scholarly journals Bub1 is essential for assembly of the functional inner centromere

2007 ◽  
Vol 176 (7) ◽  
pp. 919-928 ◽  
Author(s):  
Yekaterina Boyarchuk ◽  
Adrian Salic ◽  
Mary Dasso ◽  
Alexei Arnaoutov
Keyword(s):  
Sister Chromatid ◽  
Kinase Activity ◽  
Centromeric Region ◽  
Protein Complexes ◽  
Multiple Points ◽  
Biochemical Pathways ◽  
Microtubule Attachment ◽  
Egg Extract ◽  
Chromatid Cohesion ◽  
Chromosomal Passenger

During mitosis, the inner centromeric region (ICR) recruits protein complexes that regulate sister chromatid cohesion, monitor tension, and modulate microtubule attachment. Biochemical pathways that govern formation of the inner centromere remain elusive. The kinetochore protein Bub1 was shown to promote assembly of the outer kinetochore components, such as BubR1 and CENP-F, on centromeres. Bub1 was also implicated in targeting of Shugoshin (Sgo) to the ICR. We show that Bub1 works as a master organizer of the ICR. Depletion of Bub1 from Xenopus laevis egg extract or from HeLa cells resulted in both destabilization and displacement of chromosomal passenger complex (CPC) from the ICR. Moreover, soluble Bub1 controls the binding of Sgo to chromatin, whereas the CPC restricts loading of Sgo specifically onto centromeres. We further provide evidence that Bub1 kinase activity is pivotal for recruitment of all of these components. Together, our findings demonstrate that Bub1 acts at multiple points to assure the correct kinetochore formation.

scholarly journals Division of labour between different PP2A-B56 complexes during mitosis

2018 ◽  
Author(s):  
Giulia Vallardi ◽  
Lindsey A Allan ◽  
Lisa Crozier ◽  
Adrian T Saurin
Keyword(s):  
Sister Chromatid ◽  
Critical Region ◽  
Spindle Assembly Checkpoint ◽  
Specific Interaction ◽  
Division Of Labour ◽  
Specific Interactions ◽  
Microtubule Attachment ◽  
Chromatid Cohesion ◽  
Terminal Loop ◽  
Selective Interactions

PP2A-B56 is a serine/threonine phosphatase complex that regulates several major mitotic processes, including sister chromatid cohesion, kinetochore-microtubule attachment and the spindle assembly checkpoint. We show here that these key functions are divided between B56 isoforms that localise differentially to either the centromere or kinetochore. The centromeric B56 isoforms rely on a specific interaction with Sgo2, whereas the kinetochore isoforms bind preferentially to BubR1 and other proteins containing an LxxIxE motif. In addition to these selective interactions, Sgo1 also contributes to both localisations by collaborating with BubR1 to maintain B56 isoforms at the kinetochore and helping to anchor the Sgo2/B56 complex at the centromere. A series of chimaeras were used to map the critical region in B56 to a small C-terminal loop that specifies which interactions are favoured and therefore defines where B56 isoforms localise during prometaphase. Together, this study describes how different PP2A-B56 complexes utilise isoform-specific interactions to control distinct processes during mitosis.

scholarly journals Cohesin, condensin, and the intramolecular centromere loop together generate the mitotic chromatin spring

2011 ◽  
Vol 193 (7) ◽  
pp. 1167-1180 ◽  
Author(s):  
Andrew D. Stephens ◽  
Julian Haase ◽  
Leandra Vicci ◽  
Russell M. Taylor ◽  
Kerry Bloom
Keyword(s):  
Sister Chromatid ◽  
Protein Complexes ◽  
Spindle Microtubule ◽  
Spindle Axis ◽  
Chromatid Cohesion ◽  
Length Regulation ◽  
Spindle Microtubules ◽  
Mechanistic Basis ◽  
Structural Maintenance Of Chromosomes ◽  
Mitotic Chromatin

Sister chromatid cohesion provides the mechanistic basis, together with spindle microtubules, for generating tension between bioriented chromosomes in metaphase. Pericentric chromatin forms an intramolecular loop that protrudes bidirectionally from the sister chromatid axis. The centromere lies on the surface of the chromosome at the apex of each loop. The cohesin and condensin structural maintenance of chromosomes (SMC) protein complexes are concentrated within the pericentric chromatin, but whether they contribute to tension-generating mechanisms is not known. To understand how pericentric chromatin is packaged and resists tension, we map the position of cohesin (SMC3), condensin (SMC4), and pericentric LacO arrays within the spindle. Condensin lies proximal to the spindle axis and is responsible for axial compaction of pericentric chromatin. Cohesin is radially displaced from the spindle axis and confines pericentric chromatin. Pericentric cohesin and condensin contribute to spindle length regulation and dynamics in metaphase. Together with the intramolecular centromere loop, these SMC complexes constitute a molecular spring that balances spindle microtubule force in metaphase.

scholarly journals CDK11p58 kinase activity is required to protect sister chromatid cohesion at centromeres in mitosis

2014 ◽  
Vol 22 (3) ◽  
pp. 267-276 ◽  
Author(s):  
Tarik Rakkaa ◽  
Christophe Escudé ◽  
Régis Giet ◽  
Laura Magnaghi-Jaulin ◽  
Christian Jaulin
Keyword(s):  
Sister Chromatid ◽  
Kinase Activity ◽  
Sister Chromatid Cohesion ◽  
Chromatid Cohesion

Sister chromatid cohesion and genome stability in vertebrate cells

2003 ◽  
Vol 31 (1) ◽  
pp. 263-265 ◽  
Author(s):  
C. Morrison ◽  
P. Vagnarelli ◽  
E. Sonoda ◽  
S. Takeda ◽  
W.C. Earnshaw
Keyword(s):  
Dna Repair ◽  
Chromosome Segregation ◽  
Sister Chromatid ◽  
Genome Stability ◽  
Sister Chromatid Cohesion ◽  
Spindle Poles ◽  
Chromatid Cohesion ◽  
Chromosomal Passenger ◽  
Passenger Protein

For successful eukaryotic mitosis, sister chromatid pairs remain linked after replication until their kinetochores have been attached to opposite spindle poles by microtubules. This linkage is broken at the metaphase–anaphase transition and the sisters separate. In budding yeast, this sister chromatid cohesion requires a multi-protein complex called cohesin. A key component of cohesin is Scc1/Mcd1 (Rad21 in fission yeast). Disruption of the chicken orthologue of Scc1 by gene targeting in DT40 cells causes premature sister chromatid separation. Cohesion between sister chromatids is likely to provide a substrate for post-replicative DNA repair by homologous recombination. In keeping with this role of cohesion, Scc1 mutants also show defects in the repair of spontaneous and induced DNA damage. Scc1-deficient cells frequently fail to complete metaphase chromosome alignment and show chromosome segregation defects, suggesting aberrant kinetochore function. Consistent with this, the chromosomal passenger protein, INCENP (inner centromere protein) fails to localize to centromeres. Survivin, another passenger protein and one which interacts with INCENP, also fails to localize to centromeres in Scc1-deficient cells. These results show that cohesin maintains genomic stability by ensuring appropriate DNA repair and equal chromosome segregation at mitosis.

scholarly journals Division of labour between PP2A-B56 isoforms at the centromere and kinetochore

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Giulia Vallardi ◽  
Lindsey A Allan ◽  
Lisa Crozier ◽  
Adrian T Saurin
Keyword(s):  
Sister Chromatid ◽  
Critical Region ◽  
Spindle Assembly Checkpoint ◽  
Specific Interaction ◽  
Division Of Labour ◽  
Specific Interactions ◽  
Microtubule Attachment ◽  
Binding Partners ◽  
Chromatid Cohesion ◽  
Terminal Loop

PP2A-B56 is a serine/threonine phosphatase complex that regulates several major mitotic processes, including sister chromatid cohesion, kinetochore-microtubule attachment and the spindle assembly checkpoint. We show here that these key functions are divided between different B56 isoforms that localise to either the centromere or kinetochore. The centromeric isoforms rely on a specific interaction with Sgo2, whereas the kinetochore isoforms bind preferentially to BubR1 and other proteins containing an LxxIxE motif. In addition to these selective binding partners, Sgo1 helps to anchor PP2A-B56 at both locations: it collaborates with BubR1 to maintain B56 at the kinetochore and it helps to preserve the Sgo2/B56 complex at the centromere. A series of chimaeras were generated to map the critical region in B56 down to a small C-terminal loop that regulates the key interactions and defines B56 localisation. Together, this study describes how different PP2A-B56 complexes utilise isoform-specific interactions to control distinct processes during mitosis.

Cohesin dependent compaction of mitotic chromosomes

2016 ◽  
Author(s):  
Stephanie A Schalbetter ◽  
Anton Goloborodko ◽  
Geoffrey Fudenberg ◽  
Jon M Belton ◽  
Catrina Miles ◽  
...  
Keyword(s):  
Sister Chromatid ◽  
Mitotic Chromosome ◽  
Protein Complexes ◽  
Budding Yeast ◽  
Mitotic Chromosomes ◽  
Chromosome Conformation ◽  
Sister Chromatids ◽  
Chromatid Cohesion ◽  
Structural Maintenance Of Chromosomes

Structural Maintenance of Chromosomes (SMC) protein complexes are key determinants of chromosome conformation. Using Hi-C and polymer modelling, we study how cohesin and condensin, two deeply-conserved SMC complexes, organize chromosomes in budding yeast. The canonical role of cohesins is to co-align sister chromatids whilst condensins generally compact mitotic chromosomes. We find strikingly different roles in budding yeast mitosis. First, cohesin is responsible for compacting mitotic chromosomes arms, independent of and in addition to its role in sister-chromatid cohesion. Cohesin dependent mitotic chromosome compaction can be fully accounted for through cis-looping of chromatin by loop extrusion. Second, condensin is dispensable for compaction along chromosomal arms and instead plays a specialized role, structuring rDNA and peri-centromeric regions. Our results argue that the conserved mechanism of SMC complexes is to form chromatin loops and that SMC-dependent looping is readily deployed in a range of contexts to functionally organize chromosomes.

scholarly journals RAD21L, a novel cohesin subunit implicated in linking homologous chromosomes in mammalian meiosis

2011 ◽  
Vol 192 (2) ◽  
pp. 263-276 ◽  
Author(s):  
Jibak Lee ◽  
Tatsuya Hirano
Keyword(s):  
Molecular Markers ◽  
Sister Chromatid ◽  
Protein Complexes ◽  
Strand Break ◽  
S Phase ◽  
Homologous Chromosomes ◽  
Dna Double Strand Break ◽  
Chromatid Cohesion ◽  
Cohesin Subunit ◽  
Mitosis And Meiosis

Cohesins are multi-subunit protein complexes that regulate sister chromatid cohesion during mitosis and meiosis. Here we identified a novel kleisin subunit of cohesins, RAD21L, which is conserved among vertebrates. In mice, RAD21L is expressed exclusively in early meiosis: it apparently replaces RAD21 in premeiotic S phase, becomes detectable on the axial elements in leptotene, and stays on the axial/lateral elements until mid pachytene. RAD21L then disappears, and is replaced with RAD21. This behavior of RAD21L is unique and distinct from that of REC8, another meiosis-specific kleisin subunit. Remarkably, the disappearance of RAD21L at mid pachytene correlates with the completion of DNA double-strand break repair and the formation of crossovers as judged by colabeling with molecular markers, γ-H2AX, MSH4, and MLH1. RAD21L associates with SMC3, STAG3, and either SMC1α or SMC1β. Our results suggest that cohesin complexes containing RAD21L may be involved in synapsis initiation and crossover recombination between homologous chromosomes.

scholarly journals Identification of Protein Complexes Required for Efficient Sister Chromatid Cohesion

2004 ◽  
Vol 15 (4) ◽  
pp. 1736-1745 ◽  
Author(s):  
Melanie L. Mayer ◽  
Isabelle Pot ◽  
Michael Chang ◽  
Hong Xu ◽  
Victoria Aneliunas ◽  
...  
Keyword(s):  
Sister Chromatid ◽  
Protein Complexes ◽  
Sister Chromatid Cohesion ◽  
Spectrometric Analysis ◽  
Replication Factor C ◽  
Synthetic Genetic Array ◽  
Cell Extracts ◽  
Chromatid Cohesion ◽  
Factor C ◽  
Chromosomal Loci

Ctf8p is a component of Ctf18-RFC, an alternative replication factor C-like complex required for efficient sister chromatid cohesion in Saccharomyces cerevisiae. We performed synthetic genetic array (SGA) analysis with a ctf8 deletion strain as a primary screen to identify other nonessential genes required for efficient sister chromatid cohesion. We then assessed proficiency of cohesion at three chromosomal loci in strains containing deletions of the genes identified in the ctf8 SGA screen. Deletion of seven genes (CHL1, CSM3, BIM1, KAR3, TOF1, CTF4, and VIK1) resulted in defective sister chromatid cohesion. Mass spectrometric analysis of immunoprecipitated complexes identified a physical association between Kar3p and Vik1p and an interaction between Csm3p and Tof1p that we confirmed by coimmunoprecipitation from cell extracts. These data indicate that synthetic genetic array analysis coupled with specific secondary screens can effectively identify protein complexes functionally related to a reference gene. Furthermore, we find that genes involved in mitotic spindle integrity and positioning have a previously unrecognized role in sister chromatid cohesion.

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