential role in the assembly of the active replicative helicase and origin activation, while non-essential histone-fold subunits serve a critical function in parental histone redeposition onto newly synthesised DNA. Furthermore, Pol epsilon plays a structural role in linking the RFC–Ctf18 clamp loader to the replisome, supporting processive DNA synthesis, DNA damage response signalling as well as sister chromatid cohesion. In this minireview, we discuss recent biochemical and structural work that begins to explain various aspects of eukaryotic chromosome replication, with a focus on the multiple roles of Pol epsilon in this process.
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17
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Grabarczyk DB. The Fork Protection Complex: A Regulatory Hub at the Head of the Replisome. Subcell Biochem 2022; 99:83-107. [PMID: 36151374 DOI: 10.1007/978-3-031-00793-4_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
As well as accurately duplicating DNA, the eukaryotic replisome performs a variety of other crucial tasks to maintain genomic stability. For example, organizational elements, like cohesin, must be transferred from the front of the fork to the new strands, and when there is replication stress, forks need to be protected and checkpoint signalling activated. The Tof1-Csm3 (or Timeless-Tipin in humans) Fork Protection Complex (FPC) ensures efficient replisome progression and is required for a range of replication-associated activities. Recent studies have begun to reveal the structure of this complex, and how it functions within the replisome to perform its diverse roles. The core of the FPC acts as a DNA grip on the front of the replisome to regulate fork progression. Other flexibly linked domains and motifs mediate interactions with proteins and specific DNA structures, enabling the FPC to act as a hub at the head of the replication fork.
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Affiliation(s)
- Daniel B Grabarczyk
- Rudolf Virchow Center for Integrative and Translational Bioimaging, Institute for Structural Biology, University of Würzburg, Würzburg, Germany.
- Research Institute of Molecular Pathology, Vienna BioCenter, Vienna, Austria.
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van Schie JJM, de Lange J. The Interplay of Cohesin and the Replisome at Processive and Stressed DNA Replication Forks. Cells 2021; 10:3455. [PMID: 34943967 PMCID: PMC8700348 DOI: 10.3390/cells10123455] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/04/2021] [Accepted: 12/06/2021] [Indexed: 12/12/2022] Open
Abstract
The cohesin complex facilitates faithful chromosome segregation by pairing the sister chromatids after DNA replication until mitosis. In addition, cohesin contributes to proficient and error-free DNA replication. Replisome progression and establishment of sister chromatid cohesion are intimately intertwined processes. Here, we review how the key factors in DNA replication and cohesion establishment cooperate in unperturbed conditions and during DNA replication stress. We discuss the detailed molecular mechanisms of cohesin recruitment and the entrapment of replicated sister chromatids at the replisome, the subsequent stabilization of sister chromatid cohesion via SMC3 acetylation, as well as the role and regulation of cohesin in the response to DNA replication stress.
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Affiliation(s)
- Janne J. M. van Schie
- Cancer Center Amsterdam, Department of Human Genetics, Section Oncogenetics, Amsterdam University Medical Centers, De Boelelaan 1118, 1081 HV Amsterdam, The Netherlands
| | - Job de Lange
- Cancer Center Amsterdam, Department of Human Genetics, Section Oncogenetics, Amsterdam University Medical Centers, De Boelelaan 1118, 1081 HV Amsterdam, The Netherlands
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19
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Chang S, Zhu Y, Xi Y, Gao F, Lu J, Dong L, Ma C, Li H. High DSCC1 Level Predicts Poor Prognosis of Lung Adenocarcinoma. Int J Gen Med 2021; 14:6961-6974. [PMID: 34707388 PMCID: PMC8542575 DOI: 10.2147/ijgm.s329482] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 08/20/2021] [Indexed: 12/04/2022] Open
Abstract
Purpose To evaluate the role of DSCC1 in LUAD. Patients and Methods Based on TCGA and GTEx, the Wilcoxon rank-sum test was used to compare the expression differences of DSCC1 between the normal samples of GTEx combined TCGA and the unpaired tumor samples of TCGA, and to compare DSCC1 expression values between tumor tissues and paired normal LUAD tissues in the TCGA cohort. Kruskal–Wallis rank-sum test, Wilcoxon rank-sum test, and logistics regression were used to compare the relationship between the expression of DSCC1 and the clinicopathological parameters. The biological function of DSCC1 was annotated by GSEA and ssGSEA, while Kaplan–Meier and Cox regression analysis were used to evaluate the prognostic value of DSCC1. Furthermore, the time-dependent ROC curve was used to analyze the diagnostic efficacy of DSCC1 in LUAD. Results We downloaded the RNA-Seq data of 513 LUAD cases. The expression of DSCC1 was significantly correlated with T stage (OR = 1.04(1.02–1.07), P = 0.002), pathological stage (OR=1.03 (1.01–1.05), P = 0.008) and TP53 status (OR=1.10 (1.07–1.14), P < 0.001). The high expression of DSCC1 was significantly correlated with DSS (HR=1.56 (1.07–2.26), P = 0.021) and OS (HR=1.53 (1.14–2.05), P = 0.004). Moreover, ROC curve analysis (AUC=0.845, CI (0.820-0.870)) indicated DSCC1 as a potential diagnostic molecule for LUAD. In the group with high DSCC1 expression phenotype, down-regulation of EGFR signal, reduction of IL-6 deprivation, cell cycle, and p53 signal pathway were significantly abundant. Spearman correlation analysis showed that the expression of DSCC1 was positively correlated with the infiltration of Th2 cells, T Helper cells. Conclusion Our results suggest that DSCC1 may be an important biomarker for the treatment of LUAD.
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Affiliation(s)
- Sisi Chang
- Department of Oncology, Henan Provincial Hospital of Traditional Chinese Medicine (The Second Affiliated Hospital of Henan University of Traditional Chinese Medicine), Zhengzhou, Henan Province, People's Republic of China
| | - Yahui Zhu
- Department of Oncology, Henan University of Traditional Chinese Medicine, Zhengzhou, Henan Province, People's Republic of China
| | - Yutan Xi
- Department of Oncology, Henan University of Traditional Chinese Medicine, Zhengzhou, Henan Province, People's Republic of China
| | - Fuyan Gao
- Department of Oncology, Henan University of Traditional Chinese Medicine, Zhengzhou, Henan Province, People's Republic of China
| | - Juanjuan Lu
- Department of Oncology, Henan University of Traditional Chinese Medicine, Zhengzhou, Henan Province, People's Republic of China
| | - Liang Dong
- Department of Oncology, Henan Provincial Hospital of Traditional Chinese Medicine (The Second Affiliated Hospital of Henan University of Traditional Chinese Medicine), Zhengzhou, Henan Province, People's Republic of China
| | - Chunzheng Ma
- Department of Oncology, Henan Provincial Hospital of Traditional Chinese Medicine (The Second Affiliated Hospital of Henan University of Traditional Chinese Medicine), Zhengzhou, Henan Province, People's Republic of China
| | - Honglin Li
- Department of Oncology, Henan Provincial Hospital of Traditional Chinese Medicine (The Second Affiliated Hospital of Henan University of Traditional Chinese Medicine), Zhengzhou, Henan Province, People's Republic of China
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20
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Henrikus SS, Costa A. Towards a Structural Mechanism for Sister Chromatid Cohesion Establishment at the Eukaryotic Replication Fork. BIOLOGY 2021; 10:466. [PMID: 34073213 PMCID: PMC8229022 DOI: 10.3390/biology10060466] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 05/18/2021] [Accepted: 05/19/2021] [Indexed: 12/23/2022]
Abstract
Cohesion between replicated chromosomes is essential for chromatin dynamics and equal segregation of duplicated genetic material. In the G1 phase, the ring-shaped cohesin complex is loaded onto duplex DNA, enriching at replication start sites, or "origins". During the same phase of the cell cycle, and also at the origin sites, two MCM helicases are loaded as symmetric double hexamers around duplex DNA. During the S phase, and through the action of replication factors, cohesin switches from encircling one parental duplex DNA to topologically enclosing the two duplicated DNA filaments, which are known as sister chromatids. Despite its vital importance, the structural mechanism leading to sister chromatid cohesion establishment at the replication fork is mostly elusive. Here we review the current understanding of the molecular interactions between the replication machinery and cohesin, which support sister chromatid cohesion establishment and cohesin function. In particular, we discuss how cryo-EM is shedding light on the mechanisms of DNA replication and cohesin loading processes. We further expound how frontier cryo-EM approaches, combined with biochemistry and single-molecule fluorescence assays, can lead to understanding the molecular basis of sister chromatid cohesion establishment at the replication fork.
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Affiliation(s)
| | - Alessandro Costa
- Macromolecular Machines Laboratory, The Francis Crick Institute, London NW1 1AT, UK;
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21
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A novel role for Dun1 in the regulation of origin firing upon hyper-acetylation of H3K56. PLoS Genet 2021; 17:e1009391. [PMID: 33600490 PMCID: PMC7924802 DOI: 10.1371/journal.pgen.1009391] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 03/02/2021] [Accepted: 02/01/2021] [Indexed: 01/27/2023] Open
Abstract
During DNA replication newly synthesized histones are incorporated into the chromatin of the replicating sister chromatids. In the yeast Saccharomyces cerevisiae new histone H3 molecules are acetylated at lysine 56. This modification is carefully regulated during the cell cycle, and any disruption of this process is a source of genomic instability. Here we show that the protein kinase Dun1 is necessary in order to maintain viability in the absence of the histone deacetylases Hst3 and Hst4, which remove the acetyl moiety from histone H3. This lethality is not due to the well-characterized role of Dun1 in upregulating dNTPs, but rather because Dun1 is needed in order to counteract the checkpoint kinase Rad53 (human CHK2) that represses the activity of late firing origins. Deletion of CTF18, encoding the large subunit of an alternative RFC-like complex (RLC), but not of components of the Elg1 or Rad24 RLCs, is enough to overcome the dependency of cells with hyper-acetylated histones on Dun1. We show that the detrimental function of Ctf18 depends on its interaction with the leading strand polymerase, Polε. Our results thus show that the main problem of cells with hyper-acetylated histones is the regulation of their temporal and replication programs, and uncover novel functions for the Dun1 protein kinase and the Ctf18 clamp loader. Within the cell’s nucleus the DNA is wrapped around proteins called histones. Upon DNA replication, newly synthesized H3 histones are acetylated at lysine 56. This acetylation is significant for the cell because when it is not removed in a timely manner it leads to genomic instability. We have investigated the source of this instability and discovered that the kinase Dun1, usually implicated in the regulation of dNTPs, the building blocks of DNA, has a novel, dNTP-independent, essential role when histones are hyper-acetylated. The essential role of Dun1 is in the regulation of the temporal program of DNA replication. Thus, our results uncover what the main defect is in cells unable to regulate the acetylation of histones, while revealing new functions for well-characterized proteins with roles in genome stability maintenance.
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22
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Lee KY, Park SH. Eukaryotic clamp loaders and unloaders in the maintenance of genome stability. Exp Mol Med 2020; 52:1948-1958. [PMID: 33339954 PMCID: PMC8080817 DOI: 10.1038/s12276-020-00533-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 10/08/2020] [Accepted: 10/12/2020] [Indexed: 12/22/2022] Open
Abstract
Eukaryotic sliding clamp proliferating cell nuclear antigen (PCNA) plays a critical role as a processivity factor for DNA polymerases and as a binding and acting platform for many proteins. The ring-shaped PCNA homotrimer and the DNA damage checkpoint clamp 9-1-1 are loaded onto DNA by clamp loaders. PCNA can be loaded by the pentameric replication factor C (RFC) complex and the CTF18-RFC-like complex (RLC) in vitro. In cells, each complex loads PCNA for different purposes; RFC-loaded PCNA is essential for DNA replication, while CTF18-RLC-loaded PCNA participates in cohesion establishment and checkpoint activation. After completing its tasks, PCNA is unloaded by ATAD5 (Elg1 in yeast)-RLC. The 9-1-1 clamp is loaded at DNA damage sites by RAD17 (Rad24 in yeast)-RLC. All five RFC complex components, but none of the three large subunits of RLC, CTF18, ATAD5, or RAD17, are essential for cell survival; however, deficiency of the three RLC proteins leads to genomic instability. In this review, we describe recent findings that contribute to the understanding of the basic roles of the RFC complex and RLCs and how genomic instability due to deficiency of the three RLCs is linked to the molecular and cellular activity of RLC, particularly focusing on ATAD5 (Elg1). The attachment and removal of clamp proteins that encircle DNA as it is copied and assist its replication and maintenance is mediated by DNA clamp loader and unloader proteins; defects in loading and unloading can increase the rate of damaging mutations. Kyoo-young Lee and Su Hyung Park at the Institute for Basic Science in Ulsan, South Korea, review current understanding of the activity of clamp loading and unloading proteins. They examine research on the proteins in eukaryotic cells, those containing a cell nucleus, making their discussion relevant to understanding the stability of the human genome. They focus particular attention on a protein called ATAD5, which is involved in unloading the clamp proteins. Deficiencies in ATAD5 function have been implicated in genetic instability that might lead to several different types of cancer.
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Affiliation(s)
- Kyoo-Young Lee
- Center for Genomic Integrity, Institute for Basic Science, Ulsan, Korea.
| | - Su Hyung Park
- Center for Genomic Integrity, Institute for Basic Science, Ulsan, Korea
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23
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Stokes K, Winczura A, Song B, Piccoli GD, Grabarczyk DB. Ctf18-RFC and DNA Pol ϵ form a stable leading strand polymerase/clamp loader complex required for normal and perturbed DNA replication. Nucleic Acids Res 2020; 48:8128-8145. [PMID: 32585006 PMCID: PMC7641331 DOI: 10.1093/nar/gkaa541] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 06/05/2020] [Accepted: 06/16/2020] [Indexed: 12/28/2022] Open
Abstract
The eukaryotic replisome must faithfully replicate DNA and cope with replication fork blocks and stalling, while simultaneously promoting sister chromatid cohesion. Ctf18-RFC is an alternative PCNA loader that links all these processes together by an unknown mechanism. Here, we use integrative structural biology combined with yeast genetics and biochemistry to highlight the specific functions that Ctf18-RFC plays within the leading strand machinery via an interaction with the catalytic domain of DNA Pol ϵ. We show that a large and unusually flexible interface enables this interaction to occur constitutively throughout the cell cycle and regardless of whether forks are replicating or stalled. We reveal that, by being anchored to the leading strand polymerase, Ctf18-RFC can rapidly signal fork stalling to activate the S phase checkpoint. Moreover, we demonstrate that, independently of checkpoint signaling or chromosome cohesion, Ctf18-RFC functions in parallel to Chl1 and Mrc1 to protect replication forks and cell viability.
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Affiliation(s)
- Katy Stokes
- University of Warwick, Warwick Medical School, Coventry, UK
| | | | - Boyuan Song
- Rudolf Virchow Center for Integrative and Translational Bioimaging, Institute for Structural Biology, University of Würzburg, Josef-Schneider-Str. 2, Würzburg 97080, Germany.,Department of Biochemistry, Biocenter, University of Würzburg, Am Hubland, Würzburg 97074, Germany
| | | | - Daniel B Grabarczyk
- Rudolf Virchow Center for Integrative and Translational Bioimaging, Institute for Structural Biology, University of Würzburg, Josef-Schneider-Str. 2, Würzburg 97080, Germany
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24
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Jin G, Wang W, Cheng P, Tian Y, Zhang L, Niu H. DNA replication and sister chromatid cohesion 1 promotes breast carcinoma progression by modulating the Wnt/β-catenin signaling and p53 protein. J Biosci 2020. [DOI: 10.1007/s12038-020-00100-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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25
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Yuan Z, Li H. Molecular mechanisms of eukaryotic origin initiation, replication fork progression, and chromatin maintenance. Biochem J 2020; 477:3499-3525. [PMID: 32970141 PMCID: PMC7574821 DOI: 10.1042/bcj20200065] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 08/29/2020] [Accepted: 09/04/2020] [Indexed: 12/13/2022]
Abstract
Eukaryotic DNA replication is a highly dynamic and tightly regulated process. Replication involves several dozens of replication proteins, including the initiators ORC and Cdc6, replicative CMG helicase, DNA polymerase α-primase, leading-strand DNA polymerase ε, and lagging-strand DNA polymerase δ. These proteins work together in a spatially and temporally controlled manner to synthesize new DNA from the parental DNA templates. During DNA replication, epigenetic information imprinted on DNA and histone proteins is also copied to the daughter DNA to maintain the chromatin status. DNA methyltransferase 1 is primarily responsible for copying the parental DNA methylation pattern into the nascent DNA. Epigenetic information encoded in histones is transferred via a more complex and less well-understood process termed replication-couple nucleosome assembly. Here, we summarize the most recent structural and biochemical insights into DNA replication initiation, replication fork elongation, chromatin assembly and maintenance, and related regulatory mechanisms.
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Affiliation(s)
- Zuanning Yuan
- Structural Biology Program, Van Andel Institute, Grand Rapids, Michigan, U.S.A
| | - Huilin Li
- Structural Biology Program, Van Andel Institute, Grand Rapids, Michigan, U.S.A
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26
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Grabarczyk DB. Crystal structure and interactions of the Tof1-Csm3 (Timeless-Tipin) fork protection complex. Nucleic Acids Res 2020; 48:6996-7004. [PMID: 32469068 PMCID: PMC7337906 DOI: 10.1093/nar/gkaa456] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 05/14/2020] [Accepted: 05/20/2020] [Indexed: 11/13/2022] Open
Abstract
The Tof1-Csm3 fork protection complex has a central role in the replisome-it promotes the progression of DNA replication forks and protects them when they stall, while also enabling cohesion establishment and checkpoint responses. Here, I present the crystal structure of the Tof1-Csm3 complex from Chaetomium thermophilum at 3.1 Å resolution. The structure reveals that both proteins together form an extended alpha helical repeat structure, which suggests a mechanical or scaffolding role for the complex. Expanding on this idea, I characterize a DNA interacting region and a cancer-associated Mrc1 binding site. This study provides the molecular basis for understanding the functions of the Tof1-Csm3 complex, its human orthologue the Timeless-Tipin complex and additionally the Drosophila circadian rhythm protein Timeless.
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Affiliation(s)
- Daniel B Grabarczyk
- Rudolf Virchow Center for Experimental Biomedicine, Institute for Structural Biology, University of Würzburg, Josef-Schneider-Str. 2, Würzburg, Germany
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27
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Srinivasan M, Fumasoni M, Petela NJ, Murray A, Nasmyth KA. Cohesion is established during DNA replication utilising chromosome associated cohesin rings as well as those loaded de novo onto nascent DNAs. eLife 2020; 9:e56611. [PMID: 32515737 PMCID: PMC7282809 DOI: 10.7554/elife.56611] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 05/26/2020] [Indexed: 12/23/2022] Open
Abstract
Sister chromatid cohesion essential for mitotic chromosome segregation is thought to involve the co-entrapment of sister DNAs within cohesin rings. Although cohesin can load onto chromosomes throughout the cell cycle, it only builds cohesion during S phase. A key question is whether cohesion is generated by conversion of cohesin complexes associated with un-replicated DNAs ahead of replication forks into cohesive structures behind them, or from nucleoplasmic cohesin that is loaded de novo onto nascent DNAs associated with forks, a process that would be dependent on cohesin's Scc2 subunit. We show here that in S. cerevisiae, both mechanisms exist and that each requires a different set of replisome-associated proteins. Cohesion produced by cohesin conversion requires Tof1/Csm3, Ctf4 and Chl1 but not Scc2 while that created by Scc2-dependent de novo loading at replication forks requires the Ctf18-RFC complex. The association of specific replisome proteins with different types of cohesion establishment opens the way to a mechanistic understanding of an aspect of DNA replication unique to eukaryotic cells.
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Affiliation(s)
| | - Marco Fumasoni
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
| | - Naomi J Petela
- Department of Biochemistry, University of OxfordOxfordUnited Kingdom
| | - Andrew Murray
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
| | - Kim A Nasmyth
- Department of Biochemistry, University of OxfordOxfordUnited Kingdom
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Liu HW, Bouchoux C, Panarotto M, Kakui Y, Patel H, Uhlmann F. Division of Labor between PCNA Loaders in DNA Replication and Sister Chromatid Cohesion Establishment. Mol Cell 2020; 78:725-738.e4. [PMID: 32277910 PMCID: PMC7242910 DOI: 10.1016/j.molcel.2020.03.017] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 12/17/2019] [Accepted: 03/10/2020] [Indexed: 01/26/2023]
Abstract
Concomitant with DNA replication, the chromosomal cohesin complex establishes cohesion between newly replicated sister chromatids. Several replication-fork-associated "cohesion establishment factors," including the multifunctional Ctf18-RFC complex, aid this process in as yet unknown ways. Here, we show that Ctf18-RFC's role in sister chromatid cohesion correlates with PCNA loading but is separable from its role in the replication checkpoint. Ctf18-RFC loads PCNA with a slight preference for the leading strand, which is dispensable for DNA replication. Conversely, the canonical Rfc1-RFC complex preferentially loads PCNA onto the lagging strand, which is crucial for DNA replication but dispensable for sister chromatid cohesion. The downstream effector of Ctf18-RFC is cohesin acetylation, which we place toward a late step during replication maturation. Our results suggest that Ctf18-RFC enriches and balances PCNA levels at the replication fork, beyond the needs of DNA replication, to promote establishment of sister chromatid cohesion and possibly other post-replicative processes.
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Affiliation(s)
- Hon Wing Liu
- Chromosome Segregation Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Céline Bouchoux
- Chromosome Segregation Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Mélanie Panarotto
- Chromosome Segregation Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Yasutaka Kakui
- Chromosome Segregation Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Harshil Patel
- Bioinformatics and Biostatistics Science Technology Platform, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Frank Uhlmann
- Chromosome Segregation Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
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29
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Kim JT, Cho HJ, Park SY, Oh BM, Hwang YS, Baek KE, Lee YH, Kim HC, Lee HG. DNA Replication and Sister Chromatid Cohesion 1 (DSCC1) of the Replication Factor Complex CTF18-RFC is Critical for Colon Cancer Cell Growth. J Cancer 2019; 10:6142-6153. [PMID: 31762824 PMCID: PMC6856584 DOI: 10.7150/jca.32339] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 08/26/2019] [Indexed: 01/01/2023] Open
Abstract
DNA replication and sister chromatid cohesion 1 (DSCC1) combines with chromosome transmission-fidelity protein 18 (CTF18) to form a CTF18-DSCC1-CTF8 (CTF18-1-8) module, which in combination with CTF18-replication factor C (RFC) acts as a proliferating cell nuclear antigen (PCNA) loader during DNA replication-associated processes. It was found that DSCC1 was overexpressed in tumor tissues from patients with colon cancer and that the survival probability of patients with colon cancer was lower when the expression of cytosolic DSCC1 was higher in tumor regions (P=0.047). By using DSCC1- or CTF18-knockdown cell lines (HCT116-shDSCC1 or HCT116-shCTF18, respectively), it was confirmed that DSCC1-knockdown inhibits cell proliferation and invasion, but that CTF18-knockdown does not. Tumors in mice xenografted with shDSCC1 cells were significantly smaller compared with those in mice in the mock group or those xenografted with shCTF18 cells. The shDSCC1 cells were highly sensitive to γ-irradiation and other DNA replication inhibitory treatments, resulting in low cell viability. The present results suggested that DSCC1 is the most important component in the CTF18-1-8 module for CTF18-RFC and is highly relevant to the growth and metastasis of colon cancer cells, and, therefore, it may be a potential therapeutic target for colon cancer treatment.
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Affiliation(s)
- Jong-Tae Kim
- Immunotherapy Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Republic of Korea
| | - Hee Jun Cho
- Immunotherapy Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Republic of Korea
| | - Sang Yoon Park
- Immunotherapy Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Republic of Korea
| | - Byung Moo Oh
- Immunotherapy Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Republic of Korea.,Department of Biomolecular Science, University of Science and Technology (UST), Daejeon, Republic of Korea
| | - Yo Sep Hwang
- Immunotherapy Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Republic of Korea.,Department of Biomolecular Science, University of Science and Technology (UST), Daejeon, Republic of Korea
| | - Kyoung Eun Baek
- Immunotherapy Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Republic of Korea
| | - Young-Ha Lee
- Department of Infection Biology, Chungnam National University School of Medicine, Daejeon, Republic of Korea
| | - Hee Cheol Kim
- Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Hee Gu Lee
- Immunotherapy Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Republic of Korea.,Department of Biomolecular Science, University of Science and Technology (UST), Daejeon, Republic of Korea
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30
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Winczura A, Appanah R, Tatham MH, Hay RT, De Piccoli G. The S phase checkpoint promotes the Smc5/6 complex dependent SUMOylation of Pol2, the catalytic subunit of DNA polymerase ε. PLoS Genet 2019; 15:e1008427. [PMID: 31765407 PMCID: PMC6876773 DOI: 10.1371/journal.pgen.1008427] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 09/16/2019] [Indexed: 12/31/2022] Open
Abstract
Replication fork stalling and accumulation of single-stranded DNA trigger the S phase checkpoint, a signalling cascade that, in budding yeast, leads to the activation of the Rad53 kinase. Rad53 is essential in maintaining cell viability, but its targets of regulation are still partially unknown. Here we show that Rad53 drives the hyper-SUMOylation of Pol2, the catalytic subunit of DNA polymerase ε, principally following replication forks stalling induced by nucleotide depletion. Pol2 is the main target of SUMOylation within the replisome and its modification requires the SUMO-ligase Mms21, a subunit of the Smc5/6 complex. Moreover, the Smc5/6 complex co-purifies with Pol ε, independently of other replisome components. Finally, we map Pol2 SUMOylation to a single site within the N-terminal catalytic domain and identify a SUMO-interacting motif at the C-terminus of Pol2. These data suggest that the S phase checkpoint regulate Pol ε during replication stress through Pol2 SUMOylation and SUMO-binding ability.
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Affiliation(s)
- Alicja Winczura
- Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Rowin Appanah
- Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Michael H. Tatham
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, United Kingdom
| | - Ronald T. Hay
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, United Kingdom
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31
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Xie XW, Wang XY, Liao WJ, Fei R, Cong X, Chen Q, Wei L, Chen HS, Wang Y. Effect of Upregulated DNA Replication and Sister Chromatid Cohesion 1 Expression on Proliferation and Prognosis in Hepatocellular Carcinoma. Chin Med J (Engl) 2018; 131:2827-2835. [PMID: 30511685 PMCID: PMC6278189 DOI: 10.4103/0366-6999.246076] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Background: DNA replication and sister chromatid cohesion 1 (DSCC1) (also called DCC1) is a component of an alternative replication factor C complex that loads proliferating cell nuclear antigen onto DNA during S phase of the cell cycle. It is located at 8q24 and frequently amplified in hepatocellular carcinoma (HCC). However, the role of DSCC1 in the carcinogenesis and progress of HCC has not been fully investigated. Here, we aimed to assert the importance of DSCC1 in the HCC. Methods: In this study, copy number variation data and RNA sequencing data were used to calculate the DNA copy number and mRNA expression of DSCC1 in HCC. Quantitative polymerase chain reaction, Western blotting, and immunohistochemistry analysis were used to determine the mRNA and protein level of DSCC1 in HCC. The Kaplan–Meier analysis and univariate and multivariate Cox regression analysis were used to assess the association of DSCC1 with the overall survival (OS) of HCC patients. Moreover, lentiviral shRNA was used to knockdown DSCC1, and then, colony-forming assay, cell cycle assay, and cell proliferation assay were performed to evaluate the impact of DSCC1 silencing on HCC cell lines. Results: We found that DSCC1 was amplified and highly expressed in HCC tumor tissues than in nontumor tissues. We then found that the overexpression of both mRNA and protein of DSCC1 was linked to the bad prognosis of HCC patients. Astonishingly, the protein level of DSCC1 was an independent prognostic factor for OS (hazard ratio, 1.79; 95% confidence interval, 1.17–2.74; P = 0.007). Furthermore, the clonogenic capacity of DSCC1-amplified HCC cell lines (MHCC-97H, MHCC-97L, and Hep3B) was significantly inhibited by transduction of a lentiviral shRNA that targets DSCC1. We also showed that knockdown of DSCC1 induced G0–G1 cell cycle arrest (increased from 60% to more than 80%) and greatly inhibited the proliferation of HCC cell lines. Conclusion: These results suggest that DSCC1 is a putative HCC driver gene that promotes proliferation and is associated with poor prognosis in HCC.
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Affiliation(s)
- Xing-Wang Xie
- Chinese Center for Disease Control and Prevention, Beijing 102206, China
| | - Xue-Yan Wang
- Peking University Hepatology Institute, Beijing Key Laboratory of Hepatitis C and Immunotherapy for Liver Disease, Peking University People's Hospital, Beijing 100044, China
| | - Wei-Jia Liao
- Laboratory of Hepatobiliary and Pancreatic Surgery, Affiliated Hospital of Guilin Medical University, Guilin, Guangxi 541001, China
| | - Ran Fei
- Peking University Hepatology Institute, Beijing Key Laboratory of Hepatitis C and Immunotherapy for Liver Disease, Peking University People's Hospital, Beijing 100044, China
| | - Xu Cong
- Peking University Hepatology Institute, Beijing Key Laboratory of Hepatitis C and Immunotherapy for Liver Disease, Peking University People's Hospital, Beijing 100044, China
| | - Qian Chen
- Laboratory of Hepatobiliary and Pancreatic Surgery, Affiliated Hospital of Guilin Medical University, Guilin, Guangxi 541001, China
| | - Lai Wei
- Peking University Hepatology Institute, Beijing Key Laboratory of Hepatitis C and Immunotherapy for Liver Disease, Peking University People's Hospital, Beijing 100044, China
| | - Hong-Song Chen
- Peking University Hepatology Institute, Beijing Key Laboratory of Hepatitis C and Immunotherapy for Liver Disease, Peking University People's Hospital, Beijing 100044, China
| | - Yu Wang
- Chinese Center for Disease Control and Prevention, Beijing 102206, China
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32
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Burby PE, Simmons LA. A bacterial DNA repair pathway specific to a natural antibiotic. Mol Microbiol 2018; 111:338-353. [PMID: 30379365 DOI: 10.1111/mmi.14158] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/28/2018] [Indexed: 12/17/2022]
Abstract
All organisms possess DNA repair pathways that are used to maintain the integrity of their genetic material. Although many DNA repair pathways are well understood, new pathways continue to be discovered. Here, we report an antibiotic specific DNA repair pathway in Bacillus subtilis that is composed of a previously uncharacterized helicase (mrfA) and exonuclease (mrfB). Deletion of mrfA and mrfB results in sensitivity to the DNA damaging agent mitomycin C, but not to any other type of DNA damage tested. We show that MrfAB function independent of canonical nucleotide excision repair, forming a novel excision repair pathway. We demonstrate that MrfB is a metal-dependent exonuclease and that the N-terminus of MrfB is required for interaction with MrfA. We determined that MrfAB failed to unhook interstrand cross-links in vivo, suggesting that MrfAB are specific to the monoadduct or the intrastrand cross-link. A phylogenetic analysis uncovered MrfAB homologs in diverse bacterial phyla, and cross-complementation indicates that MrfAB function is conserved in closely related species. B. subtilis is a soil dwelling organism and mitomycin C is a natural antibiotic produced by the soil bacterium Streptomyces lavendulae. The specificity of MrfAB suggests that these proteins are an adaptation to environments with mitomycin producing bacteria.
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Affiliation(s)
- Peter E Burby
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Lyle A Simmons
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
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33
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Villa-Hernández S, Bermejo R. Replisome-Cohesin Interfacing: A Molecular Perspective. Bioessays 2018; 40:e1800109. [PMID: 30106480 DOI: 10.1002/bies.201800109] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 07/23/2018] [Indexed: 12/27/2022]
Abstract
Cohesion is established in S-phase through the action of key replisome factors as replication forks engage cohesin molecules. By holding sister chromatids together, cohesion critically assists both an equal segregation of the duplicated genetic material and an efficient repair of DNA breaks. Nonetheless, the molecular events leading the entrapment of nascent chromatids by cohesin during replication are only beginning to be understood. The authors describe here the essential structural features of the cohesin complex in connection to its ability to associate DNA molecules and review the current knowledge on the architectural-functional organization of the eukaryotic replisome, significantly advanced by recent biochemical and structural studies. In light of this novel insight, the authors discuss the mechanisms proposed to assist interfacing of replisomes with chromatin-bound cohesin complexes and elaborate on models for nascent chromatids entrapment by cohesin in the environment of the replication fork.
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Affiliation(s)
- Sara Villa-Hernández
- Centro de Investigaciones Biológicas (CIB-CSIC), Calle Ramiro de Maeztu 928040 Madrid, Spain
| | - Rodrigo Bermejo
- Centro de Investigaciones Biológicas (CIB-CSIC), Calle Ramiro de Maeztu 928040 Madrid, Spain
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34
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Pellegrini L. Dual Roles of Ctf18-RFC: Loading the Clamp and Angling for the Polymerase. Structure 2018; 26:1-2. [DOI: 10.1016/j.str.2017.12.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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