The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Tatsuya Hirano - One of the best experts on this subject based on the ideXlab platform.
-
Reconstitution of mitotic Chromatids with a minimum set of purified factors
Nature Cell Biology, 2015Co-Authors: Keishi Shintomi, Tatsuro S. Takahashi, Tatsuya HiranoAbstract:The assembly of mitotic chromosomes, each composed of a pair of rod-shaped Chromatids, is an essential prerequisite for accurate transmission of the genome during cell division. It remains poorly understood, however, how this fundamental process might be achieved and regulated in the cell. Here we report an in vitro system in which mitotic Chromatids can be reconstituted by mixing a simple substrate with only six purified factors: core histones, three histone chaperones (nucleoplasmin, Nap1 and FACT), topoisomerase II (topo II) and condensin I. We find that octameric nucleosomes containing the embryonic variant H2A.X-F are highly susceptible to FACT and function as the most productive substrate for subsequent actions of topo II and condensin I. Cdk1 phosphorylation of condensin I is the sole mitosis-specific modification required for Chromatid reconstitution. This experimental system will enhance our understanding of the mechanisms of action of individual factors and their cooperation during this process. Hirano and colleagues have reconstituted mitotic chromatin condensation in cell-free extracts using six purified factors, including histone chaperones, topoisomerase II and condensin I.
-
Condensin confers the longitudinal rigidity of chromosomes
Nature Cell Biology, 2015Co-Authors: Martin Houlard, Jonathan Godwin, Jean Metson, Tatsuya Hirano, Kim NasmythAbstract:In addition to inter-Chromatid cohesion, mitotic and meiotic Chromatids must have three physical properties: compaction into ‘threads’ roughly co-linear with their DNA sequence, intra-Chromatid cohesion determining their rigidity, and a mechanism to promote sister Chromatid disentanglement. A fundamental issue in chromosome biology is whether a single molecular process accounts for all three features. There is universal agreement that a pair of Smc–kleisin complexes called condensin I and II facilitate sister Chromatid disentanglement, but whether they also confer thread formation or longitudinal rigidity is either controversial or has never been directly addressed respectively. We show here that condensin II (beta-kleisin) has an essential role in all three processes during meiosis I in mouse oocytes and that its function overlaps with that of condensin I (gamma-kleisin), which is otherwise redundant. Pre-assembled meiotic bivalents unravel when condensin is inactivated by TEV cleavage, proving that it actually holds chromatin fibres together. By inactivating condensin I or II before the first meiotic division in mouse oocytes, Nasmyth and colleagues demonstrate that condensin is needed for chromatin thread formation and chromosome rigidity.
-
Condensin confers the longitudinal rigidity of chromosomes
Nature Cell Biology, 2015Co-Authors: Martin Houlard, Jonathan Godwin, Jean Metson, Jibak Lee, Tatsuya Hirano, Kim NasmythAbstract:In addition to inter-Chromatid cohesion, mitotic and meiotic Chromatids must have three physical properties: compaction into 'threads' roughly co-linear with their DNA sequence, intra-Chromatid cohesion determining their rigidity, and a mechanism to promote sister Chromatid disentanglement. A fundamental issue in chromosome biology is whether a single molecular process accounts for all three features. There is universal agreement that a pair of Smc-kleisin complexes called condensin I and II facilitate sister Chromatid disentanglement, but whether they also confer thread formation or longitudinal rigidity is either controversial or has never been directly addressed respectively. We show here that condensin II (beta-kleisin) has an essential role in all three processes during meiosis I in mouse oocytes and that its function overlaps with that of condensin I (gamma-kleisin), which is otherwise redundant. Pre-assembled meiotic bivalents unravel when condensin is inactivated by TEV cleavage, proving that it actually holds chromatin fibres together.
-
human wapl is a cohesin binding protein that promotes sister Chromatid resolution in mitotic prophase
Current Biology, 2006Co-Authors: Rita Gandhi, Peter J Gillespie, Tatsuya HiranoAbstract:BACKGROUND: The linkage between duplicated chromosomes (sister Chromatids) is established during S phase by the action of cohesin, a multisubunit complex conserved from yeast to humans. Most cohesin dissociates from chromosome arms when the cell enters mitotic prophase, leading to the formation of metaphase chromosomes with two cytologically discernible Chromatids. This process is known as sister-Chromatid resolution. Although two mitotic kinases have been implicated in this process, it remains unknown exactly how the cohesin-mediated linkage is destabilized at a mechanistic level. RESULTS: The wings apart-like (Wapl) protein was originally identified as a gene product that potentially regulates heterochromatin organization in Drosophila melanogaster. We show that the human ortholog of Wapl is a cohesin-binding protein that facilitates cohesin's timely release from chromosome arms during prophase. Depletion of Wapl from HeLa cells causes transient accumulation of prometaphase-like cells with chromosomes that display poorly resolved sister Chromatids with a high level of cohesin. Reduction of cohesin relieves the Wapl-depletion phenotype, and depletion of Wapl rescues premature sister separation observed in Sgo1-depleted or Esco2-depleted cells. Conversely, overexpression of Wapl causes premature separation of sister Chromatids. Wapl physically associates with cohesin in HeLa-cell nuclear extracts. Remarkably, in vitro reconstitution experiments demonstrate that Wapl forms a stoichiometric, ternary complex with two regulatory subunits of cohesin, implicating its noncatalytic function in inactivating cohesin's ability to interact with chromatin. CONCLUSIONS: Wapl is a new regulator of sister Chromatid resolution and promotes release of cohesin from chromosomes by directly interacting with its regulatory subunits.
-
scc2 couples replication licensing to sister Chromatid cohesion in xenopus egg extracts
Current Biology, 2004Co-Authors: Peter J Gillespie, Tatsuya HiranoAbstract:Abstract The cohesin complex is a central player in sister Chromatid cohesion, a process that ensures the faithful segregation of chromosomes in mitosis and meiosis [1, 2]. Previous genetic studies in yeast show that Scc2/Mis4, a HEAT-repeat-containing protein, is required for the loading of cohesin onto chromatin [3, 4]. In this study, we have identified two isoforms of Scc2 in humans and Xenopus (termed Scc2A and Scc2B), which are encoded by a single gene but have different carboxyl termini created by alternative splicing. Both Scc2A and Scc2B bind to chromatin concomitant with cohesin during DNA replication in Xenopus egg extracts. Simultaneous immunodepletion of Scc2A and Scc2B from the extracts impairs the association of cohesin with chromatin, leading to severe defects in sister Chromatid pairing in the subsequent mitosis. The loading of Scc2 onto chromatin is inhibited in extracts treated with geminin but not with p21 CIP1 , suggesting that this step depends on replication licensing but not on the initiation of DNA replication. Upon mitotic entry, Scc2 is removed from chromatin through a mechanism that requires cdc2 but not aurora B or polo-like kinase. Our results suggest that vertebrate Scc2 couples replication licensing to sister Chromatid cohesion by facilitating the loading of cohesin onto chromatin.
Jan-michael Peters - One of the best experts on this subject based on the ideXlab platform.
-
sister Chromatid sensitive hi c reveals the conformation of replicated human chromosomes
bioRxiv, 2020Co-Authors: Michael Mitter, Catherina Gasser, Zsuzsanna Takacs, Christoph C H Langer, Wen Tang, Gregor Jessberger, Charlie T Beales, Eva Neuner, Stefan L Ameres, Jan-michael PetersAbstract:Abstract The three-dimensional organization of the genome supports regulated gene expression, recombination, DNA repair, and chromosome segregation during mitosis. Chromosome conformation capture (Hi-C)1–3 has revealed a complex genomic landscape of internal chromosome structures in vertebrate cells4–11 yet how sister Chromatids topologically interact in replicated chromosomes has remained elusive due to their identical sequences. Here, we present sister-Chromatid-sensitive Hi-C (scsHi-C) based on nascent DNA labeling with 4-thio-thymidine. Genome-wide conformation maps of human chromosomes revealed that sister Chromatid pairs interact most frequently at the boundaries of topologically associating domains (TADs). Continuous loading of a dynamic cohesin pool separates sister-Chromatid pairs inside TADs and is required to focus sister Chromatid contacts at TAD boundaries. We identified a subset of TADs that are overall highly paired, characterized by facultative heterochromatin, as well as insulated topological domains that form separately within individual sister Chromatids. The rich pattern of sister Chromatid topologies and our scsHi-C technology will make it possible to dissect how physical interactions between identical DNA molecules contribute to DNA repair, gene expression, chromosome segregation, and potentially other biological processes.
-
dynamics of sister Chromatid resolution during cell cycle progression
Journal of Cell Biology, 2018Co-Authors: Rugile Stanyte, Jan-michael Peters, Johannes Nuebler, Claudia Blaukopf, Rudolf Hoefler, Roman R Stocsits, Daniel W GerlichAbstract:Faithful genome transmission in dividing cells requires that the two copies of each chromosome’s DNA package into separate but physically linked sister Chromatids. The linkage between sister Chromatids is mediated by cohesin, yet where sister Chromatids are linked and how they resolve during cell cycle progression has remained unclear. In this study, we investigated sister Chromatid organization in live human cells using dCas9-mEGFP labeling of endogenous genomic loci. We detected substantial sister locus separation during G2 phase irrespective of the proximity to cohesin enrichment sites. Almost all sister loci separated within a few hours after their respective replication and then rapidly equilibrated their average distances within dynamic chromatin polymers. Our findings explain why the topology of sister Chromatid resolution in G2 largely reflects the DNA replication program. Furthermore, these data suggest that cohesin enrichment sites are not persistent cohesive sites in human cells. Rather, cohesion might occur at variable genomic positions within the cell population.
-
dynamics of sister Chromatid resolution during cell cycle progression
bioRxiv, 2018Co-Authors: Rugile Stanyte, Jan-michael Peters, Johannes Nuebler, Claudia Blaukopf, Rudolf Hoefler, Roman R Stocsits, Daniel W GerlichAbstract:Faithful genome transmission in dividing cells requires that the two copies of each chromosome's DNA package into separate, but physically linked, sister Chromatids. The linkage between sister Chromatids is mediated by cohesin, yet where sister Chromatids are linked and how they resolve during cell cycle progression has remained unclear. Here, we investigated sister Chromatid organization in live human cells using dCas9-mEGFP labelling of endogenous genomic loci. We detected substantial sister locus separation during G2 phase, irrespective of the proximity to cohesin enrichment sites. Almost all sister loci separated within a few hours after their respective replication, and then rapidly equilibrated their average distances within dynamic chromatin polymers. Our findings explain why the topology of sister Chromatid resolution in G2 largely reflects the DNA replication program. Further, these data suggest that cohesin enrichment sites are not persistent cohesive sites in human cells. Rather, cohesion might occur at variable genomic positions within the cell population.
-
The Deubiquitinase USP37 Regulates Chromosome Cohesion and Mitotic Progression
Current Biology, 2015Co-Authors: Christina Yeh, Mikhail Bashkurov, Petra Van Der Lelij, Sally W.t. Cheung, Jan-michael Peters, Etienne Coyaud, Brian Raught, Laurence PelletierAbstract:A bipolar mitotic spindle facilitates the equal segregation of chromosomes to two daughter cells. To achieve bipolar attachment of microtubules to kinetochores of sister Chromatids, Chromatids must remain paired after replication. This cohesion is mediated by the conserved cohesin complex comprised of SMC1, SMC3, SCC1, and either SA1 or SA2 in humans. Because defects in spindle assembly or sister Chromatid cohesion can lead to aneuploidy in daughter cells, proper regulation of these processes is essential for fidelity in chromosome segregation [1]. In an RNAi screen for regulators of spindle assembly, we identify the deubiquitinase USP37 as a regulator of mitotic progression, centrosome integrity, and chromosome alignment. USP37 associates with cohesin and contributes to sister Chromatid resolution. Cohesion defects are rescued by expression of an RNAi-resistant USP37, but not the catalytically impaired USP37C350A mutant. Further, USP37 associates with WAPL, a negative regulator of cohesion necessary for cohesin release in prophase [2, 3], in a manner dependent on USP37's second and third ubiquitin-interacting motifs. Depletion of USP37 reduces the stability of chromatin-associated WAPL and increases the fraction of WAPL that is more heavily ubiquitylated in mitosis. Consistently, overexpression of USP37C350A results in increased modification of WAPL, and addition of purified USP37WT, but not USP37C350A, to WAPL immunoprecipitates results in a reduction of ubiquitylated products. Taken together, our results ascribe a novel function for USP37 in mitotic progression and further suggest that USP37 positively regulates the stability of chromatin-associated WAPL to facilitate sister Chromatid resolution.
-
sororin is required for stable binding of cohesin to chromatin and for sister Chromatid cohesion in interphase
Current Biology, 2007Co-Authors: Julia Schmitz, Erwan Watrin, Peter Lenart, Karl Mechtler, Jan-michael PetersAbstract:Sister Chromatid cohesion depends on cohesin [1-3]. Cohesin associates with chromatin dynamically throughout interphase [4]. During DNA replication, cohesin establishes cohesion [5], and this process coincides with the generation of a cohesin subpopulation that is more stably bound to chromatin [4]. In mitosis, cohesin is removed from chromosomes, enabling sister Chromatid separation [6]. How cohesin associates with chromatin and establishes cohesion is poorly understood. By searching for proteins that are associated with chromatin-bound cohesin, we have identified sororin, a protein that was known to be required for cohesion [7]. To obtain further insight into sororin's function, we have addressed when during the cell cycle sororin is required for cohesion. We show that sororin is dispensable for the association of cohesin with chromatin but that sororin is essential for proper cohesion during G2 phase. Like cohesin, sororin is also needed for efficient repair of DNA double-strand breaks in G2. Finally, sororin is required for the presence of normal amounts of the stably chromatin-bound cohesin population in G2. Our data indicate that sororin interacts with chromatin-bound cohesin and functions during the establishment or maintenance of cohesion in S or G2 phase, respectively.
Frank Uhlmann - One of the best experts on this subject based on the ideXlab platform.
-
Conserved roles of chromatin remodellers in cohesin loading onto chromatin
Current Genetics, 2020Co-Authors: Sofía Muñoz, Francesca Passarelli, Frank UhlmannAbstract:Cohesin is a conserved, ring-shaped protein complex that topologically entraps DNA. This ability makes this member of the structural maintenance of chromosomes (SMC) complex family a central hub of chromosome dynamics regulation. Besides its essential role in sister Chromatid cohesion, cohesin shapes the interphase chromatin domain architecture and plays important roles in transcriptional regulation and DNA repair. Cohesin is loaded onto chromosomes at centromeres, at the promoters of highly expressed genes, as well as at DNA replication forks and sites of DNA damage. However, the features that determine these binding sites are still incompletely understood. We recently described a role of the budding yeast RSC chromatin remodeler in cohesin loading onto chromosomes. RSC has a dual function, both as a physical chromatin receptor of the Scc2/Scc4 cohesin loader complex, as well as by providing a nucleosome-free template for cohesin loading. Here, we show that the role of RSC in sister Chromatid cohesion is conserved in fission yeast. We discuss what is known about the broader conservation of the contribution of chromatin remodelers to cohesin loading onto chromatin.
-
Condensin aids sister Chromatid decatenation by topoisomerase II
Nucleic Acids Research, 2013Co-Authors: Adrian Charbin, Céline Bouchoux, Frank UhlmannAbstract:The condensin complex is a key determinant of mitotic chromosome architecture. In addition, condensin promotes resolution of sister Chromatids during anaphase, a function that is conserved from prokaryotes to human. Anaphase bridges observed in cells lacking condensin are reminiscent of chromosome segregation failure after inactivation of topoisomerase II (topo II), the enzyme that removes catenanes persisting between sister Chromatids following DNA replication. Circumstantial evidence has linked condensin to sister Chromatid decatenation but, because of the difficulty of observing chromosome catenation, this link has remained indirect. Alternative models for how condensin facilitates chromosome resolution have been put forward. Here, we follow the catenation status of circular minichromosomes of three sizes during the Saccharomyeces cerevisiae cell cycle. Catenanes are produced during DNA replication and are for the most part swiftly resolved during and following S-phase, aided by sister Chromatid separation. Complete resolution, however, requires the condensin complex, a dependency that becomes more pronounced with increasing chromosome size. Our results provide evidence that condensin prevents deleterious anaphase bridges during chromosome segregation by promoting sister Chromatid decatenation.
-
A matter of choice: the establishment of sister Chromatid cohesion
EMBO Reports, 2009Co-Authors: Frank UhlmannAbstract:Sister Chromatid cohesion is the basis for the recognition of chromosomal DNA replication products for their bipolar segregation in mitosis. Fundamental to sister Chromatid cohesion is the ring-shaped cohesin complex, which is loaded onto chromosomes long before the initiation of DNA replication and is thought to hold replicated sister Chromatids together by topological embrace. What happens to cohesin when the replication fork approaches, and how cohesin recognizes newly synthesized sister Chromatids, is poorly understood. The characterization of a number of cohesion establishment factors has begun to provide hints as to the reactions involved. Cohesin is a member of the evolutionarily conserved family of Smc subunit-based protein complexes that contribute to many aspects of chromosome biology by mediating long-range DNA interactions. I propose that the establishment of cohesion equates to the selective stabilization of those cohesin-mediated DNA interactions that link sister Chromatids in the wake of replication forks.
-
characterization of fission yeast cohesin essential anaphase proteolysis of rad21 phosphorylated in the s phase
Genes & Development, 2000Co-Authors: Takeshi Tomonaga, Koji Nagao, Yosuke Kawasaki, Kanji Furuya, Akiko Murakami, Jun Morishita, Tatsuro Yuasa, Takashi Sutani, Stephen E Kearsey, Frank UhlmannAbstract:Cohesin complex acts in the formation and maintenance of sister Chromatid cohesion during and after S phase. Budding yeast Scc1p/Mcd1p, an essential subunit, is cleaved and dissociates from chromosomes in anaphase, leading to sister Chromatid separation. Most cohesin in higher eukaryotes, in contrast, is dissociated from chromosomes well before anaphase. The universal role of cohesin during anaphase thus remains to be determined. We report here initial characterization of four putative cohesin subunits, Psm1, Psm3, Rad21, and Psc3, in fission yeast. They are essential for sister Chromatid cohesion. Immunoprecipitation demonstrates stable complex formation of Rad21 with Psm1 and Psm3 but not with Psc3. Chromatin immunoprecipitation shows that cohesin subunits are enriched in broad centromere regions and that the level of centromere-associated Rad21 did not change from metaphase to anaphase, very different from budding yeast. In contrast, Rad21 containing similar cleavage sites to those of Scc1p/Mcd1p is cleaved specifically in anaphase. This cleavage is essential, although the amount of cleaved product is very small (<5%). Mis4, another sister Chromatid cohesion protein, plays an essential role for loading Rad21 on chromatin. A simple model is presented to explain the specific behavior of fission yeast cohesin and why only a tiny fraction of Rad21 is sufficient to be cleaved for normal anaphase.
-
Cohesion between sister Chromatids must be established during DNA replication
Current Biology, 1998Co-Authors: Frank Uhlmann, Kim NasmythAbstract:Abstract Background: Cohesion between sister Chromatids, which opposes the splitting force exerted by the mitotic spindle during metaphase, is essential for their segregation to opposite poles of the cell during anaphase. In Saccharomyces cerevisiae , cohesion depends on a set of chromosomal proteins called cohesins, which include structural maintenance of chromosomes 1p (Smc1p), Smc3p and sister Chromatid cohesion 1p (Scc1p). Strains with mutations in the genes encoding these proteins separate sister Chromatids prematurely and fail to align them in metaphase. This leads to missegregation of chromosomes in the following anaphase. Results: In a normal cell cycle, Scc1p was synthesized and recruited to chromosomes at the onset of S phase. Using cells that expressed Scc1p exclusively from a galactose-inducible promoter, we showed that if Scc1p was synthesised only after completion of S phase, it still bound to chromosomes but failed to promote sister Chromatid cohesion. Conclusions: Cohesion between sister Chromatids must be established during DNA replication, possibly following the passage of a replication fork. Furthermore, Scc1p (and other cohesins) are needed both for maintaining cohesion during mitosis and for establishing it during S phase. Establishment of sister Chromatid cohesion is therefore an essential but hitherto neglected aspect of S phase.
Kim Nasmyth - One of the best experts on this subject based on the ideXlab platform.
-
Condensin confers the longitudinal rigidity of chromosomes
Nature Cell Biology, 2015Co-Authors: Martin Houlard, Jonathan Godwin, Jean Metson, Tatsuya Hirano, Kim NasmythAbstract:In addition to inter-Chromatid cohesion, mitotic and meiotic Chromatids must have three physical properties: compaction into ‘threads’ roughly co-linear with their DNA sequence, intra-Chromatid cohesion determining their rigidity, and a mechanism to promote sister Chromatid disentanglement. A fundamental issue in chromosome biology is whether a single molecular process accounts for all three features. There is universal agreement that a pair of Smc–kleisin complexes called condensin I and II facilitate sister Chromatid disentanglement, but whether they also confer thread formation or longitudinal rigidity is either controversial or has never been directly addressed respectively. We show here that condensin II (beta-kleisin) has an essential role in all three processes during meiosis I in mouse oocytes and that its function overlaps with that of condensin I (gamma-kleisin), which is otherwise redundant. Pre-assembled meiotic bivalents unravel when condensin is inactivated by TEV cleavage, proving that it actually holds chromatin fibres together. By inactivating condensin I or II before the first meiotic division in mouse oocytes, Nasmyth and colleagues demonstrate that condensin is needed for chromatin thread formation and chromosome rigidity.
-
Condensin confers the longitudinal rigidity of chromosomes
Nature Cell Biology, 2015Co-Authors: Martin Houlard, Jonathan Godwin, Jean Metson, Jibak Lee, Tatsuya Hirano, Kim NasmythAbstract:In addition to inter-Chromatid cohesion, mitotic and meiotic Chromatids must have three physical properties: compaction into 'threads' roughly co-linear with their DNA sequence, intra-Chromatid cohesion determining their rigidity, and a mechanism to promote sister Chromatid disentanglement. A fundamental issue in chromosome biology is whether a single molecular process accounts for all three features. There is universal agreement that a pair of Smc-kleisin complexes called condensin I and II facilitate sister Chromatid disentanglement, but whether they also confer thread formation or longitudinal rigidity is either controversial or has never been directly addressed respectively. We show here that condensin II (beta-kleisin) has an essential role in all three processes during meiosis I in mouse oocytes and that its function overlaps with that of condensin I (gamma-kleisin), which is otherwise redundant. Pre-assembled meiotic bivalents unravel when condensin is inactivated by TEV cleavage, proving that it actually holds chromatin fibres together.
-
human scc4 is required for cohesin binding to chromatin sister Chromatid cohesion and mitotic progression
Current Biology, 2006Co-Authors: Erwan Watrin, Kim Nasmyth, Alexander Schleiffer, Koichi Tanaka, Frank Eisenhaber, Jan-michael PetersAbstract:Summary Background Sister-Chromatid cohesion depends on the cohesin complex whose association with chromatin is mediated by Scc2 and Scc4 in budding yeast. Both cohesin and Scc2 have been conserved from yeast to humans, but no Scc4 orthologs have been identified. Mutation of Scc2 orthologs causes defects in cohesion, transcription, and development, resulting in Cornelia de Lange syndrome in humans. Results We have identified a family of tetratricopeptide repeat proteins that share weak sequence similarities with yeast Scc4. This family includes MAU-2, which is required for development of the nervous system in Caenorhabditis elegans . We show that the human member of this family is associated with Scc2, is bound to chromatin from telophase until prophase, and is required for association of cohesin with chromatin during interphase. Cells lacking Scc4 lose sister-Chromatid cohesion precociously and arrest in prometaphase. Mitotic chromosomes in Scc4-depleted cells lack cohesin, even though the cohesin-protecting proteins Sgo1 and Bub1 are normally enriched at centromeres and separase does not seem to be active. Conclusion Our data indicate that human Scc4 is required for the association of cohesin with chromatin, which is a prerequisite for the establishment of sister-Chromatid cohesion and for chromosome biorientation in mitosis. The proteinaceous machinery that is required for loading of cohesin onto chromatin is therefore conserved from yeast to humans. The finding that Caenorhabditis elegans MAU-2 is an ortholog of Scc4 further supports the notion that the Scc2-Scc4 complex is required for developmental processes in metazoans.
-
Cohesion between sister Chromatids must be established during DNA replication
Current Biology, 1998Co-Authors: Frank Uhlmann, Kim NasmythAbstract:Abstract Background: Cohesion between sister Chromatids, which opposes the splitting force exerted by the mitotic spindle during metaphase, is essential for their segregation to opposite poles of the cell during anaphase. In Saccharomyces cerevisiae , cohesion depends on a set of chromosomal proteins called cohesins, which include structural maintenance of chromosomes 1p (Smc1p), Smc3p and sister Chromatid cohesion 1p (Scc1p). Strains with mutations in the genes encoding these proteins separate sister Chromatids prematurely and fail to align them in metaphase. This leads to missegregation of chromosomes in the following anaphase. Results: In a normal cell cycle, Scc1p was synthesized and recruited to chromosomes at the onset of S phase. Using cells that expressed Scc1p exclusively from a galactose-inducible promoter, we showed that if Scc1p was synthesised only after completion of S phase, it still bound to chromosomes but failed to promote sister Chromatid cohesion. Conclusions: Cohesion between sister Chromatids must be established during DNA replication, possibly following the passage of a replication fork. Furthermore, Scc1p (and other cohesins) are needed both for maintaining cohesion during mitosis and for establishing it during S phase. Establishment of sister Chromatid cohesion is therefore an essential but hitherto neglected aspect of S phase.
Susannah Rankin - One of the best experts on this subject based on the ideXlab platform.
-
cohesion fatigue induces Chromatid separation in cells delayed at metaphase
Current Biology, 2011Co-Authors: John R Daum, Susannah Rankin, Tamara A Potapova, Sushama Sivakumar, Jeremy J Daniel, Jennifer N Flynn, Gary J GorbskyAbstract:Summary Background Chromosome instability is thought to be a major contributor to cancer malignancy and birth defects. For balanced chromosome segregation in mitosis, kinetochores on sister Chromatids bind and pull on microtubules emanating from opposite spindle poles. This tension contributes to the correction of improper kinetochore attachments and is opposed by the cohesin complex that holds the sister Chromatids together. Normally, within minutes of alignment at the metaphase plate, Chromatid cohesion is released, allowing each cohort of Chromatids to move synchronously to opposite poles in anaphase, an event closely coordinated with mitotic exit. Results Here we show that during experimentally induced metaphase delay, spindle pulling forces can cause asynchronous Chromatid separation, a phenomenon we term "cohesion fatigue." Cohesion fatigue is not blocked by inhibition of Plk1, a kinase essential for the "prophase pathway" of cohesin release from chromosomes, or by depletion of separase, the protease that normally drives Chromatid separation at anaphase. Cohesion fatigue is inhibited by drug-induced depolymerization of mitotic spindle microtubules and by experimentally increasing the levels of cohesin on mitotic chromosomes. In cells undergoing cohesion fatigue, cohesin proteins remain associated with the separated Chromatids. Conclusion In cells arrested at metaphase, pulling forces originating from kinetochore-microtubule interactions can, with time, rupture normal sister Chromatid cohesion. This cohesion fatigue, resulting in unscheduled Chromatid separation in cells delayed at metaphase, constitutes a previously overlooked source for chromosome instability in mitosis and meiosis.
-
sororin cooperates with the acetyltransferase eco2 to ensure dna replication dependent sister Chromatid cohesion
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Andrea Lafont, Jianhua Song, Susannah RankinAbstract:Sister Chromatids are held together, from the time they are made during S phase until they are pulled apart just before cell division, by a protein complex called cohesin. The mechanistic details by which sister Chromatid cohesion is established and maintained have remained elusive, particularly in vertebrate systems. Sororin, a protein that interacts with the cohesin complex, is essential for cohesion in vertebrates, but how it participates in the process is unknown. Here we demonstrate that sororin recruitment depends on active DNA replication and that sororin loading onto chromosomes depends upon another essential cohesion factor, the acetyltransferase Eco2. We find that Eco2, like sororin, is a substrate of the anaphase-promoting complex (APC), which ensures that protein levels remain low before S phase. These findings demonstrate that sororin and Eco2 work together to form a unique regulatory module that limits cohesion to cells with replicated chromatin and support a model in which cohesion in vertebrates is not fully established until the G2 phase of the cell cycle.
-
sororin a substrate of the anaphase promoting complex is required for sister Chromatid cohesion in vertebrates
Molecular Cell, 2005Co-Authors: Susannah Rankin, Nagi G Ayad, Marc W KirschnerAbstract:We have identified a regulator of sister Chromatid cohesion in a screen for cell cycle-controlled proteins. This 35 kDa protein is degraded through anaphase-promoting complex (APC)-dependent ubiquitination in G1. The protein is nuclear in interphase cells, dispersed from the chromatin in mitosis, and interacts with the cohesin complex. In Xenopus embryos, overexpression of the protein causes failure to resolve and segregate sister Chromatids in mitosis and an increase in the level of cohesin associated with metaphase chromosomes. In cultured cells, depletion of the protein causes mitotic arrest and complete failure of sister Chromatid cohesion. This protein is thus an essential, cell cycle-dependent mediator of sister Chromatid cohesion. Based on sequence analysis, this protein has no apparent orthologs outside of the vertebrates. We speculate that the protein, which we have named sororin, regulates the ability of the cohesin complex to mediate sister Chromatid cohesion, perhaps by altering the nature of the interaction of cohesin with the chromosomes.