1
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Royzenblat SK, Freddolino L. Spatio-temporal organization of the E. coli chromosome from base to cellular length scales. EcoSal Plus 2024:eesp00012022. [PMID: 38864557 DOI: 10.1128/ecosalplus.esp-0001-2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 04/17/2024] [Indexed: 06/13/2024]
Abstract
Escherichia coli has been a vital model organism for studying chromosomal structure, thanks, in part, to its small and circular genome (4.6 million base pairs) and well-characterized biochemical pathways. Over the last several decades, we have made considerable progress in understanding the intricacies of the structure and subsequent function of the E. coli nucleoid. At the smallest scale, DNA, with no physical constraints, takes on a shape reminiscent of a randomly twisted cable, forming mostly random coils but partly affected by its stiffness. This ball-of-spaghetti-like shape forms a structure several times too large to fit into the cell. Once the physiological constraints of the cell are added, the DNA takes on overtwisted (negatively supercoiled) structures, which are shaped by an intricate interplay of many proteins carrying out essential biological processes. At shorter length scales (up to about 1 kb), nucleoid-associated proteins organize and condense the chromosome by inducing loops, bends, and forming bridges. Zooming out further and including cellular processes, topological domains are formed, which are flanked by supercoiling barriers. At the megabase-scale both large, highly self-interacting regions (macrodomains) and strong contacts between distant but co-regulated genes have been observed. At the largest scale, the nucleoid forms a helical ellipsoid. In this review, we will explore the history and recent advances that pave the way for a better understanding of E. coli chromosome organization and structure, discussing the cellular processes that drive changes in DNA shape, and what contributes to compaction and formation of dynamic structures, and in turn how bacterial chromatin affects key processes such as transcription and replication.
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Affiliation(s)
- Sonya K Royzenblat
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Lydia Freddolino
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Department of Computational Medicine & Bioinformatics, University of Michigan Medical School, Ann Arbor, Michigan, USA
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2
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Seba M, Boccard F, Duigou S. Activity of MukBEF for chromosome management in E. coli and its inhibition by MatP. eLife 2024; 12:RP91185. [PMID: 38315099 PMCID: PMC10945525 DOI: 10.7554/elife.91185] [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] [Indexed: 02/07/2024] Open
Abstract
Structural maintenance of chromosomes (SMC) complexes share conserved structures and serve a common role in maintaining chromosome architecture. In the bacterium Escherichia coli, the SMC complex MukBEF is necessary for rapid growth and the accurate segregation and positioning of the chromosome, although the specific molecular mechanisms involved are still unknown. Here, we used a number of in vivo assays to reveal how MukBEF controls chromosome conformation and how the MatP/matS system prevents MukBEF activity. Our results indicate that the loading of MukBEF occurs preferentially on newly replicated DNA, at multiple loci on the chromosome where it can promote long-range contacts in cis even though MukBEF can promote long-range contacts in the absence of replication. Using Hi-C and ChIP-seq analyses in strains with rearranged chromosomes, the prevention of MukBEF activity increases with the number of matS sites and this effect likely results from the unloading of MukBEF by MatP. Altogether, our results reveal how MukBEF operates to control chromosome folding and segregation in E. coli.
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Affiliation(s)
- Mohammed Seba
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell, Gif-sur-Yvette, France
| | - Frederic Boccard
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell, Gif-sur-Yvette, France
| | - Stéphane Duigou
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell, Gif-sur-Yvette, France
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3
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Deep A, Liang Q, Enustun E, Pogliano J, Corbett KD. Architecture and infection-sensing mechanism of the bacterial PARIS defense system. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.02.573835. [PMID: 38260510 PMCID: PMC10802264 DOI: 10.1101/2024.01.02.573835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Bacteria and the viruses that infect them (bacteriophages or phages) are engaged in an evolutionary arms race that has resulted in the development of hundreds of bacterial defense systems and myriad phage-encoded counterdefenses1-5. While the mechanisms of many bacterial defense systems are known1, how these systems avoid toxicity outside infection yet activate quickly upon sensing phage infection is less well understood. Here, we show that the bacterial Phage Anti-Restriction-Induced System (PARIS) operates as a toxin-antitoxin system, in which the antitoxin AriA sequesters and inactivates the toxin AriB until triggered by the T7 phage counterdefense protein Ocr. Using cryoelectron microscopy (cryoEM), we show that AriA is structurally similar to dimeric SMC-family ATPases but assembles into a distinctive homohexameric complex through two distinct oligomerization interfaces. In the absence of infection, the AriA hexamer binds up to three monomers of AriB, maintaining them in an inactive state. Ocr binding to the AriA-AriB complex triggers rearrangement of the AriA hexamer, releasing AriB and allowing it to dimerize and activate. AriB is a toprim/OLD-family nuclease whose activation arrests cell growth and inhibits phage propagation by globally inhibiting protein translation. Collectively, our findings reveal the intricate molecular mechanisms of a bacterial defense system that evolved in response to a phage counterdefense protein, and highlight how an SMC-family ATPase has been adapted as a bacterial infection sensor.
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Affiliation(s)
- Amar Deep
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla CA, USA
| | - Qishan Liang
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla CA, USA
| | - Eray Enustun
- Department of Molecular Biology, University of California San Diego, La Jolla CA, USA
| | - Joe Pogliano
- Department of Molecular Biology, University of California San Diego, La Jolla CA, USA
| | - Kevin D. Corbett
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla CA, USA
- Department of Molecular Biology, University of California San Diego, La Jolla CA, USA
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4
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Zhou M. DNA sliding and loop formation by E. coli SMC complex: MukBEF. Biochem Biophys Rep 2022; 31:101297. [PMID: 35770038 PMCID: PMC9234588 DOI: 10.1016/j.bbrep.2022.101297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 05/08/2022] [Accepted: 06/06/2022] [Indexed: 11/29/2022] Open
Abstract
SMC (structural maintenance of chromosomes) complexes share conserved architectures and function in chromosome maintenance via an unknown mechanism. Here we have used single-molecule techniques to study MukBEF, the SMC complex in Escherichia coli. Real-time movies show MukB alone can compact DNA and ATP inhibits DNA compaction by MukB. We observed that DNA unidirectionally slides through MukB, potentially by a ratchet mechanism, and the sliding speed depends on the elastic energy stored in the DNA. MukE, MukF and ATP binding stabilize MukB and DNA interaction, and ATP hydrolysis regulates the loading/unloading of MukBEF from DNA. Our data suggests a new model for how MukBEF organizes the bacterial chromosome in vivo; and this model will be relevant for other SMC proteins. ATP-independent DNA compaction by MukB. DNA unidirectionally slides through MukB, potentially by a ratchet mechanism. MukE, MukF and ATP binding stabilize MukB and DNA interaction. DNA sliding via ratchet driven by entropic force model for chromosome organization by SMC complex.
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5
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Hallett ST, Campbell Harry I, Schellenberger P, Zhou L, Cronin N, Baxter J, Etheridge T, Murray J, Oliver A. Cryo-EM structure of the Smc5/6 holo-complex. Nucleic Acids Res 2022; 50:9505-9520. [PMID: 35993814 PMCID: PMC9458440 DOI: 10.1093/nar/gkac692] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 07/14/2022] [Accepted: 07/30/2022] [Indexed: 01/06/2023] Open
Abstract
The Smc5/6 complex plays an essential role in the resolution of recombination intermediates formed during mitosis or meiosis, or as a result of the cellular response to replication stress. It also functions as a restriction factor preventing viral replication. Here, we report the cryogenic EM (cryo-EM) structure of the six-subunit budding yeast Smc5/6 holo-complex, reconstituted from recombinant proteins expressed in insect cells - providing both an architectural overview of the entire complex and an understanding of how the Nse1/3/4 subcomplex binds to the hetero-dimeric SMC protein core. In addition, we demonstrate that a region within the head domain of Smc5, equivalent to the 'W-loop' of Smc4 or 'F-loop' of Smc1, mediates an important interaction with Nse1. Notably, mutations that alter the surface-charge profile of the region of Nse1 which accepts the Smc5-loop, lead to a slow-growth phenotype and a global reduction in the chromatin-associated fraction of the Smc5/6 complex, as judged by single molecule localisation microscopy experiments in live yeast. Moreover, when taken together, our data indicates functional equivalence between the structurally unrelated KITE and HAWK accessory subunits associated with SMC complexes.
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Affiliation(s)
- Stephen T Hallett
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, UK
| | - Isabella Campbell Harry
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, UK
| | - Pascale Schellenberger
- Electron Microscopy Imaging Centre, School of Life Sciences, University of Sussex, Falmer, UK
| | - Lihong Zhou
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, UK
| | - Nora B Cronin
- London Consortium for CryoEM (LonCEM) Facility, The Francis Crick Institute, London, UK
| | - Jonathan Baxter
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, UK
| | - Thomas J Etheridge
- Correspondence may also be addressed to Thomas J. Etheridge. Tel: +44 1273 678123;
| | - Johanne M Murray
- Correspondence may also be addressed to Johanne M. Murray. Tel: +44 1273 877191;
| | - Antony W Oliver
- To whom correspondence should be addressed. Tel: +44 1273 678349;
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6
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Nomidis SK, Carlon E, Gruber S, Marko JF. DNA tension-modulated translocation and loop extrusion by SMC complexes revealed by molecular dynamics simulations. Nucleic Acids Res 2022; 50:4974-4987. [PMID: 35474142 PMCID: PMC9122525 DOI: 10.1093/nar/gkac268] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 03/21/2022] [Accepted: 04/04/2022] [Indexed: 12/19/2022] Open
Abstract
Structural Maintenance of Chromosomes (SMC) complexes play essential roles in genome organization across all domains of life. To determine how the activities of these large (≈50 nm) complexes are controlled by ATP binding and hydrolysis, we developed a molecular dynamics model that accounts for conformational motions of the SMC and DNA. The model combines DNA loop capture with an ATP-induced ‘power stroke’ to translocate the SMC complex along DNA. This process is sensitive to DNA tension: at low tension (0.1 pN), the model makes loop-capture steps of average 60 nm and up to 200 nm along DNA (larger than the complex itself), while at higher tension, a distinct inchworm-like translocation mode appears. By tethering DNA to an experimentally-observed additional binding site (‘safety belt’), the model SMC complex can perform loop extrusion (LE). The dependence of LE on DNA tension is distinct for fixed DNA tension vs. fixed DNA end points: LE reversal occurs above 0.5 pN for fixed tension, while LE stalling without reversal occurs at about 2 pN for fixed end points. Our model matches recent experimental results for condensin and cohesin, and makes testable predictions for how specific structural variations affect SMC function.
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Affiliation(s)
- Stefanos K Nomidis
- Laboratory for Soft Matter and Biophysics, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
- Flemish Institute for Technological Research (VITO), Boeretang 200, B-2400 Mol, Belgium
| | - Enrico Carlon
- Laboratory for Soft Matter and Biophysics, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
| | - Stephan Gruber
- Départment de Microbiologie Fondamentale, Université de Lausanne, 1015 Lausanne, Switzerland
| | - John F Marko
- To whom correspondence should be addressed. Tel: +1 847 467 1276; Fax: +1 847 467 1380;
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7
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Intersubunit and intrasubunit interactions driving the MukBEF ATPase. J Biol Chem 2022; 298:101964. [PMID: 35452680 PMCID: PMC9127220 DOI: 10.1016/j.jbc.2022.101964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 04/15/2022] [Accepted: 04/16/2022] [Indexed: 11/23/2022] Open
Abstract
MukBEF, a structural maintenance of chromosome-like protein complex consisting of an ATPase, MukB, and two interacting subunits, MukE and MukF, functions as the bacterial condensin. It is likely that MukBEF compacts DNA via an ATP hydrolysis-dependent DNA loop-extrusion reaction similar to that demonstrated for the yeast structural maintenance of chromosome proteins condensin and cohesin. MukB also interacts with the ParC subunit of the cellular chromosomal decatenase topoisomerase IV, an interaction that is required for proper chromosome condensation and segregation in Escherichia coli, although it suppresses the MukB ATPase activity. Other structural determinants and interactions that regulate the ATPase activity of MukBEF are not clear. Here, we have investigated the MukBEF ATPase activity, identifying intersubunit and intrasubunit interactions by protein-protein crosslinking and site-specific mutagenesis. We show that interactions between the hinge of MukB and its neck region are essential for the ATPase activity, that the ParC subunit of topoisomerase IV inhibits the MukB ATPase by preventing this interaction, that MukE interaction with DNA is likely essential for viability, and that interactions between MukF and the MukB neck region are necessary for ATPase activity and viability.
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8
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Qian JW, Wang XY, Deng K, Li DF, Guo L. Crystal structure of the chromosome partition protein MukE homodimer. Biochem Biophys Res Commun 2021; 589:229-233. [PMID: 34929446 DOI: 10.1016/j.bbrc.2021.12.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 12/08/2021] [Accepted: 12/12/2021] [Indexed: 11/15/2022]
Abstract
The SMC (structural maintenance of chromosomes) proteins are known to be involved in chromosome pairing or aggregation and play an important role in cell cycle and division. Different from SMC-ScpAB complex maintaining chromosome structure in most bacteria, the MukB-MukE-MukF complex is responsible for chromosome condensation in E. coli and some γ-proteobacter. Though different models were proposed to illustrate the mechanism of how the MukBEF complex worked, the assembly of the MukBEF complex is a key. The MukE dimer interacted with the middle region of one MukF molecule, and was clamped by the N- and C-terminal domain of the latter, and then was involved in the interaction with the head domain of MukB. To reveal the structural basis of MukE involved in the dynamic equilibrium of potential different MukBEF assemblies, we determined the MukE structure at 2.44 Å resolution. We found that the binding cavity for the α10, β4 and β5 of MukF (residues 296-327) in the MukE dimer has been occupied by the α9 and β7 strand of MukE. We proposed that the highly dynamic C-terminal region (173-225) was important for the MukE-F assembly and then involved in the MukBEF complex formation.
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Affiliation(s)
- Jia-Wei Qian
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; College of Life and Health Sciences, Northeastern University, Shenyang, 110169, China
| | - Xiao-Yan Wang
- Department of Biochemistry and Molecular Biology, College of Basic Medicine, Hubei University of Medicine, Shiyan, 442000, China
| | - Kai Deng
- Reproductive Medicine Center, Renmin Hospital, Hubei University of Medicine, Shiyan, 442000, China
| | - De-Feng Li
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Lu Guo
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
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9
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Bürmann F, Funke LFH, Chin JW, Löwe J. Cryo-EM structure of MukBEF reveals DNA loop entrapment at chromosomal unloading sites. Mol Cell 2021; 81:4891-4906.e8. [PMID: 34739874 PMCID: PMC8669397 DOI: 10.1016/j.molcel.2021.10.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/31/2021] [Accepted: 10/12/2021] [Indexed: 11/25/2022]
Abstract
The ring-like structural maintenance of chromosomes (SMC) complex MukBEF folds the genome of Escherichia coli and related bacteria into large loops, presumably by active DNA loop extrusion. MukBEF activity within the replication terminus macrodomain is suppressed by the sequence-specific unloader MatP. Here, we present the complete atomic structure of MukBEF in complex with MatP and DNA as determined by electron cryomicroscopy (cryo-EM). The complex binds two distinct DNA double helices corresponding to the arms of a plectonemic loop. MatP-bound DNA threads through the MukBEF ring, while the second DNA is clamped by the kleisin MukF, MukE, and the MukB ATPase heads. Combinatorial cysteine cross-linking confirms this topology of DNA loop entrapment in vivo. Our findings illuminate how a class of near-ubiquitous DNA organizers with important roles in genome maintenance interacts with the bacterial chromosome.
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Affiliation(s)
- Frank Bürmann
- MRC Laboratory of Molecular Biology, Structural Studies Division, Cambridge Biomedical Campus, Cambridge, UK.
| | - Louise F H Funke
- MRC Laboratory of Molecular Biology, Protein and Nucleic Acid Chemistry Division, Cambridge Biomedical Campus, Cambridge, UK
| | - Jason W Chin
- MRC Laboratory of Molecular Biology, Protein and Nucleic Acid Chemistry Division, Cambridge Biomedical Campus, Cambridge, UK
| | - Jan Löwe
- MRC Laboratory of Molecular Biology, Structural Studies Division, Cambridge Biomedical Campus, Cambridge, UK.
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10
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Prince JP, Bolla JR, Fisher GLM, Mäkelä J, Fournier M, Robinson CV, Arciszewska LK, Sherratt DJ. Acyl carrier protein promotes MukBEF action in Escherichia coli chromosome organization-segregation. Nat Commun 2021; 12:6721. [PMID: 34795302 PMCID: PMC8602292 DOI: 10.1038/s41467-021-27107-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 11/02/2021] [Indexed: 11/22/2022] Open
Abstract
Structural Maintenance of Chromosomes (SMC) complexes act ubiquitously to compact DNA linearly, thereby facilitating chromosome organization-segregation. SMC proteins have a conserved architecture, with a dimerization hinge and an ATPase head domain separated by a long antiparallel intramolecular coiled-coil. Dimeric SMC proteins interact with essential accessory proteins, kleisins that bridge the two subunits of an SMC dimer, and HAWK/KITE proteins that interact with kleisins. The ATPase activity of the Escherichia coli SMC protein, MukB, which is essential for its in vivo function, requires its interaction with the dimeric kleisin, MukF that in turn interacts with the KITE protein, MukE. Here we demonstrate that, in addition, MukB interacts specifically with Acyl Carrier Protein (AcpP) that has essential functions in fatty acid synthesis. We characterize the AcpP interaction at the joint of the MukB coiled-coil and show that the interaction is necessary for MukB ATPase and for MukBEF function in vivo.
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Affiliation(s)
- Josh P. Prince
- grid.4991.50000 0004 1936 8948Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK ,grid.14105.310000000122478951Present Address: Meiosis Group, Medical Research Council London Institute of Medical Sciences, Du Cane Road, London, W12 0NN UK
| | - Jani R. Bolla
- grid.4991.50000 0004 1936 8948Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ UK ,The Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford, OX1 3QU UK ,grid.4991.50000 0004 1936 8948Present Address: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Gemma L. M. Fisher
- grid.4991.50000 0004 1936 8948Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK ,grid.14105.310000000122478951Present Address: DNA Motors Group, Medical Research Council London Institute of Medical Sciences, Du Cane Road, London, W12 0NN UK
| | - Jarno Mäkelä
- grid.4991.50000 0004 1936 8948Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK ,grid.168010.e0000000419368956Present Address: ChEM-H Institute, Stanford University, 290 Jane Stanford Way, Stanford, CA 94305 USA
| | - Marjorie Fournier
- grid.4991.50000 0004 1936 8948Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Carol V. Robinson
- grid.4991.50000 0004 1936 8948Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ UK ,The Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford, OX1 3QU UK
| | - Lidia K. Arciszewska
- grid.4991.50000 0004 1936 8948Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - David J. Sherratt
- grid.4991.50000 0004 1936 8948Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
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11
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Kumar R, Bahng S, Marians KJ. The MukB-topoisomerase IV interaction mutually suppresses their catalytic activities. Nucleic Acids Res 2021; 50:2621-2634. [PMID: 34747485 PMCID: PMC8934648 DOI: 10.1093/nar/gkab1027] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 10/11/2021] [Accepted: 10/13/2021] [Indexed: 02/05/2023] Open
Abstract
The bacterial condensin MukB and the cellular chromosomal decatenase, topoisomerase IV interact and this interaction is required for proper condensation and topological ordering of the chromosome. Here, we show that Topo IV stimulates MukB DNA condensation by stabilizing loops in DNA: MukB alone can condense nicked plasmid DNA into a protein–DNA complex that has greater electrophoretic mobility than that of the DNA alone, but both MukB and Topo IV are required for a similar condensation of a linear DNA representing long stretches of the chromosome. Remarkably, we show that rather than MukB stimulating the decatenase activity of Topo IV, as has been argued previously, in stoichiometric complexes of the two enzymes each inhibits the activity of the other: the ParC subunit of Topo IV inhibits the MukF-stimulated ATPase activity of MukB and MukB inhibits both DNA crossover trapping and DNA cleavage by Topo IV. These observations suggest that when in complex on the DNA, Topo IV inhibits the motor function of MukB and the two proteins provide a stable scaffold for chromosomal DNA condensation.
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Affiliation(s)
- Rupesh Kumar
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Soon Bahng
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Kenneth J Marians
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
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12
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Fisher GL, Bolla JR, Rajasekar KV, Mäkelä J, Baker R, Zhou M, Prince JP, Stracy M, Robinson CV, Arciszewska LK, Sherratt DJ. Competitive binding of MatP and topoisomerase IV to the MukB hinge domain. eLife 2021; 10:70444. [PMID: 34585666 PMCID: PMC8523169 DOI: 10.7554/elife.70444] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 09/21/2021] [Indexed: 11/13/2022] Open
Abstract
Structural Maintenance of Chromosomes (SMC) complexes have ubiquitous roles in compacting DNA linearly, thereby promoting chromosome organization-segregation. Interaction between the Escherichia coli SMC complex, MukBEF, and matS-bound MatP in the chromosome replication termination region, ter, results in depletion of MukBEF from ter, a process essential for efficient daughter chromosome individualization and for preferential association of MukBEF with the replication origin region. Chromosome-associated MukBEF complexes also interact with topoisomerase IV (ParC2E2), so that their chromosome distribution mirrors that of MukBEF. We demonstrate that MatP and ParC have an overlapping binding interface on the MukB hinge, leading to their mutually exclusive binding, which occurs with the same dimer to dimer stoichiometry. Furthermore, we show that matS DNA competes with the MukB hinge for MatP binding. Cells expressing MukBEF complexes that are mutated at the ParC/MatP binding interface are impaired in ParC binding and have a mild defect in MukBEF function. These data highlight competitive binding as a means of globally regulating MukBEF-topoisomerase IV activity in space and time.
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Affiliation(s)
- Gemma Lm Fisher
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Jani R Bolla
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, United Kingdom.,The Kavli Institute for Nanoscience Discovery, Oxford, United Kingdom
| | | | - Jarno Mäkelä
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Rachel Baker
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Man Zhou
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Josh P Prince
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Mathew Stracy
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Carol V Robinson
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, United Kingdom.,The Kavli Institute for Nanoscience Discovery, Oxford, United Kingdom
| | | | - David J Sherratt
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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13
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Taschner M, Basquin J, Steigenberger B, Schäfer IB, Soh YM, Basquin C, Lorentzen E, Räschle M, Scheltema RA, Gruber S. Nse5/6 inhibits the Smc5/6 ATPase and modulates DNA substrate binding. EMBO J 2021; 40:e107807. [PMID: 34191293 PMCID: PMC8327961 DOI: 10.15252/embj.2021107807] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 06/10/2021] [Accepted: 06/11/2021] [Indexed: 12/23/2022] Open
Abstract
Eukaryotic cells employ three SMC (structural maintenance of chromosomes) complexes to control DNA folding and topology. The Smc5/6 complex plays roles in DNA repair and in preventing the accumulation of deleterious DNA junctions. To elucidate how specific features of Smc5/6 govern these functions, we reconstituted the yeast holo‐complex. We found that the Nse5/6 sub‐complex strongly inhibited the Smc5/6 ATPase by preventing productive ATP binding. This inhibition was relieved by plasmid DNA binding but not by short linear DNA, while opposing effects were observed without Nse5/6. We uncovered two binding sites for Nse5/6 on Smc5/6, based on an Nse5/6 crystal structure and cross‐linking mass spectrometry data. One binding site is located at the Smc5/6 arms and one at the heads, the latter likely exerting inhibitory effects on ATP hydrolysis. Cysteine cross‐linking demonstrated that the interaction with Nse5/6 anchored the ATPase domains in a non‐productive state, which was destabilized by ATP and DNA. Under similar conditions, the Nse4/3/1 module detached from the ATPase. Altogether, we show how DNA substrate selection is modulated by direct inhibition of the Smc5/6 ATPase by Nse5/6.
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Affiliation(s)
- Michael Taschner
- Department of Fundamental Microbiology (DMF), Faculty of Biology and Medicine (FBM), University of Lausanne (UNIL), Lausanne, Switzerland
| | - Jérôme Basquin
- Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Barbara Steigenberger
- Max Planck Institute of Biochemistry, Martinsried, Germany.,Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.,Netherlands Proteomics Centre, Utrecht, The Netherlands
| | | | - Young-Min Soh
- Department of Fundamental Microbiology (DMF), Faculty of Biology and Medicine (FBM), University of Lausanne (UNIL), Lausanne, Switzerland
| | - Claire Basquin
- Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Esben Lorentzen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Markus Räschle
- Molecular Genetics, University of Kaiserslautern, Kaiserslautern, Germany
| | - Richard A Scheltema
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.,Netherlands Proteomics Centre, Utrecht, The Netherlands
| | - Stephan Gruber
- Department of Fundamental Microbiology (DMF), Faculty of Biology and Medicine (FBM), University of Lausanne (UNIL), Lausanne, Switzerland
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14
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MukB Is a Gene Necessary for Rapid Proliferation of Vibrio vulnificus in the Systemic Circulation but Not at the Local Infection Site in the Mouse Wound Infection Model. Microorganisms 2021; 9:microorganisms9050934. [PMID: 33925415 PMCID: PMC8145103 DOI: 10.3390/microorganisms9050934] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 04/20/2021] [Accepted: 04/24/2021] [Indexed: 12/19/2022] Open
Abstract
Vibrio vulnificus causes rapid septicemia in susceptible individuals who have ingested contaminated foods or have open wounds exposed to seawater contaminated with the bacteria. Despite antibiotic therapy and aggressive debridement, mortality from septicemia is high. In this study, we showed that MukB mutation (mukB::Tn) affected the proliferation of V. vulnificus in the systemic circulation but not at the inoculation site in the wound infection model. A comparison of mukB::Tn with WT and a mukB complement strain (mukB::Tn/pmukB) on the bacterial burden in the muscle at the infection site showed that spreading and proliferation of the mukB::Tn strain was similar to those of the other strains. However, the bacterial burden of mukB::Tn in the spleen was reduced compared to that of the WT strain in the wound infection model. In a competition experiment, we found a lower bacterial burden of mukB::Tn in the spleen than that of the WT strain infecting the systemic circulation. Here, we report on a gene required for the rapid proliferation of V. vulnificus only in the systemic circulation and potentially required for its survival. Our finding may provide a novel therapeutic target for V. vulnificus septicemia.
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15
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Krishnan A, Burroughs AM, Iyer LM, Aravind L. Comprehensive classification of ABC ATPases and their functional radiation in nucleoprotein dynamics and biological conflict systems. Nucleic Acids Res 2020; 48:10045-10075. [PMID: 32894288 DOI: 10.1093/nar/gkaa726] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 08/17/2020] [Accepted: 08/20/2020] [Indexed: 12/13/2022] Open
Abstract
ABC ATPases form one of the largest clades of P-loop NTPase fold enzymes that catalyze ATP-hydrolysis and utilize its free energy for a staggering range of functions from transport to nucleoprotein dynamics. Using sensitive sequence and structure analysis with comparative genomics, for the first time we provide a comprehensive classification of the ABC ATPase superfamily. ABC ATPases developed structural hallmarks that unambiguously distinguish them from other P-loop NTPases such as an alternative to arginine-finger-based catalysis. At least five and up to eight distinct clades of ABC ATPases are reconstructed as being present in the last universal common ancestor. They underwent distinct phases of structural innovation with the emergence of inserts constituting conserved binding interfaces for proteins or nucleic acids and the adoption of a unique dimeric toroidal configuration for DNA-threading. Specifically, several clades have also extensively radiated in counter-invader conflict systems where they serve as nodal nucleotide-dependent sensory and energetic components regulating a diversity of effectors (including some previously unrecognized) acting independently or together with restriction-modification systems. We present a unified mechanism for ABC ATPase function across disparate systems like RNA editing, translation, metabolism, DNA repair, and biological conflicts, and some unexpected recruitments, such as MutS ATPases in secondary metabolism.
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Affiliation(s)
- Arunkumar Krishnan
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - A Maxwell Burroughs
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Lakshminarayan M Iyer
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - L Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
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16
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Weyburne E, Bosco G. Cancer-associated mutations in the condensin II subunit CAPH2 cause genomic instability through telomere dysfunction and anaphase chromosome bridges. J Cell Physiol 2020; 236:3579-3598. [PMID: 33078399 PMCID: PMC7983937 DOI: 10.1002/jcp.30113] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 09/21/2020] [Accepted: 09/23/2020] [Indexed: 01/10/2023]
Abstract
Genome instability in cancer drives tumor heterogeneity, undermines the success of therapies, and leads to metastasis and recurrence. Condensins are conserved chromatin‐binding proteins that promote genomic stability, mainly by ensuring proper condensation of chromatin and mitotic chromosome segregation. Condensin mutations are found in human tumors, but it is not known how or even if such mutations promote cancer progression. In this study, we focus on condensin II subunit CAPH2 and specific CAPH2 mutations reported to be enriched in human cancer patients, and we test how CAPH2 cancer‐specific mutations may lead to condensin II complex dysfunction and contribute to genome instability. We find that R551P, R551S, and S556F mutations in CAPH2 cause genomic instability by causing DNA damage, anaphase defects, micronuclei, and chromosomal instability. DNA damage and anaphase defects are caused primarily by ataxia telangiectasia and Rad3‐related‐dependent telomere dysfunction, as anaphase bridges are enriched for telomeric repeat sequences. We also show that these mutations decrease the binding of CAPH2 to the ATPase subunit SMC4 as well as the rest of the condensin II complex, and decrease the amount of CAPH2 protein bound to chromatin. Thus, in vivo the R551P, R551S, and S556F cancer‐specific CAPH2 mutant proteins are likely to impair condensin II complex formation, impede condensin II activity during mitosis and interphase, and promote genetic heterogeneity in cell populations that can lead to clonal outgrowth of cancer cells with highly diverse genotypes.
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Affiliation(s)
- Emily Weyburne
- Department of Molecular and Systems Biology, Dartmouth College, Hanover, New Hampshire, USA
| | - Giovanni Bosco
- Department of Molecular and Systems Biology, Dartmouth College, Hanover, New Hampshire, USA
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17
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Vondrova L, Kolesar P, Adamus M, Nociar M, Oliver AW, Palecek JJ. A role of the Nse4 kleisin and Nse1/Nse3 KITE subunits in the ATPase cycle of SMC5/6. Sci Rep 2020; 10:9694. [PMID: 32546830 PMCID: PMC7297730 DOI: 10.1038/s41598-020-66647-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 05/20/2020] [Indexed: 12/03/2022] Open
Abstract
The SMC (Structural Maintenance of Chromosomes) complexes are composed of SMC dimers, kleisin and kleisin-interacting (HAWK or KITE) subunits. Mutual interactions of these subunits constitute the basal architecture of the SMC complexes. In addition, binding of ATP molecules to the SMC subunits and their hydrolysis drive dynamics of these complexes. Here, we developed new systems to follow the interactions between SMC5/6 subunits and the relative stability of the complex. First, we show that the N-terminal domain of the Nse4 kleisin molecule binds to the SMC6 neck and bridges it to the SMC5 head. Second, binding of the Nse1 and Nse3 KITE proteins to the Nse4 linker increased stability of the ATP-free SMC5/6 complex. In contrast, binding of ATP to SMC5/6 containing KITE subunits significantly decreased its stability. Elongation of the Nse4 linker partially suppressed instability of the ATP-bound complex, suggesting that the binding of the KITE proteins to the Nse4 linker constrains its limited size. Our data suggest that the KITE proteins may shape the Nse4 linker to fit the ATP-free complex optimally and to facilitate opening of the complex upon ATP binding. This mechanism suggests an important role of the KITE subunits in the dynamics of the SMC5/6 complexes.
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Affiliation(s)
- Lucie Vondrova
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
| | - Peter Kolesar
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
| | - Marek Adamus
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
| | - Matej Nociar
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
| | - Antony W Oliver
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9RQ, United Kingdom
| | - Jan J Palecek
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic. .,Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic.
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18
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Loop extrusion: theory meets single-molecule experiments. Curr Opin Cell Biol 2020; 64:124-138. [PMID: 32534241 DOI: 10.1016/j.ceb.2020.04.011] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 04/24/2020] [Accepted: 04/28/2020] [Indexed: 11/20/2022]
Abstract
Chromosomes are organized as chromatin loops that promote segregation, enhancer-promoter interactions, and other genomic functions. Loops were hypothesized to form by 'loop extrusion,' by which structural maintenance of chromosomes (SMC) complexes, such as condensin and cohesin, bind to chromatin, reel it in, and extrude it as a loop. However, such exotic motor activity had never been observed. Following an explosion of indirect evidence, recent single-molecule experiments directly imaged DNA loop extrusion by condensin and cohesin in vitro. These experiments observe rapid (kb/s) extrusion that requires ATP hydrolysis and stalls under pN forces. Surprisingly, condensin extrudes loops asymmetrically, challenging previous models. Extrusion by cohesin is symmetric but requires the protein Nipbl. We discuss how SMC complexes may perform their functions on chromatin in vivo.
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19
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Banigan EJ, van den Berg AA, Brandão HB, Marko JF, Mirny LA. Chromosome organization by one-sided and two-sided loop extrusion. eLife 2020; 9:e53558. [PMID: 32250245 PMCID: PMC7295573 DOI: 10.7554/elife.53558] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 04/03/2020] [Indexed: 12/19/2022] Open
Abstract
SMC complexes, such as condensin or cohesin, organize chromatin throughout the cell cycle by a process known as loop extrusion. SMC complexes reel in DNA, extruding and progressively growing DNA loops. Modeling assuming two-sided loop extrusion reproduces key features of chromatin organization across different organisms. In vitro single-molecule experiments confirmed that yeast condensins extrude loops, however, they remain anchored to their loading sites and extrude loops in a 'one-sided' manner. We therefore simulate one-sided loop extrusion to investigate whether 'one-sided' complexes can compact mitotic chromosomes, organize interphase domains, and juxtapose bacterial chromosomal arms, as can be done by 'two-sided' loop extruders. While one-sided loop extrusion cannot reproduce these phenomena, variants can recapitulate in vivo observations. We predict that SMC complexes in vivo constitute effectively two-sided motors or exhibit biased loading and propose relevant experiments. Our work suggests that loop extrusion is a viable general mechanism of chromatin organization.
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Affiliation(s)
- Edward J Banigan
- Institute for Medical Engineering & Science, Massachusetts Institute of TechnologyCambridgeUnited States
- Department of Physics, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Aafke A van den Berg
- Institute for Medical Engineering & Science, Massachusetts Institute of TechnologyCambridgeUnited States
- Department of Physics, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Hugo B Brandão
- Harvard Graduate Program in Biophysics, Harvard UniversityCambridgeUnited States
| | - John F Marko
- Departments of Molecular Biosciences and Physics & Astronomy, Northwestern UniversityEvanstonUnited States
| | - Leonid A Mirny
- Institute for Medical Engineering & Science, Massachusetts Institute of TechnologyCambridgeUnited States
- Department of Physics, Massachusetts Institute of TechnologyCambridgeUnited States
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20
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Organization of the Escherichia coli Chromosome by a MukBEF Axial Core. Mol Cell 2020; 78:250-260.e5. [PMID: 32097603 PMCID: PMC7163298 DOI: 10.1016/j.molcel.2020.02.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 12/03/2019] [Accepted: 02/03/2020] [Indexed: 01/22/2023]
Abstract
Structural maintenance of chromosomes (SMC) complexes organize chromosomes ubiquitously, thereby contributing to their faithful segregation. We demonstrate that under conditions of increased chromosome occupancy of the Escherichia coli SMC complex, MukBEF, the chromosome is organized as a series of loops around a thin (<130 nm) MukBEF axial core, whose length is ∼1,100 times shorter than the chromosomal DNA. The linear order of chromosomal loci is maintained in the axial cores, whose formation requires MukBEF ATP hydrolysis. Axial core structure in non-replicating chromosomes is predominantly linear (1 μm) but becomes circular (1.5 μm) in the absence of MatP because of its failure to displace MukBEF from the 800 kbp replication termination region (ter). Displacement of MukBEF from ter by MatP in wild-type cells directs MukBEF colocalization with the replication origin. We conclude that MukBEF individualizes and compacts the chromosome lengthwise, demonstrating a chromosome organization mechanism similar to condensin in mitotic chromosome formation. MukBEF forms a chromosome axial core dependent on ATP hydrolysis MukBEF compacts the chromosome lengthwise while avoiding links between replichores MatP determines the shape of the axial core by displacing MukBEF from ter The displacement by MatP directs MukBEF colocalization with the replication origin
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21
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Hassler M, Shaltiel IA, Kschonsak M, Simon B, Merkel F, Thärichen L, Bailey HJ, Macošek J, Bravo S, Metz J, Hennig J, Haering CH. Structural Basis of an Asymmetric Condensin ATPase Cycle. Mol Cell 2020; 74:1175-1188.e9. [PMID: 31226277 PMCID: PMC6591010 DOI: 10.1016/j.molcel.2019.03.037] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 03/16/2019] [Accepted: 03/27/2019] [Indexed: 01/20/2023]
Abstract
The condensin protein complex plays a key role in the structural organization of genomes. How the ATPase activity of its SMC subunits drives large-scale changes in chromosome topology has remained unknown. Here we reconstruct, at near-atomic resolution, the sequence of events that take place during the condensin ATPase cycle. We show that ATP binding induces a conformational switch in the Smc4 head domain that releases its hitherto undescribed interaction with the Ycs4 HEAT-repeat subunit and promotes its engagement with the Smc2 head into an asymmetric heterodimer. SMC head dimerization subsequently enables nucleotide binding at the second active site and disengages the Brn1 kleisin subunit from the Smc2 coiled coil to open the condensin ring. These large-scale transitions in the condensin architecture lay out a mechanistic path for its ability to extrude DNA helices into large loop structures.
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Affiliation(s)
- Markus Hassler
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Indra A Shaltiel
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Marc Kschonsak
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Bernd Simon
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Fabian Merkel
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany; Collaboration for Joint PhD degree between EMBL and Heidelberg University, Faculty of Biosciences, Heidelberg, Germany
| | - Lena Thärichen
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Henry J Bailey
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Jakub Macošek
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Sol Bravo
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Jutta Metz
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Janosch Hennig
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Christian H Haering
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany; Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
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22
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Abstract
How genomes are organized within cells and how the 3D architecture of a genome influences cellular functions are significant questions in biology. A bacterial genomic DNA resides inside cells in a highly condensed and functionally organized form called nucleoid (nucleus-like structure without a nuclear membrane). The Escherichia coli chromosome or nucleoid is composed of the genomic DNA, RNA, and protein. The nucleoid forms by condensation and functional arrangement of a single chromosomal DNA with the help of chromosomal architectural proteins and RNA molecules as well as DNA supercoiling. Although a high-resolution structure of a bacterial nucleoid is yet to come, five decades of research has established the following salient features of the E. coli nucleoid elaborated below: 1) The chromosomal DNA is on the average a negatively supercoiled molecule that is folded as plectonemic loops, which are confined into many independent topological domains due to supercoiling diffusion barriers; 2) The loops spatially organize into megabase size regions called macrodomains, which are defined by more frequent physical interactions among DNA sites within the same macrodomain than between different macrodomains; 3) The condensed and spatially organized DNA takes the form of a helical ellipsoid radially confined in the cell; and 4) The DNA in the chromosome appears to have a condition-dependent 3-D structure that is linked to gene expression so that the nucleoid architecture and gene transcription are tightly interdependent, influencing each other reciprocally. Current advents of high-resolution microscopy, single-molecule analysis and molecular structure determination of the components are expected to reveal the total structure and function of the bacterial nucleoid.
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Affiliation(s)
- Subhash C. Verma
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (SCV); (SLA)
| | - Zhong Qian
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Sankar L. Adhya
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (SCV); (SLA)
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23
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Elbatsh AMO, Kim E, Eeftens JM, Raaijmakers JA, van der Weide RH, García-Nieto A, Bravo S, Ganji M, Uit de Bos J, Teunissen H, Medema RH, de Wit E, Haering CH, Dekker C, Rowland BD. Distinct Roles for Condensin's Two ATPase Sites in Chromosome Condensation. Mol Cell 2019; 76:724-737.e5. [PMID: 31629658 PMCID: PMC6900782 DOI: 10.1016/j.molcel.2019.09.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 07/17/2019] [Accepted: 09/13/2019] [Indexed: 01/19/2023]
Abstract
Condensin is a conserved SMC complex that uses its ATPase machinery to structure genomes, but how it does so is largely unknown. We show that condensin's ATPase has a dual role in chromosome condensation. Mutation of one ATPase site impairs condensation, while mutating the second site results in hyperactive condensin that compacts DNA faster than wild-type, both in vivo and in vitro. Whereas one site drives loop formation, the second site is involved in the formation of more stable higher-order Z loop structures. Using hyperactive condensin I, we reveal that condensin II is not intrinsically needed for the shortening of mitotic chromosomes. Condensin II rather is required for a straight chromosomal axis and enables faithful chromosome segregation by counteracting the formation of ultrafine DNA bridges. SMC complexes with distinct roles for each ATPase site likely reflect a universal principle that enables these molecular machines to intricately control chromosome architecture.
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Affiliation(s)
- Ahmed M O Elbatsh
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Eugene Kim
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Jorine M Eeftens
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Jonne A Raaijmakers
- Division of Cell Biology, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Robin H van der Weide
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Alberto García-Nieto
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Sol Bravo
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Mahipal Ganji
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Jelmi Uit de Bos
- Division of Cell Biology, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Hans Teunissen
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - René H Medema
- Division of Cell Biology, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Elzo de Wit
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Christian H Haering
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands.
| | - Benjamin D Rowland
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands.
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24
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Abstract
Structural maintenance of chromosomes (SMC) complexes are key organizers of chromosome architecture in all kingdoms of life. Despite seemingly divergent functions, such as chromosome segregation, chromosome maintenance, sister chromatid cohesion, and mitotic chromosome compaction, it appears that these complexes function via highly conserved mechanisms and that they represent a novel class of DNA translocases.
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Affiliation(s)
- Stanislau Yatskevich
- Laboratory of Molecular Biology, Medical Research Council, Cambridge University, Cambridge CB2 0QH, United Kingdom
| | - James Rhodes
- Department of Biochemistry, Oxford University, Oxford OX1 3QU, United Kingdom;
| | - Kim Nasmyth
- Department of Biochemistry, Oxford University, Oxford OX1 3QU, United Kingdom;
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25
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Rajasekar KV, Baker R, Fisher GLM, Bolla JR, Mäkelä J, Tang M, Zawadzka K, Koczy O, Wagner F, Robinson CV, Arciszewska LK, Sherratt DJ. Dynamic architecture of the Escherichia coli structural maintenance of chromosomes (SMC) complex, MukBEF. Nucleic Acids Res 2019; 47:9696-9707. [PMID: 31400115 PMCID: PMC6765140 DOI: 10.1093/nar/gkz696] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 07/23/2019] [Accepted: 07/31/2019] [Indexed: 12/18/2022] Open
Abstract
Ubiquitous Structural Maintenance of Chromosomes (SMC) complexes use a proteinaceous ring-shaped architecture to organize and individualize chromosomes, thereby facilitating chromosome segregation. They utilize cycles of adenosine triphosphate (ATP) binding and hydrolysis to transport themselves rapidly with respect to DNA, a process requiring protein conformational changes and multiple DNA contact sites. By analysing changes in the architecture and stoichiometry of the Escherichia coli SMC complex, MukBEF, as a function of nucleotide binding to MukB and subsequent ATP hydrolysis, we demonstrate directly the formation of dimer of MukBEF dimer complexes, dependent on dimeric MukF kleisin. Using truncated and full length MukB, in combination with MukEF, we show that engagement of the MukB ATPase heads on nucleotide binding directs the formation of dimers of heads-engaged dimer complexes. Complex formation requires functional interactions between the C- and N-terminal domains of MukF with the MukB head and neck, respectively, and MukE, which organizes the complexes by stabilizing binding of MukB heads to MukF. In the absence of head engagement, a MukF dimer bound by MukE forms complexes containing only a dimer of MukB. Finally, we demonstrate that cells expressing MukBEF complexes in which MukF is monomeric are Muk−, with the complexes failing to associate with chromosomes.
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Affiliation(s)
- Karthik V Rajasekar
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Rachel Baker
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Gemma L M Fisher
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Jani R Bolla
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, UK
| | - Jarno Mäkelä
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Minzhe Tang
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Katarzyna Zawadzka
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Oliwia Koczy
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Florence Wagner
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Carol V Robinson
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, UK
| | - Lidia K Arciszewska
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - David J Sherratt
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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26
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Chromosome organization in bacteria: mechanistic insights into genome structure and function. Nat Rev Genet 2019; 21:227-242. [DOI: 10.1038/s41576-019-0185-4] [Citation(s) in RCA: 93] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/07/2019] [Indexed: 12/28/2022]
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27
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Abstract
Protein complexes built of structural maintenance of chromosomes (SMC) and kleisin subunits, including cohesin, condensin and the Smc5/6 complex, are master organizers of genome architecture in all kingdoms of life. How these large ring-shaped molecular machines use the energy of ATP hydrolysis to change the topology of chromatin fibers has remained a central unresolved question of chromosome biology. A currently emerging concept suggests that the common principle that underlies the essential functions of SMC protein complexes in the control of gene expression, chromosome segregation or DNA damage repair is their ability to expand DNA into large loop structures. Here, we review the current knowledge about the biochemical and structural properties of SMC protein complexes that might enable them to extrude DNA loops and compare their action to other motor proteins and nucleic acid translocases. We evaluate the currently predominant models of active loop extrusion and propose a detailed version of a 'scrunching' model, which reconciles much of the available mechanistic data and provides an elegant explanation for how SMC protein complexes fulfill an array of seemingly diverse tasks during the organization of genomes.
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28
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Brandão HB, Paul P, van den Berg AA, Rudner DZ, Wang X, Mirny LA. RNA polymerases as moving barriers to condensin loop extrusion. Proc Natl Acad Sci U S A 2019; 116:20489-20499. [PMID: 31548377 PMCID: PMC6789630 DOI: 10.1073/pnas.1907009116] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To separate replicated sister chromatids during mitosis, eukaryotes and prokaryotes have structural maintenance of chromosome (SMC) condensin complexes that were recently shown to organize chromosomes by a process known as DNA loop extrusion. In rapidly dividing bacterial cells, the process of separating sister chromatids occurs concomitantly with ongoing transcription. How transcription interferes with the condensin loop-extrusion process is largely unexplored, but recent experiments have shown that sites of high transcription may directionally affect condensin loop extrusion. We quantitatively investigate different mechanisms of interaction between condensin and elongating RNA polymerases (RNAPs) and find that RNAPs are likely steric barriers that can push and interact with condensins. Supported by chromosome conformation capture and chromatin immunoprecipitation for cells after transcription inhibition and RNAP degradation, we argue that translocating condensins must bypass transcribing RNAPs within ∼1 to 2 s of an encounter at rRNA genes and within ∼10 s at protein-coding genes. Thus, while individual RNAPs have little effect on the progress of loop extrusion, long, highly transcribed operons can significantly impede the extrusion process. Our data and quantitative models further suggest that bacterial condensin loop extrusion occurs by 2 independent, uncoupled motor activities; the motors translocate on DNA in opposing directions and function together to enlarge chromosomal loops, each independently bypassing steric barriers in their path. Our study provides a quantitative link between transcription and 3D genome organization and proposes a mechanism of interactions between SMC complexes and elongating transcription machinery relevant from bacteria to higher eukaryotes.
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Affiliation(s)
- Hugo B Brandão
- Graduate Program in Biophysics, Harvard University, Cambridge, MA 02138
| | - Payel Paul
- Department of Biology, Indiana University, Bloomington, IN 47405
| | - Aafke A van den Berg
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - David Z Rudner
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115
| | - Xindan Wang
- Department of Biology, Indiana University, Bloomington, IN 47405;
| | - Leonid A Mirny
- Graduate Program in Biophysics, Harvard University, Cambridge, MA 02138;
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139
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29
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Abstract
Condensins in bacteria are one of the most important factors involved in the organization of long threads of DNA into compact chromosomes. The organization of DNA by condensins is vital to many DNA transactions including DNA repair and chromosome segregation. Although some of the activities of condensins are well studied, the mechanism of the overall process executed by condensins, DNA compaction, remains unclear. Here, we describe some of the methods used routinely in our laboratory to understand the mechanism of DNA compaction by Escherichia coli condensin MukB.
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30
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In Vivo and In Vitro Assay for Monitoring the Topological Loading of Bacterial Condensins on DNA. Methods Mol Biol 2019. [PMID: 31147918 DOI: 10.1007/978-1-4939-9520-2_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Condensins play essential roles in the compaction and segregation of chromosomal DNA in life forms ranging from bacteria to higher organisms. To elucidate the molecular mechanisms underlying these roles, it is crucial to determine how and where condensins are loaded to chromosomal DNA. Here, we describe in vivo and in vitro assays for monitoring the topological loading of two bacterial condensins, Smc-ScpAB and MukBEF. A key step in these assays is washing the samples with a high concentration of salt in order to discriminate between electrostatic and topological binding of the bacterial condensins to DNA. In addition, isolation of bacterial condensin and DNA complexes prevents any undesired interaction between them due to cross-linking reagents. These methodologies provide reproducible and reliable results for the loading of topologically bound proteins such as bacterial condensins.
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31
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Bürmann F, Lee BG, Than T, Sinn L, O'Reilly FJ, Yatskevich S, Rappsilber J, Hu B, Nasmyth K, Löwe J. A folded conformation of MukBEF and cohesin. Nat Struct Mol Biol 2019; 26:227-236. [PMID: 30833788 PMCID: PMC6433275 DOI: 10.1038/s41594-019-0196-z] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Accepted: 01/25/2019] [Indexed: 11/09/2022]
Abstract
Structural maintenance of chromosomes (SMC)-kleisin complexes organize chromosomal DNAs in all domains of life, with key roles in chromosome segregation, DNA repair and regulation of gene expression. They function through the entrapment and active translocation of DNA, but the underlying conformational changes are largely unclear. Using structural biology, mass spectrometry and cross-linking, we investigated the architecture of two evolutionarily distant SMC-kleisin complexes: MukBEF from Escherichia coli, and cohesin from Saccharomyces cerevisiae. We show that both contain a dynamic coiled-coil discontinuity, the elbow, near the middle of their arms that permits a folded conformation. Bending at the elbow brings into proximity the hinge dimerization domain and the head-kleisin module, situated at opposite ends of the arms. Our findings favour SMC activity models that include a large conformational change in the arms, such as a relative movement between DNA contact sites during DNA loading and translocation.
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Affiliation(s)
| | | | - Thane Than
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, UK
| | - Ludwig Sinn
- Bioanalytics, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | - Francis J O'Reilly
- Bioanalytics, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | - Stanislau Yatskevich
- Department of Biochemistry, University of Oxford, Oxford, UK
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Juri Rappsilber
- Bioanalytics, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
- Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh, UK
| | - Bin Hu
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, UK
| | - Kim Nasmyth
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Jan Löwe
- MRC Laboratory of Molecular Biology, Cambridge, UK.
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32
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Voulgaris M, Gligoris TG. A Protocol for Assaying the ATPase Activity of Recombinant Cohesin Holocomplexes. Methods Mol Biol 2019; 2004:197-208. [PMID: 31147919 DOI: 10.1007/978-1-4939-9520-2_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2023]
Abstract
Cohesin and other members of the structural maintenance of chromosomes (SMC)-kleisin family such as condensin and Smc5-6, as well as central players in genome function and structure such as topoisomerases, DNA and RNA polymerases, and DNA repair enzymes contain nucleotide binding domains (NBD) which bind and eventually cleave ATP. The released energy is harnessed in various ways by these enzymes in order to fulfill their essential functions. However, unlike other enzymes, Smc-kleisin complexes-well sized, elongated and multisubunit in nature-have only recently been purified as holocomplexes. This progress offers both the opportunity and the challenge to determine in detail the potency of the ATPase activity of these large protein assemblies-typically exceeding 0.5 MDa in molecular weight-and examine its mechanistic features. We describe here in further detail a combined comprehensive protocol which we have successfully employed before for assaying the ATPase activity of recombinant budding yeast cohesin holocomplexes. We believe that with small and appropriate modifications the methods described here should be applicable to other ATPase complexes.
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33
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Paleček JJ, Vondrová L, Zábrady K, Otočka J. Multicomponent Yeast Two-Hybrid System: Applications to Study Protein-Protein Interactions in SMC Complexes. Methods Mol Biol 2019; 2004:79-90. [PMID: 31147911 DOI: 10.1007/978-1-4939-9520-2_7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Analysis of protein-protein interactions (PPI) is key for the understanding of most protein assemblies including structural maintenance of chromosomes (SMC) complexes. SMC complexes are composed of SMC proteins, kleisin, and kleisin-interacting subunits. These subunits interact in specific ways to constitute and regulate the closed structure of the complexes. Specifically, kleisin molecules bridge the SMC dimers and the kleisin-interacting subunits modulate stability of the bridge. Here we describe a multicomponent version of a yeast two-hybrid (Y2H) method and its application for analysis of the bridging role of the Nse4 kleisin in the SMC5/6 complex. Using this technique, we also show a stabilizing effect of KITE (kleisin-interacting tandem winged-helix element) proteins on SMC5/6.
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Affiliation(s)
- Jan Josef Paleček
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic. .,Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Brno, Czech Republic.
| | - Lucie Vondrová
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Kateřina Zábrady
- Genome Damage and Stability Centre, University of Sussex, Brighton, UK
| | - Jakub Otočka
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic
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34
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Palecek JJ. SMC5/6: Multifunctional Player in Replication. Genes (Basel) 2018; 10:genes10010007. [PMID: 30583551 PMCID: PMC6356406 DOI: 10.3390/genes10010007] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 12/18/2018] [Accepted: 12/19/2018] [Indexed: 12/13/2022] Open
Abstract
The genome replication process is challenged at many levels. Replication must proceed through different problematic sites and obstacles, some of which can pause or even reverse the replication fork (RF). In addition, replication of DNA within chromosomes must deal with their topological constraints and spatial organization. One of the most important factors organizing DNA into higher-order structures are Structural Maintenance of Chromosome (SMC) complexes. In prokaryotes, SMC complexes ensure proper chromosomal partitioning during replication. In eukaryotes, cohesin and SMC5/6 complexes assist in replication. Interestingly, the SMC5/6 complexes seem to be involved in replication in many ways. They stabilize stalled RFs, restrain RF regression, participate in the restart of collapsed RFs, and buffer topological constraints during RF progression. In this (mini) review, I present an overview of these replication-related functions of SMC5/6.
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Affiliation(s)
- Jan J Palecek
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic.
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic.
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35
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Baxter J, Oliver AW, Schalbetter SA. Are SMC Complexes Loop Extruding Factors? Linking Theory With Fact. Bioessays 2018; 41:e1800182. [PMID: 30506702 DOI: 10.1002/bies.201800182] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 11/05/2018] [Indexed: 01/24/2023]
Abstract
The extreme length of chromosomal DNA requires organizing mechanisms to both promote functional genetic interactions and ensure faithful chromosome segregation when cells divide. Microscopy and genome-wide contact frequency analyses indicate that intra-chromosomal looping of DNA is a primary pathway of chromosomal organization during all stages of the cell cycle. DNA loop extrusion has emerged as a unifying model for how chromosome loops are formed in cis in different genomic contexts and cell cycle stages. The highly conserved family of SMC complexes have been found to be required for DNA cis-looping and have been suggested to be the enzymatic core of loop extruding machines. Here, the current body of evidence available for the in vivo and in vitro action of SMC complexes is discussed and compared to the predictions made by the loop extrusion model. How SMC complexes may differentially act on chromatin to generate DNA loops and how they could work to generate the dynamic and functionally appropriate organization of DNA in cells is explored.
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Affiliation(s)
- Jonathan Baxter
- Genome Damage and Stability Centre, Science Park Road, University of Sussex, Falmer, Brighton, East Sussex BN1 9RQ, UK
| | - Antony W Oliver
- Genome Damage and Stability Centre, Science Park Road, University of Sussex, Falmer, Brighton, East Sussex BN1 9RQ, UK
| | - Stephanie A Schalbetter
- Genome Damage and Stability Centre, Science Park Road, University of Sussex, Falmer, Brighton, East Sussex BN1 9RQ, UK
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