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Human cohesin compacts DNA by loop extrusion.

ABSTRACT: Cohesin is a chromosome-bound, multisubunit adenosine triphosphatase complex. After loading onto chromosomes, it generates loops to regulate chromosome functions. It has been suggested that cohesin organizes the genome through loop extrusion, but direct evidence is lacking. Here, we used single-molecule imaging to show that the recombinant human cohesin-NIPBL complex compacts both naked and nucleosome-bound DNA by extruding DNA loops. DNA compaction by cohesin requires adenosine triphosphate (ATP) hydrolysis and is force sensitive. This compaction is processive over tens of kilobases at an average rate of 0.5 kilobases per second. Compaction of double-tethered DNA suggests that a cohesin dimer extrudes DNA loops bidirectionally. Our results establish cohesin-NIPBL as an ATP-driven molecular machine capable of loop extrusion.

SUBMITTER: Kim Y

PROVIDER: S-EPMC7387118 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Human cohesin compacts DNA by loop extrusion.

Kim Yoori Y Shi Zhubing Z Zhang Hongshan H Finkelstein Ilya J IJ Yu Hongtao H

Science (New York, N.Y.) 20191128 6471

Cohesin is a chromosome-bound, multisubunit adenosine triphosphatase complex. After loading onto chromosomes, it generates loops to regulate chromosome functions. It has been suggested that cohesin organizes the genome through loop extrusion, but direct evidence is lacking. Here, we used single-molecule imaging to show that the recombinant human cohesin-NIPBL complex compacts both naked and nucleosome-bound DNA by extruding DNA loops. DNA compaction by cohesin requires adenosine triphosphate (AT ...[more]

PMID: 31780627

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Cohesin mediates DNA loop extrusion by a "swing and clamp" mechanism.

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Cohesin-mediated DNA loop extrusion resolves sister chromatids in G2 phase

Project description:Genetic information is stored in linear DNA molecules, which fold extensively inside cells. DNA replication along the folded template path yields two sister chromatids that initially occupy the same nuclear region in a highly intertwined arrangement. Dividing cells must disentangle and condense the sister chromatids into separate bodies such that a microtubule-based spindle can move them to opposite poles. While the spindle-mediated transport of sister chromatids has been studied in detail, the chromosome-intrinsic mechanics pre-segregating sister chromatids have remained elusive. Here, we show that human sister chromatids resolve extensively already during interphase, in a process dependent on the loop-extruding activity of cohesin, but not that of condensins. Increasing cohesin’s looping capability increases sister DNA resolution in interphase nuclei to an extent normally seen only during mitosis, despite the presence of abundant arm cohesion. That cohesin can resolve sister chromatids so extensively in the absence of mitosis-specific activities indicates that DNA loop extrusion is a generic mechanism for segregating replicated genomes, shared across different Structural Maintenance of Chromosomes (SMC) protein complexes in all kingdoms of life.

2023-04-12 | GSE227694 | GEO

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Project description:Most animal genomes are partitioned into Topologically Associating Domains (TADs), created by cohesin-mediated loop extrusion and defined by convergently oriented CTCF sites. The dynamics of loop extrusion and its regulation remains poorly characterized in vivo. Here, we tracked TAD anchors in living human cells to visualize and quantify cohesin-dependent loop extrusion across multiple endogenous genomic regions. We show that TADs are dynamic structures whose anchors are brought in proximity about once per hour and for 6-19 min (~16% of the time). TADs are continuously subjected to extrusion by multiple cohesin complexes, extruding loops at ~0.1 kb/s. Remarkably, despite strong differences of Hi-C patterns between the chromatin regions, their dynamics is consistent with the same density, residence time and speed of cohesin. Our results suggest that TAD dynamics is governed primarily by CTCF site location and affinity, which allows genome-wide predictive models of cohesin-dependent interactions.

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Cohesin-dependent chromosome loop extrusion is limited by transcription and stalled replication forks.

Project description:Genome function depends on regulated chromosome folding, and loop extrusion by the protein complex cohesin is essential for this multilayered organization. The chromosomal positioning of cohesin is controlled by transcription, and the complex also localizes to stalled replication forks. However, the role of transcription and replication in chromosome looping remains unclear. Here, we show that reduction of chromosome-bound RNA polymerase weakens normal cohesin loop extrusion boundaries, allowing cohesin to form new long-range chromosome cis interactions. Stress response genes induced by transcription inhibition are also shown to act as new loop extrusion boundaries. Furthermore, cohesin loop extrusion during early S phase is jointly controlled by transcription and replication units. Together, the results reveal that replication and transcription machineries are chromosome-folding regulators that block the progression of loop-extruding cohesin, opening for new perspectives on cohesin's roles in genome function and stability.

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