scholarly journals Condensins under the microscope

2018 ◽  
Vol 217 (7) ◽  
pp. 2229-2231 ◽  
Author(s):  
Kazuhiro Maeshima ◽  
Kayo Hibino ◽  
Damien F. Hudson
Keyword(s):  
Quantitative Data ◽  
Mitotic Chromosome ◽  
State Of The Art ◽  
Imaging Techniques ◽  
Mechanistic Model ◽  
Chromosome Condensation ◽  
Mitotic Chromosomes ◽  
Cell Biol ◽  
Key Players ◽  
Mitotic Chromosome Condensation

Condensins are key players in mitotic chromosome condensation. Using an elegant combination of state-of-the-art imaging techniques, Walther et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201801048) counted the number of Condensins, examined their behaviors on human mitotic chromosomes, and integrated the quantitative data to propose a new mechanistic model for chromosome condensation.

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 A Human Condensin Complex Containing hCAP-C–hCAP-E and CNAP1, a Homolog of Xenopus XCAP-D2, Colocalizes with Phosphorylated Histone H3 during the Early Stage of Mitotic Chromosome Condensation

2000 ◽  
Vol 20 (18) ◽  
pp. 6996-7006 ◽  
Author(s):  
John A. Schmiesing ◽  
Heather C. Gregson ◽  
Sharleen Zhou ◽  
Kyoko Yokomori
Keyword(s):  
Mammalian Cells ◽  
Structural Changes ◽  
Mitotic Chromosome ◽  
Early Stage ◽  
Histone H3 ◽  
Chromosome Condensation ◽  
Early Prophase ◽  
Mitotic Chromosomes ◽  
Condensin Complex ◽  
Mitotic Chromosome Condensation

ABSTRACT Structural maintenance of chromosomes (SMC) family proteins play critical roles in structural changes of chromosomes. Previously, we identified two human SMC family proteins, hCAP-C and hCAP-E, which form a heterodimeric complex (hCAP-C–hCAP-E) in the cell. Based on the sequence conservation and mitotic chromosome localization, hCAP-C–hCAP-E was determined to be the human ortholog of theXenopus SMC complex, XCAP-C–XCAP-E. XCAP-C–XCAP-E is a component of the multiprotein complex termed condensin, required for mitotic chromosome condensation in vitro. However, presence of such a complex has not been demonstrated in mammalian cells. Coimmunoprecipitation of the endogenous hCAP-C–hCAP-E complex from HeLa extracts identified a 155-kDa protein interacting with hCAP-C–hCAP-E, termed condensation-related SMC-associated protein 1 (CNAP1). CNAP1 associates with mitotic chromosomes and is homologous toXenopus condensin component XCAP-D2, indicating the presence of a condensin complex in human cells. Chromosome association of human condensin is mitosis specific, and the majority of condensin dissociates from chromosomes and is sequestered in the cytoplasm throughout interphase. However, a subpopulation of the complex was found to remain on chromosomes as foci in the interphase nucleus. During late G2/early prophase, the larger nuclear condensin foci colocalize with phosphorylated histone H3 clusters on partially condensed regions of chromosomes. These results suggest that mitosis-specific function of human condensin may be regulated by cell cycle-specific subcellular localization of the complex, and the nuclear condensin that associates with interphase chromosomes is involved in the reinitiation of mitotic chromosome condensation in conjunction with phosphorylation of histone H3.

scholarly journals Axial contraction and short-range compaction of chromatin synergistically promote mitotic chromosome condensation

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Tom Kruitwagen ◽  
Annina Denoth-Lippuner ◽  
Bryan J Wilkins ◽  
Heinz Neumann ◽  
Yves Barral
Keyword(s):  
Short Range ◽  
Mitotic Chromosome ◽  
Chromosome Condensation ◽  
Yeast Cells ◽  
Histone H4 ◽  
Mitotic Chromosomes ◽  
Chromatin Compaction ◽  
Early Anaphase ◽  
Local Compaction ◽  
Mitotic Chromosome Condensation

The segregation of eukaryotic chromosomes during mitosis requires their extensive folding into units of manageable size for the mitotic spindle. Here, we report on how phosphorylation at serine 10 of histone H3 (H3 S10) contributes to this process. Using a fluorescence-based assay to study local compaction of the chromatin fiber in living yeast cells, we show that chromosome condensation entails two temporally and mechanistically distinct processes. Initially, nucleosome-nucleosome interaction triggered by H3 S10 phosphorylation and deacetylation of histone H4 promote short-range compaction of chromatin during early anaphase. Independently, condensin mediates the axial contraction of chromosome arms, a process peaking later in anaphase. Whereas defects in chromatin compaction have no observable effect on axial contraction and condensin inactivation does not affect short-range chromatin compaction, inactivation of both pathways causes synergistic defects in chromosome segregation and cell viability. Furthermore, both pathways rely at least partially on the deacetylase Hst2, suggesting that this protein helps coordinating chromatin compaction and axial contraction to properly shape mitotic chromosomes.

scholarly journals Integration of biological data by kernels on graph nodes allows prediction of new genes involved in mitotic chromosome condensation

2014 ◽  
Vol 25 (16) ◽  
pp. 2522-2536 ◽  
Author(s):  
Jean-Karim Hériché ◽  
Jon G. Lees ◽  
Ian Morilla ◽  
Thomas Walter ◽  
Boryana Petrova ◽  
...  
Keyword(s):  
Experimental Validation ◽  
Mitotic Chromosome ◽  
Chromosome Condensation ◽  
Biological Data ◽  
Cell Functions ◽  
Functional Relationships ◽  
New Genes ◽  
Public Data ◽  
Mitotic Chromosome Condensation ◽  
Graph Nodes

The advent of genome-wide RNA interference (RNAi)–based screens puts us in the position to identify genes for all functions human cells carry out. However, for many functions, assay complexity and cost make genome-scale knockdown experiments impossible. Methods to predict genes required for cell functions are therefore needed to focus RNAi screens from the whole genome on the most likely candidates. Although different bioinformatics tools for gene function prediction exist, they lack experimental validation and are therefore rarely used by experimentalists. To address this, we developed an effective computational gene selection strategy that represents public data about genes as graphs and then analyzes these graphs using kernels on graph nodes to predict functional relationships. To demonstrate its performance, we predicted human genes required for a poorly understood cellular function—mitotic chromosome condensation—and experimentally validated the top 100 candidates with a focused RNAi screen by automated microscopy. Quantitative analysis of the images demonstrated that the candidates were indeed strongly enriched in condensation genes, including the discovery of several new factors. By combining bioinformatics prediction with experimental validation, our study shows that kernels on graph nodes are powerful tools to integrate public biological data and predict genes involved in cellular functions of interest.

scholarly journals Centromeric Localization of Dispersed Pol III Genes in Fission Yeast

2010 ◽  
Vol 21 (2) ◽  
pp. 254-265 ◽  
Author(s):  
Osamu Iwasaki ◽  
Atsunari Tanaka ◽  
Hideki Tanizawa ◽  
Shiv I.S. Grewal ◽  
Ken-ichi Noma
Keyword(s):  
Genome Organization ◽  
Gene Locus ◽  
Mitotic Chromosome ◽  
Three Dimensional ◽  
Rrna Genes ◽  
Mitotic Chromosomes ◽  
Gene Encoding ◽  
5S Rrna Genes ◽  
Pol Iii ◽  
Mitotic Chromosome Condensation

The eukaryotic genome is a complex three-dimensional entity residing in the nucleus. We present evidence that Pol III–transcribed genes such as tRNA and 5S rRNA genes can localize to centromeres and contribute to a global genome organization. Furthermore, we find that ectopic insertion of Pol III genes into a non-Pol III gene locus results in the centromeric localization of the locus. We show that the centromeric localization of Pol III genes is mediated by condensin, which interacts with the Pol III transcription machinery, and that transcription levels of the Pol III genes are negatively correlated with the centromeric localization of Pol III genes. This centromeric localization of Pol III genes initially observed in interphase becomes prominent during mitosis, when chromosomes are condensed. Remarkably, defective mitotic chromosome condensation by a condensin mutation, cut3-477, which reduces the centromeric localization of Pol III genes, is suppressed by a mutation in the sfc3 gene encoding the Pol III transcription factor TFIIIC subunit, sfc3-1. The sfc3-1 mutation promotes the centromeric localization of Pol III genes. Our study suggests there are functional links between the process of the centromeric localization of dispersed Pol III genes, their transcription, and the assembly of condensed mitotic chromosomes.

scholarly journals Condensin targets and reduces unwound DNA structures associated with transcription in mitotic chromosome condensation

2015 ◽  
Vol 6 (1) ◽  
Author(s):  
Takashi Sutani ◽  
Toyonori Sakata ◽  
Ryuichiro Nakato ◽  
Koji Masuda ◽  
Mai Ishibashi ◽  
...  
Keyword(s):  
Mitotic Chromosome ◽  
Chromosome Condensation ◽  
Dna Structures ◽  
Mitotic Chromosome Condensation

scholarly journals Mitotic chromosome condensation requires phosphorylation of the centromeric protein KNL-2 in C. elegans

2021 ◽  
Author(s):  
Joanna M Wenda ◽  
Reinier F Prosée ◽  
Caroline Gabus ◽  
Florian A Steiner
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Chromosome Condensation ◽  
Embryonic Lethality ◽  
Phosphorylation Sites ◽  
C Elegans ◽  
Microtubule Attachment ◽  
Centromeric Protein ◽  
Mitotic Chromosome Condensation

Centromeres are chromosomal regions that serve as sites for kinetochore formation and microtubule attachment, processes that are essential for chromosome segregation during mitosis. Centromeres are almost universally defined by the histone variant CENP-A. In the holocentric nematode C. elegans, CENP-A deposition depends on the loading factor KNL-2. Depletion of either CENP-A or KNL-2 results in defects in centromere maintenance, chromosome condensation and kinetochore formation, leading to chromosome segregation failure. Here, we show that KNL-2 is phosphorylated by CDK-1, and that mutation of three C-terminal phosphorylation sites causes chromosome segregation defects and an increase in embryonic lethality. In strains expressing phosphodeficient KNL-2, CENP-A and kinetochore proteins are properly localised, indicating that the role of KNL-2 in centromere maintenance is not affected. Instead, the mutant embryos exhibit reduced mitotic levels of condensin II on chromosomes and significant chromosome condensation impairment. Our findings separate the functions of KNL-2 in CENP-A loading and chromosome condensation and demonstrate that KNL-2 phosphorylation regulates the cooperation between centromeric regions and the condensation machinery in C. elegans.

scholarly journals Novel insights into mitotic chromosome condensation

F1000Research ◽  
2016 ◽  
Vol 5 ◽  
pp. 1807 ◽  
Author(s):  
Ewa Piskadlo ◽  
Raquel A. Oliveira
Keyword(s):  
Cell Division ◽  
Topoisomerase Ii ◽  
Mitotic Chromosome ◽  
Nuclear Division ◽  
Chromosome Condensation ◽  
Cell Division Cycle ◽  
Chromosome Organization ◽  
Condensation Process ◽  
Successful Completion ◽  
Mitotic Chromosome Condensation

The fidelity of mitosis is essential for life, and successful completion of this process relies on drastic changes in chromosome organization at the onset of nuclear division. The mechanisms that govern chromosome compaction at every cell division cycle are still far from full comprehension, yet recent studies provide novel insights into this problem, challenging classical views on mitotic chromosome assembly. Here, we briefly introduce various models for chromosome assembly and known factors involved in the condensation process (e.g. condensin complexes and topoisomerase II). We will then focus on a few selected studies that have recently brought novel insights into the mysterious way chromosomes are condensed during nuclear division.

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