1
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Łazowski K, Woodgate R, Fijalkowska IJ. Escherichia coli DNA replication: the old model organism still holds many surprises. FEMS Microbiol Rev 2024; 48:fuae018. [PMID: 38982189 PMCID: PMC11253446 DOI: 10.1093/femsre/fuae018] [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: 05/09/2024] [Revised: 06/26/2024] [Accepted: 07/08/2024] [Indexed: 07/11/2024] Open
Abstract
Research on Escherichia coli DNA replication paved the groundwork for many breakthrough discoveries with important implications for our understanding of human molecular biology, due to the high level of conservation of key molecular processes involved. To this day, it attracts a lot of attention, partially by virtue of being an important model organism, but also because the understanding of factors influencing replication fidelity might be important for studies on the emergence of antibiotic resistance. Importantly, the wide access to high-resolution single-molecule and live-cell imaging, whole genome sequencing, and cryo-electron microscopy techniques, which were greatly popularized in the last decade, allows us to revisit certain assumptions about the replisomes and offers very detailed insight into how they work. For many parts of the replisome, step-by-step mechanisms have been reconstituted, and some new players identified. This review summarizes the latest developments in the area, focusing on (a) the structure of the replisome and mechanisms of action of its components, (b) organization of replisome transactions and repair, (c) replisome dynamics, and (d) factors influencing the base and sugar fidelity of DNA synthesis.
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Affiliation(s)
- Krystian Łazowski
- Laboratory of DNA Replication and Genome Stability, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, United States
| | - Iwona J Fijalkowska
- Laboratory of DNA Replication and Genome Stability, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
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2
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Simonsen S, Søgaard CK, Olsen JG, Otterlei M, Kragelund BB. The bacterial DNA sliding clamp, β-clamp: structure, interactions, dynamics and drug discovery. Cell Mol Life Sci 2024; 81:245. [PMID: 38814467 PMCID: PMC11139829 DOI: 10.1007/s00018-024-05252-w] [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: 03/14/2024] [Revised: 04/22/2024] [Accepted: 04/23/2024] [Indexed: 05/31/2024]
Abstract
DNA replication is a tightly coordinated event carried out by a multiprotein replication complex. An essential factor in the bacterial replication complex is the ring-shaped DNA sliding clamp, β-clamp, ensuring processive DNA replication and DNA repair through tethering of polymerases and DNA repair proteins to DNA. β -clamp is a hub protein with multiple interaction partners all binding through a conserved clamp binding sequence motif. Due to its central role as a DNA scaffold protein, β-clamp is an interesting target for antimicrobial drugs, yet little effort has been put into understanding the functional interactions of β-clamp. In this review, we scrutinize the β-clamp structure and dynamics, examine how its interactions with a plethora of binding partners are regulated through short linear binding motifs and discuss how contexts play into selection. We describe the dynamic process of clamp loading onto DNA and cover the recent advances in drug development targeting β-clamp. Despite decades of research in β-clamps and recent landmark structural insight, much remains undisclosed fostering an increased focus on this very central protein.
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Affiliation(s)
- Signe Simonsen
- Linderstrøm-Lang Centre for Protein Science, University of Copenhagen, Ole Maaløes Vej 5, 2200, Copenhagen N, Denmark
- Structural Biology and NMR Laboratory, University of Copenhagen, Ole Maaløes Vej 5, 2200, Copenhagen N, Denmark
| | - Caroline K Søgaard
- Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Johan G Olsen
- Linderstrøm-Lang Centre for Protein Science, University of Copenhagen, Ole Maaløes Vej 5, 2200, Copenhagen N, Denmark
- Structural Biology and NMR Laboratory, University of Copenhagen, Ole Maaløes Vej 5, 2200, Copenhagen N, Denmark
- Department of Biology, REPIN, University of Copenhagen, Ole Maaløes Vej 5, 2200, Copenhagen N, Denmark
| | - Marit Otterlei
- Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
| | - Birthe B Kragelund
- Linderstrøm-Lang Centre for Protein Science, University of Copenhagen, Ole Maaløes Vej 5, 2200, Copenhagen N, Denmark.
- Structural Biology and NMR Laboratory, University of Copenhagen, Ole Maaløes Vej 5, 2200, Copenhagen N, Denmark.
- Department of Biology, REPIN, University of Copenhagen, Ole Maaløes Vej 5, 2200, Copenhagen N, Denmark.
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3
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Yuan H, Liu RD, Gao ZY, Zhong LT, Zhou YC, Tan JH, Huang ZS, Li Z, Chen SB. Targeting ATP-binding site of WRN Helicase: Identification of novel inhibitors through pocket analysis and Molecular Dynamics-Enhanced virtual screening. Bioorg Med Chem Lett 2024; 104:129711. [PMID: 38521175 DOI: 10.1016/j.bmcl.2024.129711] [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: 08/16/2023] [Revised: 03/14/2024] [Accepted: 03/20/2024] [Indexed: 03/25/2024]
Abstract
WRN helicase is a critical protein involved in maintaining genomic stability, utilizing ATP hydrolysis to dissolve DNA secondary structures. It has been identified as a promising synthetic lethal target for microsatellite instable (MSI) cancers. However, few WRN helicase inhibitors have been discovered, and their potential binding sites remain unexplored. In this study, we analyzed potential binding sites for WRN inhibitors and focused on the ATP-binding site for screening new inhibitors. Through molecular dynamics-enhanced virtual screening, we identified two compounds, h6 and h15, which effectively inhibited WRN's helicase and ATPase activity in vitro. Importantly, these compounds selectively targeted WRN's ATPase activity, setting them apart from other non-homologous proteins with ATPase activity. In comparison to the homologous protein BLM, h6 exhibits some degree of selectivity towards WRN. We also investigated the binding mode of these compounds to WRN's ATP-binding sites. These findings offer a promising strategy for discovering new WRN inhibitors and present two novel scaffolds, which might be potential for the development of MSI cancer treatment.
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Affiliation(s)
- Hao Yuan
- School of Pharmaceutical Sciences, Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Sun Yat-sen University, Guangzhou 510006, China
| | - Run-Duo Liu
- School of Pharmaceutical Sciences, Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Sun Yat-sen University, Guangzhou 510006, China
| | - Zhuo-Yu Gao
- School of Pharmaceutical Sciences, Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Sun Yat-sen University, Guangzhou 510006, China
| | - Li-Ting Zhong
- School of Pharmaceutical Sciences, Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Sun Yat-sen University, Guangzhou 510006, China
| | - Ying-Chen Zhou
- School of Pharmaceutical Sciences, Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Sun Yat-sen University, Guangzhou 510006, China
| | - Jia-Heng Tan
- School of Pharmaceutical Sciences, Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Sun Yat-sen University, Guangzhou 510006, China
| | - Zhi-Shu Huang
- School of Pharmaceutical Sciences, Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Sun Yat-sen University, Guangzhou 510006, China
| | - Zhe Li
- School of Pharmaceutical Sciences, Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Sun Yat-sen University, Guangzhou 510006, China.
| | - Shuo-Bin Chen
- School of Pharmaceutical Sciences, Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Sun Yat-sen University, Guangzhou 510006, China.
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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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Landeck JT, Pajak J, Norman EK, Sedivy EL, Kelch BA. Differences between bacteria and eukaryotes in clamp loader mechanism, a conserved process underlying DNA replication. J Biol Chem 2024; 300:107166. [PMID: 38490435 PMCID: PMC11044049 DOI: 10.1016/j.jbc.2024.107166] [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: 01/10/2024] [Revised: 02/23/2024] [Accepted: 03/01/2024] [Indexed: 03/17/2024] Open
Abstract
Clamp loaders are pentameric ATPases that place circular sliding clamps onto DNA, where they function in DNA replication and genome integrity. The central activity of a clamp loader is the opening of the ring-shaped sliding clamp and the subsequent binding to primer-template (p/t)-junctions. The general architecture of clamp loaders is conserved across all life, suggesting that their mechanism is retained. Recent structural studies of the eukaryotic clamp loader replication factor C (RFC) revealed that it functions using a crab-claw mechanism, where clamp opening is coupled to a massive conformational change in the loader. Here we investigate the clamp loading mechanism of the Escherichia coli clamp loader at high resolution using cryo-electron microscopy. We find that the E. coli clamp loader opens the clamp using a crab-claw motion at a single pivot point, whereas the eukaryotic RFC loader uses motions distributed across the complex. Furthermore, we find clamp opening occurs in multiple steps, starting with a partly open state with a spiral conformation, and proceeding to a wide open clamp in a surprising planar geometry. Finally, our structures in the presence of p/t-junctions illustrate how the clamp closes around p/t-junctions and how the clamp loader initiates release from the loaded clamp. Our results reveal mechanistic distinctions in a macromolecular machine that is conserved across all domains of life.
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Affiliation(s)
- Jacob T Landeck
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, USA
| | - Joshua Pajak
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, USA
| | - Emily K Norman
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, USA
| | - Emma L Sedivy
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, USA
| | - Brian A Kelch
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, USA.
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6
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Landeck JT, Pajak J, Norman EK, Sedivy EL, Kelch BA. Differences in clamp loader mechanism between bacteria and eukaryotes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.30.569468. [PMID: 38076975 PMCID: PMC10705477 DOI: 10.1101/2023.11.30.569468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Clamp loaders are pentameric ATPases that place circular sliding clamps onto DNA, where they function in DNA replication and genome integrity. The central activity of a clamp loader is the opening of the ring-shaped sliding clamp, and the subsequent binding to primer-template (p/t)-junctions. The general architecture of clamp loaders is conserved across all life, suggesting that their mechanism is retained. Recent structural studies of the eukaryotic clamp loader Replication Factor C (RFC) revealed that it functions using a crab-claw mechanism, where clamp opening is coupled to a massive conformational change in the loader. Here we investigate the clamp loading mechanism of the E. coli clamp loader at high resolution using cryo-electron microscopy (cryo-EM). We find that the E. coli clamp loader opens the clamp using a crab-claw motion at a single pivot point, whereas the eukaryotic RFC loader uses motions distributed across the complex. Furthermore, we find clamp opening occurs in multiple steps, starting with a partly open state with a spiral conformation, and proceeding to a wide open clamp in a surprising planar geometry. Finally, our structures in the presence of p/t-junctions illustrate how clamp closes around p/t-junctions and how the clamp loader initiates release from the loaded clamp. Our results reveal mechanistic distinctions in a macromolecular machine that is conserved across all domains of life.
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Affiliation(s)
- Jacob T. Landeck
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester MA
| | - Joshua Pajak
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester MA
| | - Emily K. Norman
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester MA
| | - Emma L. Sedivy
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester MA
| | - Brian A. Kelch
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester MA
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7
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Gaubitz C, Liu X, Pajak J, Stone NP, Hayes JA, Demo G, Kelch BA. Cryo-EM structures reveal high-resolution mechanism of a DNA polymerase sliding clamp loader. eLife 2022; 11:e74175. [PMID: 35179493 PMCID: PMC8893722 DOI: 10.7554/elife.74175] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 02/01/2022] [Indexed: 11/13/2022] Open
Abstract
Sliding clamps are ring-shaped protein complexes that are integral to the DNA replication machinery of all life. Sliding clamps are opened and installed onto DNA by clamp loader AAA+ ATPase complexes. However, how a clamp loader opens and closes the sliding clamp around DNA is still unknown. Here, we describe structures of the Saccharomyces cerevisiae clamp loader Replication Factor C (RFC) bound to its cognate sliding clamp Proliferating Cell Nuclear Antigen (PCNA) en route to successful loading. RFC first binds to PCNA in a dynamic, closed conformation that blocks both ATPase activity and DNA binding. RFC then opens the PCNA ring through a large-scale 'crab-claw' expansion of both RFC and PCNA that explains how RFC prefers initial binding of PCNA over DNA. Next, the open RFC:PCNA complex binds DNA and interrogates the primer-template junction using a surprising base-flipping mechanism. Our structures indicate that initial PCNA opening and subsequent closure around DNA do not require ATP hydrolysis, but are driven by binding energy. ATP hydrolysis, which is necessary for RFC release, is triggered by interactions with both PCNA and DNA, explaining RFC's switch-like ATPase activity. Our work reveals how a AAA+ machine undergoes dramatic conformational changes for achieving binding preference and substrate remodeling.
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Affiliation(s)
- Christl Gaubitz
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - Xingchen Liu
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - Joshua Pajak
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - Nicholas P Stone
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - Janelle A Hayes
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - Gabriel Demo
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester MA & Central European Institute of Technology, Masaryk UniversityBrnoCzech Republic
| | - Brian A Kelch
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical SchoolWorcesterUnited States
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8
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Liu B, Li S, Liu Y, Chen H, Hu Z, Wang Z, Zhao Y, Zhang L, Ma B, Wang H, Matthews S, Wang Y, Zhang K. Bacteriophage Twort protein Gp168 is a β-clamp inhibitor by occupying the DNA sliding channel. Nucleic Acids Res 2021; 49:11367-11378. [PMID: 34614154 PMCID: PMC8565349 DOI: 10.1093/nar/gkab875] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 09/13/2021] [Accepted: 09/16/2021] [Indexed: 11/22/2022] Open
Abstract
Bacterial chromosome replication is mainly catalyzed by DNA polymerase III, whose beta subunits enable rapid processive DNA replication. Enabled by the clamp-loading complex, the two beta subunits form a ring-like clamp around DNA and keep the polymerase sliding along. Given the essential role of β-clamp, its inhibitors have been explored for antibacterial purposes. Similarly, β-clamp is an ideal target for bacteriophages to shut off host DNA synthesis during host takeover. The Gp168 protein of phage Twort is such an example, which binds to the β-clamp of Staphylococcus aureus and prevents it from loading onto DNA causing replication arrest. Here, we report a cryo-EM structure of the clamp–Gp168 complex at 3.2-Å resolution. In the structure of the complex, the Gp168 dimer occupies the DNA sliding channel of β-clamp and blocks its loading onto DNA, which represents a new inhibitory mechanism against β-clamp function. Interestingly, the key residues responsible for this interaction on the β-clamp are well conserved among bacteria. We therefore demonstrate that Gp168 is potentially a cross-species β-clamp inhibitor, as it forms complex with the Bacillus subtilis β-clamp. Our findings reveal an alternative mechanism for bacteriophages to inhibit β-clamp and provide a new strategy to combat bacterial drug resistance.
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Affiliation(s)
- Bing Liu
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China.,Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Shanshan Li
- MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Laboratory for Physical Sciences at the Microscale and Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
| | - Yang Liu
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China
| | - Huan Chen
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China
| | - Zhenyue Hu
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China
| | - Zhihao Wang
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China.,Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Yimin Zhao
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Lei Zhang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Biyun Ma
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China
| | - Hongliang Wang
- Department of Pathogen Biology and Immunology, Xi'an Jiaotong University Health Science Center, Xi'an, Shaanxi 710061, China
| | - Steve Matthews
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Yawen Wang
- BioBank, The First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, China
| | - Kaiming Zhang
- MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Laboratory for Physical Sciences at the Microscale and Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
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9
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Khan YA, White KI, Brunger AT. The AAA+ superfamily: a review of the structural and mechanistic principles of these molecular machines. Crit Rev Biochem Mol Biol 2021; 57:156-187. [PMID: 34632886 DOI: 10.1080/10409238.2021.1979460] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
ATPases associated with diverse cellular activities (AAA+ proteins) are a superfamily of proteins found throughout all domains of life. The hallmark of this family is a conserved AAA+ domain responsible for a diverse range of cellular activities. Typically, AAA+ proteins transduce chemical energy from the hydrolysis of ATP into mechanical energy through conformational change, which can drive a variety of biological processes. AAA+ proteins operate in a variety of cellular contexts with diverse functions including disassembly of SNARE proteins, protein quality control, DNA replication, ribosome assembly, and viral replication. This breadth of function illustrates both the importance of AAA+ proteins in health and disease and emphasizes the importance of understanding conserved mechanisms of chemo-mechanical energy transduction. This review is divided into three major portions. First, the core AAA+ fold is presented. Next, the seven different clades of AAA+ proteins and structural details and reclassification pertaining to proteins in each clade are described. Finally, two well-known AAA+ proteins, NSF and its close relative p97, are reviewed in detail.
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Affiliation(s)
- Yousuf A Khan
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA.,Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA.,Department of Structural Biology, Stanford University, Stanford, CA, USA.,Department of Photon Science, Stanford University, Stanford, CA, USA.,Center for Biomedical Informatics Research, Stanford University, Stanford, CA, USA
| | - K Ian White
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA.,Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA.,Department of Structural Biology, Stanford University, Stanford, CA, USA.,Department of Photon Science, Stanford University, Stanford, CA, USA.,Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Axel T Brunger
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA.,Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA.,Department of Structural Biology, Stanford University, Stanford, CA, USA.,Department of Photon Science, Stanford University, Stanford, CA, USA.,Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
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10
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Abstract
The faithful and timely copying of DNA by molecular machines known as replisomes depends on a disparate suite of enzymes and scaffolding factors working together in a highly orchestrated manner. Large, dynamic protein-nucleic acid assemblies that selectively morph between distinct conformations and compositional states underpin this critical cellular process. In this article, we discuss recent progress outlining the physical basis of replisome construction and progression in eukaryotes.
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Affiliation(s)
- Ilan Attali
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA;
| | - Michael R Botchan
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
| | - James M Berger
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA;
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11
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Structure of the human clamp loader reveals an autoinhibited conformation of a substrate-bound AAA+ switch. Proc Natl Acad Sci U S A 2020; 117:23571-23580. [PMID: 32907938 DOI: 10.1073/pnas.2007437117] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
DNA replication requires the sliding clamp, a ring-shaped protein complex that encircles DNA, where it acts as an essential cofactor for DNA polymerases and other proteins. The sliding clamp needs to be opened and installed onto DNA by a clamp loader ATPase of the AAA+ family. The human clamp loader replication factor C (RFC) and sliding clamp proliferating cell nuclear antigen (PCNA) are both essential and play critical roles in several diseases. Despite decades of study, no structure of human RFC has been resolved. Here, we report the structure of human RFC bound to PCNA by cryogenic electron microscopy to an overall resolution of ∼3.4 Å. The active sites of RFC are fully bound to adenosine 5'-triphosphate (ATP) analogs, which is expected to induce opening of the sliding clamp. However, we observe the complex in a conformation before PCNA opening, with the clamp loader ATPase modules forming an overtwisted spiral that is incapable of binding DNA or hydrolyzing ATP. The autoinhibited conformation observed here has many similarities to a previous yeast RFC:PCNA crystal structure, suggesting that eukaryotic clamp loaders adopt a similar autoinhibited state early on in clamp loading. Our results point to a "limited change/induced fit" mechanism in which the clamp first opens, followed by DNA binding, inducing opening of the loader to release autoinhibition. The proposed change from an overtwisted to an active conformation reveals an additional regulatory mechanism for AAA+ ATPases. Finally, our structural analysis of disease mutations leads to a mechanistic explanation for the role of RFC in human health.
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12
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Liu W. The structure of the checkpoint clamp 9-1-1 complex and clamp loader Rad24-RFC in Saccharomyces cerevisiae. Biochem Biophys Res Commun 2019; 515:688-692. [PMID: 31182279 DOI: 10.1016/j.bbrc.2019.05.138] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 05/22/2019] [Indexed: 01/22/2023]
Abstract
The 9-1-1 complex is a circular heterotrimeric complex composed of Rad9-Hus1-Rad1. In response to DNA damage, the 9-1-1 complex will be loaded onto the DNA damage site by clamp loader Rad24-RFC to activate the cell cycle checkpoint. The C-terminal of Ddc1/Rad9 is critical for checkpoint activation. However, there is little structural information about the intact 9-1-1 complex and the interaction with Rad24-RFC. Here, we determined the structure of the intact 9-1-1 complex in S. cerevisiae by cryo-Electron Microscopy (cryo-EM) and identified the Ddc1 C-tail module for the first time. We found that the C-terminal of Ddc1 has structural flexibility and it plays a critical role for Mec1/Ddc2 activation in G1/G2 phase. At the same time, we got a glimpse of the structure of Rad24-RFC and captured the interaction between the 9-1-1 complex and Rad24-RFC. The structural information greatly helped us to understand the process of clamp-loading.
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Affiliation(s)
- Wei Liu
- School of Life Sciences, University of Science and Technology of China, Hefei, 230027, China.
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13
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Dynamics of the E. coli β-Clamp Dimer Interface and Its Influence on DNA Loading. Biophys J 2019; 117:587-601. [PMID: 31349986 DOI: 10.1016/j.bpj.2019.06.035] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 06/21/2019] [Accepted: 06/27/2019] [Indexed: 01/17/2023] Open
Abstract
The ring-shaped sliding clamp proteins have crucial roles in the regulation of DNA replication, recombination, and repair in all organisms. We previously showed that the Escherichia coli β-clamp is dynamic in solution, transiently visiting conformational states in which Domain 1 at the dimer interface is more flexible and prone to unfolding. This work aims to understand how the stability of the dimer interface influences clamp-opening dynamics and clamp loading by designing and characterizing stabilizing and destabilizing mutations in the clamp. The variants with stabilizing mutations conferred similar or increased thermostability and had similar quaternary structure as compared to the wild type. These variants stimulated the ATPase function of the clamp loader, complemented cell growth of a temperature-sensitive strain, and were successfully loaded onto a DNA substrate. The L82D and L82E I272A variants with purported destabilizing mutations had decreased thermostability, did not complement the growth of a temperature-sensitive strain, and had weakened dimerization as determined by native trapped ion mobility spectrometry-mass spectrometry. The β L82E variant had a reduced melting temperature but dimerized and complemented growth of a temperature-sensitive strain. All three clamps with destabilizing mutations had perturbed loading on DNA. Molecular dynamics simulations indicate altered hydrogen-bonding patterns at the dimer interface, and cross-correlation analysis showed the largest perturbations in the destabilized variants, consistent with the observed change in the conformations and functions of these clamps.
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14
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Oakley AJ. A structural view of bacterial DNA replication. Protein Sci 2019; 28:990-1004. [PMID: 30945375 DOI: 10.1002/pro.3615] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 04/03/2019] [Indexed: 11/11/2022]
Abstract
DNA replication mechanisms are conserved across all organisms. The proteins required to initiate, coordinate, and complete the replication process are best characterized in model organisms such as Escherichia coli. These include nucleotide triphosphate-driven nanomachines such as the DNA-unwinding helicase DnaB and the clamp loader complex that loads DNA-clamps onto primer-template junctions. DNA-clamps are required for the processivity of the DNA polymerase III core, a heterotrimer of α, ε, and θ, required for leading- and lagging-strand synthesis. DnaB binds the DnaG primase that synthesizes RNA primers on both strands. Representative structures are available for most classes of DNA replication proteins, although there are gaps in our understanding of their interactions and the structural transitions that occur in nanomachines such as the helicase, clamp loader, and replicase core as they function. Reviewed here is the structural biology of these bacterial DNA replication proteins and prospects for future research.
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Affiliation(s)
- Aaron J Oakley
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, and Illawarra Health and Medical Research Institute, Wollongong, New South Wales, Australia
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15
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Xu RG, Jenkins HT, Antson AA, Greive SJ. Structure of the large terminase from a hyperthermophilic virus reveals a unique mechanism for oligomerization and ATP hydrolysis. Nucleic Acids Res 2018; 45:13029-13042. [PMID: 29069443 PMCID: PMC5727402 DOI: 10.1093/nar/gkx947] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2017] [Accepted: 10/13/2017] [Indexed: 11/23/2022] Open
Abstract
The crystal structure of the large terminase from the Geobacillus stearothermophilus bacteriophage D6E shows a unique relative orientation of the N-terminal adenosine triphosphatase (ATPase) and C-terminal nuclease domains. This monomeric ‘initiation’ state with the two domains ‘locked’ together is stabilized via a conserved C-terminal arm, which may interact with the portal protein during motor assembly, as predicted for several bacteriophages. Further work supports the formation of an active oligomeric state: (i) AUC data demonstrate the presence of oligomers; (ii) mutational analysis reveals a trans-arginine finger, R158, indispensable for ATP hydrolysis; (iii) the location of this arginine is conserved with the HerA/FtsK ATPase superfamily; (iv) a molecular docking model of the pentamer is compatible with the location of the identified arginine finger. However, this pentameric model is structurally incompatible with the monomeric ‘initiation’ state and is supported by the observed increase in kcat of ATP hydrolysis, from 7.8 ± 0.1 min−1 to 457.7 ± 9.2 min−1 upon removal of the C-terminal nuclease domain. Taken together, these structural, biophysical and biochemical data suggest a model where transition from the ‘initiation’ state into a catalytically competent pentameric state, is accompanied by substantial domain rearrangements, triggered by the removal of the C-terminal arm from the ATPase active site.
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Affiliation(s)
- Rui-Gang Xu
- York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, UK
| | - Huw T Jenkins
- York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, UK
| | - Alfred A Antson
- York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, UK
| | - Sandra J Greive
- York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, UK
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16
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Sysoeva TA. Assessing heterogeneity in oligomeric AAA+ machines. Cell Mol Life Sci 2017; 74:1001-1018. [PMID: 27669691 PMCID: PMC11107579 DOI: 10.1007/s00018-016-2374-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 09/13/2016] [Accepted: 09/19/2016] [Indexed: 10/20/2022]
Abstract
ATPases Associated with various cellular Activities (AAA+ ATPases) are molecular motors that use the energy of ATP binding and hydrolysis to remodel their target macromolecules. The majority of these ATPases form ring-shaped hexamers in which the active sites are located at the interfaces between neighboring subunits. Structural changes initiate in an active site and propagate to distant motor parts that interface and reshape the target macromolecules, thereby performing mechanical work. During the functioning cycle, the AAA+ motor transits through multiple distinct states. Ring architecture and placement of the catalytic sites at the intersubunit interfaces allow for a unique level of coordination among subunits of the motor. This in turn results in conformational differences among subunits and overall asymmetry of the motor ring as it functions. To date, a large amount of structural information has been gathered for different AAA+ motors, but even for the most characterized of them only a few structural states are known and the full mechanistic cycle cannot be yet reconstructed. Therefore, the first part of this work will provide a broad overview of what arrangements of AAA+ subunits have been structurally observed focusing on diversity of ATPase oligomeric ensembles and heterogeneity within the ensembles. The second part of this review will concentrate on methods that assess structural and functional heterogeneity among subunits of AAA+ motors, thus bringing us closer to understanding the mechanism of these fascinating molecular motors.
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Affiliation(s)
- Tatyana A Sysoeva
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA.
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17
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Kelch BA. Review: The lord of the rings: Structure and mechanism of the sliding clamp loader. Biopolymers 2017; 105:532-46. [PMID: 26918303 DOI: 10.1002/bip.22827] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 02/15/2016] [Accepted: 02/23/2016] [Indexed: 12/15/2022]
Abstract
Sliding clamps are ring-shaped polymerase processivity factors that act as master regulators of cellular replication by coordinating multiple functions on DNA to ensure faithful transmission of genetic and epigenetic information. Dedicated AAA+ ATPase machines called clamp loaders actively place clamps on DNA, thereby governing clamp function by controlling when and where clamps are used. Clamp loaders are also important model systems for understanding the basic principles of AAA+ mechanism and function. After nearly 30 years of study, the ATP-dependent mechanism of opening and loading of clamps is now becoming clear. Here I review the structural and mechanistic aspects of the clamp loading process, as well as comment on questions that will be addressed by future studies. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 532-546, 2016.
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Affiliation(s)
- Brian A Kelch
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, 01605
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18
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Tocilj A, On KF, Yuan Z, Sun J, Elkayam E, Li H, Stillman B, Joshua-Tor L. Structure of the active form of human origin recognition complex and its ATPase motor module. eLife 2017; 6. [PMID: 28112645 PMCID: PMC5291709 DOI: 10.7554/elife.20818] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 01/15/2017] [Indexed: 12/21/2022] Open
Abstract
Binding of the Origin Recognition Complex (ORC) to origins of replication marks the first step in the initiation of replication of the genome in all eukaryotic cells. Here, we report the structure of the active form of human ORC determined by X-ray crystallography and cryo-electron microscopy. The complex is composed of an ORC1/4/5 motor module lobe in an organization reminiscent of the DNA polymerase clamp loader complexes. A second lobe contains the ORC2/3 subunits. The complex is organized as a double-layered shallow corkscrew, with the AAA+ and AAA+-like domains forming one layer, and the winged-helix domains (WHDs) forming a top layer. CDC6 fits easily between ORC1 and ORC2, completing the ring and the DNA-binding channel, forming an additional ATP hydrolysis site. Analysis of the ATPase activity of the complex provides a basis for understanding ORC activity as well as molecular defects observed in Meier-Gorlin Syndrome mutations. DOI:http://dx.doi.org/10.7554/eLife.20818.001
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Affiliation(s)
- Ante Tocilj
- W. M. Keck Structural Biology Laboratory, Cold Spring Harbor, New York, United States.,Howard Hughes Medical Institute, Cold Spring Harbor, New York, United States.,Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States
| | - Kin Fan On
- W. M. Keck Structural Biology Laboratory, Cold Spring Harbor, New York, United States.,Howard Hughes Medical Institute, Cold Spring Harbor, New York, United States.,Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States
| | - Zuanning Yuan
- Biology Department, Brookhaven National Laboratory, New York, United States.,Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, United States
| | - Jingchuan Sun
- Biology Department, Brookhaven National Laboratory, New York, United States
| | - Elad Elkayam
- W. M. Keck Structural Biology Laboratory, Cold Spring Harbor, New York, United States.,Howard Hughes Medical Institute, Cold Spring Harbor, New York, United States.,Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States
| | - Huilin Li
- Biology Department, Brookhaven National Laboratory, New York, United States.,Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, United States
| | - Bruce Stillman
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States
| | - Leemor Joshua-Tor
- W. M. Keck Structural Biology Laboratory, Cold Spring Harbor, New York, United States.,Howard Hughes Medical Institute, Cold Spring Harbor, New York, United States.,Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States
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19
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Abstract
DNA replication in Escherichia coli initiates at oriC, the origin of replication and proceeds bidirectionally, resulting in two replication forks that travel in opposite directions from the origin. Here, we focus on events at the replication fork. The replication machinery (or replisome), first assembled on both forks at oriC, contains the DnaB helicase for strand separation, and the DNA polymerase III holoenzyme (Pol III HE) for DNA synthesis. DnaB interacts transiently with the DnaG primase for RNA priming on both strands. The Pol III HE is made up of three subassemblies: (i) the αɛθ core polymerase complex that is present in two (or three) copies to simultaneously copy both DNA strands, (ii) the β2 sliding clamp that interacts with the core polymerase to ensure its processivity, and (iii) the seven-subunit clamp loader complex that loads β2 onto primer-template junctions and interacts with the α polymerase subunit of the core and the DnaB helicase to organize the two (or three) core polymerases. Here, we review the structures of the enzymatic components of replisomes, and the protein-protein and protein-DNA interactions that ensure they remain intact while undergoing substantial dynamic changes as they function to copy both the leading and lagging strands simultaneously during coordinated replication.
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Affiliation(s)
- J S Lewis
- Centre for Medical & Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - S Jergic
- Centre for Medical & Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - N E Dixon
- Centre for Medical & Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia.
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20
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Abstract
A range of enzymes in DNA replication and repair bind to DNA-clamps: torus-shaped proteins that encircle double-stranded DNA and act as mobile tethers. Clamps from viruses (such as gp45 from the T4 bacteriophage) and eukaryotes (PCNAs) are homotrimers, each protomer containing two repeats of the DNA-clamp motif, while bacterial clamps (pol III β) are homodimers, each protomer containing three DNA-clamp motifs. Clamps need to be flexible enough to allow opening and loading onto primed DNA by clamp loader complexes. Equilibrium and steered molecular dynamics simulations have been used to study DNA-clamp conformation in open and closed forms. The E. coli and PCNA clamps appear to prefer closed, planar conformations. Remarkably, gp45 appears to prefer an open right-handed spiral conformation in solution, in agreement with previously reported biophysical data. The structural preferences of DNA clamps in solution have implications for understanding the duty cycle of clamp-loaders.
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21
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Tondnevis F, Weiss TM, Matsui T, Bloom LB, McKenna R. Solution structure of an "open" E. coli Pol III clamp loader sliding clamp complex. J Struct Biol 2016; 194:272-81. [PMID: 26968362 DOI: 10.1016/j.jsb.2016.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Revised: 03/03/2016] [Accepted: 03/05/2016] [Indexed: 01/06/2023]
Abstract
Sliding clamps are opened and loaded onto primer template junctions by clamp loaders, and once loaded on DNA, confer processivity to replicative polymerases. Previously determined crystal structures of eukaryotic and T4 clamp loader-clamp complexes have captured the sliding clamps in either closed or only partially open interface conformations. In these solution structure studies, we have captured for the first time the clamp loader-sliding clamp complex from Escherichia coli using size exclusion chromatography coupled to small angle X-ray scattering (SEC-SAXS). The data suggests the sliding clamp is in an open conformation which is wide enough to permit duplex DNA binding. The data also provides information about spatial arrangement of the sliding clamp with respect to the clamp loader subunits and is compared to complex crystal structures determined from other organisms.
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Affiliation(s)
- Farzaneh Tondnevis
- Biochemistry and Molecular Biology, University of Florida, PO Box 100245, Gainesville, FL 32610, United States
| | - Thomas M Weiss
- Stanford Synchrotron Radiation Lightsource, 2575 Sand Hill Road, MS69, Menlo Park, CA 94025, United States
| | - Tsutomu Matsui
- Stanford Synchrotron Radiation Lightsource, 2575 Sand Hill Road, MS69, Menlo Park, CA 94025, United States
| | - Linda B Bloom
- Biochemistry and Molecular Biology, University of Florida, PO Box 100245, Gainesville, FL 32610, United States
| | - Robert McKenna
- Biochemistry and Molecular Biology, University of Florida, PO Box 100245, Gainesville, FL 32610, United States.
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22
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Tondnevis F, Gillilan RE, Bloom LB, McKenna R. Solution study of the Escherichia coli DNA polymerase III clamp loader reveals the location of the dynamic ψχ heterodimer. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2015; 2:054701. [PMID: 26798827 PMCID: PMC4711647 DOI: 10.1063/1.4927407] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 07/15/2015] [Indexed: 06/05/2023]
Abstract
Several X-ray crystal structures of the E. coli core clamp loader containing the five core (δ', δ, and three truncated γ) subunits have been determined, but they lack the ψ and χ subunits. We report the first solution structure of the complete seven-subunit clamp loader complex using small angle X-ray scattering. This structure not only provides information about the location of the χ and ψ subunits but also provides a model of the dynamic nature of the clamp loader complex.
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Affiliation(s)
- Farzaneh Tondnevis
- Biochemistry and Molecular Biology, University of Florida , P.O. BOX 100245, Gainesville, Florida 32610, USA
| | - Richard E Gillilan
- Cornell High Energy Synchrotron Source (CHESS), Cornell University , 161 Synchrotron Drive, Ithaca, New York 14853, USA
| | - Linda B Bloom
- Biochemistry and Molecular Biology, University of Florida , P.O. BOX 100245, Gainesville, Florida 32610, USA
| | - Robert McKenna
- Biochemistry and Molecular Biology, University of Florida , P.O. BOX 100245, Gainesville, Florida 32610, USA
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23
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Abstract
To achieve the high degree of processivity required for DNA replication, DNA polymerases associate with ring-shaped sliding clamps that encircle the template DNA and slide freely along it. The closed circular structure of sliding clamps necessitates an enzyme-catalyzed mechanism, which not only opens them for assembly and closes them around DNA, but specifically targets them to sites where DNA synthesis is initiated and orients them correctly for replication. Such a feat is performed by multisubunit complexes known as clamp loaders, which use ATP to open sliding clamp rings and place them around the 3' end of primer-template (PT) junctions. Here we discuss the structure and composition of sliding clamps and clamp loaders from the three domains of life as well as T4 bacteriophage, and provide our current understanding of the clamp-loading process.
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Affiliation(s)
- Mark Hedglin
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
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24
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Afonso JP, Chintakayala K, Suwannachart C, Sedelnikova S, Giles K, Hoyes JB, Soultanas P, Rafferty JB, Oldham NJ. Insights into the structure and assembly of the Bacillus subtilis clamp-loader complex and its interaction with the replicative helicase. Nucleic Acids Res 2013; 41:5115-26. [PMID: 23525462 PMCID: PMC3643586 DOI: 10.1093/nar/gkt173] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The clamp-loader complex plays a crucial role in DNA replication by loading the β-clamp onto primed DNA to be used by the replicative polymerase. Relatively little is known about the stoichiometry, structure and assembly pathway of this complex, and how it interacts with the replicative helicase, in Gram-positive organisms. Analysis of full and partial complexes by mass spectrometry revealed that a hetero-pentameric τ3-δ-δ' Bacillus subtilis clamp-loader assembles via multiple pathways, which differ from those exhibited by the Gram-negative model Escherichia coli. Based on this information, a homology model of the B. subtilis τ3-δ-δ' complex was constructed, which revealed the spatial positioning of the full C-terminal τ domain. The structure of the δ subunit was determined by X-ray crystallography and shown to differ from that of E. coli in the nature of the amino acids comprising the τ and δ' binding regions. Most notably, the τ-δ interaction appears to be hydrophilic in nature compared with the hydrophobic interaction in E. coli. Finally, the interaction between τ3 and the replicative helicase DnaB was driven by ATP/Mg(2+) conformational changes in DnaB, and evidence is provided that hydrolysis of one ATP molecule by the DnaB hexamer is sufficient to stabilize its interaction with τ3.
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Affiliation(s)
- José P Afonso
- School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
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25
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Robinson A, Causer RJ, Dixon NE. Architecture and conservation of the bacterial DNA replication machinery, an underexploited drug target. Curr Drug Targets 2012; 13:352-72. [PMID: 22206257 PMCID: PMC3290774 DOI: 10.2174/138945012799424598] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 11/03/2011] [Accepted: 11/05/2011] [Indexed: 11/22/2022]
Abstract
New antibiotics with novel modes of action are required to combat the growing threat posed by multi-drug resistant bacteria. Over the last decade, genome sequencing and other high-throughput techniques have provided tremendous insight into the molecular processes underlying cellular functions in a wide range of bacterial species. We can now use these data to assess the degree of conservation of certain aspects of bacterial physiology, to help choose the best cellular targets for development of new broad-spectrum antibacterials. DNA replication is a conserved and essential process, and the large number of proteins that interact to replicate DNA in bacteria are distinct from those in eukaryotes and archaea; yet none of the antibiotics in current clinical use acts directly on the replication machinery. Bacterial DNA synthesis thus appears to be an underexploited drug target. However, before this system can be targeted for drug design, it is important to understand which parts are conserved and which are not, as this will have implications for the spectrum of activity of any new inhibitors against bacterial species, as well as the potential for development of drug resistance. In this review we assess similarities and differences in replication components and mechanisms across the bacteria, highlight current progress towards the discovery of novel replication inhibitors, and suggest those aspects of the replication machinery that have the greatest potential as drug targets.
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Affiliation(s)
- Andrew Robinson
- School of Chemistry, University of Wollongong, NSW 2522, Australia
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26
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Rajagopala SV, Sikorski P, Caufield JH, Tovchigrechko A, Uetz P. Studying protein complexes by the yeast two-hybrid system. Methods 2012; 58:392-9. [PMID: 22841565 DOI: 10.1016/j.ymeth.2012.07.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2012] [Revised: 07/10/2012] [Accepted: 07/12/2012] [Indexed: 01/13/2023] Open
Abstract
Protein complexes are typically analyzed by affinity purification and subsequent mass spectrometric analysis. However, in most cases the structure and topology of the complexes remains elusive from such studies. Here we investigate how the yeast two-hybrid system can be used to analyze direct interactions among proteins in a complex. First we tested all pairwise interactions among the seven proteins of Escherichia coli DNA polymerase III as well as an uncharacterized complex that includes MntR and PerR. Four and seven interactions were identified in these two complexes, respectively. In addition, we review Y2H data for three other complexes of known structure which serve as "gold-standards", namely Varicella Zoster Virus (VZV) ribonucleotide reductase (RNR), the yeast proteasome, and bacteriophage lambda. Finally, we review an Y2H analysis of the human spliceosome which may serve as an example for a dynamic mega-complex.
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27
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Kelch BA, Makino DL, O'Donnell M, Kuriyan J. Clamp loader ATPases and the evolution of DNA replication machinery. BMC Biol 2012; 10:34. [PMID: 22520345 PMCID: PMC3331839 DOI: 10.1186/1741-7007-10-34] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 04/20/2012] [Indexed: 11/19/2022] Open
Abstract
Clamp loaders are pentameric ATPases of the AAA+ family that operate to ensure processive DNA replication. They do so by loading onto DNA the ring-shaped sliding clamps that tether the polymerase to the DNA. Structural and biochemical analysis of clamp loaders has shown how, despite differences in composition across different branches of life, all clamp loaders undergo the same concerted conformational transformations, which generate a binding surface for the open clamp and an internal spiral chamber into which the DNA at the replication fork can slide, triggering ATP hydrolysis, release of the clamp loader, and closure of the clamp round the DNA. We review here the current understanding of the clamp loader mechanism and discuss the implications of the differences between clamp loaders from the different branches of life.
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Affiliation(s)
- Brian A Kelch
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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28
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Abstract
Bacterial replicases are complex, tripartite replicative machines. They contain a polymerase, polymerase III (Pol III), a β₂ processivity factor, and a DnaX complex ATPase that loads β₂ onto DNA and chaperones Pol III onto the newly loaded β₂. Bacterial replicases are highly processive, yet cycle rapidly during Okazaki fragment synthesis in a regulated way. Many bacteria encode both a full-length τ and a shorter γ form of DnaX by a variety of mechanisms. γ appears to be uniquely placed in a single position relative to two τ protomers in a pentameric ring. The polymerase catalytic subunit of Pol III, α, contains a PHP domain that not only binds to a prototypical ε Mg²⁺-dependent exonuclease, but also contains a second Zn²⁺-dependent proofreading exonuclease, at least in some bacteria. This review focuses on a critical evaluation of recent literature and concepts pertaining to the above issues and suggests specific areas that require further investigation.
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Affiliation(s)
- Charles S McHenry
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA.
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29
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Page AN, George NP, Marceau AH, Cox MM, Keck JL. Structure and biochemical activities of Escherichia coli MgsA. J Biol Chem 2011; 286:12075-85. [PMID: 21297161 PMCID: PMC3069411 DOI: 10.1074/jbc.m110.210187] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Revised: 01/14/2011] [Indexed: 11/06/2022] Open
Abstract
Bacterial "maintenance of genome stability protein A" (MgsA) and related eukaryotic enzymes play important roles in cellular responses to stalled DNA replication processes. Sequence information identifies MgsA enzymes as members of the clamp loader clade of AAA+ proteins, but structural information defining the family has been limited. Here, the x-ray crystal structure of Escherichia coli MgsA is described, revealing a homotetrameric arrangement for the protein that distinguishes it from other clamp loader clade AAA+ proteins. Each MgsA protomer is composed of three elements as follows: ATP-binding and helical lid domains (conserved among AAA+ proteins) and a tetramerization domain. Although the tetramerization domains bury the greatest amount of surface area in the MgsA oligomer, each of the domains participates in oligomerization to form a highly intertwined quaternary structure. Phosphate is bound at each AAA+ ATP-binding site, but the active sites do not appear to be in a catalytically competent conformation due to displacement of Arg finger residues. E. coli MgsA is also shown to form a complex with the single-stranded DNA-binding protein through co-purification and biochemical studies. MgsA DNA-dependent ATPase activity is inhibited by single-stranded DNA-binding protein. Together, these structural and biochemical observations provide insights into the mechanisms of MgsA family AAA+ proteins.
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Affiliation(s)
- Asher N. Page
- From the Department of Biochemistry, University of Wisconsin and
| | - Nicholas P. George
- the Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
| | - Aimee H. Marceau
- the Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
| | - Michael M. Cox
- From the Department of Biochemistry, University of Wisconsin and
| | - James L. Keck
- the Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706
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30
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Doppelt-Azeroual O, Delfaud F, Moriaud F, de Brevern AG. Fast and automated functional classification with MED-SuMo: an application on purine-binding proteins. Protein Sci 2010; 19:847-67. [PMID: 20162627 DOI: 10.1002/pro.364] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Ligand-protein interactions are essential for biological processes, and precise characterization of protein binding sites is crucial to understand protein functions. MED-SuMo is a powerful technology to localize similar local regions on protein surfaces. Its heuristic is based on a 3D representation of macromolecules using specific surface chemical features associating chemical characteristics with geometrical properties. MED-SMA is an automated and fast method to classify binding sites. It is based on MED-SuMo technology, which builds a similarity graph, and it uses the Markov Clustering algorithm. Purine binding sites are well studied as drug targets. Here, purine binding sites of the Protein DataBank (PDB) are classified. Proteins potentially inhibited or activated through the same mechanism are gathered. Results are analyzed according to PROSITE annotations and to carefully refined functional annotations extracted from the PDB. As expected, binding sites associated with related mechanisms are gathered, for example, the Small GTPases. Nevertheless, protein kinases from different Kinome families are also found together, for example, Aurora-A and CDK2 proteins which are inhibited by the same drugs. Representative examples of different clusters are presented. The effectiveness of the MED-SMA approach is demonstrated as it gathers binding sites of proteins with similar structure-activity relationships. Moreover, an efficient new protocol associates structures absent of cocrystallized ligands to the purine clusters enabling those structures to be associated with a specific binding mechanism. Applications of this classification by binding mode similarity include target-based drug design and prediction of cross-reactivity and therefore potential toxic side effects.
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Affiliation(s)
- Olivia Doppelt-Azeroual
- INSERM UMR-S 665, Dynamique des Structures et Interactions des Macromolécules Biologiques (DSIMB), Université Paris Diderot-Paris 7, Institut National de la Transfusion Sanguine (INTS), 6, rue Alexandre Cabanel, 75739 Paris cedex 15, France.
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31
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Human mitochondrial mTERF wraps around DNA through a left-handed superhelical tandem repeat. Nat Struct Mol Biol 2010; 17:891-3. [PMID: 20543826 DOI: 10.1038/nsmb.1859] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2010] [Accepted: 05/25/2010] [Indexed: 11/08/2022]
Abstract
The regulation of mitochondrial DNA (mtDNA) processes is slowly being characterized at a structural level. We present here crystal structures of human mitochondrial regulator mTERF, a transcription termination factor also implicated in replication pausing, in complex with double-stranded DNA oligonucleotides containing the tRNA(Leu)(UUR) gene sequence. mTERF comprises nine left-handed helical tandem repeats that form a left-handed superhelix, the Zurdo domain.
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32
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Reyes-Lamothe R, Sherratt DJ, Leake MC. Stoichiometry and architecture of active DNA replication machinery in Escherichia coli. Science 2010; 328:498-501. [PMID: 20413500 PMCID: PMC2859602 DOI: 10.1126/science.1185757] [Citation(s) in RCA: 293] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The multiprotein replisome complex that replicates DNA has been extensively characterized in vitro, but its composition and architecture in vivo is unknown. Using millisecond single-molecule fluorescence microscopy in living cells expressing fluorescent derivatives of replisome components, we have examined replisome stoichiometry and architecture. Active Escherichia coli replisomes contain three molecules of the replicative polymerase, rather than the historically accepted two. These are associated with three molecules of tau, a clamp loader component that trimerizes polymerase. Only two of the three sliding clamps are always associated with the core replisome. Single-strand binding protein has a broader spatial distribution than the core components, with 5 to 11 tetramers per replisome. This in vivo technique could provide single-molecule insight into other molecular machines.
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Affiliation(s)
| | | | - Mark C. Leake
- Department of Biochemistry, University of Oxford, UK
- Department of Physics, University of Oxford, UK
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33
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McNally R, Bowman GD, Goedken ER, O'Donnell M, Kuriyan J. Analysis of the role of PCNA-DNA contacts during clamp loading. BMC STRUCTURAL BIOLOGY 2010; 10:3. [PMID: 20113510 PMCID: PMC2824762 DOI: 10.1186/1472-6807-10-3] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Accepted: 01/30/2010] [Indexed: 11/10/2022]
Abstract
BACKGROUND Sliding clamps, such as Proliferating Cell Nuclear Antigen (PCNA) in eukaryotes, are ring-shaped protein complexes that encircle DNA and enable highly processive DNA replication by serving as docking sites for DNA polymerases. In an ATP-dependent reaction, clamp loader complexes, such as the Replication Factor-C (RFC) complex in eukaryotes, open the clamp and load it around primer-template DNA. RESULTS We built a model of RFC bound to PCNA and DNA based on existing crystal structures of clamp loaders. This model suggests that DNA would enter the clamp at an angle during clamp loading, thereby interacting with positively charged residues in the center of PCNA. We show that simultaneous mutation of Lys 20, Lys 77, Arg 80, and Arg 149, which interact with DNA in the RFC-PCNA-DNA model, compromises the ability of yeast PCNA to stimulate the DNA-dependent ATPase activity of RFC when the DNA is long enough to extend through the clamp. Fluorescence anisotropy binding experiments show that the inability of the mutant clamp proteins to stimulate RFC ATPase activity is likely caused by reduction in the affinity of the RFC-PCNA complex for DNA. We obtained several crystal forms of yeast PCNA-DNA complexes, measuring X-ray diffraction data to 3.0 A resolution for one such complex. The resulting electron density maps show that DNA is bound in a tilted orientation relative to PCNA, but makes different contacts than those implicated in clamp loading. Because of apparent partial disorder in the DNA, we restricted refinement of the DNA to a rigid body model. This result contrasts with previous analysis of a bacterial clamp bound to DNA, where the DNA was well resolved. CONCLUSION Mutational analysis of PCNA suggests that positively charged residues in the center of the clamp create a binding surface that makes contact with DNA. Disruption of this positive surface, which had not previously been implicated in clamp loading function, reduces RFC ATPase activity in the presence of DNA, most likely by reducing the affinity of RFC and PCNA for DNA. The interaction of DNA is not, however, restricted to one orientation, as indicated by analysis of the PCNA-DNA co-crystals.
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Affiliation(s)
- Randall McNally
- Department of Molecular and Cell Biology, Department of Chemistry, California Institute for Quantitative Biosciences (QB3), Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720, USA
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34
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Thompson JA, Paschall CO, O'Donnell M, Bloom LB. A slow ATP-induced conformational change limits the rate of DNA binding but not the rate of beta clamp binding by the escherichia coli gamma complex clamp loader. J Biol Chem 2009; 284:32147-57. [PMID: 19759003 DOI: 10.1074/jbc.m109.045997] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Escherichia coli, the gamma complex clamp loader loads the beta-sliding clamp onto DNA. The beta clamp tethers DNA polymerase III to DNA and enhances the efficiency of replication by increasing the processivity of DNA synthesis. In the presence of ATP, gamma complex binds beta and DNA to form a ternary complex. Binding to primed template DNA triggers gamma complex to hydrolyze ATP and release the clamp onto DNA. Here, we investigated the kinetics of forming a ternary complex by measuring rates of gamma complex binding beta and DNA. A fluorescence intensity-based beta binding assay was developed in which the fluorescence of pyrene covalently attached to beta increases when bound by gamma complex. Using this assay, an association rate constant of 2.3 x 10(7) m(-1) s(-1) for gamma complex binding beta was determined. The rate of beta binding was the same in experiments in which gamma complex was preincubated with ATP before adding beta or added directly to beta and ATP. In contrast, when gamma complex is preincubated with ATP, DNA binding is faster than when gamma complex is added to DNA and ATP at the same time. Slow DNA binding in the absence of ATP preincubation is the result of a rate-limiting ATP-induced conformational change. Our results strongly suggest that the ATP-induced conformational changes that promote beta binding and DNA binding differ. The slow ATP-induced conformational change that precedes DNA binding may provide a kinetic preference for gamma complex to bind beta before DNA during the clamp loading reaction cycle.
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Affiliation(s)
- Jennifer A Thompson
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610-0245, USA
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35
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Zhuang Z, Ai Y. Processivity factor of DNA polymerase and its expanding role in normal and translesion DNA synthesis. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1804:1081-93. [PMID: 19576301 DOI: 10.1016/j.bbapap.2009.06.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Revised: 06/16/2009] [Accepted: 06/22/2009] [Indexed: 11/30/2022]
Abstract
Clamp protein or clamp, initially identified as the processivity factor of the replicative DNA polymerase, is indispensable for the timely and faithful replication of DNA genome. Clamp encircles duplex DNA and physically interacts with DNA polymerase. Clamps from different organisms share remarkable similarities in both structure and function. Loading of clamp onto DNA requires the activity of clamp loader. Although all clamp loaders act by converting the chemical energy derived from ATP hydrolysis to mechanical force, intriguing differences exist in the mechanistic details of clamp loading. The structure and function of clamp in normal and translesion DNA synthesis has been subjected to extensive investigations. This review summarizes the current understanding of clamps from three kingdoms of life and the mechanism of loading by their cognate clamp loaders. We also discuss the recent findings on the interactions between clamp and DNA, as well as between clamp and DNA polymerase (both the replicative and specialized DNA polymerases). Lastly the role of clamp in modulating polymerase exchange is discussed in the context of translesion DNA synthesis.
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Affiliation(s)
- Zhihao Zhuang
- Department of Chemistry and Biochemistry, 214A Drake Hall, University of Delaware, Newark, DE, 19716, USA.
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36
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Simonetta KR, Kazmirski SL, Goedken ER, Cantor AJ, Kelch BA, McNally R, Seyedin SN, Makino DL, O'Donnell M, Kuriyan J. The mechanism of ATP-dependent primer-template recognition by a clamp loader complex. Cell 2009; 137:659-71. [PMID: 19450514 DOI: 10.1016/j.cell.2009.03.044] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2008] [Revised: 01/22/2009] [Accepted: 03/25/2009] [Indexed: 10/20/2022]
Abstract
Clamp loaders load sliding clamps onto primer-template DNA. The structure of the E. coli clamp loader bound to DNA reveals the formation of an ATP-dependent spiral of ATPase domains that tracks only the template strand, allowing recognition of both RNA and DNA primers. Unlike hexameric helicases, in which DNA translocation requires distinct conformations of the ATPase domains, the clamp loader spiral is symmetric and is set up to trigger release upon DNA recognition. Specificity for primed DNA arises from blockage of the end of the primer and accommodation of the emerging template along a surface groove. A related structure reveals how the psi protein, essential for coupling the clamp loader to single-stranded DNA-binding protein (SSB), binds to the clamp loader. By stabilizing a conformation of the clamp loader that is consistent with the ATPase spiral observed upon DNA binding, psi binding promotes the clamp-loading activity of the complex.
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Affiliation(s)
- Kyle R Simonetta
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720, USA
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37
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Meyer PA, Ye P, Suh MH, Zhang M, Fu J. Structure of the 12-subunit RNA polymerase II refined with the aid of anomalous diffraction data. J Biol Chem 2009; 284:12933-9. [PMID: 19289466 DOI: 10.1074/jbc.m809199200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RNA polymerase II (Pol II) is the central enzyme of eukaryotic gene expression machinery. Complete definition of the three-dimensional structure of Pol II is essential for understanding the mechanisms that regulate transcription via protein-protein interactions within the Pol II apparatus. To date a series of Pol II-related crystal structures have been reported. However, certain peptide regions, including several that are implicated to interact with regulatory factors, remain obscure. Here we describe conformations for two such regions that are close to the Pol II surface and assume seemingly flexible loop structures. One is located in the TFIIF-interacting Protrusion domain, whereas the other is in the TFIIE-interacting Clamp domain. This structural definition was aided by the application of an advanced crystallographic refinement approach that utilizes the single anomalous diffraction (SAD) from zinc ions bound intrinsically in Pol II. The SAD-based strategy allowed the 12-subunit Pol II model to be fully refined up to 3.8 A with excellent stereochemical properties, demonstrating the effectiveness of the SAD approach for the refinement of large structures at low-to-moderate resolutions. Our results also define additional components of the free Pol II, including the functionally critical Fork Loop-1 and Fork Loop-2 elements. As such, this refined Pol II model provides the most complete structural reference for future analyses of complex structures formed between Pol II and its regulatory factors.
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Affiliation(s)
- Peter A Meyer
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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38
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Bloom LB. Loading clamps for DNA replication and repair. DNA Repair (Amst) 2009; 8:570-8. [PMID: 19213612 DOI: 10.1016/j.dnarep.2008.12.014] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Accepted: 12/19/2008] [Indexed: 01/25/2023]
Abstract
Sliding clamps and clamp loaders were initially identified as DNA polymerase processivity factors. Sliding clamps are ring-shaped protein complexes that encircle and slide along duplex DNA, and clamp loaders are enzymes that load these clamps onto DNA. When bound to a sliding clamp, DNA polymerases remain tightly associated with the template being copied, but are able to translocate along DNA at rates limited by rates of nucleotide incorporation. Many different enzymes required for DNA replication and repair use sliding clamps. Clamps not only increase the processivity of these enzymes, but may also serve as an attachment point to coordinate the activities of enzymes required for a given process. Clamp loaders are members of the AAA+ family of ATPases and use energy from ATP binding and hydrolysis to catalyze the mechanical reaction of loading clamps onto DNA. Many structural and functional features of clamps and clamp loaders are conserved across all domains of life. Here, the mechanism of clamp loading is reviewed by comparing features of prokaryotic and eukaryotic clamps and clamp loaders.
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Affiliation(s)
- Linda B Bloom
- Department of Biochemistry & Molecular Biology, University of Florida, Gainesville, FL 32610-0245, United States.
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39
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You CC, Agasti S, Rotello V. Isomeric Control of Protein Recognition with Amino Acid- and Dipeptide-Functionalized Gold Nanoparticles. Chemistry 2007; 14:143-50. [DOI: 10.1002/chem.200701234] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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40
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Neuwald AF. The CHAIN program: forging evolutionary links to underlying mechanisms. Trends Biochem Sci 2007; 32:487-93. [PMID: 17962021 DOI: 10.1016/j.tibs.2007.08.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Revised: 08/13/2007] [Accepted: 08/17/2007] [Indexed: 11/25/2022]
Abstract
Proteins evolve new functions by modifying and extending the molecular machinery of an ancestral protein. Such changes show up as divergent sequence patterns, which are conserved in descendent proteins that maintain the divergent function. After multiply-aligning a set of input sequences, the CHAIN program partitions the sequences into two functionally divergent groups and then outputs an alignment that is annotated to reveal the selective pressures imposed on divergent residue positions. If atomic coordinates are also provided, hydrogen bonds and other atomic interactions associated with various categories of divergent residues are graphically displayed. Such analyses establish links between protein evolutionary divergence and functionally crucial atomic features and, as a result, can suggest plausible molecular mechanisms for experimental testing. This is illustrated here by its application to bacterial clamp-loader ATPases.
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Affiliation(s)
- Andrew F Neuwald
- The J. Craig Venter Institute, 9704 Medical Center Drive, Rockville, MD 20850, USA.
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41
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Su XC, Jergic S, Keniry MA, Dixon NE, Otting G. Solution structure of Domains IVa and V of the tau subunit of Escherichia coli DNA polymerase III and interaction with the alpha subunit. Nucleic Acids Res 2007; 35:2825-32. [PMID: 17452361 PMCID: PMC1888800 DOI: 10.1093/nar/gkm080] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The solution structure of the C-terminal Domain V of the τ subunit of E. coli DNA polymerase III was determined by nuclear magnetic resonance (NMR) spectroscopy. The fold is unique to τ subunits. Amino acid sequence conservation is pronounced for hydrophobic residues that form the structural core of the protein, indicating that the fold is representative for τ subunits from a wide range of different bacteria. The interaction between the polymerase subunits τ and α was studied by NMR experiments where α was incubated with full-length C-terminal domain (τC16), and domains shortened at the C-terminus by 11 and 18 residues, respectively. The only interacting residues were found in the C-terminal 30-residue segment of τ, most of which is structurally disordered in free τC16. Since the N- and C-termini of the structured core of τC16 are located close to each other, this limits the possible distance between α and the pentameric δτ2γδ′ clamp–loader complex and, hence, between the two α subunits involved in leading- and lagging-strand DNA synthesis. Analysis of an N-terminally extended construct (τC22) showed that τC14 presents the only part of Domains IVa and V of τ which comprises a globular fold in the absence of other interaction partners.
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Affiliation(s)
| | | | | | | | - Gottfried Otting
- *To whom correspondence should be addressed. +61-2-61256507+61-2-61250750
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42
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Anderson SG, Williams CR, O'donnell M, Bloom LB. A function for the psi subunit in loading the Escherichia coli DNA polymerase sliding clamp. J Biol Chem 2007; 282:7035-45. [PMID: 17210572 DOI: 10.1074/jbc.m610136200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Crystal structures of an Escherichia coli clamp loader have provided insight into the mechanism by which this molecular machine assembles ring-shaped sliding clamps onto DNA. The contributions made to the clamp loading reaction by two subunits, chi and psi, which are not present in the crystal structures, were determined by measuring the activities of three forms of the clamp loader, gamma(3)deltadelta', gamma(3)deltadelta'psi, and gamma(3)deltadelta'psichi. The psi subunit is important for stabilizing an ATP-induced conformational state with high affinity for DNA, whereas the chi subunit does not contribute directly to clamp loading in our assays lacking single-stranded DNA-binding protein. The psi subunit also increases the affinity of the clamp loader for the clamp in assays in which ATPgammaS is substituted for ATP. Interestingly, the affinity of the gamma(3)deltadelta' complex for beta is no greater in the presence than in the absence of ATPgammaS. A role for psi in stabilizing or promoting ATP- and ATPgammaS-induced conformational changes may explain why large conformational differences were not seen in gamma(3)deltadelta' structures with and without bound ATPgammaS. The beta clamp partially compensates for the activity of psi when this subunit is not present and possibly serves as a scaffold on which the clamp loader adopts the appropriate conformation for DNA binding and clamp loading. Results from our work and others suggest that the psi subunit may introduce a temporal order to the clamp loading reaction in which clamp binding precedes DNA binding.
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Affiliation(s)
- Stephen G Anderson
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610-0245, USA
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43
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Neuwald AF. Hypothesis: bacterial clamp loader ATPase activation through DNA-dependent repositioning of the catalytic base and of a trans-acting catalytic threonine. Nucleic Acids Res 2006; 34:5280-90. [PMID: 17012286 PMCID: PMC1636414 DOI: 10.1093/nar/gkl519] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The prokaryotic DNA polymerase III clamp loader complex loads the β clamp onto DNA to link the replication complex to DNA during processive synthesis and unloads it again once synthesis is complete. This minimal complex consists of one δ, one δ′ and three γ subunits, all of which possess an AAA+ module—though only the γ subunit exhibits ATPase activity. Here clues to underlying clamp loader mechanisms are obtained through Bayesian inference of various categories of selective constraints imposed on the γ and δ′ subunits. It is proposed that a conserved histidine is ionized via electron transfer involving structurally adjacent residues within the sensor 1 region of γ's AAA+ module. The resultant positive charge on this histidine inhibits ATPase activity by drawing the negatively charged catalytic base away from the active site. It is also proposed that this arrangement is disrupted upon interaction of DNA with basic residues in γ implicated previously in DNA binding, regarding which a lysine that is near the sensor 1 region and that is highly conserved both in bacterial and in eukaryotic clamp loader ATPases appears to play a critical role. γ ATPases also appear to utilize a trans-acting threonine that is donated by helix 6 of an adjacent γ or δ′ subunit and that assists in the activation of a water molecule for nucleophilic attack on the γ phosphorous atom of ATP. As eukaryotic and archaeal clamp loaders lack most of these key residues, it appears that eubacteria utilize a fundamentally different mechanism for clamp loader activation than do these other organisms.
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Affiliation(s)
- Andrew F Neuwald
- Cold Spring Harbor Laboratory, 1 Bungtown Road PO Box 100, Cold Spring Harbor, NY 11724, USA
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44
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Johnson A, Yao NY, Bowman GD, Kuriyan J, O'Donnell M. The replication factor C clamp loader requires arginine finger sensors to drive DNA binding and proliferating cell nuclear antigen loading. J Biol Chem 2006; 281:35531-43. [PMID: 16980295 DOI: 10.1074/jbc.m606090200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Replication factor C (RFC) is an AAA+ heteropentamer that couples the energy of ATP binding and hydrolysis to the loading of the DNA polymerase processivity clamp, proliferating cell nuclear antigen (PCNA), onto DNA. RFC consists of five subunits in a spiral arrangement (RFC-A, -B, -C, -D, and -E, corresponding to subunits RFC1, RFC4, RFC3, RFC2, and RFC5, respectively). The RFC subunits are AAA+ family proteins and the complex contains four ATP sites (sites A, B, C, and D) located at subunit interfaces. In each ATP site, an arginine residue from one subunit is located near the gamma-phosphate of ATP bound in the adjacent subunit. These arginines act as "arginine fingers" that can potentially perform two functions: sensing that ATP is bound and catalyzing ATP hydrolysis. In this study, the arginine fingers in RFC were mutated to examine the steps in the PCNA loading mechanism that occur after RFC binds ATP. This report finds that the ATP sites of RFC function in distinct steps during loading of PCNA onto DNA. ATP binding to RFC powers recruitment and opening of PCNA and activates a gamma-phosphate sensor in ATP site C that promotes DNA association. ATP hydrolysis in site D is uniquely stimulated by PCNA, and we propose that this event is coupled to PCNA closure around DNA, which starts an ordered hydrolysis around the ring. PCNA closure severs contact to RFC subunits D and E (RFC2 and RFC5), and the gamma-phosphate sensor of ATP site C is switched off, resulting in low affinity of RFC for DNA and ejection of RFC from the site of PCNA loading.
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Affiliation(s)
- Aaron Johnson
- Laboratory of DNA Replication, Howard Hughes Medical Institute and Rockefeller University, New York, New York 10021, USA
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45
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Joly N, Schumacher J, Buck M. Heterogeneous nucleotide occupancy stimulates functionality of phage shock protein F, an AAA+ transcriptional activator. J Biol Chem 2006; 281:34997-5007. [PMID: 16973614 DOI: 10.1074/jbc.m606628200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The catalytic AAA+ domain (PspF1-275) of an enhancer-binding protein is necessary and sufficient to contact sigma54-RNA polymerase holoenzyme (Esigma54), remodel it, and in so doing catalyze open promoter complex formation. Whether ATP binding and hydrolysis is coordinated between subunits of PspF and the precise nature of the nucleotide(s) bound to the oligomeric forms responsible for substrate remodeling are unknown. We demonstrate that ADP stimulates the intrinsic ATPase activity of PspF1-275 and propose that this heterogeneous nucleotide occupancy in a PspF1-275 hexamer is functionally important for specific activity. Binding of ADP and ATP triggers the formation of functional PspF1-275 hexamers as shown by a gain of specific activity. Furthermore, ATP concentrations congruent with stoichiometric ATP binding to PspF1-275 inhibit ATP hydrolysis and Esigma54-promoter open complex formation. Demonstration of a heterogeneous nucleotide-bound state of a functional PspF1-275.Esigma54 complex provides clear biochemical evidence for heterogeneous nucleotide occupancy in this AAA+ protein. Based on our data, we propose a stochastic nucleotide binding and a coordinated hydrolysis mechanism in PspF1-275 hexamers.
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Affiliation(s)
- Nicolas Joly
- Division of Biology, Sir Alexander Fleming Building, Imperial College London, London SW7 2AZ, United Kingdom
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46
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Indiani C, O'Donnell M. The replication clamp-loading machine at work in the three domains of life. Nat Rev Mol Cell Biol 2006; 7:751-61. [PMID: 16955075 DOI: 10.1038/nrm2022] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Sliding clamps are ring-shaped proteins that tether DNA polymerases to DNA, which enables the rapid and processive synthesis of both leading and lagging strands at the replication fork. The clamp-loading machinery must repeatedly load sliding-clamp factors onto primed sites at the replication fork. Recent structural and biochemical analyses provide unique insights into how these clamp-loading ATPase machines function to load clamps onto the DNA. Moreover, these studies highlight the evolutionary conservation of the clamp-loading process in the three domains of life.
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Affiliation(s)
- Chiara Indiani
- Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, New York 10021, USA
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47
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Abstract
Sliding clamps and clamp loaders are processivity factors required for efficient DNA replication. Sliding clamps are ring-shaped complexes that tether DNA polymerases to DNA to increase the processivity of synthesis. Clamp loaders assemble these ring-shaped clamps onto DNA in an ATP-dependent reaction. The overall process of clamp loading is dynamic in that protein-protein and protein-DNA interactions must actively change in a coordinated fashion to complete the mechanical clamp-loading reaction cycle. The clamp loader must initially have a high affinity for both the clamp and DNA to bring these macromolecules together, but then must release the clamp on DNA for synthesis to begin. Evidence is presented for a mechanism in which the clamp-loading reaction comprises a series of binding reactions to ATP, the clamp, DNA, and ADP, each of which promotes some change in the conformation of the clamp loader that alters interactions with the next component of the pathway. These changes in interactions must be rapid enough to allow the clamp loader to keep pace with replication fork movement. This review focuses on the measurement of dynamic and transient interactions required to assemble the Escherichia coli sliding clamp on DNA.
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Affiliation(s)
- Linda B Bloom
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610-0245, USA.
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48
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Yao NY, Johnson A, Bowman GD, Kuriyan J, O'Donnell M. Mechanism of proliferating cell nuclear antigen clamp opening by replication factor C. J Biol Chem 2006; 281:17528-17539. [PMID: 16608854 DOI: 10.1074/jbc.m601273200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The eukaryotic replication factor C (RFC) clamp loader is an AAA+ spiral-shaped heteropentamer that opens and closes the circular proliferating cell nuclear antigen (PCNA) clamp processivity factor on DNA. In this study, we examined the roles of individual RFC subunits in opening the PCNA clamp. Interestingly, Rfc1, which occupies the position analogous to the delta clamp-opening subunit in the Escherichia coli clamp loader, is not required to open PCNA. The Rfc5 subunit is required to open PCNA. Consistent with this result, Rfc2.3.4.5 and Rfc2.5 subassemblies are capable of opening and unloading PCNA from circular DNA. Rfc5 is positioned opposite the PCNA interface from Rfc1, and therefore, its action with Rfc2 in opening PCNA indicates that PCNA is opened from the opposite side of the interface that the E. coli delta wrench acts upon. This marks a significant departure in the mechanism of eukaryotic and prokaryotic clamp loaders. Interestingly, the Rad.RFC DNA damage checkpoint clamp loader unloads PCNA clamps from DNA. We propose that Rad.RFC may clear PCNA from DNA to facilitate shutdown of replication in the face of DNA damage.
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Affiliation(s)
- Nina Y Yao
- Rockefeller University, New York, New York 10021
| | | | - Greg D Bowman
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - John Kuriyan
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720; Howard Hughes Medical Institute, New York, New York 10021; Departments of Molecular and Cell Biology and Chemistry, Howard Hughes Medical Institute, University of California, Berkeley, California 94720
| | - Mike O'Donnell
- Rockefeller University, New York, New York 10021; Howard Hughes Medical Institute, New York, New York 10021.
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Kazmirski SL, Zhao Y, Bowman GD, O'donnell M, Kuriyan J. Out-of-plane motions in open sliding clamps: molecular dynamics simulations of eukaryotic and archaeal proliferating cell nuclear antigen. Proc Natl Acad Sci U S A 2005; 102:13801-6. [PMID: 16169903 PMCID: PMC1215310 DOI: 10.1073/pnas.0506430102] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sliding clamps are ring-like multimeric proteins that encircle duplex DNA and serve as mobile DNA-bound platforms that are essential for efficient DNA replication and repair. Sliding clamps are placed on DNA by clamp loader complexes, in which the clamp-interacting elements are organized in a right-handed spiral assembly. To understand how the flat, ring-like clamps might interact with the spiral interaction surface of the clamp loader complex, we have performed molecular dynamics simulations of sliding clamps (proliferating cell nuclear antigen from the budding yeast, humans, and an archaeal species) in which we have removed one of the three subunits so as to release the constraint of ring closure. The simulations reveal significant structural fluctuations corresponding to lateral opening and out-of-plane distortions of the clamp, which result principally from bending and twisting of the beta-sheets that span the intermolecular interfaces, with smaller but similar contributions from beta-sheets that span the intramolecular interfaces within each subunit. With the integrity of these beta-sheets intact, the predominant fluctuations seen in the simulations are oscillations between lateral openings and right-handed spirals. The tendency for clamps to adopt a right-handed spiral conformation implies that once opened, the conformation of the clamp can easily match the spiraling of clamp loader subunits, a feature that is intrinsic to the recognition of DNA and subsequent hydrolysis of ATP by the clamp-bound clamp loader complex.
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Affiliation(s)
- Steven L Kazmirski
- Department of Molecular and Cell Biology , Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA
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Miyata T, Suzuki H, Oyama T, Mayanagi K, Ishino Y, Morikawa K. Open clamp structure in the clamp-loading complex visualized by electron microscopic image analysis. Proc Natl Acad Sci U S A 2005; 102:13795-800. [PMID: 16169902 PMCID: PMC1236569 DOI: 10.1073/pnas.0506447102] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ring-shaped sliding clamps and clamp loader ATPases are essential factors for rapid and accurate DNA replication. The clamp ring is opened and resealed at the primer-template junctions by the ATP-fueled clamp loader function. The processivity of the DNA polymerase is conferred by its attachment to the clamp loaded onto the DNA. In eukarya and archaea, the replication factor C (RFC) and the proliferating cell nuclear antigen (PCNA) play crucial roles as the clamp loader and the clamp, respectively. Here, we report the electron microscopic structure of an archaeal RFC-PCNA-DNA complex at 12-A resolution. This complex exhibits excellent fitting of each atomic structure of RFC, PCNA, and the primed DNA. The PCNA ring retains an open conformation by extensive interactions with RFC, with a distorted spring washer-like conformation. The complex appears to represent the intermediate, where the PCNA ring is kept open before ATP hydrolysis by RFC.
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Affiliation(s)
- Tomoko Miyata
- Department of Structural Biology, Biomolecular Engineering Research Institute, 6-2-3 Furuedai, Suita, Osaka 565-0874, Japan
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