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The cohesin ring uses its hinge to organize DNA using non-topological as well as topological mechanisms

ABSTRACT: As predicted by the notion that sister chromatid cohesion is mediated by entrapment of sister DNAs inside cohesin rings, there is a perfect correlation between co-entrapment of circular minichromosomes and sister chromatid cohesion. In most cells where cohesin loads onto chromosomes but fails to form cohesion, loading is accompanied by entrapment of individual DNAs. However, cohesin with a hinge whose positively charged lumen has been neutralized not only loads onto and translocates along chromatin but also organizes it into chromatid-like threads, despite largely failing to entrap DNAs inside its ring. Thus, cohesin engages chromatin in both a non-topological and a topological manner. Further, mutation of three highly conserved lysines within the Smc1 hinge abolishes all loading without affecting cohesin’s initial recruitment to centromers or its ability to hydrolyze ATP. We suggest that loading and translocation are mediated by conformational changes in cohesin’s hinge driven by cycles of ATP hydrolysis.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE105005 | GEO | 2018/04/23

REPOSITORIES: GEO

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Transport of DNA within cohesin involves clamping on top of engaged heads by Scc2 and entrapment within the ring by Scc3

Project description:In addition to extruding DNA loops, cohesin entraps within its SMC-kleisin ring (S-K) individual DNAs during G1 and sister DNAs during S-phase. All three activities require related hook-shaped proteins called Scc2 and Scc3. Using thiol-specific crosslinking we provide rigorous proof of entrapment activity in vitro. Scc2 alone promotes entrapment of DNAs in the E-S and E-K compartments, between ATP-bound engaged heads and the SMC hinge and associated kleisin, respectively. This does not require ATP hydrolysis nor is it accompanied by entrapment within S-K rings, which is a slower process requiring Scc3. Cryo-EM reveals that DNAs transported into E-S/E-K compartments are “clamped” in a sub-compartment created by Scc2’s association with engaged heads whose coiled coils are folded around their elbow. We suggest that clamping may be a recurrent feature of cohesin complexes active in loop extrusion and that this conformation precedes the S-K entrapment required for sister chromatid cohesion.

2020-09-03 | GSE156616 | GEO

Releasing activity disengages cohesin’s Smc3/Scc1 interface in a process blocked by acetylation

Project description:Sister chromatid cohesion conferred by entrapment of sister DNAs within a tripartite ring formed between cohesin’s Scc1, Smc1, and Smc3 subunits is generated during S and eventually destroyed at anaphase through cleavage of Scc1 by separase. Throughout the cell cycle, cohesin’s association with chromosomes is controlled by opposing activities: loading by the Scc2/4 complex and release by a separase independent releasing activity. Co-entrapment of sister DNAs during replication is accompanied by acetylation of Smc3 by Eco1, which blocks releasing activity and ensures that sisters remain stably connected. Because fusion of Smc3 to Scc1 prevents release and bypasses the requirement for Eco1, we suggested that release is mediated by disengagement of the Smc3/Scc1 interface. We now show that all mutations capable of bypassing Eco1, be they in cohesin’s Smc1, Smc3, Scc1,Wapl, Pds5, or Scc3 subunits, greatly reduce dissociation of N-terminal cleavage fragments of Scc1 (NScc1) from Smc3. We show that this process involves interaction between Smc ATPase heads and is inhibited by Smc3 acetylation

2016-02-18 | GSE76890 | GEO

Cohesin mediates DNA loop extrusion and sister chromatid cohesion by distinct mechanisms [Hi-C]

Project description: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, which can extrude DNA into loops but is unable to mediate cohesion. Our results suggest that the latter defect arises during cohesion establishment. The observation that cohesin’s cohesion and loop extrusion activities can be 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 wildtype 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.

2023-10-25 | GSE235771 | GEO

Cohesin mediates DNA loop extrusion and sister chromatid cohesion by distinct mechanisms [ChIP-seq]

2023-10-25 | GSE235770 | GEO

Releasing activity disengages cohesinâs Smc3/Scc1 interface in a process blocked by acetylation

Project description:Sister chromatid cohesion conferred by entrapment of sister DNAs within a tripartite ring formed between cohesinâs Scc1, Smc1, and Smc3 subunits is generated during S and eventually destroyed at anaphase through cleavage of Scc1 by separase. Throughout the cell cycle, cohesinâs association with chromosomes is controlled by opposing activities: loading by the Scc2/4 complex and release by a separase independent releasing activity. Co-entrapment of sister DNAs during replication is accompanied by acetylation of Smc3 by Eco1, which blocks releasing activity and ensures that sisters remain stably connected. Because fusion of Smc3 to Scc1 prevents release and bypasses the requirement for Eco1, we suggested that release is mediated by disengagement of the Smc3/Scc1 interface. We now show that all mutations capable of bypassing Eco1, be they in cohesinâs Smc1, Smc3, Scc1,Wapl, Pds5, or Scc3 subunits, greatly reduce dissociation of N-terminal cleavage fragments of Scc1 (NScc1) from Smc3. We show that this process involves interaction between Smc ATPase heads and is inhibited by Smc3 acetylation Effect of mutations QQ and EQ in Smc3 on cohesin loading onto chromosomes

2016-02-18 | E-GEOD-76890 | biostudies-arrayexpress

Evidence that Loading of Cohesin Onto Chromosomes Involves Opening of Its SMC Hinge

Project description:Cohesin is a multisubunit complex that mediates sister-chromatid cohesion. Its Smc1 and Smc3 subunits possess ABC-like ATPases at one end of 50 nm long coiled coils. At the other ends are pseudosymmetrical hinge domains that interact to create V-shaped Smc1/Smc3 heterodimers. N- and C-terminal domains within cohesin's kleisin subunit Scc1 bind to Smc3 and Smc1 ATPase heads respectively, thereby creating a huge tripartite ring. It has been suggested that cohesin associates with chromosomes by trapping DNA within its ring. Opening of the ring due to cleavage of Scc1 by separase destroys sister-chromatid cohesion and triggers anaphase. We show that cohesin's hinges are not merely dimerization domains. They are essential for cohesin's association with chromosomes, which is blocked by artificially holding hinge domains together but not by preventing Scc1's dissociation from SMC ATPase heads. Our results suggest that entry of DNA into cohesin's ring requires transient dissociation of Smc1 and Smc3 hinge domains. Keywords: Cohesin loading, Scc1, Smc1, Smc3, Hinge opening, ChIP-chip

2006-11-05 | GSE4827 | GEO

Isw1 contributes to cohesin association with centromeres and pericentromeric regions

Project description:Cohesin is a highly conserved, multiprotein complex whose canonical function is to hold sister chromatids together to ensure accurate chromosome segregation. Cohesin association with chromatin relies on the separate Scc2-Scc4 complex that enables cohesin ring opening and topological entrapment of sister DNAs. Cohesin loading at centromeres also requires the CTF19 kinetochore subcomplex that recruits Scc2-Scc4, ensuring efficient and targeted cohesin binding. After loading at centromeres, cohesin rapidly translocates to neighboring pericentromeric regions. In an attempt to better understand how sister chromatid cohesion is regulated, we performed a proteomic screen in budding yeast that identified the Isw1 chromatin remodeler as a cohesin binding partner. We found that while cohesin can associate with both Isw1-containing complexes, ISW1a and ISW1b, however only ISW1a localizes to centromeres. There, ISW1a utilizes its chromatin remodeling activity to allow efficient translocation of cohesin loaded through CTF19 at centromeres to pericentromeres. Consistently, lack of Isw1 results in cohesin and cohesin loader retainment at CENs and periCENs. Interestingly, lack of Isw1 resulted in changes in the nucleosomal landscape at the CENs and pericentromeric regions, suggesting that chromatin organization may be a crucial determinant of cohesin loading. Finally, we provide evidence that the role of ISW1a at the CENs is to restrict the activity of the RSC complex. Taken together, our results support the notion of a key role of chromatin environment for cohesin functions.

2023-05-16 | GSE232315 | GEO

Crosslinking/mass spectrometry (CLMS) analysis of Cohesin complex

Project description:The ring-shaped cohesin complex is thought to fulfil its roles in sister chromatid cohesion, genome stability and gene regulation by topologically encircling DNAs. The ring is formed by two Structural Maintenance of Chromosome (SMC) subunits, whose ATPase heads are linked by a kleisin subunit. Additional components, including the Mis4Scc2/NIPL cohesin loader, engage the kleisin. We applied crosslinking mass spectrometry to characterize cohesion complex in two conditions: initial binding and gripping state.

2020-08-04 | PXD018608 | Pride

Scc2 Is a Potent Activator of Cohesin's ATPase that Promotes Loading by Binding Scc1 without Pds5

Project description:In addition to sharing with condensin an ability to organize DNA into chromatids, cohesin regulates enhancer-promoter interactions and confers sister chromatid cohesion. Association with chromosomes is regulated by hook-shaped HEAT repeat proteins that Associate With its Kleisin (Scc1) subunit (HAWKs), namely Scc3, Pds5, and Scc2. Unlike Pds5, Scc2 is not a stable cohesin constituent but, as shown here, transiently displaces Pds5 during loading. Scc1 mutations that compromise its interaction with Scc2 adversely affect cohesin’s ATPase activity, loading, and translocation while Scc2 mutations that alter how the ATPase responds to DNA abolish loading despite cohesin’s initial association with loading sites. Lastly, Scc2 mutations that permit loading in the absence of Scc4 increase Scc2’s association with chromosomal cohesin and reduce that of Pds5. We suggest that cohesin switches between two states, one with Pds5 bound to Scc1 that is not able to hydrolyse ATP efficiently but is capable of release from chromosomes and another in which Scc2, transiently replacing Pds5, stimulates the ATP hydrolysis necessary for loading and translocation away from loading sites.

2018-07-17 | GSE106182 | GEO

Identification and functional characterization of proteins interacting with cohesin complex in yeast Saccharomyces cerevisiae.

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2023-10-24 | PXD037034 | Pride

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