Similar Datasets
Project description:Three-dimensional organization of mitotic chromosomes is established by cohesin and condensin complexes. In the centromere, cohesin maintains sister chromatid pairing until anaphase onset, while condensin provides elastic resistance to spindle forces. However, how condensin and cohesin structure vertebrate centromeres remains unclear. By super-resolution imaging, Capture-C analysis and polymer modeling we show that vertebrate centromeres are partitioned into two condensin-dependent subdomains during mitosis. This bipartite sub-structure is found in human, mouse and chicken centromeres, and is therefore a fundamental feature of vertebrate centromere. Super-resolution imaging and electron tomography reveal that bipartite centromeres assemble bipartite kinetochores with each subdomain capable of binding a distinct microtubule bundle. Cohesin helps to link the centromere subdomains, limiting their separation in response to spindle forces and preventing merotelic attachments. The two-domain structure described here may have implications for avoiding chromosomal instability as uncoupling of centromere subdomains is a common feature of lagging chromosomes in cancer cells.
2024-04-01 | GSE254181 | GEO
Project description:Three-dimensional organization of mitotic chromosomes is established by cohesin and condensin complexes. In the centromere, cohesin maintains sister chromatid pairing until anaphase onset, while condensin provides elastic resistance to spindle forces. However, how condensin and cohesin structure vertebrate centromeres remains unclear. By super-resolution imaging, Capture-C analysis and polymer modeling we show that vertebrate centromeres are partitioned into two condensin-dependent subdomains during mitosis. This bipartite sub-structure is found in human, mouse and chicken centromeres, and is therefore a fundamental feature of vertebrate centromere. Super-resolution imaging and electron tomography reveal that bipartite centromeres assemble bipartite kinetochores with each subdomain capable of binding a distinct microtubule bundle. Cohesin helps to link the centromere subdomains, limiting their separation in response to spindle forces and preventing merotelic attachments. The two-domain structure described here may have implications for avoiding chromosomal instability as uncoupling of centromere subdomains is a common feature of lagging chromosomes in cancer cells.
2024-04-01 | GSE254180 | GEO
Project description:Three-dimensional organization of mitotic chromosomes is established by cohesin and condensin complexes. In the centromere, cohesin maintains sister chromatid pairing until anaphase onset, while condensin provides elastic resistance to spindle forces. However, how condensin and cohesin structure vertebrate centromeres remains unclear. By super-resolution imaging, Capture-C analysis and polymer modeling we show that vertebrate centromeres are partitioned into two condensin-dependent subdomains during mitosis. This bipartite sub-structure is found in human, mouse and chicken centromeres, and is therefore a fundamental feature of vertebrate centromere. Super-resolution imaging and electron tomography reveal that bipartite centromeres assemble bipartite kinetochores with each subdomain capable of binding a distinct microtubule bundle. Cohesin helps to link the centromere subdomains, limiting their separation in response to spindle forces and preventing merotelic attachments. The two-domain structure described here may have implications for avoiding chromosomal instability as uncoupling of centromere subdomains is a common feature of lagging chromosomes in cancer cells.
2024-04-01 | GSE254659 | GEO
Project description:Semi-conservative segregation of nucleosomes to sister chromatids during DNA replication creates gaps that must be filled by new nucleosome assembly. We analyzed the cell-cycle timing of centromeric chromatin assembly in Drosophila, which contains the H3 variant CID (CENP-A in humans), as well as CENP-C and CAL1, which are required for CID localization. Pulse-chase experiments show that CID and CENP-C levels decrease by 50% at each cell division, as predicted for semi-conservative segregation and inheritance, whereas CAL1 displays higher turnover. Quench-chase-pulse experiments demonstrate that there is a significant lag between replication and replenishment of centromeric chromatin. Surprisingly, new CID is recruited to centromeres in metaphase, by a mechanism that does not require an intact mitotic spindle, but does require proteasome activity. Interestingly, new CAL1 is recruited to centromeres before CID in prophase. Furthermore, CAL1, but not CENP-C, is found in complex with pre-nucleosomal CID. Finally, CENP-C displays yet a different pattern of incorporation, during both interphase and mitosis. The unusual timing of CID recruitment and unique dynamics of CAL1 identify a distinct centromere assembly pathway in Drosophila and suggest that CAL1 is a key regulator of centromere propagation.
| S-EPMC3093364 | biostudies-literature
Project description:This SuperSeries is composed of the SubSeries listed below.
2021-06-17 | GSE168251 | GEO
Project description:Timely dissolution of sister-chromatid cohesion in mitosis ensures accurate chromosome segregation to guard against aneuploidy and tumorigenesis. The complex of shugoshin and protein phosphatase 2A (SGO1-PP2A) protects cohesin at centromeres from premature removal by mitotic kinases and WAPL in prophase. Here we address the regulation and mechanism of human SGO1 in centromeric cohesion protection, and show that cyclin-dependent kinase (CDK)-mediated, mitosis-specific phosphorylation of SGO1 activates its cohesion-protection function and enables its direct binding to cohesin. The phospho-SGO1-bound cohesin complex contains PP2A, PDS5 and hypophosphorylated sororin, but lacks WAPL. Expression of non-phosphorylatable sororin bypasses the requirement for SGO1-PP2A in centromeric cohesion. Thus, mitotic phosphorylation of SGO1 targets SGO1-PP2A to cohesin, promotes dephosphorylation of PDS5-bound sororin and protects centromeric cohesin from WAPL. PP2A-orchestrated, site-selective dephosphorylation of cohesin and its regulators underlies centromeric cohesion protection.
| S-EPMC3531828 | biostudies-literature
Project description:Sister chromatid cohesion is essential for tension-sensing mechanisms that monitor bipolar attachment of replicated chromatids in metaphase. Cohesion is mediated by the association of cohesins along the length of sister chromatid arms. In contrast, centromeric cohesin generates intrastrand cohesion and sister centromeres, while highly cohesin enriched, are separated by >800 nm at metaphase in yeast. Removal of cohesin is necessary for sister chromatid separation during anaphase, and this is regulated by evolutionarily conserved polo-like kinase (Cdc5 in yeast, Plk1 in humans). Here we address how high levels of cohesins at centromeric chromatin are removed. Cdc5 associates with centromeric chromatin and cohesin-associated regions. Maximum enrichment of Cdc5 in centromeric chromatin occurs during the metaphase-to-anaphase transition and coincides with the removal of chromosome-associated cohesin. Cdc5 interacts with cohesin in vivo, and cohesin is required for association of Cdc5 at centromeric chromatin. Cohesin removal from centromeric chromatin requires Cdc5 but removal at distal chromosomal arm sites does not. Our results define a novel role for Cdc5 in regulating removal of centromeric cohesins and faithful chromosome segregation.
| S-EPMC4945145 | biostudies-literature
Project description:Centromeres are epigenetically defined chromatin domains marked by the presence of the histone H3 variant CENP-A. Here we review recent structural and biochemical work on CENP-A, and advances in understanding the mechanisms that propagate and read centromeric chromatin domains.
| S-EPMC3319190 | biostudies-literature
Project description:Orderly termination of sister-chromatid cohesion during mitosis is critical for accurate chromosome segregation. During prophase, mitotic kinases phosphorylate cohesin and its protector sororin, triggering Wapl-dependent cohesin release from chromosome arms. The shugoshin (Sgo1)-PP2A complex protects centromeric cohesin until its cleavage by separase at anaphase onset. Here, we report the crystal structure of a human cohesin subcomplex comprising SA2 and Scc1. Multiple HEAT repeats of SA2 form a dragon-shaped structure. Scc1 makes extensive contacts with SA2, with one binding hotspot. Sgo1 and Wapl compete for binding to a conserved site on SA2-Scc1. At this site, mutations of SA2 residues that disrupt Wapl binding bypass the Sgo1 requirement in cohesion protection. Thus, in addition to recruiting PP2A to dephosphorylate cohesin and sororin, Sgo1 physically shields cohesin from Wapl. This unexpected, direct antagonism between Sgo1 and Wapl augments centromeric cohesion protection.
| S-EPMC4190070 | biostudies-literature
Project description:Cohesin is the protein complex responsible for maintaining sister chromatid cohesion. Cohesin interacts with centromeres and specific loci along chromosome arms known as Chromosome Attachment Regions (CARs). The cohesin holocomplex contains four subunits. Two of them, Smc1p (Structural maintenance of chromosome 1 protein) and Smc3p, are long coiled-coil proteins, which heterodimerize with each other at one end. They are joined together at the other end by a third subunit, Scc1p, which also binds to the fourth subunit, Scc3p. How cohesin interacts with chromosomes is not known, although several models have been proposed, in part on the basis of in vitro assembly of purified cohesin proteins. To be able to observe in vivo cohesin-chromatin interactions, we have modified a Minichromosome Affinity Purification (MAP) method to isolate a CAR-containing centromeric minichromosome attached to in vivo assembled cohesin. Transmission Electron Microscopy (TEM) analysis of these minichromosomes suggests that cohesin assumes a rod shape and interacts with replicated minichromosome at one end of that rod. Additionally, our data implies that more than one cohesin molecule interacts with each pair of replicated minichromsomes. These molecules seem to be packed into a single thick rod, suggesting that the Smc1p and Smc3p subunits may interact extensively.
| S-EPMC2408725 | biostudies-literature