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Condensin I folds the C. elegans genome [Hi-C]

ABSTRACT: Structural Maintenance of chromosomes (SMC) complexes, cohesin and condensins, have been named after their roles during meiosis and mitosis. Recent data in mammalian cells and Drosophila have described the additional role of cohesin for genome folding into loops and domains during interphase. However, determinants of genome folding in holocentric species remain unclear. Using high resolution chromosome conformation capture, we show that overlapping large-scale nuclear localization and small-scale epigenomic states compartmentalize the C. elegans genome. By systematically and acutely inactivating each SMC complex, we observe that in contrast to other studied systems, cohesin creates small loops, while condensin I has a major role in genome folding: its inactivation causes genome-wide decompaction, chromosome mixing, loss of loops and TAD structures and reinforcement of fine-scale epigenomic compartments. Counter-intuitively, removal of condensin I and its X-specific variant condensin IDC from the X chromosomes led to the formation of a loop compartment coinciding with a subset of previously characterized loading sites for condensin IDC and bound by the X-targeting complex SDC. While transcriptional changes were limited for all autosomes upon cohesin and condensin II inactivation, removal of condensin I/IDC from the X chromosome led to transcriptional up-regulation of X-linked genes demonstrating that a sustained role for condensin IDC in gene regulation. Finally, while condensin I inactivation leads to reduced lifespan, we show that this reduction is due to X-specific gene upregulation rather than global genome decompaction.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE199721 | GEO | 2024/04/18

REPOSITORIES: GEO

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Condensin I folds the C. elegans genome [Ribo-Zero-seq]

Project description:Structural Maintenance of chromosomes (SMC) complexes, cohesin and condensins, have been named after their roles during meiosis and mitosis. Recent data in mammalian cells and Drosophila have described the additional role of cohesin for genome folding into loops and domains during interphase. However, determinants of genome folding in holocentric species remain unclear. Using high resolution chromosome conformation capture, we show that overlapping large-scale nuclear localization and small-scale epigenomic states compartmentalize the C. elegans genome. By systematically and acutely inactivating each SMC complex, we observe that in contrast to other studied systems, cohesin creates small loops, while condensin I has a major role in genome folding: its inactivation causes genome-wide decompaction, chromosome mixing, loss of loops and TAD structures and reinforcement of fine-scale epigenomic compartments. Counter-intuitively, removal of condensin I and its X-specific variant condensin IDC from the X chromosomes led to the formation of a loop compartment coinciding with a subset of previously characterized loading sites for condensin IDC and bound by the X-targeting complex SDC. While transcriptional changes were limited for all autosomes upon cohesin and condensin II inactivation, removal of condensin I/IDC from the X chromosome led to transcriptional up-regulation of X-linked genes demonstrating that a sustained role for condensin IDC in gene regulation. Finally, while condensin I inactivation leads to reduced lifespan, we show that this reduction is due to X-specific gene upregulation rather than global genome decompaction.

2024-04-18 | GSE199719 | GEO

Condensin I folds the C. elegans genome [RNA-seq]

2024-04-18 | GSE199717 | GEO

Transcription-dependent positioning of Structural Maintenance of Chromosome complexes across the genome: RNA-Seq

Project description:The Structural Maintenance of Chromosomes (SMC) complexes regulate the chromosome structures essential for proper genome regulation and cell viability. In mammals, the coordinated actions of the SMC complexes condensin I, condensin II and cohesin regulate dynamic chromosome structures throughout the cell cycle, but it is not clear how these complexes are positioned across the genome. We report here that condensin I, condensin II and cohesin occupy active euchromatic regions of the embryonic stem cell genome, but not heterochromatic regions. Like cohesin, we find that condensin II is deposited at active genes by the SMC loading factor Nipbl. The recruitment of Condensin II to active genes is dependent on their transcriptional activation. Subsequent transcriptional elongation by RNA polymerase II distributes condensin II across gene bodies. During mitosis, condensin I occupies the same set of active genes occupied by condensin II during interphase. Thus, SMC complexes are positioned in the genome by transcription-dependent processes, indicating that condensin-dependent condensation mechanisms are preferentially utilized in euchromatic regions. RNA-seq in mES cells after known-down of Smc1, CapH2 or Smc2.

2013-10-28 | E-GEOD-46316 | biostudies-arrayexpress

Transcription-dependent positioning of Structural Maintenance of Chromosome complexes across the genome: RNA-Seq

2013-10-28 | GSE46316 | GEO

Sister chromatid cohesion halts DNA loop expansion

Project description:Eukaryotic genomes are folded into DNA loops mediated by SMC complexes, like cohesin, condensin and Smc5/6. This organization regulates different DNA related processes along the cell cycle such as transcription, recombination, segregation and DNA repair. During G2/M phases, SMC complexes mediated DNA loops coexist with cohesin complexes involved in sister chromatid cohesion (SCC). It remains unknown whether SCC and DNA loop expansion influence each other and if they cooperate to regulate DNA-related processes. Here we show that SCC is indeed a barrier to DNA loop expansion mediated by cohesin in G2.

2024-01-30 | GSE237031 | GEO

Cohesin-dependent compaction of mitotic chromosomes in budding yeast

Project description: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 (Hi-C) analyses indicate that intra-chromosomal looping of DNA is a primary pathway of chromosomal organization during all stages of the cell cycle (Dekker, J. & Mirny, L. . Cell 164, 1110–1121 (2016). Although the enzymatic pathways required for DNA loop formation are yet to be fully characterized, the activity of the SMC family of proteins has been consistently associated with this process in interphase and mitosis. Here we use Hi-C to study the reorganization of budding yeast chromosome conformation in early mitosis and the role of SMCs in this process. Using polymer simulations, we find that the differences between interphase and mitotic Hi-C maps can be explained by the formation of intra-chromosomal (cis-) loops in mitotic chromosomes. We demonstrate that mitotic SMC cohesin activity is required for formation of cis-loops, independently of sister-chromatid cohesion. In contrast, SMC condensin is not required for loop formation in these early mitotic cells. Rather condensin activity promotes distinct higher order structures in the chromosomes at centromeres and in the rDNA proximal regions. Thus we demonstrate that cohesin-dependent cis-loops provide the primary higher order organization of budding yeast mitotic chromosomes, independently of condensin and sister chromatid cohesion.

2017-03-22 | GSE87311 | GEO

SMC Complexes Are Guarded by the SUMO Protease Ulp2 Against SUMO-Chain-Mediated Turnover

Project description:Structural maintenance of chromosomes (SMC) complexes, cohesin, condensin and Smc5/6, are essential for viability and participate in multiple processes, including sister chromatid cohesion, chromosome condensation, and DNA repair. Here we show that SUMO chains target all three SMC complexes and are antagonized by the SUMO protease Ulp2 to prevent their turnover. We uncover that the essential role of the cohesin-associated subunit Pds5 is to counteract SUMO chains jointly with Ulp2. Importantly, fusion of Ulp2 to kleisin Scc1 supports viability of PDS5 null cells and protects cohesin from proteasomal degradation mediated by the SUMO-targeted ubiquitin ligase Slx5/Slx8. The lethality of PDS5 deleted cells can also be bypassed by simultaneous loss of the PCNA unloader, Elg1, and the cohesin releaser, Wpl1, but only when Ulp2 is functional. Condensin and Smc5/6 complex are similarly guarded by Ulp2 against unscheduled SUMO-chain assembly, which we propose to time the availability of SMC complexes on chromatin.

2021-08-05 | PXD022717 | Pride

Bacillus subtilis SMC complexes juxtapose chromosome arms as they travel from origin to terminus

Project description:Structural maintenance of chromosomes (SMC) complexes play critical roles in chromosome dynamics in virtually all organisms but how they function remains poorly understood. In Bacillus subtilis, SMC condensin complexes are topologically loaded at centromeric sites adjacent to the replication origin. Here we provide evidence that these ring-shaped assemblies tether the left and right chromosome arms together while traveling from the origin to the terminus (>2 Mb) at rates >50kb/min. Condensin movement scales linearly with time arguing for an active transport mechanism. These data support a model in which SMC complexes function by processively enlarging DNA loops. Loop formation followed by processive enlargement provides a mechanism for how condensin complexes compact and resolve sister chromatids in mitosis and how cohesin generates topologically associating domains (TADs) during interphase.

2017-02-03 | GSE85612 | GEO

Cryo-EM structures of holo condensin reveal a subunit flip-flop mechanism

Project description:This data is from BS3 crosslinked condensin tetramer How protein complexes of the SMC family fold DNA into the large loops that are fundamental for the 3D organization of genomes is a central unresolved question of chromosome biology. We used electron cryomicroscopy to investigate the reaction cycle of the SMC complex condensin, which is a key determinant of chromosome morphology and behavior during mitosis. Our structures of the Saccharomyces cerevisiae condensin holo complex at different functional stages suggest that ATP binding induces the transition from a folded-rod SMC conformation into an open architecture and triggers the exchange of the two HEAT-repeat subunits at the SMC ATPase head domains. We propose that these steps result in the interconversion of DNA binding sites in the catalytic core that form the basis of the DNA translocation and loop-extrusion activities of condensin.

2020-07-28 | PXD019275 | Pride

Cryo-EM structures of holo condensin reveal a subunit flip-flop mechanism

Project description:This data is from sulfo-SDA crosslinked condensin pentamer. Two datsets, one without atp aand one with ATP. How protein complexes of the SMC family fold DNA into the large loops that are fundamental for the 3D organization of genomes is a central unresolved question of chromosome biology. We used electron cryomicroscopy to investigate the reaction cycle of the SMC complex condensin, which is a key determinant of chromosome morphology and behavior during mitosis. Our structures of the Saccharomyces cerevisiae condensin holo complex at different functional stages suggest that ATP binding induces the transition from a folded-rod SMC conformation into an open architecture and triggers the exchange of the two HEAT-repeat subunits at the SMC ATPase head domains. We propose that these steps result in the interconversion of DNA binding sites in the catalytic core that form the basis of the DNA translocation and loop-extrusion activities of condensin.

2020-07-28 | PXD019274 | Pride

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