scholarly journals The human Mis12 complex is required for kinetochore assembly and proper chromosome segregation

2006 ◽  
Vol 173 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Susan L. Kline ◽  
Iain M. Cheeseman ◽  
Tetsuya Hori ◽  
Tatsuo Fukagawa ◽  
Arshad Desai
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Essential Role ◽  
Stable Complex ◽  
Wild Type ◽  
Outer Plate ◽  
Checkpoint Protein ◽  
Kinetochore Assembly ◽  
Attachment Sites ◽  
Spindle Microtubules

During cell division, kinetochores form the primary chromosomal attachment sites for spindle microtubules. We previously identified a network of 10 interacting kinetochore proteins conserved between Caenorhabditis elegans and humans. In this study, we investigate three proteins in the human network (hDsn1Q9H410, hNnf1PMF1, and hNsl1DC31). Using coexpression in bacteria and fractionation of mitotic extracts, we demonstrate that these proteins form a stable complex with the conserved kinetochore component hMis12. Human or chicken cells depleted of Mis12 complex subunits are delayed in mitosis with misaligned chromosomes and defects in chromosome biorientation. Aligned chromosomes exhibited reduced centromere stretch and diminished kinetochore microtubule bundles. Consistent with this, localization of the outer plate constituent Ndc80HEC1 was severely reduced. The checkpoint protein BubR1, the fibrous corona component centromere protein (CENP) E, and the inner kinetochore proteins CENP-A and CENP-H also failed to accumulate to wild-type levels in depleted cells. These results indicate that a four-subunit Mis12 complex plays an essential role in chromosome segregation in vertebrates and contributes to mitotic kinetochore assembly.

scholarly journals CENP-C is a blueprint for constitutive centromere–associated network assembly within human kinetochores

2015 ◽  
Vol 210 (1) ◽  
pp. 11-22 ◽  
Author(s):  
Kerstin Klare ◽  
John R. Weir ◽  
Federica Basilico ◽  
Tomasz Zimniak ◽  
Lucia Massimiliano ◽  
...  
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
The Other ◽  
Microtubule Binding ◽  
Kinetochore Assembly ◽  
Binding Interface ◽  
Other Hand ◽  
Spindle Microtubules ◽  
Data Point

Kinetochores are multisubunit complexes that assemble on centromeres to bind spindle microtubules and promote faithful chromosome segregation during cell division. A 16-subunit complex named the constitutive centromere–associated network (CCAN) creates the centromere–kinetochore interface. CENP-C, a CCAN subunit, is crucial for kinetochore assembly because it links centromeres with the microtubule-binding interface of kinetochores. The role of CENP-C in CCAN organization, on the other hand, had been incompletely understood. In this paper, we combined biochemical reconstitution and cellular investigations to unveil how CENP-C promotes kinetochore targeting of other CCAN subunits. The so-called PEST domain in the N-terminal half of CENP-C interacted directly with the four-subunit CCAN subcomplex CENP-HIKM. We identified crucial determinants of this interaction whose mutation prevented kinetochore localization of CENP-HIKM and of CENP-TW, another CCAN subcomplex. When considered together with previous observations, our data point to CENP-C as a blueprint for kinetochore assembly.

scholarly journals Bub1 mediates cell death in response to chromosome missegregation and acts to suppress spontaneous tumorigenesis

2007 ◽  
Vol 179 (2) ◽  
pp. 255-267 ◽  
Author(s):  
Karthik Jeganathan ◽  
Liviu Malureanu ◽  
Darren J. Baker ◽  
Susan C. Abraham ◽  
Jan M. van Deursen
Keyword(s):  
Cell Death ◽  
Chromosome Segregation ◽  
Physiological Role ◽  
Mitotic Checkpoint ◽  
Critical Threshold ◽  
Wild Type ◽  
Checkpoint Protein ◽  
Chromosome Missegregation ◽  
Mitotic Checkpoint Protein

The physiological role of the mitotic checkpoint protein Bub1 is unknown. To study this role, we generated a series of mutant mice with a gradient of reduced Bub1 expression using wild-type, hypomorphic, and knockout alleles. Bub1 hypomorphic mice are viable, fertile, and overtly normal despite weakened mitotic checkpoint activity and high percentages of aneuploid cells. Bub1 haploinsufficient mice, which have a milder reduction in Bub1 protein than Bub1 hypomorphic mice, also exhibit reduced checkpoint activity and increased aneuploidy, but to a lesser extent. Although cells from Bub1 hypomorphic and haploinsufficient mice have similar rates of chromosome missegregation, cell death after an aberrant separation decreases dramatically with declining Bub1 levels. Importantly, Bub1 hypomorphic mice are highly susceptible to spontaneous tumors, whereas Bub1 haploinsufficient mice are not. These findings demonstrate that loss of Bub1 below a critical threshold drives spontaneous tumorigenesis and suggest that in addition to ensuring proper chromosome segregation, Bub1 is important for mediating cell death when chromosomes missegregate.

scholarly journals A Chromatin-associated Kinesin-related Protein Required for Normal Mitotic Chromosome Segregation in Drosophila

1997 ◽  
Vol 139 (6) ◽  
pp. 1361-1371 ◽  
Author(s):  
Isabel Molina ◽  
Sigrid Baars ◽  
Julie A. Brill ◽  
Karen G. Hales ◽  
Margaret T. Fuller ◽  
...  
Keyword(s):  
Cell Division ◽  
Gene Product ◽  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Related Protein ◽  
Wild Type ◽  
Type Function ◽  
Microtubule Motor ◽  
Mitotic Figures ◽  
Bipolar Spindles

The tiovivo (tio) gene of Drosophila encodes a kinesin-related protein, KLP38B, that colocalizes with condensed chromatin during cell division. Wild-type function of the tio gene product KLP38B is required for normal chromosome segregation during mitosis. Mitotic cells in tio larval brains displayed circular mitotic figures, increased ploidy, and abnormal anaphase figures. KLP38B mRNA is maternally provided and expressed in cells about to undergo division. We propose that KLP38B, perhaps redundantly with other chromosome-associated microtubule motor proteins, contributes to interactions between chromosome arms and microtubules important for establishing bipolar attachment of chromosomes and assembly of stable bipolar spindles.

scholarly journals Functional Analysis of Kinetochore Assembly in Caenorhabditis elegans

2001 ◽  
Vol 153 (6) ◽  
pp. 1209-1226 ◽  
Author(s):  
Karen Oegema ◽  
Arshad Desai ◽  
Sonja Rybina ◽  
Matthew Kirkham ◽  
Anthony A. Hyman
Keyword(s):  
Caenorhabditis Elegans ◽  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Mitotic Chromosomes ◽  
Cell Stage ◽  
Kinetochore Assembly ◽  
Chromosomal Passenger ◽  
Complete Failure ◽  
Spindle Microtubules ◽  
The One

In all eukaryotes, segregation of mitotic chromosomes requires their interaction with spindle microtubules. To dissect this interaction, we use live and fixed assays in the one-cell stage Caenorhabditis elegans embryo. We compare the consequences of depleting homologues of the centromeric histone CENP-A, the kinetochore structural component CENP-C, and the chromosomal passenger protein INCENP. Depletion of either CeCENP-A or CeCENP-C results in an identical “kinetochore null” phenotype, characterized by complete failure of mitotic chromosome segregation as well as failure to recruit other kinetochore components and to assemble a mechanically stable spindle. The similarity of their depletion phenotypes, combined with a requirement for CeCENP-A to localize CeCENP-C but not vice versa, suggest that a key step in kinetochore assembly is the recruitment of CENP-C by CENP-A–containing chromatin. Parallel analysis of CeINCENP-depleted embryos revealed mitotic chromosome segregation defects different from those observed in the absence of CeCENP-A/C. Defects are observed before and during anaphase, but the chromatin separates into two equivalently sized masses. Mechanically stable spindles assemble that show defects later in anaphase and telophase. Furthermore, kinetochore assembly and the recruitment of CeINCENP to chromosomes are independent. These results suggest distinct roles for the kinetochore and the chromosomal passengers in mitotic chromosome segregation.

scholarly journals MICROTUBULE BIOGENESIS AND CELL SHAPE IN OCHROMONAS

1973 ◽  
Vol 56 (2) ◽  
pp. 340-359 ◽  
Author(s):  
G. Benjamin Bouck ◽  
David L. Brown
Keyword(s):  
Cell Division ◽  
Cell Shape ◽  
Spindle Pole ◽  
Vegetative Cells ◽  
External Wall ◽  
Cell Form ◽  
Attachment Sites ◽  
Spindle Microtubules ◽  
Mitotic Cells

In the first of two companion papers which attempt to correlate microtubules and their nucleating sites with developmental and cell division patterns in the unicellular flagellate, Ochromonas, the distribution of cytoplasmic and mitotic microtubules and various kinetosome-related fibers are detailed. Of the five kinetosome-related fibers, which have been found in Ochromonas, two, the kineto-beak fibers and the rhizoplast fibers are utilized as attachment sites for distinct groups of microtubules. The set of microtubules attached to the kineto-beak fibers apparently shape the anterior beak region of the cell whereas the rhizoplast microtubules appear to extend into and shape the tail in vegetative cells. In mitotic cells a rhizoplast is found at each spindle pole apparently serving as foci for the spindle microtubules. These findings are discussed in relation to the less well defined attachment sites for vegetative and mitotic microtubules in other kinds of cells. It is noted that the effects of depolymerizing microtubules in vivo might be easily quantitated in whole populations since no external wall or pellicle contributes to the maintenance or the biogenesis of the characteristic cell form of Ochromonas.

scholarly journals Decoding the centromeric nucleosome through CENP-N

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Satyakrishna Pentakota ◽  
Keda Zhou ◽  
Charlotte Smith ◽  
Stefano Maffini ◽  
Arsen Petrovic ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Double Helix ◽  
Structural Basis ◽  
Binding Motif ◽  
Kinetochore Assembly ◽  
Nucleosomal Dna ◽  
Chromosome Domains ◽  
Histone H3 Variant ◽  
Spindle Microtubules ◽  
Dna Double Helix

Centromere protein (CENP) A, a histone H3 variant, is a key epigenetic determinant of chromosome domains known as centromeres. Centromeres nucleate kinetochores, multi-subunit complexes that capture spindle microtubules to promote chromosome segregation during mitosis. Two kinetochore proteins, CENP-C and CENP-N, recognize CENP-A in the context of a rare CENP-A nucleosome. Here, we reveal the structural basis for the exquisite selectivity of CENP-N for centromeres. CENP-N uses charge and space complementarity to decode the L1 loop that is unique to CENP-A. It also engages in extensive interactions with a 15-base pair segment of the distorted nucleosomal DNA double helix, in a position predicted to exclude chromatin remodelling enzymes. Besides CENP-A, stable centromere recruitment of CENP-N requires a coincident interaction with a newly identified binding motif on nucleosome-bound CENP-C. Collectively, our studies clarify how CENP-N and CENP-C decode and stabilize the non-canonical CENP-A nucleosome to enforce epigenetic centromere specification and kinetochore assembly.

scholarly journals Phosphorylation of CENP-C by Aurora B facilitates kinetochore attachment error correction in mitosis

2017 ◽  
Vol 114 (50) ◽  
pp. E10667-E10676 ◽  
Author(s):  
Xing Zhou ◽  
Fan Zheng ◽  
Chengliang Wang ◽  
Minhao Wu ◽  
Xiaozhen Zhang ◽  
...  
Keyword(s):  
Error Correction ◽  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Mitotic Chromosome ◽  
Regulatory Mechanism ◽  
Dynamic Interaction ◽  
Aurora B ◽  
Kinetochore Assembly ◽  
Important Pathway ◽  
Spindle Microtubules

Kinetochores are superprotein complexes that orchestrate chromosome segregation via a dynamic interaction with spindle microtubules. A physical connection between CENP-C and the Mis12–Ndc80–Knl1 (KMN) protein network is an important pathway that is used to assemble kinetochores on CENP-A nucleosomes. Multiple outer kinetochore components are phosphorylated by Aurora B kinase to activate the spindle assembly checkpoint (SAC) and to ensure accurate chromosome segregation. However, it is unknown whether Aurora B can phosphorylate inner kinetochore components to facilitate proper mitotic chromosome segregation. Here, we reported the structure of the fission yeast Schizosaccharomyces pombe Mis12–Nnf1 complex and showed that N-terminal residues 26–50 in Cnp3 (the CENP-C homolog of S. pombe) are responsible for interacting with the Mis12 complex. Interestingly, Thr28 of Cnp3 is a substrate of Ark1 (the Aurora B homolog of S. pombe), and phosphorylation impairs the interaction between the Cnp3 and Mis12 complex. The expression of a phosphorylation-mimicking Cnp3 mutant results in defective chromosome segregation due to improper kinetochore assembly. These results establish a previously uncharacterized regulatory mechanism involved in CENP-C–Mis12-facilitated kinetochore attachment error correction to ensure accurate chromosome segregation during mitosis.

scholarly journals Kinetochore-independent chromosome segregation driven by lateral microtubule bundles

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Christina C Muscat ◽  
Keila M Torre-Santiago ◽  
Michael V Tran ◽  
James A Powers ◽  
Sarah M Wignall
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Protein Complex ◽  
Chromosome Movement ◽  
Chromosome Dynamics ◽  
Anaphase Onset ◽  
Independent Segregation ◽  
Main Driver ◽  
Chromosome Associations ◽  
Spindle Microtubules

During cell division, chromosomes attach to spindle microtubules at sites called kinetochores, and force generated at the kinetochore-microtubule interface is the main driver of chromosome movement. Surprisingly, kinetochores are not required for chromosome segregation on acentrosomal spindles in Caenorhabditis elegans oocytes, but the mechanism driving chromosomes apart in their absence is not understood. In this study, we show that lateral microtubule–chromosome associations established during prometaphase remain intact during anaphase to facilitate separation, defining a novel form of kinetochore-independent segregation. Chromosome dynamics during congression and segregation are controlled by opposing forces; plus-end directed forces are mediated by a protein complex that forms a ring around the chromosome center and dynein on chromosome arms provides a minus-end force. At anaphase onset, ring removal shifts the balance between these forces, triggering poleward movement along lateral microtubule bundles. This represents an elegant strategy for controlling chromosomal movements during cell division distinct from the canonical kinetochore-driven mechanism.

scholarly journals The pseudo GTPase CENP-M drives human kinetochore assembly

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Federica Basilico ◽  
Stefano Maffini ◽  
John R Weir ◽  
Daniel Prumbaum ◽  
Ana M Rojas ◽  
...  
Keyword(s):  
Cell Division ◽  
Small Gtpases ◽  
Conformational Switching ◽  
Point Mutant ◽  
Kinetochore Assembly ◽  
Gtp Binding ◽  
Chromosome Alignment ◽  
Spindle Microtubules ◽  
And Function

Kinetochores, multi-subunit complexes that assemble at the interface with centromeres, bind spindle microtubules to ensure faithful delivery of chromosomes during cell division. The configuration and function of the kinetochore–centromere interface is poorly understood. We report that a protein at this interface, CENP-M, is structurally and evolutionarily related to small GTPases but is incapable of GTP-binding and conformational switching. We show that CENP-M is crucially required for the assembly and stability of a tetramer also comprising CENP-I, CENP-H, and CENP-K, the HIKM complex, which we extensively characterize through a combination of structural, biochemical, and cell biological approaches. A point mutant affecting the CENP-M/CENP-I interaction hampers kinetochore assembly and chromosome alignment and prevents kinetochore recruitment of the CENP-T/W complex, questioning a role of CENP-T/W as founder of an independent axis of kinetochore assembly. Our studies identify a single pathway having CENP-C as founder, and CENP-H/I/K/M and CENP-T/W as CENP-C-dependent followers.

scholarly journals Mitotic Chromosome Biorientation in Fission Yeast Is Enhanced by Dynein and a Minus-end–directed, Kinesin-like Protein

2007 ◽  
Vol 18 (6) ◽  
pp. 2216-2225 ◽  
Author(s):  
Ekaterina L. Grishchuk ◽  
Ilia S. Spiridonov ◽  
J. Richard McIntosh
Keyword(s):  
Fission Yeast ◽  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Spindle Pole ◽  
Ultrastructural Analysis ◽  
Yeast Cells ◽  
Mitotic Spindles ◽  
Wild Type ◽  
Spindle Poles ◽  
Spindle Microtubules

Chromosome biorientation, the attachment of sister kinetochores to sister spindle poles, is vitally important for accurate chromosome segregation. We have studied this process by following the congression of pole-proximal kinetochores and their subsequent anaphase segregation in fission yeast cells that carry deletions in any or all of this organism's minus end–directed, microtubule-dependent motors: two related kinesin 14s (Pkl1p and Klp2p) and dynein. None of these deletions abolished biorientation, but fewer chromosomes segregated normally without Pkl1p, and to a lesser degree without dynein, than in wild-type cells. In the absence of Pkl1p, which normally localizes to the spindle and its poles, the checkpoint that monitors chromosome biorientation was defective, leading to frequent precocious anaphase. Ultrastructural analysis of mutant mitotic spindles suggests that Pkl1p contributes to error-free biorientation by promoting normal spindle pole organization, whereas dynein helps to anchor a focused bundle of spindle microtubules at the pole.

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