1
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Nagasaka K, Davidson IF, Stocsits RR, Tang W, Wutz G, Batty P, Panarotto M, Litos G, Schleiffer A, Gerlich DW, Peters JM. Cohesin mediates DNA loop extrusion and sister chromatid cohesion by distinct mechanisms. Mol Cell 2023; 83:3049-3063.e6. [PMID: 37591243 DOI: 10.1016/j.molcel.2023.07.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 05/28/2023] [Accepted: 07/25/2023] [Indexed: 08/19/2023]
Abstract
Cohesin connects CTCF-binding sites and other genomic loci in cis to form chromatin loops and replicated DNA molecules in trans to mediate sister chromatid cohesion. Whether cohesin uses distinct or related mechanisms to perform these functions is unknown. Here, we describe a cohesin hinge mutant that can extrude DNA into loops but is unable to mediate cohesion in human cells. Our results suggest that the latter defect arises during cohesion establishment. The observation that cohesin's cohesion and loop extrusion activities can be partially separated indicates that cohesin uses distinct mechanisms to perform these two functions. Unexpectedly, the same hinge mutant can also not be stopped by CTCF boundaries as well as wild-type cohesin. This suggests that cohesion establishment and cohesin's interaction with CTCF boundaries depend on related mechanisms and raises the possibility that both require transient hinge opening to entrap DNA inside the cohesin ring.
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Affiliation(s)
- Kota Nagasaka
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna 1030, Austria
| | - Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna 1030, Austria
| | - Roman R Stocsits
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna 1030, Austria
| | - Wen Tang
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna 1030, Austria
| | - Gordana Wutz
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna 1030, Austria
| | - Paul Batty
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, Vienna 1030, Austria; Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna 1030, Austria
| | - Melanie Panarotto
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna 1030, Austria; Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna 1030, Austria
| | - Gabriele Litos
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna 1030, Austria
| | - Alexander Schleiffer
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna 1030, Austria; Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, Vienna 1030, Austria
| | - Daniel W Gerlich
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, Vienna 1030, Austria
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna 1030, Austria.
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2
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Barth R, Pradhan B, Kim E, Davidson IF, van der Torre J, Peters JM, Dekker C. Author Correction: Testing pseudotopological and nontopological models for SMC-driven DNA loop extrusion against roadblock-traversal experiments. Sci Rep 2023; 13:11616. [PMID: 37463951 DOI: 10.1038/s41598-023-38687-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023] Open
Affiliation(s)
- Roman Barth
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands
| | - Biswajit Pradhan
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands
- Max-Planck Institute of Biophysics, Frankfurt Am Main, Germany
| | - Eugene Kim
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands
- Max-Planck Institute of Biophysics, Frankfurt Am Main, Germany
| | - Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Jaco van der Torre
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands.
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3
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Barth R, Pradhan B, Kim E, Davidson IF, van der Torre J, Peters JM, Dekker C. Testing pseudotopological and nontopological models for SMC-driven DNA loop extrusion against roadblock-traversal experiments. Sci Rep 2023; 13:8100. [PMID: 37208374 DOI: 10.1038/s41598-023-35359-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 05/17/2023] [Indexed: 05/21/2023] Open
Abstract
DNA loop extrusion by structural-maintenance-of-chromosome (SMC) complexes has emerged as a primary organizing principle for chromosomes. The mechanism by which SMC motor proteins extrude DNA loops is still unresolved and much debated. The ring-like structure of SMC complexes prompted multiple models where the extruded DNA is topologically or pseudotopologically entrapped within the ring during loop extrusion. However, recent experiments showed the passage of roadblocks much bigger than the SMC ring size, suggesting a nontopological mechanism. Recently, attempts were made to reconcile the observed passage of large roadblocks with a pseudotopological mechanism. Here we examine the predictions of these pseudotopological models and find that they are not consistent with new experimental data on SMC roadblock encounters. Particularly, these models predict the formation of two loops and that roadblocks will reside near the stem of the loop upon encounter-both in contrast to experimental observations. Overall, the experimental data reinforce the notion of a nontopological mechanism for extrusion of DNA.
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Affiliation(s)
- Roman Barth
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands
| | - Biswajit Pradhan
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands
- Max-Planck Institute of Biophysics, Frankfurt Am Main, Germany
| | - Eugene Kim
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands
- Max-Planck Institute of Biophysics, Frankfurt Am Main, Germany
| | - Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Jaco van der Torre
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands.
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4
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Davidson IF, Barth R, Zaczek M, van der Torre J, Tang W, Nagasaka K, Janissen R, Kerssemakers J, Wutz G, Dekker C, Peters JM. CTCF is a DNA-tension-dependent barrier to cohesin-mediated loop extrusion. Nature 2023; 616:822-827. [PMID: 37076620 PMCID: PMC10132984 DOI: 10.1038/s41586-023-05961-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 03/16/2023] [Indexed: 04/21/2023]
Abstract
In eukaryotes, genomic DNA is extruded into loops by cohesin1. By restraining this process, the DNA-binding protein CCCTC-binding factor (CTCF) generates topologically associating domains (TADs)2,3 that have important roles in gene regulation and recombination during development and disease1,4-7. How CTCF establishes TAD boundaries and to what extent these are permeable to cohesin is unclear8. Here, to address these questions, we visualize interactions of single CTCF and cohesin molecules on DNA in vitro. We show that CTCF is sufficient to block diffusing cohesin, possibly reflecting how cohesive cohesin accumulates at TAD boundaries, and is also sufficient to block loop-extruding cohesin, reflecting how CTCF establishes TAD boundaries. CTCF functions asymmetrically, as predicted; however, CTCF is dependent on DNA tension. Moreover, CTCF regulates cohesin's loop-extrusion activity by changing its direction and by inducing loop shrinkage. Our data indicate that CTCF is not, as previously assumed, simply a barrier to cohesin-mediated loop extrusion but is an active regulator of this process, whereby the permeability of TAD boundaries can be modulated by DNA tension. These results reveal mechanistic principles of how CTCF controls loop extrusion and genome architecture.
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Affiliation(s)
- Iain F Davidson
- Research Institute of Molecular Pathology, Vienna BioCenter, Vienna, Austria
| | - Roman Barth
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, Netherlands
| | - Maciej Zaczek
- Research Institute of Molecular Pathology, Vienna BioCenter, Vienna, Austria
- Children's Cancer Research Institute, St Anna Kinderkrebsforschung, Vienna, Austria
| | - Jaco van der Torre
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, Netherlands
| | - Wen Tang
- Research Institute of Molecular Pathology, Vienna BioCenter, Vienna, Austria
| | - Kota Nagasaka
- Research Institute of Molecular Pathology, Vienna BioCenter, Vienna, Austria
| | - Richard Janissen
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, Netherlands
| | - Jacob Kerssemakers
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, Netherlands
| | - Gordana Wutz
- Research Institute of Molecular Pathology, Vienna BioCenter, Vienna, Austria
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, Netherlands.
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology, Vienna BioCenter, Vienna, Austria.
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Pradhan B, Barth R, Kim E, Davidson IF, Bauer B, van Laar T, Yang W, Ryu JK, van der Torre J, Peters JM, Dekker C. SMC complexes can traverse physical roadblocks bigger than their ring size. Cell Rep 2022; 41:111491. [PMID: 36261017 DOI: 10.1101/2021.07.15.452501] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Revised: 05/19/2022] [Accepted: 09/21/2022] [Indexed: 05/17/2023] Open
Abstract
Ring-shaped structural maintenance of chromosomes (SMC) complexes like condensin and cohesin extrude loops of DNA. It remains, however, unclear how they can extrude DNA loops in chromatin that is bound with proteins. Here, we use in vitro single-molecule visualization to show that nucleosomes, RNA polymerase, and dCas9 pose virtually no barrier to loop extrusion by yeast condensin. We find that even DNA-bound nanoparticles as large as 200 nm, much bigger than the SMC ring size, also translocate into DNA loops during extrusion by condensin and cohesin. This even occurs for a single-chain version of cohesin in which the ring-forming subunits are covalently linked and cannot open to entrap DNA. The data show that SMC-driven loop extrusion has surprisingly little difficulty in accommodating large roadblocks into the loop. The findings also show that the extruded DNA does not pass through the SMC ring (pseudo)topologically, hence pointing to a nontopological mechanism for DNA loop extrusion.
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Affiliation(s)
- Biswajit Pradhan
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Roman Barth
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Eugene Kim
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Benedikt Bauer
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Theo van Laar
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands; Nynke Dekker Lab, Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Wayne Yang
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Je-Kyung Ryu
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Jaco van der Torre
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands.
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Dequeker BJH, Scherr MJ, Brandão HB, Gassler J, Powell S, Gaspar I, Flyamer IM, Lalic A, Tang W, Stocsits R, Davidson IF, Peters JM, Duderstadt KE, Mirny LA, Tachibana K. MCM complexes are barriers that restrict cohesin-mediated loop extrusion. Nature 2022; 606:197-203. [PMID: 35585235 PMCID: PMC9159944 DOI: 10.1038/s41586-022-04730-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 04/06/2022] [Indexed: 12/23/2022]
Abstract
Eukaryotic genomes are compacted into loops and topologically associating domains (TADs)1-3, which contribute to transcription, recombination and genomic stability4,5. Cohesin extrudes DNA into loops that are thought to lengthen until CTCF boundaries are encountered6-12. Little is known about whether loop extrusion is impeded by DNA-bound machines. Here we show that the minichromosome maintenance (MCM) complex is a barrier that restricts loop extrusion in G1 phase. Single-nucleus Hi-C (high-resolution chromosome conformation capture) of mouse zygotes reveals that MCM loading reduces CTCF-anchored loops and decreases TAD boundary insulation, which suggests that loop extrusion is impeded before reaching CTCF. This effect extends to HCT116 cells, in which MCMs affect the number of CTCF-anchored loops and gene expression. Simulations suggest that MCMs are abundant, randomly positioned and partially permeable barriers. Single-molecule imaging shows that MCMs are physical barriers that frequently constrain cohesin translocation in vitro. Notably, chimeric yeast MCMs that contain a cohesin-interaction motif from human MCM3 induce cohesin pausing, indicating that MCMs are 'active' barriers with binding sites. These findings raise the possibility that cohesin can arrive by loop extrusion at MCMs, which determine the genomic sites at which sister chromatid cohesion is established. On the basis of in vivo, in silico and in vitro data, we conclude that distinct loop extrusion barriers shape the three-dimensional genome.
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Affiliation(s)
- Bart J H Dequeker
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), Vienna, Austria
| | - Matthias J Scherr
- Structure and Dynamics of Molecular Machines, Max Planck Institute of Biochemistry (MPIB), Martinsried, Germany
| | - Hugo B Brandão
- Harvard Program in Biophysics, Harvard University, Cambridge, MA, USA
- Illumina Inc., San Diego, CA, USA
| | - Johanna Gassler
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), Vienna, Austria
- Department of Totipotency, Max Planck Institute of Biochemistry (MPIB), Martinsried, Germany
| | - Sean Powell
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), Vienna, Austria
| | - Imre Gaspar
- Department of Totipotency, Max Planck Institute of Biochemistry (MPIB), Martinsried, Germany
| | - Ilya M Flyamer
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine (IGMM), University of Edinburgh, Edinburgh, UK
| | - Aleksandar Lalic
- Department of Totipotency, Max Planck Institute of Biochemistry (MPIB), Martinsried, Germany
| | - Wen Tang
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - Roman Stocsits
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - Karl E Duderstadt
- Structure and Dynamics of Molecular Machines, Max Planck Institute of Biochemistry (MPIB), Martinsried, Germany.
- Department of Physics, Technical University of Munich, Garching, Germany.
| | - Leonid A Mirny
- Department of Physics, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA.
| | - Kikuë Tachibana
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), Vienna, Austria.
- Department of Totipotency, Max Planck Institute of Biochemistry (MPIB), Martinsried, Germany.
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7
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Panarotto M, Davidson IF, Litos G, Schleiffer A, Peters JM. Cornelia de Lange syndrome mutations in NIPBL can impair cohesin-mediated DNA loop extrusion. Proc Natl Acad Sci U S A 2022; 119:e2201029119. [PMID: 35476527 PMCID: PMC9170158 DOI: 10.1073/pnas.2201029119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Accepted: 03/25/2022] [Indexed: 11/22/2022] Open
Abstract
Cornelia de Lange syndrome (CdLS) is a developmental multisystem disorder frequently associated with mutations in NIPBL. CdLS is thought to arise from developmental gene regulation defects, but how NIPBL mutations cause these is unknown. Here we show that several NIPBL mutations impair the DNA loop extrusion activity of cohesin. Because this activity is required for the formation of chromatin loops and topologically associating domains, which have important roles in gene regulation, our results suggest that defects in cohesin-mediated loop extrusion contribute to the etiology of CdLS by altering interactions between developmental genes and their enhancers.
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Affiliation(s)
- Melanie Panarotto
- Research Institute of Molecular Pathology, Vienna BioCenter, 1030 Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, A-1030 Vienna, Austria
| | - Iain F. Davidson
- Research Institute of Molecular Pathology, Vienna BioCenter, 1030 Vienna, Austria
| | - Gabriele Litos
- Research Institute of Molecular Pathology, Vienna BioCenter, 1030 Vienna, Austria
| | - Alexander Schleiffer
- Research Institute of Molecular Pathology, Vienna BioCenter, 1030 Vienna, Austria
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology, Vienna BioCenter, 1030 Vienna, Austria
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Bauer BW, Davidson IF, Canena D, Wutz G, Tang W, Litos G, Horn S, Hinterdorfer P, Peters JM. Cohesin mediates DNA loop extrusion by a "swing and clamp" mechanism. Cell 2021; 184:5448-5464.e22. [PMID: 34624221 PMCID: PMC8563363 DOI: 10.1016/j.cell.2021.09.016] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 08/02/2021] [Accepted: 09/09/2021] [Indexed: 10/28/2022]
Abstract
Structural maintenance of chromosomes (SMC) complexes organize genome topology in all kingdoms of life and have been proposed to perform this function by DNA loop extrusion. How this process works is unknown. Here, we have analyzed how loop extrusion is mediated by human cohesin-NIPBL complexes, which enable chromatin folding in interphase cells. We have identified DNA binding sites and large-scale conformational changes that are required for loop extrusion and have determined how these are coordinated. Our results suggest that DNA is translocated by a spontaneous 50 nm-swing of cohesin's hinge, which hands DNA over to the ATPase head of SMC3, where upon binding of ATP, DNA is clamped by NIPBL. During this process, NIPBL "jumps ship" from the hinge toward the SMC3 head and might thereby couple the spontaneous hinge swing to ATP-dependent DNA clamping. These results reveal mechanistic principles of how cohesin-NIPBL and possibly other SMC complexes mediate loop extrusion.
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Affiliation(s)
- Benedikt W Bauer
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC) Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC) Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Daniel Canena
- Insitute for Biophysics, Johannes Kepler University Linz, Life Science Center, Gruberstrasse 40, 4020 Linz, Austria
| | - Gordana Wutz
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC) Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Wen Tang
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC) Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Gabriele Litos
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC) Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Sabrina Horn
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC) Campus-Vienna-Biocenter 1, 1030 Vienna, Austria; Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, A-1030 Vienna, Austria
| | - Peter Hinterdorfer
- Insitute for Biophysics, Johannes Kepler University Linz, Life Science Center, Gruberstrasse 40, 4020 Linz, Austria
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC) Campus-Vienna-Biocenter 1, 1030 Vienna, Austria.
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9
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Abstract
Genomic DNA is folded into loops and topologically associating domains (TADs), which serve important structural and regulatory roles. It has been proposed that these genomic structures are formed by a loop extrusion process, which is mediated by structural maintenance of chromosomes (SMC) protein complexes. Recent single-molecule studies have shown that the SMC complexes condensin and cohesin are indeed able to extrude DNA into loops. In this Review, we discuss how the loop extrusion hypothesis can explain key features of genome architecture; cellular functions of loop extrusion, such as separation of replicated DNA molecules, facilitation of enhancer-promoter interactions and immunoglobulin gene recombination; and what is known about the mechanism of loop extrusion and its regulation, for example, by chromatin boundaries that depend on the DNA binding protein CTCF. We also discuss how the loop extrusion hypothesis has led to a paradigm shift in our understanding of both genome architecture and the functions of SMC complexes.
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Affiliation(s)
- Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria.
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10
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Abstract
Eukaryotic genomes are folded into loops and topologically associating domains, which contribute to chromatin structure, gene regulation, and gene recombination. These structures depend on cohesin, a ring-shaped DNA-entrapping adenosine triphosphatase (ATPase) complex that has been proposed to form loops by extrusion. Such an activity has been observed for condensin, which forms loops in mitosis, but not for cohesin. Using biochemical reconstitution, we found that single human cohesin complexes form DNA loops symmetrically at rates up to 2.1 kilo-base pairs per second. Loop formation and maintenance depend on cohesin's ATPase activity and on NIPBL-MAU2, but not on topological entrapment of DNA by cohesin. During loop formation, cohesin and NIPBL-MAU2 reside at the base of loops, which indicates that they generate loops by extrusion. Our results show that cohesin and NIPBL-MAU2 form an active holoenzyme that interacts with DNA either pseudo-topologically or non-topologically to extrude genomic interphase DNA into loops.
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Affiliation(s)
- Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Benedikt Bauer
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Daniela Goetz
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Wen Tang
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Gordana Wutz
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria.
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11
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Davidson IF, Goetz D, Zaczek MP, Molodtsov MI, Huis In 't Veld PJ, Weissmann F, Litos G, Cisneros DA, Ocampo-Hafalla M, Ladurner R, Uhlmann F, Vaziri A, Peters JM. Rapid movement and transcriptional re-localization of human cohesin on DNA. EMBO J 2016; 35:2671-2685. [PMID: 27799150 PMCID: PMC5167347 DOI: 10.15252/embj.201695402] [Citation(s) in RCA: 154] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 09/08/2016] [Accepted: 10/03/2016] [Indexed: 01/17/2023] Open
Abstract
The spatial organization, correct expression, repair, and segregation of eukaryotic genomes depend on cohesin, ring-shaped protein complexes that are thought to function by entrapping DNA It has been proposed that cohesin is recruited to specific genomic locations from distal loading sites by an unknown mechanism, which depends on transcription, and it has been speculated that cohesin movements along DNA could create three-dimensional genomic organization by loop extrusion. However, whether cohesin can translocate along DNA is unknown. Here, we used single-molecule imaging to show that cohesin can diffuse rapidly on DNA in a manner consistent with topological entrapment and can pass over some DNA-bound proteins and nucleosomes but is constrained in its movement by transcription and DNA-bound CCCTC-binding factor (CTCF). These results indicate that cohesin can be positioned in the genome by moving along DNA, that transcription can provide directionality to these movements, that CTCF functions as a boundary element for moving cohesin, and they are consistent with the hypothesis that cohesin spatially organizes the genome via loop extrusion.
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Affiliation(s)
- Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | - Daniela Goetz
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | - Maciej P Zaczek
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | - Maxim I Molodtsov
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
| | | | | | - Gabriele Litos
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | - David A Cisneros
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | | | - Rene Ladurner
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
| | | | - Alipasha Vaziri
- Research Institute of Molecular Pathology (IMP), Vienna, Austria
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
- The Rockefeller University, New York, NY, USA
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12
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Brown NG, VanderLinden R, Watson ER, Weissmann F, Ordureau A, Wu KP, Zhang W, Yu S, Mercredi PY, Harrison JS, Davidson IF, Qiao R, Lu Y, Dube P, Brunner MR, Grace CRR, Miller DJ, Haselbach D, Jarvis MA, Yamaguchi M, Yanishevski D, Petzold G, Sidhu SS, Kuhlman B, Kirschner MW, Harper JW, Peters JM, Stark H, Schulman BA. Dual RING E3 Architectures Regulate Multiubiquitination and Ubiquitin Chain Elongation by APC/C. Cell 2016; 165:1440-1453. [PMID: 27259151 DOI: 10.1016/j.cell.2016.05.037] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 04/16/2016] [Accepted: 05/09/2016] [Indexed: 11/25/2022]
Abstract
Protein ubiquitination involves E1, E2, and E3 trienzyme cascades. E2 and RING E3 enzymes often collaborate to first prime a substrate with a single ubiquitin (UB) and then achieve different forms of polyubiquitination: multiubiquitination of several sites and elongation of linkage-specific UB chains. Here, cryo-EM and biochemistry show that the human E3 anaphase-promoting complex/cyclosome (APC/C) and its two partner E2s, UBE2C (aka UBCH10) and UBE2S, adopt specialized catalytic architectures for these two distinct forms of polyubiquitination. The APC/C RING constrains UBE2C proximal to a substrate and simultaneously binds a substrate-linked UB to drive processive multiubiquitination. Alternatively, during UB chain elongation, the RING does not bind UBE2S but rather lures an evolving substrate-linked UB to UBE2S positioned through a cullin interaction to generate a Lys11-linked chain. Our findings define mechanisms of APC/C regulation, and establish principles by which specialized E3-E2-substrate-UB architectures control different forms of polyubiquitination.
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Affiliation(s)
- Nicholas G Brown
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Ryan VanderLinden
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, Memphis, TN 38105, USA
| | - Edmond R Watson
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Florian Weissmann
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria
| | - Alban Ordureau
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Kuen-Phon Wu
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Wei Zhang
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, Ontario M5S3E1, Canada
| | - Shanshan Yu
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Peter Y Mercredi
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Joseph S Harrison
- Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria
| | - Renping Qiao
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria
| | - Ying Lu
- Department of Systems Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - Prakash Dube
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Michael R Brunner
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Christy R R Grace
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Darcie J Miller
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - David Haselbach
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Marc A Jarvis
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria
| | - Masaya Yamaguchi
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - David Yanishevski
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Georg Petzold
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria
| | - Sachdev S Sidhu
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, Ontario M5S3E1, Canada
| | - Brian Kuhlman
- Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Marc W Kirschner
- Department of Systems Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - J Wade Harper
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria.
| | - Holger Stark
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
| | - Brenda A Schulman
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, Memphis, TN 38105, USA.
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Huis in 't Veld PJ, Herzog F, Ladurner R, Davidson IF, Piric S, Kreidl E, Bhaskara V, Aebersold R, Peters JM. Characterization of a DNA exit gate in the human cohesin ring. Science 2014; 346:968-72. [PMID: 25414306 DOI: 10.1126/science.1256904] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Chromosome segregation depends on sister chromatid cohesion mediated by cohesin. The cohesin subunits Smc1, Smc3, and Scc1 form tripartite rings that are thought to open at distinct sites to allow entry and exit of DNA. However, direct evidence for the existence of open forms of cohesin is lacking. We found that cohesin's proposed DNA exit gate is formed by interactions between Scc1 and the coiled-coil region of Smc3. Mutation of this interface abolished cohesin's ability to stably associate with chromatin and to mediate cohesion. Electron microscopy revealed that weakening of the Smc3-Scc1 interface resulted in opening of cohesin rings, as did proteolytic cleavage of Scc1. These open forms may resemble intermediate states of cohesin normally generated by the release factor Wapl and the protease separase, respectively.
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Affiliation(s)
- Pim J Huis in 't Veld
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria
| | - Franz Herzog
- Department of Biology, Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, 8093 Zurich, Switzerland. Department of Biochemistry, Gene Center, Ludwig-Maximilian University, 81377 Munich, Germany
| | - Rene Ladurner
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria
| | - Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria
| | - Sabina Piric
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria
| | - Emanuel Kreidl
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria
| | - Venugopal Bhaskara
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria
| | - Ruedi Aebersold
- Department of Biology, Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, 8093 Zurich, Switzerland
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria.
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Brown NG, Watson ER, Weissmann F, Jarvis MA, VanderLinden R, Grace CRR, Frye JJ, Qiao R, Dube P, Petzold G, Cho SE, Alsharif O, Bao J, Davidson IF, Zheng JJ, Nourse A, Kurinov I, Peters JM, Stark H, Schulman BA. Mechanism of polyubiquitination by human anaphase-promoting complex: RING repurposing for ubiquitin chain assembly. Mol Cell 2014; 56:246-260. [PMID: 25306923 DOI: 10.1016/j.molcel.2014.09.009] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 08/29/2014] [Accepted: 09/03/2014] [Indexed: 11/17/2022]
Abstract
Polyubiquitination by E2 and E3 enzymes is a predominant mechanism regulating protein function. Some RING E3s, including anaphase-promoting complex/cyclosome (APC), catalyze polyubiquitination by sequential reactions with two different E2s. An initiating E2 ligates ubiquitin to an E3-bound substrate. Another E2 grows a polyubiquitin chain on the ubiquitin-primed substrate through poorly defined mechanisms. Here we show that human APC's RING domain is repurposed for dual functions in polyubiquitination. The canonical RING surface activates an initiating E2-ubiquitin intermediate for substrate modification. However, APC engages and activates its specialized ubiquitin chain-elongating E2 UBE2S in ways that differ from current paradigms. During chain assembly, a distinct APC11 RING surface helps deliver a substrate-linked ubiquitin to accept another ubiquitin from UBE2S. Our data define mechanisms of APC/UBE2S-mediated polyubiquitination, reveal diverse functions of RING E3s and E2s, and provide a framework for understanding distinctive RING E3 features specifying ubiquitin chain elongation.
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Affiliation(s)
- Nicholas G Brown
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Edmond R Watson
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, Memphis, TN 38163, USA
| | - Florian Weissmann
- Research Institute of Molecular Pathology (IMP), 1030 Vienna, Austria
| | - Marc A Jarvis
- Research Institute of Molecular Pathology (IMP), 1030 Vienna, Austria
| | - Ryan VanderLinden
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Christy R R Grace
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jeremiah J Frye
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Renping Qiao
- Research Institute of Molecular Pathology (IMP), 1030 Vienna, Austria
| | - Prakash Dube
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany; Department of 3D Electron Cryomicroscopy, Institute of Microbiology and Genetics, Georg-August Universität, 37077 Göttingen, Germany
| | - Georg Petzold
- Research Institute of Molecular Pathology (IMP), 1030 Vienna, Austria
| | - Shein Ei Cho
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Omar Alsharif
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Ju Bao
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Iain F Davidson
- Research Institute of Molecular Pathology (IMP), 1030 Vienna, Austria
| | - Jie J Zheng
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Amanda Nourse
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Igor Kurinov
- NE-CAT, Bldg. 436E, Department of Chemistry and Chemical Biology, Cornell University, Argonne, IL 60439, USA
| | | | - Holger Stark
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany; Department of 3D Electron Cryomicroscopy, Institute of Microbiology and Genetics, Georg-August Universität, 37077 Göttingen, Germany.
| | - Brenda A Schulman
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
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15
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Ladurner R, Bhaskara V, Huis in 't Veld PJ, Davidson IF, Kreidl E, Petzold G, Peters JM. Cohesin's ATPase activity couples cohesin loading onto DNA with Smc3 acetylation. Curr Biol 2014; 24:2228-37. [PMID: 25220052 PMCID: PMC4188815 DOI: 10.1016/j.cub.2014.08.011] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 07/10/2014] [Accepted: 08/06/2014] [Indexed: 12/13/2022]
Abstract
BACKGROUND Cohesin mediates sister chromatid cohesion by topologically entrapping sister DNA molecules inside its ring structure. Cohesin is loaded onto DNA by the Scc2/NIPBL-Scc4/MAU2-loading complex in a manner that depends on the adenosine triphosphatase (ATPase) activity of cohesin's Smc1 and Smc3 subunits. Subsequent cohesion establishment during DNA replication depends on Smc3 acetylation by Esco1 and Esco2 and on recruitment of sororin, which "locks" cohesin on DNA by inactivating the cohesin release factor Wapl. RESULTS Human cohesin ATPase mutants associate transiently with DNA in a manner that depends on the loading complex but cannot be stabilized on chromatin by depletion of Wapl. These mutants cannot be acetylated, fail to interact with sororin, and do not mediate cohesion. The absence of Smc3 acetylation in the ATPase mutants is not a consequence of their transient association with DNA but is directly caused by their inability to hydrolyze ATP because acetylation of wild-type cohesin also depends on ATP hydrolysis. CONCLUSIONS Our data indicate that cohesion establishment involves the following steps. First, cohesin transiently associates with DNA in a manner that depends on the loading complex. Subsequently, ATP hydrolysis by cohesin leads to entrapment of DNA and converts Smc3 into a state that can be acetylated. Finally, Smc3 acetylation leads to recruitment of sororin, inhibition of Wapl, and stabilization of cohesin on DNA. Our finding that cohesin's ATPase activity is required for both cohesin loading and Smc3 acetylation raises the possibility that cohesion establishment is directly coupled to the reaction in which cohesin entraps DNA.
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Affiliation(s)
- Rene Ladurner
- Research Institute of Molecular Pathology, Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Venugopal Bhaskara
- Research Institute of Molecular Pathology, Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | | | - Iain F Davidson
- Research Institute of Molecular Pathology, Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Emanuel Kreidl
- Research Institute of Molecular Pathology, Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Georg Petzold
- Research Institute of Molecular Pathology, Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology, Dr. Bohr-Gasse 7, 1030 Vienna, Austria.
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Mall M, Walter T, Gorjánácz M, Davidson IF, Nga Ly-Hartig TB, Ellenberg J, Mattaj IW. Mitotic lamin disassembly is triggered by lipid-mediated signaling. J Cell Biol 2012; 198:981-90. [PMID: 22986494 PMCID: PMC3444782 DOI: 10.1083/jcb.201205103] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 08/20/2012] [Indexed: 11/22/2022] Open
Abstract
Disassembly of the nuclear lamina is a key step during open mitosis in higher eukaryotes. The activity of several kinases, including CDK1 (cyclin-dependent kinase 1) and protein kinase C (PKC), has been shown to trigger mitotic lamin disassembly, yet their precise contributions are unclear. In this study, we develop a quantitative imaging assay to study mitotic lamin B1 disassembly in living cells. We find that CDK1 and PKC act in concert to mediate phosphorylation-dependent lamin B1 disassembly during mitosis. Using ribonucleic acid interference (RNAi), we showed that diacylglycerol (DAG)-dependent PKCs triggered rate-limiting steps of lamin disassembly. RNAi-mediated depletion or chemical inhibition of lipins, enzymes that produce DAG, delayed lamin disassembly to a similar extent as does PKC inhibition/depletion. Furthermore, the delay of lamin B1 disassembly after lipin depletion could be rescued by the addition of DAG. These findings suggest that lipins activate a PKC-dependent pathway during mitotic lamin disassembly and provide evidence for a lipid-mediated mitotic signaling event.
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Affiliation(s)
- Moritz Mall
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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Davidson IF, Li A, Blow JJ. Deregulated replication licensing causes DNA fragmentation consistent with head-to-tail fork collision. Mol Cell 2006; 24:433-43. [PMID: 17081992 PMCID: PMC1819398 DOI: 10.1016/j.molcel.2006.09.010] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Revised: 08/07/2006] [Accepted: 09/18/2006] [Indexed: 12/29/2022]
Abstract
Correct regulation of the replication licensing system ensures that no DNA is rereplicated in a single cell cycle. When the licensing protein Cdt1 is overexpressed in G2 phase of the cell cycle, replication origins are relicensed and the DNA is rereplicated. At the same time, checkpoint pathways are activated that block further cell cycle progression. We have studied the consequence of deregulating the licensing system by adding recombinant Cdt1 to Xenopus egg extracts. We show that Cdt1 induces checkpoint activation and the appearance of small fragments of double-stranded DNA. DNA fragmentation and strong checkpoint activation are dependent on uncontrolled rereplication and do not occur after a single coordinated round of rereplication. The DNA fragments are composed exclusively of rereplicated DNA. The unusual characteristics of these fragments suggest that they result from head-to-tail collision (rear ending) of replication forks chasing one another along the same DNA template.
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Affiliation(s)
- Iain F. Davidson
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
| | - Anatoliy Li
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
| | - J. Julian Blow
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
- Corresponding author
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Simmons JN, Davidson IF. Mediating the environment: a case study approach. Child Care Health Dev 1985; 11:195-207. [PMID: 4053288 DOI: 10.1111/j.1365-2214.1985.tb00464.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Two case studies are presented as a means of examining aspects of mediating the environment for young blind children. Following the child's history, clinical observations are offered on each case. A general discussion highlights the salient requirements of mediation with children born blind.
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Abstract
Problems of early intervention with young blind children are analysed from a conceptual perspective. Mediation is linked to the unique developmental mode of blind children and the relationship illustrated through the analysis of some familiar problems in intervention.
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