scholarly journals THE SPATIAL REGULATION OF CONDENSIN ACTIVITY IN CHROMOSOME CONDENSATION

2019 ◽  
Author(s):  
Rebecca Lamothe ◽  
Lorenzo Costantino ◽  
Douglas E Koshland
Keyword(s):  
Chromosome Segregation ◽  
Ribosomal Dna ◽  
Budding Yeast ◽  
Chromosome Condensation ◽  
Mitotic Chromosomes ◽  
Spatial Regulation ◽  
Polo Kinase ◽  
Evolutionarily Conserved

AbstractCondensin mediates chromosome condensation, which is essential for proper chromosome segregation during mitosis. Prior to anaphase of budding yeast, the ribosomal DNA (RDN) condenses to a thin loop that is distinct from the rest of the chromosomes. We provide evidence that the establishment and maintenance of this RDN condensation require the regulation of condensin by Cdc5p (polo) kinase. We show that Cdc5p is recruited to the site of condensin binding in the RDN by cohesin, a complex related to condensin. Cdc5p and cohesin prevent condensin from misfolding the RDN into an irreversibly decondensed state. From these and other observations, we propose that the spatial regulation of Cdc5p by cohesin modulates condensin activity to ensure proper RDN folding into a thin loop. This mechanism may be evolutionarily conserved, promoting the thinly condensed constrictions that occur at centromeres and RDN of mitotic chromosomes in plants and animals.

scholarly journals Structural plasticity of the living kinetochore

2017 ◽  
Vol 216 (11) ◽  
pp. 3551-3570 ◽  
Author(s):  
Karthik Dhatchinamoorthy ◽  
Manjunatha Shivaraju ◽  
Jeffrey J. Lange ◽  
Boris Rubinstein ◽  
Jay R. Unruh ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Protein Structure ◽  
Chromosome Segregation ◽  
Budding Yeast ◽  
Living Cells ◽  
Microtubule Depolymerization ◽  
Mathematical Simulations ◽  
Evolutionarily Conserved ◽  
Quantitative Examination ◽  
Insight Into

The kinetochore is a large, evolutionarily conserved protein structure that connects chromosomes with microtubules. During chromosome segregation, outer kinetochore components track depolymerizing ends of microtubules to facilitate the separation of chromosomes into two cells. In budding yeast, each chromosome has a point centromere upon which a single kinetochore is built, which attaches to a single microtubule. This defined architecture facilitates quantitative examination of kinetochores during the cell cycle. Using three independent measures—calibrated imaging, FRAP, and photoconversion—we find that the Dam1 submodule is unchanged during anaphase, whereas MIND and Ndc80 submodules add copies to form an “anaphase configuration” kinetochore. Microtubule depolymerization and kinesin-related motors contribute to copy addition. Mathematical simulations indicate that the addition of microtubule attachments could facilitate tracking during rapid microtubule depolymerization. We speculate that the minimal kinetochore configuration, which exists from G1 through metaphase, allows for correction of misattachments. Our study provides insight into dynamics and plasticity of the kinetochore structure during chromosome segregation in living cells.

scholarly journals Nanoscale structural organization and stoichiometry of the budding yeast kinetochore

2021 ◽  
Author(s):  
Konstanty Cieslinski ◽  
Yu-Le Wu ◽  
Lisa Neechyporenko ◽  
Sarah Janice Hoerner ◽  
Duccio Conti ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Single Molecule ◽  
Budding Yeast ◽  
Active Role ◽  
Quantitative Model ◽  
Binding Partner ◽  
Evolutionarily Conserved ◽  
Spindle Microtubules ◽  
Single Molecule Localization Microscopy

Proper chromosome segregation is crucial for cell division. In eukaryotes, this is achieved by the kinetochore, an evolutionarily conserved multi-protein complex that physically links the DNA to spindle microtubules, and takes an active role in monitoring and correcting erroneous spindle-chromosome attachments. Our mechanistic understanding of these functions, and how they ensure an error-free outcome of mitosis, is still limited, partly because we lack a comprehensive understanding of the kinetochore structure in the cell. In this study, we use single molecule localization microscopy to visualize individual kinetochore complexes in situ in budding yeast. For all major kinetochore proteins, we measured abundance and position within the metaphase kinetochore. Based on this comprehensive dataset, we propose a quantitative model of the budding yeast kinetochore. While confirming many aspects of previous reports based on bulk imaging of kinetochores, our results present a somewhat different but unifying model of the inner kinetochore. We find that the centromere-specialized histone Cse4 is present in more than two copies per kinetochore along with its binding partner Mif2.

scholarly journals Condensin suppresses recombination and regulates double-strand break processing at the repetitive ribosomal DNA array to ensure proper chromosome segregation during meiosis in budding yeast

2014 ◽  
Vol 25 (19) ◽  
pp. 2934-2947 ◽  
Author(s):  
Ping Li ◽  
Hui Jin ◽  
Hong-Guo Yu
Keyword(s):  
Chromosome Segregation ◽  
Ribosomal Dna ◽  
Meiotic Recombination ◽  
Budding Yeast ◽  
Strand Break ◽  
Double Strand Break ◽  
Prophase I ◽  
Rdna Array ◽  
Meiotic Dsbs ◽  
Rdna Copy

During meiosis, homologues are linked by crossover, which is required for bipolar chromosome orientation before chromosome segregation at anaphase I. The repetitive ribosomal DNA (rDNA) array, however, undergoes little or no meiotic recombination. Hyperrecombination can cause chromosome missegregation and rDNA copy number instability. We report here that condensin, a conserved protein complex required for chromosome organization, regulates double-strand break (DSB) formation and repair at the rDNA gene cluster during meiosis in budding yeast. Condensin is highly enriched at the rDNA region during prophase I, released at the prophase I/metaphase I transition, and reassociates with rDNA before anaphase I onset. We show that condensin plays a dual role in maintaining rDNA stability: it suppresses the formation of Spo11-mediated rDNA breaks, and it promotes DSB processing to ensure proper chromosome segregation. Condensin is unnecessary for the export of rDNA breaks outside the nucleolus but required for timely repair of meiotic DSBs. Our work reveals that condensin coordinates meiotic recombination with chromosome segregation at the repetitive rDNA sequence, thereby maintaining genome integrity.

scholarly journals Topoisomerase IIα is essential for maintenance of mitotic chromosome structure

2020 ◽  
Vol 117 (22) ◽  
pp. 12131-12142 ◽  
Author(s):  
Christian F. Nielsen ◽  
Tao Zhang ◽  
Marin Barisic ◽  
Paul Kalitsis ◽  
Damien F. Hudson
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Chromosome Structure ◽  
Chromatin Condensation ◽  
Chromosome Condensation ◽  
Mitotic Chromosomes ◽  
Topoisomerase Iiα ◽  
Mitotic Chromosome Condensation

Topoisomerase IIα (TOP2A) is a core component of mitotic chromosomes and important for establishing mitotic chromosome condensation. The primary roles of TOP2A in mitosis have been difficult to decipher due to its multiple functions across the cell cycle. To more precisely understand the role of TOP2A in mitosis, we used the auxin-inducible degron (AID) system to rapidly degrade the protein at different stages of the human cell cycle. Removal of TOP2A prior to mitosis does not affect prophase timing or the initiation of chromosome condensation. Instead, it prevents chromatin condensation in prometaphase, extends the length of prometaphase, and ultimately causes cells to exit mitosis without chromosome segregation occurring. Surprisingly, we find that removal of TOP2A from cells arrested in prometaphase or metaphase cause dramatic loss of compacted mitotic chromosome structure and conclude that TOP2A is crucial for maintenance of mitotic chromosomes. Treatments with drugs used to poison/inhibit TOP2A function, such as etoposide and ICRF-193, do not phenocopy the effects on chromosome structure of TOP2A degradation by AID. Our data point to a role for TOP2A as a structural chromosome maintenance enzyme locking in condensation states once sufficient compaction is achieved.

scholarly journals Exo1 recruits Cdc5 polo kinase to MutLγ to ensure efficient meiotic crossover formation

2020 ◽  
Vol 117 (48) ◽  
pp. 30577-30588
Author(s):  
Aurore Sanchez ◽  
Céline Adam ◽  
Felix Rauh ◽  
Yann Duroc ◽  
Lepakshi Ranjha ◽  
...  
Keyword(s):  
Budding Yeast ◽  
Double Strand Breaks ◽  
Spatial Control ◽  
Strand Breaks ◽  
Spatial Regulation ◽  
Polo Kinase ◽  
Meiotic Crossover ◽  
Temporal And Spatial

Crossovers generated during the repair of programmed meiotic double-strand breaks must be tightly regulated to promote accurate homolog segregation without deleterious outcomes, such as aneuploidy. The Mlh1–Mlh3 (MutLγ) endonuclease complex is critical for crossover resolution, which involves mechanistically unclear interplay between MutLγ and Exo1 and polo kinase Cdc5. Using budding yeast to gain temporal and genetic traction on crossover regulation, we find that MutLγ constitutively interacts with Exo1. Upon commitment to crossover repair, MutLγ–Exo1 associate with recombination intermediates, followed by direct Cdc5 recruitment that triggers MutLγ crossover activity. We propose that Exo1 serves as a central coordinator in this molecular interplay, providing a defined order of interaction that prevents deleterious, premature activation of crossovers. MutLγ associates at a lower frequency near centromeres, indicating that spatial regulation across chromosomal regions reduces risky crossover events. Our data elucidate the temporal and spatial control surrounding a constitutive, potentially harmful, nuclease. We also reveal a critical, noncatalytic role for Exo1, through noncanonical interaction with polo kinase. These mechanisms regulating meiotic crossovers may be conserved across species.

scholarly journals Polo kinase Cdc5 associates with centromeres to facilitate the removal of centromeric cohesin during mitosis

2016 ◽  
Vol 27 (14) ◽  
pp. 2286-2300 ◽  
Author(s):  
Prashant K. Mishra ◽  
Sultan Ciftci-Yilmaz ◽  
David Reynolds ◽  
Wei-Chun Au ◽  
Lars Boeckmann ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Sister Chromatid ◽  
Sister Chromatid Cohesion ◽  
Centromeric Chromatin ◽  
Polo Kinase ◽  
Chromatid Cohesion ◽  
Evolutionarily Conserved ◽  
Sister Chromatid Separation

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.

scholarly journals Structural and dynamic mechanisms of CBF3-guided centromeric nucleosome formation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ruifang Guan ◽  
Tengfei Lian ◽  
Bing-Rui Zhou ◽  
Emily He ◽  
Carl Wu ◽  
...  
Keyword(s):  
Dna Sequence ◽  
Chromosome Segregation ◽  
Budding Yeast ◽  
Dna Conformation ◽  
Dependent Manner ◽  
Dynamic Interactions ◽  
Nucleosome Core ◽  
Dynamic Mechanisms ◽  
Nucleosome Formation ◽  
Core Histones

AbstractAccurate chromosome segregation relies on the specific centromeric nucleosome–kinetochore interface. In budding yeast, the centromere CBF3 complex guides the deposition of CENP-A, an H3 variant, to form the centromeric nucleosome in a DNA sequence-dependent manner. Here, we determine the structures of the centromeric nucleosome containing the native CEN3 DNA and the CBF3core bound to the canonical nucleosome containing an engineered CEN3 DNA. The centromeric nucleosome core structure contains 115 base pair DNA including a CCG motif. The CBF3core specifically recognizes the nucleosomal CCG motif through the Gal4 domain while allosterically altering the DNA conformation. Cryo-EM, modeling, and mutational studies reveal that the CBF3core forms dynamic interactions with core histones H2B and CENP-A in the CEN3 nucleosome. Our results provide insights into the structure of the budding yeast centromeric nucleosome and the mechanism of its assembly, which have implications for analogous processes of human centromeric nucleosome formation.

scholarly journals Identification of a novel nucleolar protein complex required for mitotic chromosome segregation through centromeric accumulation of Aurora B

2020 ◽  
Vol 48 (12) ◽  
pp. 6583-6596
Author(s):  
Akiko Fujimura ◽  
Yuki Hayashi ◽  
Kazashi Kato ◽  
Yuichiro Kogure ◽  
Mutsuro Kameyama ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Protein Complex ◽  
Metaphase Plate ◽  
Nucleolar Protein ◽  
Aurora B ◽  
Mitotic Progression ◽  
Mitotic Chromosomes ◽  
Nucleolar Proteins ◽  
Chromatid Cohesion ◽  
Wd Repeat

Abstract The nucleolus is a membrane-less nuclear structure that disassembles when cells undergo mitosis. During mitosis, nucleolar factors are thus released from the nucleolus and dynamically change their subcellular localization; however, their functions remain largely uncharacterised. Here, we found that a nucleolar factor called nucleolar protein 11 (NOL11) forms a protein complex with two tryptophan-aspartic acid (WD) repeat proteins named WD-repeat protein 43 (WDR43) and Cirhin in mitotic cells. This complex, referred to here as the NWC (NOL11-WDR43-Cirhin) complex, exists in nucleoli during interphase and translocates to the periphery of mitotic chromosomes, i.e., perichromosomal regions. During mitotic progression, both the congression of chromosomes to the metaphase plate and sister chromatid cohesion are impaired in the absence of the NWC complex, as it is required for the centromeric enrichment of Aurora B and the associating phosphorylation of histone H3 at threonine 3. These results reveal the characteristics of a novel protein complex consisting of nucleolar proteins, which is required for regulating kinetochores and centromeres to ensure faithful chromosome segregation.

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