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Cees Dekker - One of the best experts on this subject based on the ideXlab platform.
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The condensin holocomplex cycles dynamically between open and collapsed states
Nature Structural & Molecular Biology, 2020Co-Authors: Je-kyung Ryu, Allard J. Katan, Christian H. Haering, Eli O. Sluis, Thomas Wisse, Ralph Groot, Cees DekkerAbstract:Atomic force microscopy imaging of yeast condensin indicates that condensin may extrude DNA by switching conformation between open O and collapsed B shapes, indicative of a type of scrunching model. Structural maintenance of chromosome (SMC) Protein complexes are the key organizers of the spatiotemporal structure of chromosomes. The condensin SMC complex has recently been shown to be a molecular motor that extrudes large loops of DNA, but the mechanism of this unique motor remains elusive. Using atomic force microscopy, we show that budding yeast condensin exhibits mainly open ‘O’ shapes and collapsed ‘B’ shapes, and it cycles dynamically between these two states over time, with ATP binding inducing the O to B transition. Condensin binds DNA via its globular domain and also via the hinge domain. We observe a single condensin complex at the stem of extruded DNA loops, where the neck size of the DNA loop correlates with the width of the condensin complex. The results are indicative of a type of scrunching model in which condensin extrudes DNA by a cyclic switching of its conformation between O and B shapes.
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dna loop extruding condensin complexes can traverse one another
Nature, 2020Co-Authors: Eugene Kim, Christian H. Haering, Jacob W J Kerssemakers, Indra A Shaltiel, Cees DekkerAbstract:Condensin, a key component of the structure maintenance of chromosome (SMC) Protein complexes, has recently been shown to be a motor that extrudes loops of DNA1. It remains unclear, however, how condensin complexes work together to collectively package DNA into chromosomes. Here we use time-lapse single-molecule visualization to study mutual interactions between two DNA-loop-extruding yeast condensins. We find that these motor Proteins, which, individually, extrude DNA in one direction only are able to dynamically change each other’s DNA loop sizes, even when far apart. When they are in close proximity, condensin complexes are able to traverse each other and form a loop structure, which we term a Z-loop—three double-stranded DNA helices aligned in parallel with one condensin at each edge. Z-loops can fill gaps left by single loops and can form symmetric dimer motors that pull in DNA from both sides. These findings indicate that condensin may achieve chromosomal compaction using a variety of looping structures.
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dna loop extruding condensin complexes can traverse one another
Biophysical Journal, 2020Co-Authors: Eugene Kim, Christian H. Haering, Jacob W J Kerssemakers, Indra A Shaltiel, Cees DekkerAbstract:Condensin, a key member of the Structure Maintenance of Chromosome (SMC) Protein complexes, has recently been shown to be a motor that extrudes loops of DNA1. It remains unclear, however, how condensin complexes work together to collectively package DNA into the chromosomal architecture. Here, we use time-lapse single-molecule visualization to study mutual interactions between two DNA-loop-extruding yeast condensins. We find that these one-side-pulling motor Proteins are able to dynamically change each other’s DNA loop sizes, even when located large distances apart. When coming into close proximity upon forming a loop within a loop, condensin complexes are, surprisingly, able to traverse each other and form a new type of loop structure, which we term Z loop – three double-stranded DNA helices aligned in parallel with one condensin at each edge. These Z-loops can fill gaps left by single loops and can form symmetric dimer motors that reel in DNA from both sides. These new findings indicate that condensin may achieve chromosomal compaction using a variety of looping structures.
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real time imaging of dna loop extrusion by condensin
Science, 2018Co-Authors: Mahipal Ganji, Christian H. Haering, Shveta Bisht, Eugene Kim, Indra A Shaltiel, Ana Kalichava, Cees DekkerAbstract:It has been hypothesized that SMC Protein complexes such as condensin and cohesin spatially organize chromosomes by extruding DNA into large loops. We directly visualized the formation and processive extension of DNA loops by yeast condensin in real time. Our findings constitute unambiguous evidence for loop extrusion. We observed that a single condensin complex is able to extrude tens of kilobase pairs of DNA at a force-dependent speed of up to 1500 base pairs per second, using the energy of adenosine triphosphate hydrolysis. Condensin-induced loop extrusion was strictly asymmetric, which demonstrates that condensin anchors onto DNA and reels it in from only one side. Active DNA loop extrusion by SMC complexes may provide the universal unifying principle for genome organization.
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real time detection of condensin driven dna compaction reveals a multistep binding mechanism
The EMBO Journal, 2017Co-Authors: Jorine M. Eeftens, Marc Kschonsak, Christian H. Haering, Shveta Bisht, Jacob W J Kerssemakers, Cees DekkerAbstract:Condensin, a conserved member of the SMC Protein family of ring-shaped multi-subunit Protein complexes, is essential for structuring and compacting chromosomes. Despite its key role, its molecular mechanism has remained largely unknown. Here, we employ single-molecule magnetic tweezers to measure, in real time, the compaction of individual DNA molecules by the budding yeast condensin complex. We show that compaction can proceed in large steps, driving DNA molecules into a fully condensed state against forces of up to 2 pN. Compaction can be reversed by applying high forces or adding buffer of high ionic strength. While condensin can stably bind DNA in the absence of ATP, ATP hydrolysis by the SMC subunits is required for rendering the association salt insensitive and for the subsequent compaction process. Our results indicate that the condensin reaction cycle involves two distinct steps, where condensin first binds DNA through electrostatic interactions before using ATP hydrolysis to encircle the DNA topologically within its ring structure, which initiates DNA compaction. The finding that both binding modes are essential for its DNA compaction activity has important implications for understanding the mechanism of chromosome compaction.
Christian H. Haering - One of the best experts on this subject based on the ideXlab platform.
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structural insights into dna loop extrusion by SMC Protein complexes
Current Opinion in Structural Biology, 2020Co-Authors: Sumanjit Datta, Christian H. Haering, Lea LecomteAbstract:Structural Maintenance of Chromosomes (SMC) Protein complexes play key roles in the three-dimensional organization of genomes in all kingdoms of life. Recent insights from chromosome contact mapping experiments and single-molecule imaging assays suggest that these complexes achieve distinct cellular functions by extruding large loops of DNA while they move along the chromatin fiber. In this short review, we summarize recent insights into the molecular architecture of these unconventional DNA motor complexes, their interaction with their DNA substrates, and the remarkable dynamic changes they can undergo during their ATPase reaction cycle.
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The condensin holocomplex cycles dynamically between open and collapsed states
Nature Structural & Molecular Biology, 2020Co-Authors: Je-kyung Ryu, Allard J. Katan, Christian H. Haering, Eli O. Sluis, Thomas Wisse, Ralph Groot, Cees DekkerAbstract:Atomic force microscopy imaging of yeast condensin indicates that condensin may extrude DNA by switching conformation between open O and collapsed B shapes, indicative of a type of scrunching model. Structural maintenance of chromosome (SMC) Protein complexes are the key organizers of the spatiotemporal structure of chromosomes. The condensin SMC complex has recently been shown to be a molecular motor that extrudes large loops of DNA, but the mechanism of this unique motor remains elusive. Using atomic force microscopy, we show that budding yeast condensin exhibits mainly open ‘O’ shapes and collapsed ‘B’ shapes, and it cycles dynamically between these two states over time, with ATP binding inducing the O to B transition. Condensin binds DNA via its globular domain and also via the hinge domain. We observe a single condensin complex at the stem of extruded DNA loops, where the neck size of the DNA loop correlates with the width of the condensin complex. The results are indicative of a type of scrunching model in which condensin extrudes DNA by a cyclic switching of its conformation between O and B shapes.
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dna loop extruding condensin complexes can traverse one another
Nature, 2020Co-Authors: Eugene Kim, Christian H. Haering, Jacob W J Kerssemakers, Indra A Shaltiel, Cees DekkerAbstract:Condensin, a key component of the structure maintenance of chromosome (SMC) Protein complexes, has recently been shown to be a motor that extrudes loops of DNA1. It remains unclear, however, how condensin complexes work together to collectively package DNA into chromosomes. Here we use time-lapse single-molecule visualization to study mutual interactions between two DNA-loop-extruding yeast condensins. We find that these motor Proteins, which, individually, extrude DNA in one direction only are able to dynamically change each other’s DNA loop sizes, even when far apart. When they are in close proximity, condensin complexes are able to traverse each other and form a loop structure, which we term a Z-loop—three double-stranded DNA helices aligned in parallel with one condensin at each edge. Z-loops can fill gaps left by single loops and can form symmetric dimer motors that pull in DNA from both sides. These findings indicate that condensin may achieve chromosomal compaction using a variety of looping structures.
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dna loop extruding condensin complexes can traverse one another
Biophysical Journal, 2020Co-Authors: Eugene Kim, Christian H. Haering, Jacob W J Kerssemakers, Indra A Shaltiel, Cees DekkerAbstract:Condensin, a key member of the Structure Maintenance of Chromosome (SMC) Protein complexes, has recently been shown to be a motor that extrudes loops of DNA1. It remains unclear, however, how condensin complexes work together to collectively package DNA into the chromosomal architecture. Here, we use time-lapse single-molecule visualization to study mutual interactions between two DNA-loop-extruding yeast condensins. We find that these one-side-pulling motor Proteins are able to dynamically change each other’s DNA loop sizes, even when located large distances apart. When coming into close proximity upon forming a loop within a loop, condensin complexes are, surprisingly, able to traverse each other and form a new type of loop structure, which we term Z loop – three double-stranded DNA helices aligned in parallel with one condensin at each edge. These Z-loops can fill gaps left by single loops and can form symmetric dimer motors that reel in DNA from both sides. These new findings indicate that condensin may achieve chromosomal compaction using a variety of looping structures.
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real time imaging of dna loop extrusion by condensin
Science, 2018Co-Authors: Mahipal Ganji, Christian H. Haering, Shveta Bisht, Eugene Kim, Indra A Shaltiel, Ana Kalichava, Cees DekkerAbstract:It has been hypothesized that SMC Protein complexes such as condensin and cohesin spatially organize chromosomes by extruding DNA into large loops. We directly visualized the formation and processive extension of DNA loops by yeast condensin in real time. Our findings constitute unambiguous evidence for loop extrusion. We observed that a single condensin complex is able to extrude tens of kilobase pairs of DNA at a force-dependent speed of up to 1500 base pairs per second, using the energy of adenosine triphosphate hydrolysis. Condensin-induced loop extrusion was strictly asymmetric, which demonstrates that condensin anchors onto DNA and reels it in from only one side. Active DNA loop extrusion by SMC complexes may provide the universal unifying principle for genome organization.
Jacob W J Kerssemakers - One of the best experts on this subject based on the ideXlab platform.
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dna loop extruding condensin complexes can traverse one another
Nature, 2020Co-Authors: Eugene Kim, Christian H. Haering, Jacob W J Kerssemakers, Indra A Shaltiel, Cees DekkerAbstract:Condensin, a key component of the structure maintenance of chromosome (SMC) Protein complexes, has recently been shown to be a motor that extrudes loops of DNA1. It remains unclear, however, how condensin complexes work together to collectively package DNA into chromosomes. Here we use time-lapse single-molecule visualization to study mutual interactions between two DNA-loop-extruding yeast condensins. We find that these motor Proteins, which, individually, extrude DNA in one direction only are able to dynamically change each other’s DNA loop sizes, even when far apart. When they are in close proximity, condensin complexes are able to traverse each other and form a loop structure, which we term a Z-loop—three double-stranded DNA helices aligned in parallel with one condensin at each edge. Z-loops can fill gaps left by single loops and can form symmetric dimer motors that pull in DNA from both sides. These findings indicate that condensin may achieve chromosomal compaction using a variety of looping structures.
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dna loop extruding condensin complexes can traverse one another
Biophysical Journal, 2020Co-Authors: Eugene Kim, Christian H. Haering, Jacob W J Kerssemakers, Indra A Shaltiel, Cees DekkerAbstract:Condensin, a key member of the Structure Maintenance of Chromosome (SMC) Protein complexes, has recently been shown to be a motor that extrudes loops of DNA1. It remains unclear, however, how condensin complexes work together to collectively package DNA into the chromosomal architecture. Here, we use time-lapse single-molecule visualization to study mutual interactions between two DNA-loop-extruding yeast condensins. We find that these one-side-pulling motor Proteins are able to dynamically change each other’s DNA loop sizes, even when located large distances apart. When coming into close proximity upon forming a loop within a loop, condensin complexes are, surprisingly, able to traverse each other and form a new type of loop structure, which we term Z loop – three double-stranded DNA helices aligned in parallel with one condensin at each edge. These Z-loops can fill gaps left by single loops and can form symmetric dimer motors that reel in DNA from both sides. These new findings indicate that condensin may achieve chromosomal compaction using a variety of looping structures.
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real time detection of condensin driven dna compaction reveals a multistep binding mechanism
The EMBO Journal, 2017Co-Authors: Jorine M. Eeftens, Marc Kschonsak, Christian H. Haering, Shveta Bisht, Jacob W J Kerssemakers, Cees DekkerAbstract:Condensin, a conserved member of the SMC Protein family of ring-shaped multi-subunit Protein complexes, is essential for structuring and compacting chromosomes. Despite its key role, its molecular mechanism has remained largely unknown. Here, we employ single-molecule magnetic tweezers to measure, in real time, the compaction of individual DNA molecules by the budding yeast condensin complex. We show that compaction can proceed in large steps, driving DNA molecules into a fully condensed state against forces of up to 2 pN. Compaction can be reversed by applying high forces or adding buffer of high ionic strength. While condensin can stably bind DNA in the absence of ATP, ATP hydrolysis by the SMC subunits is required for rendering the association salt insensitive and for the subsequent compaction process. Our results indicate that the condensin reaction cycle involves two distinct steps, where condensin first binds DNA through electrostatic interactions before using ATP hydrolysis to encircle the DNA topologically within its ring structure, which initiates DNA compaction. The finding that both binding modes are essential for its DNA compaction activity has important implications for understanding the mechanism of chromosome compaction.
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real time detection of condensin driven dna compaction reveals a multistep binding mechanism
bioRxiv, 2017Co-Authors: Jorine M. Eeftens, Christian H. Haering, Shveta Bisht, Jacob W J Kerssemakers, Cees DekkerAbstract:Condensin, a conserved member of the SMC Protein family of ring-shaped multi-subunit Protein complexes, is essential for structuring and compacting chromosomes. Despite its key role, its molecular mechanism has remained largely unknown. Here, we employ single-molecule magnetic tweezers to measure, in real-time, the compaction of individual DNA molecules by the budding yeast condensin complex. We show that compaction proceeds in large (~200nm) steps, driving DNA molecules into a fully condensed state against forces of up to 2pN. Compaction can be reversed by applying high forces or adding buffer of high ionic strength. While condensin can stably bind DNA in the absence of ATP, ATP hydrolysis by the SMC subunits is required for rendering the association salt-insensitive and for subsequent compaction. Our results indicate that the condensin reaction cycle involves two distinct steps, where condensin first binds DNA through electrostatic interactions before using ATP hydrolysis to encircle the DNA topologically within its ring structure, which initiates DNA compaction. The finding that both binding modes are essential for its DNA compaction activity has important implications for understanding the mechanism of chromosome compaction.
Tatsuya Hirano - One of the best experts on this subject based on the ideXlab platform.
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hinge mediated dimerization of SMC Protein is essential for its dynamic interaction with dna
The EMBO Journal, 2002Co-Authors: Michiko Hirano, Tatsuya HiranoAbstract:Structural maintenance of chromosomes (SMC) Proteins play central roles in regulating higher order chromosome dynamics from bacteria to humans. As judged by electron microscopy, the SMC homodimer from Bacillus subtilis (BsSMC) is composed of two antiparallel, coiled-coil arms with a flexible hinge. Site-directed cross-linking experiments show here that dimerization of BsSMC is mediated by a hinge–hinge interaction between self-folded monomers. This architecture is conserved in the eukaryotic SMC2–SMC4 heterodimer. Analysis of different deletion mutants of BsSMC unexpectedly reveals that the major DNA-binding activity does not reside in the catalytic ATPase domains located at the ends of a dimer. Instead, point mutations in the hinge domain that disturb dimerization of BsSMC drastically reduce its ability to interact with DNA. Proper hinge function is essential for BsSMC to recognize distinct DNA topology, and mutant Proteins with altered hinge angles cross-link double-stranded DNA in a nucleotide-dependent manner. We propose that the hinge domain of SMC Proteins is not a simple dimerization site, but rather it acts as an essential determinant of dynamic SMC–DNA interactions.
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condensin and cohesin display different arm conformations with characteristic hinge angles
Journal of Cell Biology, 2002Co-Authors: David E Anderson, Harold P Erickson, Ana Losada, Tatsuya HiranoAbstract:Structural maintenance of chromosomes (SMC) Proteins play central roles in higher-order chromosome dynamics from bacteria to humans. In eukaryotes, two different SMC Protein complexes, condensin and cohesin, regulate chromosome condensation and sister chromatid cohesion, respectively. Each of the complexes consists of a heterodimeric pair of SMC subunits and two or three non-SMC subunits. Previous studies have shown that a bacterial SMC homodimer has a symmetrical structure in which two long coiled-coil arms are connected by a flexible hinge. A catalytic domain with DNA- and ATP-binding activities is located at the distal end of each arm. We report here the visualization of vertebrate condensin and cohesin by electron microscopy. Both complexes display the two-armed structure characteristic of SMC Proteins, but their conformations are remarkably different. The hinge of condensin is closed and the coiled-coil arms are placed close together. In contrast, the hinge of cohesin is wide open and the coiled-coils are spread apart from each other. The non-SMC subunits of both condensin and cohesin form a globular complex bound to the catalytic domains of the SMC heterodimers. We propose that the "closed" conformation of condensin and the "open" conformation of cohesin are important structural properties that contribute to their specialized biochemical and physiological functions.
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identification of xenopus SMC Protein complexes required for sister chromatid cohesion
Genes & Development, 1998Co-Authors: Ana Losada, Michiko Hirano, Tatsuya HiranoAbstract:The structural maintenance of chromosomes (SMC) family is a growing family of chromosomal ATPases. The founding class of SMC Protein complexes, condensins, plays a central role in mitotic chromosome condensation. We report here a new class of SMC Protein complexes containing XSMC1 and XSMC3, Xenopus homologs of yeast SMC1p and SMC3p, respectively. The Protein complexes (termed cohesins) exist as two major forms with sedimentation coefficients of 9S and 14S. 9S cohesin is a heterodimer of XSMC1 and XSMC3, whereas 14S cohesin contains three additional subunits. One of them has been identified as a Xenopus homolog of the Schizosaccharomyces pombe Rad21p implicated in DNA repair and the Saccharomyces cerevisiae Scc1p/Mcd1p implicated in sister chromatid cohesion. 14S cohesin binds to interphase chromatin independently of DNA replication and dissociates from it at the onset of mitosis. Immunodepletion of cohesins during interphase causes defects in sister chromatid cohesion in subsequent mitosis, whereas condensation is unaffected. These results suggest that proper assembly of mitotic chromosomes is regulated by two distinct classes of SMC Protein complexes, cohesins and condensins.
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SMC Protein complexes and higher order chromosome dynamics
Current Opinion in Cell Biology, 1998Co-Authors: Tatsuya HiranoAbstract:The structural maintenance of chromosome (SMC) family of Proteins represents an expanding group of chromosomal ATPases that are highly conserved among Bacteria, Archaea and Eukarya. During the past year, significant progress has been made towards understanding the cellular functions and molecular activities of this new class of Proteins. Emerging evidence suggests that eukaryotic SMC Proteins form large Protein complexes with non-SMC subunits and act as key components for a wide variety of higher-order chromosome dynamics.
Eugene Kim - One of the best experts on this subject based on the ideXlab platform.
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bridging induced phase separation induced by cohesin SMC Protein complexes
Science Advances, 2021Co-Authors: Je-kyung Ryu, Allard J. Katan, Eugene Kim, Ralph Groot, Celine Bouchoux, Hon Wing Liu, Masashi Minamino, Andrea Bonato, Davide Marenduzzo, Davide MichielettoAbstract:Structural maintenance of chromosome (SMC) Protein complexes are able to extrude DNA loops. While loop extrusion constitutes a fundamental building block of chromosomes, other factors may be equally important. Here, we show that yeast cohesin exhibits pronounced clustering on DNA, with all the hallmarks of biomolecular condensation. DNA-cohesin clusters exhibit liquid-like behavior, showing fusion of clusters, rapid fluorescence recovery after photobleaching and exchange of cohesin with the environment. Strikingly, the in vitro clustering is DNA length dependent, as cohesin forms clusters only on DNA exceeding 3 kilo–base pairs. We discuss how bridging-induced phase separation, a previously unobserved type of biological condensation, can explain the DNA-cohesin clustering through DNA-cohesin-DNA bridges. We confirm that, in yeast cells in vivo, a fraction of cohesin associates with chromatin in a manner consistent with bridging-induced phase separation. Biomolecular condensation by SMC Proteins constitutes a new basic principle by which SMC complexes direct genome organization.
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phase separation induced by cohesin SMC Protein complexes
bioRxiv, 2020Co-Authors: Je-kyung Ryu, Allard J. Katan, Eugene Kim, Ralph Groot, Celine Bouchoux, Hon Wing Liu, Masashi Minamino, Andrea Bonato, Davide Marenduzzo, Davide MichielettoAbstract:Abstract Cohesin is a key Protein complex that organizes the spatial structure of chromosomes during interphase. Here, we show that yeast cohesin shows pronounced clustering on DNA in an ATP-independent manner, exhibiting all the hallmarks of phase separation. In vitro visualization of cohesin on DNA shows DNA-cohesin clusters that exhibit liquid-like behavior. This includes mutual fusion and reversible dissociation upon depleting the cohesin concentration, increasing the ionic strength, or adding 1,6-hexanediol, conditions that disrupt weak interactions. We discuss how bridging-induced phase separation can explain the DNA-cohesin clustering through DNA-cohesin-DNA bridges. We confirm that, in vivo, a fraction of cohesin associates with chromatin in yeast cells in a manner consistent with phase separation. Our findings establish that SMC Proteins can exhibit phase separation, which has potential to clarify previously unexplained aspects of in vivo SMC behavior and constitute an additional principle by which SMC complexes impact genome organization. One sentence summary Yeast cohesin complex is observed to phase separate with DNA into liquid droplets, which it accomplishes by ATP-independent DNA bridging.
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dna loop extruding condensin complexes can traverse one another
Nature, 2020Co-Authors: Eugene Kim, Christian H. Haering, Jacob W J Kerssemakers, Indra A Shaltiel, Cees DekkerAbstract:Condensin, a key component of the structure maintenance of chromosome (SMC) Protein complexes, has recently been shown to be a motor that extrudes loops of DNA1. It remains unclear, however, how condensin complexes work together to collectively package DNA into chromosomes. Here we use time-lapse single-molecule visualization to study mutual interactions between two DNA-loop-extruding yeast condensins. We find that these motor Proteins, which, individually, extrude DNA in one direction only are able to dynamically change each other’s DNA loop sizes, even when far apart. When they are in close proximity, condensin complexes are able to traverse each other and form a loop structure, which we term a Z-loop—three double-stranded DNA helices aligned in parallel with one condensin at each edge. Z-loops can fill gaps left by single loops and can form symmetric dimer motors that pull in DNA from both sides. These findings indicate that condensin may achieve chromosomal compaction using a variety of looping structures.
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dna loop extruding condensin complexes can traverse one another
Biophysical Journal, 2020Co-Authors: Eugene Kim, Christian H. Haering, Jacob W J Kerssemakers, Indra A Shaltiel, Cees DekkerAbstract:Condensin, a key member of the Structure Maintenance of Chromosome (SMC) Protein complexes, has recently been shown to be a motor that extrudes loops of DNA1. It remains unclear, however, how condensin complexes work together to collectively package DNA into the chromosomal architecture. Here, we use time-lapse single-molecule visualization to study mutual interactions between two DNA-loop-extruding yeast condensins. We find that these one-side-pulling motor Proteins are able to dynamically change each other’s DNA loop sizes, even when located large distances apart. When coming into close proximity upon forming a loop within a loop, condensin complexes are, surprisingly, able to traverse each other and form a new type of loop structure, which we term Z loop – three double-stranded DNA helices aligned in parallel with one condensin at each edge. These Z-loops can fill gaps left by single loops and can form symmetric dimer motors that reel in DNA from both sides. These new findings indicate that condensin may achieve chromosomal compaction using a variety of looping structures.
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real time imaging of dna loop extrusion by condensin
Science, 2018Co-Authors: Mahipal Ganji, Christian H. Haering, Shveta Bisht, Eugene Kim, Indra A Shaltiel, Ana Kalichava, Cees DekkerAbstract:It has been hypothesized that SMC Protein complexes such as condensin and cohesin spatially organize chromosomes by extruding DNA into large loops. We directly visualized the formation and processive extension of DNA loops by yeast condensin in real time. Our findings constitute unambiguous evidence for loop extrusion. We observed that a single condensin complex is able to extrude tens of kilobase pairs of DNA at a force-dependent speed of up to 1500 base pairs per second, using the energy of adenosine triphosphate hydrolysis. Condensin-induced loop extrusion was strictly asymmetric, which demonstrates that condensin anchors onto DNA and reels it in from only one side. Active DNA loop extrusion by SMC complexes may provide the universal unifying principle for genome organization.