1
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Ma J, Yi G, Ye M, MacGregor-Chatwin C, Sheng Y, Lu Y, Li M, Li Q, Wang D, Gilbert RJC, Zhang P. Open architecture of archaea MCM and dsDNA complexes resolved using monodispersed streptavidin affinity CryoEM. Nat Commun 2024; 15:10304. [PMID: 39604363 PMCID: PMC11603195 DOI: 10.1038/s41467-024-53745-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: 01/20/2024] [Accepted: 10/18/2024] [Indexed: 11/29/2024] Open
Abstract
The cryo-electron microscopy (cryoEM) method has enabled high-resolution structure determination of numerous biomolecules and complexes. Nevertheless, cryoEM sample preparation of challenging proteins and complexes, especially those with low abundance or with preferential orientation, remains a major hurdle. We developed an affinity-grid method employing monodispersed single particle streptavidin on a lipid monolayer to enhance particle absorption on the grid surface and alleviate sample exposure to the air-water interface. Using this approach, we successfully enriched the Thermococcus kodakarensis mini-chromosome maintenance complex 3 (MCM3) on cryoEM grids through biotinylation and resolved its structure. We further utilized this affinity method to tether the biotin-tagged dsDNA to selectively enrich a stable MCM3-ATP-dsDNA complex for cryoEM structure determination. Intriguingly, both MCM3 apo and dsDNA bound structures exhibit left-handed open spiral conformations, distinct from other reported MCM structures. The large open gate is sufficient to accommodate a dsDNA which could potentially be melted. The value of mspSA affinity method was further demonstrated by mitigating the issue of preferential angular distribution of HIV-1 capsid protein hexamer and RNA polymerase II elongation complex from Saccharomyces cerevisiae.
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Affiliation(s)
- Jianbing Ma
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
- CAS Key Laboratory of Infection and Immunity, National Laboratory of Macromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Gangshun Yi
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
- Calleva Research Centre for Evolution and Human Sciences, Magdalen College, University of Oxford, Oxford, UK
| | - Mingda Ye
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | | | - Yuewen Sheng
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
| | - Ying Lu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Ming Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Qingrong Li
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
| | - Dong Wang
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
| | - Robert J C Gilbert
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
- Calleva Research Centre for Evolution and Human Sciences, Magdalen College, University of Oxford, Oxford, UK
| | - Peijun Zhang
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK.
- Chinese Academy of Medical Sciences Oxford Institute, University of Oxford, Oxford, UK.
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2
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Two Distinct Modes of DNA Binding by an MCM Helicase Enable DNA Translocation. Int J Mol Sci 2022; 23:ijms232314678. [PMID: 36499022 PMCID: PMC9735655 DOI: 10.3390/ijms232314678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 11/11/2022] [Accepted: 11/16/2022] [Indexed: 11/26/2022] Open
Abstract
A six-subunit ATPase ring forms the central hub of the replication forks in all domains of life. This ring performs a helicase function to separate the two complementary DNA strands to be replicated and drives the replication machinery along the DNA. Disruption of this helicase/ATPase ring is associated with genetic instability and diseases such as cancer. The helicase/ATPase rings of eukaryotes and archaea consist of six minichromosome maintenance (MCM) proteins. Prior structural studies have shown that MCM rings bind one encircled strand of DNA in a spiral staircase, suggesting that the ring pulls this strand of DNA through its central pore in a hand-over-hand mechanism where the subunit at the bottom of the staircase dissociates from DNA and re-binds DNA one step above the staircase. With high-resolution cryo-EM, we show that the MCM ring of the archaeal organism Saccharolobus solfataricus binds an encircled DNA strand in two different modes with different numbers of subunits engaged to DNA, illustrating a plausible mechanism for the alternating steps of DNA dissociation and re-association that occur during DNA translocation.
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3
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Mohammed Khalid AA, Parisse P, Medagli B, Onesti S, Casalis L. Atomic Force Microscopy Investigation of the Interactions between the MCM Helicase and DNA. MATERIALS 2021; 14:ma14030687. [PMID: 33540751 PMCID: PMC7867263 DOI: 10.3390/ma14030687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/21/2021] [Accepted: 01/26/2021] [Indexed: 11/16/2022]
Abstract
The MCM (minichromosome maintenance) protein complex forms an hexameric ring and has a key role in the replication machinery of Eukaryotes and Archaea, where it functions as the replicative helicase opening up the DNA double helix ahead of the polymerases. Here, we present a study of the interaction between DNA and the archaeal MCM complex from Methanothermobacter thermautotrophicus by means of atomic force microscopy (AFM) single molecule imaging. We first optimized the protocol (surface treatment and buffer conditions) to obtain AFM images of surface-equilibrated DNA molecules before and after the interaction with the protein complex. We discriminated between two modes of interaction, one in which the protein induces a sharp bend in the DNA, and one where there is no bending. We found that the presence of the MCM complex also affects the DNA contour length. A possible interpretation of the observed behavior is that in one case the hexameric ring encircles the dsDNA, while in the other the nucleic acid wraps on the outside of the ring, undergoing a change of direction. We confirmed this topographical assignment by testing two mutants, one affecting the N-terminal β-hairpins projecting towards the central channel, and thus preventing DNA loading, the other lacking an external subdomain and thus preventing wrapping. The statistical analysis of the distribution of the protein complexes between the two modes, together with the dissection of the changes of DNA contour length and binding angle upon interaction, for the wild type and the two mutants, is consistent with the hypothesis. We discuss the results in view of the various modes of nucleic acid interactions that have been proposed for both archaeal and eukaryotic MCM complexes.
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Affiliation(s)
- Amna Abdalla Mohammed Khalid
- Elettra-Sincrotrone Trieste, 34149 Trieste, Italy; (A.A.M.K.); (B.M.)
- Department of Physics, PhD School in Nanotechnology, University of Trieste, 34127 Trieste, Italy
| | - Pietro Parisse
- Elettra-Sincrotrone Trieste, 34149 Trieste, Italy; (A.A.M.K.); (B.M.)
- Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche (IOM-CNR), 34149 Trieste, Italy
- Correspondence: (P.P.); (S.O.); (L.C.)
| | - Barbara Medagli
- Elettra-Sincrotrone Trieste, 34149 Trieste, Italy; (A.A.M.K.); (B.M.)
- Department of Chemical and Pharmaceutical Sciences, University of Trieste, 34127 Trieste, Italy
| | - Silvia Onesti
- Elettra-Sincrotrone Trieste, 34149 Trieste, Italy; (A.A.M.K.); (B.M.)
- Correspondence: (P.P.); (S.O.); (L.C.)
| | - Loredana Casalis
- Elettra-Sincrotrone Trieste, 34149 Trieste, Italy; (A.A.M.K.); (B.M.)
- Correspondence: (P.P.); (S.O.); (L.C.)
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4
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Anatomy of a twin DNA replication factory. Biochem Soc Trans 2020; 48:2769-2778. [PMID: 33300972 PMCID: PMC7752080 DOI: 10.1042/bst20200640] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 11/13/2020] [Accepted: 11/17/2020] [Indexed: 11/30/2022]
Abstract
The replication of DNA in chromosomes is initiated at sequences called origins at which two replisome machines are assembled at replication forks that move in opposite directions. Interestingly, in vivo studies observe that the two replication forks remain fastened together, often referred to as a replication factory. Replication factories containing two replisomes are well documented in cellular studies of bacteria (Escherichia coli and Bacillus subtilis) and the eukaryote, Saccharomyces cerevisiae. This basic twin replisome factory architecture may also be preserved in higher eukaryotes. Despite many years of documenting the existence of replication factories, the molecular details of how the two replisome machines are tethered together has been completely unknown in any organism. Recent structural studies shed new light on the architecture of a eukaryote replisome factory, which brings with it a new twist on how a replication factory may function.
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5
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Abstract
It is now well recognized that the information processing machineries of archaea are far more closely related to those of eukaryotes than to those of their prokaryotic cousins, the bacteria. Extensive studies have been performed on the structure and function of the archaeal DNA replication origins, the proteins that define them, and the macromolecular assemblies that drive DNA unwinding and nascent strand synthesis. The results from various archaeal organisms across the archaeal domain of life show surprising levels of diversity at many levels-ranging from cell cycle organization to chromosome ploidy to replication mode and nature of the replicative polymerases. In the following, we describe recent advances in the field, highlighting conserved features and lineage-specific innovations.
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Affiliation(s)
- Mark D Greci
- Department of Biology, Indiana University, Bloomington, Indiana 47405, USA;
| | - Stephen D Bell
- Department of Biology, Indiana University, Bloomington, Indiana 47405, USA; .,Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, USA
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6
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Yuan Z, Georgescu R, Bai L, Zhang D, Li H, O'Donnell ME. DNA unwinding mechanism of a eukaryotic replicative CMG helicase. Nat Commun 2020; 11:688. [PMID: 32019936 PMCID: PMC7000775 DOI: 10.1038/s41467-020-14577-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 01/17/2020] [Indexed: 11/09/2022] Open
Abstract
High-resolution structures have not been reported for replicative helicases at a replication fork at atomic resolution, a prerequisite to understanding the unwinding mechanism. The eukaryotic replicative CMG (Cdc45, Mcm2-7, GINS) helicase contains a Mcm2-7 motor ring, with the N-tier ring in front and the C-tier motor ring behind. The N-tier ring is structurally divided into a zinc finger (ZF) sub-ring followed by the oligosaccharide/oligonucleotide-binding (OB) fold ring. Here we report the cryo-EM structure of CMG on forked DNA at 3.9 Å, revealing that parental DNA enters the ZF sub-ring and strand separation occurs at the bottom of the ZF sub-ring, where the lagging strand is blocked and diverted sideways by OB hairpin-loops of Mcm3, Mcm4, Mcm6, and Mcm7. Thus, instead of employing a specific steric exclusion process, or even a separation pin, unwinding is achieved via a "dam-and-diversion tunnel" mechanism that does not require specific protein-DNA interaction. The C-tier motor ring contains spirally configured PS1 and H2I loops of Mcms 2, 3, 5, 6 that translocate on the spirally-configured leading strand, and thereby pull the preceding DNA segment through the diversion tunnel for strand separation.
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Affiliation(s)
- Zuanning Yuan
- Structural Biology Program, Van Andel Institute, Grand Rapids, MI, USA
| | - Roxana Georgescu
- Howard Hughes Medical Institute, Chevy Chase, MD, USA.,DNA Replication Laboratory, The Rockefeller University, New York, NY, USA
| | - Lin Bai
- Structural Biology Program, Van Andel Institute, Grand Rapids, MI, USA
| | - Dan Zhang
- DNA Replication Laboratory, The Rockefeller University, New York, NY, USA
| | - Huilin Li
- Structural Biology Program, Van Andel Institute, Grand Rapids, MI, USA.
| | - Michael E O'Donnell
- Howard Hughes Medical Institute, Chevy Chase, MD, USA. .,DNA Replication Laboratory, The Rockefeller University, New York, NY, USA.
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7
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Mohapatra S, Lin CT, Feng XA, Basu A, Ha T. Single-Molecule Analysis and Engineering of DNA Motors. Chem Rev 2019; 120:36-78. [DOI: 10.1021/acs.chemrev.9b00361] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
| | | | | | | | - Taekjip Ha
- Howard Hughes Medical Institute, Baltimore, Maryland 21205, United States
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8
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Perera HM, Trakselis MA. Amidst multiple binding orientations on fork DNA, Saccharolobus MCM helicase proceeds N-first for unwinding. eLife 2019; 8:46096. [PMID: 31661075 PMCID: PMC6831031 DOI: 10.7554/elife.46096] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 10/23/2019] [Indexed: 11/13/2022] Open
Abstract
DNA replication requires that the duplex genomic DNA strands be separated; a function that is implemented by ring-shaped hexameric helicases in all Domains. Helicases are composed of two domains, an N- terminal DNA binding domain (NTD) and a C- terminal motor domain (CTD). Replication is controlled by loading of helicases at origins of replication, activation to preferentially encircle one strand, and then translocation to begin separation of the two strands. Using a combination of site-specific DNA footprinting, single-turnover unwinding assays, and unique fluorescence translocation monitoring, we have been able to quantify the binding distribution and the translocation orientation of Saccharolobus (formally Sulfolobus) solfataricus MCM on DNA. Our results show that both the DNA substrate and the C-terminal winged-helix (WH) domain influence the orientation but that translocation on DNA proceeds N-first.
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Affiliation(s)
- Himasha M Perera
- Department of Chemistry and Biochemistry, Baylor University, Waco, United States
| | - Michael A Trakselis
- Department of Chemistry and Biochemistry, Baylor University, Waco, United States
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9
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Champasa K, Blank C, Friedman LJ, Gelles J, Bell SP. A conserved Mcm4 motif is required for Mcm2-7 double-hexamer formation and origin DNA unwinding. eLife 2019; 8:45538. [PMID: 31385807 PMCID: PMC6701924 DOI: 10.7554/elife.45538] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 08/05/2019] [Indexed: 11/13/2022] Open
Abstract
Licensing of eukaryotic origins of replication requires DNA loading of two copies of the Mcm2-7 replicative helicase to form a head-to-head double-hexamer, ensuring activated helicases depart the origin bidirectionally. To understand the formation and importance of this double-hexamer, we identified mutations in a conserved and essential Mcm4 motif that permit loading of two Mcm2-7 complexes but are defective for double-hexamer formation. Single-molecule studies show mutant Mcm2-7 forms initial hexamer-hexamer interactions; however, the resulting complex is unstable. Kinetic analyses of wild-type and mutant Mcm2-7 reveal a limited time window for double-hexamer formation following second Mcm2-7 association, suggesting that this process is facilitated. Double-hexamer formation is required for extensive origin DNA unwinding but not initial DNA melting or recruitment of helicase-activation proteins (Cdc45, GINS, Mcm10). Our findings elucidate dynamic mechanisms of origin licensing, and identify the transition between initial DNA melting and extensive unwinding as the first initiation event requiring double-hexamer formation.
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Affiliation(s)
- Kanokwan Champasa
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
| | - Caitlin Blank
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States.,Microbiology Graduate Program, Massachusetts Institute of Technology, Cambridge, United States
| | - Larry J Friedman
- Department of Biochemistry, Brandeis University, Waltham, United States
| | - Jeff Gelles
- Department of Biochemistry, Brandeis University, Waltham, United States
| | - Stephen P Bell
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
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10
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Li H, O'Donnell ME. The Eukaryotic CMG Helicase at the Replication Fork: Emerging Architecture Reveals an Unexpected Mechanism. Bioessays 2018; 40. [PMID: 29405332 DOI: 10.1002/bies.201700208] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 12/27/2017] [Indexed: 01/12/2023]
Abstract
The eukaryotic helicase is an 11-subunit machine containing an Mcm2-7 motor ring that encircles DNA, Cdc45 and the GINS tetramer, referred to as CMG (Cdc45, Mcm2-7, GINS). CMG is "built" on DNA at origins in two steps. First, two Mcm2-7 rings are assembled around duplex DNA at origins in G1 phase, forming the Mcm2-7 "double hexamer." In a second step, in S phase Cdc45 and GINS are assembled onto each Mcm2-7 ring, hence producing two CMGs that ultimately form two replication forks that travel in opposite directions. Here, we review recent findings about CMG structure and function. The CMG unwinds the parental duplex and is also the organizing center of the replisome: it binds DNA polymerases and other factors. EM studies reveal a 20-subunit core replisome with the leading Pol ϵ and lagging Pol α-primase on opposite faces of CMG, forming a fundamentally asymmetric architecture. Structural studies of CMG at a replication fork reveal unexpected details of how CMG engages the DNA fork. The structures of CMG and the Mcm2-7 double hexamer on DNA suggest a completely unanticipated process for formation of bidirectional replication forks at origins.
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Affiliation(s)
- Huilin Li
- Cryo-EM Structural Biology Laboratory, Van Andel Research Institute, Grand Rapids, MI 49503, USA
| | - Michael E O'Donnell
- Department of DNA Replication, Rockefeller University and HHMI, New York, NY 10065, USA
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11
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The ring-shaped hexameric helicases that function at DNA replication forks. Nat Struct Mol Biol 2018; 25:122-130. [PMID: 29379175 DOI: 10.1038/s41594-018-0024-x] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 11/27/2017] [Indexed: 11/08/2022]
Abstract
DNA replication requires separation of genomic duplex DNA strands, an operation that is performed by a hexameric ring-shaped helicase in all domains of life. The structures and chemomechanical actions of these fascinating machines are coming into sharper focus. Although there is no evolutionary relationship between the hexameric helicases of bacteria and those of archaea and eukaryotes, they share many fundamental features. Here we review recent studies of these two groups of hexameric helicases and the unexpected distinctions they have also unveiled.
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12
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Miller JM, Chaudhary H, Marsee JD. Phylogenetic analysis predicts structural divergence for proteobacterial ClpC proteins. J Struct Biol 2017; 201:52-62. [PMID: 29129755 DOI: 10.1016/j.jsb.2017.11.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 11/06/2017] [Accepted: 11/08/2017] [Indexed: 12/29/2022]
Abstract
Regulated proteolysis is required in all organisms for the removal of misfolded or degradation-tagged protein substrates in cellular quality control pathways. The molecular machines that catalyze this process are known as ATP-dependent proteases with examples that include ClpAP and ClpCP. Clp/Hsp100 subunits form ring-structures that couple the energy of ATP binding and hydrolysis to protein unfolding and subsequent translocation of denatured protein into the compartmentalized ClpP protease for degradation. Copies of the clpA, clpC, clpE, clpK, and clpL genes are present in all characterized bacteria and their gene products are highly conserved in structure and function. However, the evolutionary relationship between these proteins remains unclear. Here we report a comprehensive phylogenetic analysis that suggests divergent evolution yielded ClpA from an ancestral ClpC protein and that ClpE/ClpL represent intermediates between ClpA/ClpC. This analysis also identifies a group of proteobacterial ClpC proteins that are likely not functional in regulated proteolysis. Our results strongly suggest that bacterial ClpC proteins should not be assumed to all function identically due to the structural differences identified here.
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Affiliation(s)
- Justin M Miller
- Middle Tennessee State University, Department of Chemistry, 1301 East Main Street, Murfreesboro, TN 37132, United States.
| | - Hamza Chaudhary
- Middle Tennessee State University, Department of Chemistry, 1301 East Main Street, Murfreesboro, TN 37132, United States
| | - Justin D Marsee
- Middle Tennessee State University, Department of Chemistry, 1301 East Main Street, Murfreesboro, TN 37132, United States
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13
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Riera A, Barbon M, Noguchi Y, Reuter LM, Schneider S, Speck C. From structure to mechanism-understanding initiation of DNA replication. Genes Dev 2017; 31:1073-1088. [PMID: 28717046 PMCID: PMC5538431 DOI: 10.1101/gad.298232.117] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In this Review, Riera et al. review recent structural and biochemical insights that start to explain how specific proteins recognize DNA replication origins, load the replicative helicase on DNA, unwind DNA, synthesize new DNA strands, and reassemble chromatin. DNA replication results in the doubling of the genome prior to cell division. This process requires the assembly of 50 or more protein factors into a replication fork. Here, we review recent structural and biochemical insights that start to explain how specific proteins recognize DNA replication origins, load the replicative helicase on DNA, unwind DNA, synthesize new DNA strands, and reassemble chromatin. We focus on the minichromosome maintenance (MCM2–7) proteins, which form the core of the eukaryotic replication fork, as this complex undergoes major structural rearrangements in order to engage with DNA, regulate its DNA-unwinding activity, and maintain genome stability.
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Affiliation(s)
- Alberto Riera
- DNA Replication Group, Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London W12 0NN, United Kingdom
| | - Marta Barbon
- DNA Replication Group, Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London W12 0NN, United Kingdom.,Medical Research Council (MRC) London Institute of Medical Sciences (LMS), London W12 0NN, United Kingdom
| | - Yasunori Noguchi
- DNA Replication Group, Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London W12 0NN, United Kingdom
| | - L Maximilian Reuter
- DNA Replication Group, Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London W12 0NN, United Kingdom
| | - Sarah Schneider
- DNA Replication Group, Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London W12 0NN, United Kingdom
| | - Christian Speck
- DNA Replication Group, Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London W12 0NN, United Kingdom.,Medical Research Council (MRC) London Institute of Medical Sciences (LMS), London W12 0NN, United Kingdom
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14
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Cryo-EM structure of Mcm2-7 double hexamer on DNA suggests a lagging-strand DNA extrusion model. Proc Natl Acad Sci U S A 2017; 114:E9529-E9538. [PMID: 29078375 PMCID: PMC5692578 DOI: 10.1073/pnas.1712537114] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
During replication initiation, the core component of the helicase-the Mcm2-7 hexamer-is loaded on origin DNA as a double hexamer (DH). The two ring-shaped hexamers are staggered, leading to a kinked axial channel. How the origin DNA interacts with the axial channel is not understood, but the interaction could provide key insights into Mcm2-7 function and regulation. Here, we report the cryo-EM structure of the Mcm2-7 DH on dsDNA and show that the DNA is zigzagged inside the central channel. Several of the Mcm subunit DNA-binding loops, such as the oligosaccharide-oligonucleotide loops, helix 2 insertion loops, and presensor 1 (PS1) loops, are well defined, and many of them interact extensively with the DNA. The PS1 loops of Mcm 3, 4, 6, and 7, but not 2 and 5, engage the lagging strand with an approximate step size of one base per subunit. Staggered coupling of the two opposing hexamers positions the DNA right in front of the two Mcm2-Mcm5 gates, with each strand being pressed against one gate. The architecture suggests that lagging-strand extrusion initiates in the middle of the DH that is composed of the zinc finger domains of both hexamers. To convert the Mcm2-7 DH structure into the Mcm2-7 hexamer structure found in the active helicase, the N-tier ring of the Mcm2-7 hexamer in the DH-dsDNA needs to tilt and shift laterally. We suggest that these N-tier ring movements cause the DNA strand separation and lagging-strand extrusion.
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15
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Neves H, Kwok HF. In sickness and in health: The many roles of the minichromosome maintenance proteins. Biochim Biophys Acta Rev Cancer 2017; 1868:295-308. [DOI: 10.1016/j.bbcan.2017.06.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 05/29/2017] [Accepted: 06/01/2017] [Indexed: 01/09/2023]
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16
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17
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Zhai Y, Cheng E, Wu H, Li N, Yung PYK, Gao N, Tye BK. Open-ringed structure of the Cdt1-Mcm2-7 complex as a precursor of the MCM double hexamer. Nat Struct Mol Biol 2017; 24:300-308. [PMID: 28191894 DOI: 10.1038/nsmb.3374] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 01/09/2017] [Indexed: 12/17/2022]
Abstract
The minichromosome maintenance complex (MCM) hexameric complex (Mcm2-7) forms the core of the eukaryotic replicative helicase. During G1 phase, two Cdt1-Mcm2-7 heptamers are loaded onto each replication origin by the origin-recognition complex (ORC) and Cdc6 to form an inactive MCM double hexamer (DH), but the detailed loading mechanism remains unclear. Here we examine the structures of the yeast MCM hexamer and Cdt1-MCM heptamer from Saccharomyces cerevisiae. Both complexes form left-handed coil structures with a 10-15-Å gap between Mcm5 and Mcm2, and a central channel that is occluded by the C-terminal domain winged-helix motif of Mcm5. Cdt1 wraps around the N-terminal regions of Mcm2, Mcm6 and Mcm4 to stabilize the whole complex. The intrinsic coiled structures of the precursors provide insights into the DH formation, and suggest a spring-action model for the MCM during the initial origin melting and the subsequent DNA unwinding.
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Affiliation(s)
- Yuanliang Zhai
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.,Institute for Advanced Study, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Erchao Cheng
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Hao Wu
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Ningning Li
- Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - Philip Yuk Kwong Yung
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Ning Gao
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Bik-Kwoon Tye
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.,Department of Molecular Biology and Genetics, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York, USA
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Fundamental Characteristics of AAA+ Protein Family Structure and Function. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2016; 2016:9294307. [PMID: 27703410 PMCID: PMC5039278 DOI: 10.1155/2016/9294307] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2016] [Accepted: 07/21/2016] [Indexed: 12/22/2022]
Abstract
Many complex cellular events depend on multiprotein complexes known as molecular machines to efficiently couple the energy derived from adenosine triphosphate hydrolysis to the generation of mechanical force. Members of the AAA+ ATPase superfamily (ATPases Associated with various cellular Activities) are critical components of many molecular machines. AAA+ proteins are defined by conserved modules that precisely position the active site elements of two adjacent subunits to catalyze ATP hydrolysis. In many cases, AAA+ proteins form a ring structure that translocates a polymeric substrate through the central channel using specialized loops that project into the central channel. We discuss the major features of AAA+ protein structure and function with an emphasis on pivotal aspects elucidated with archaeal proteins.
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Meagher M, Enemark EJ. Structure of a double hexamer of the Pyrococcus furiosus minichromosome maintenance protein N-terminal domain. ACTA CRYSTALLOGRAPHICA SECTION F-STRUCTURAL BIOLOGY COMMUNICATIONS 2016; 72:545-51. [PMID: 27380371 DOI: 10.1107/s2053230x1600858x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 05/27/2016] [Indexed: 11/11/2022]
Abstract
The crystal structure of the N-terminal domain of the Pyrococcus furiosus minichromosome maintenance (MCM) protein as a double hexamer is described. The MCM complex is a ring-shaped helicase that unwinds DNA at the replication fork of eukaryotes and archaea. Prior to replication initiation, the MCM complex assembles as an inactive double hexamer at specific sites of DNA. The presented structure is highly consistent with previous MCM double-hexamer structures and shows two MCM hexamers with a head-to-head interaction mediated by the N-terminal domain. Minor differences include a diminished head-to-head interaction and a slightly reduced inter-hexamer rotation.
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Affiliation(s)
- Martin Meagher
- Department of Structural Biology, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Eric J Enemark
- Department of Structural Biology, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
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