scholarly journals Cell division requires RNA eviction from condensing chromosomes

2020 ◽  
Vol 219 (11) ◽  
Author(s):  
Judith A. Sharp ◽  
Carlos Perea-Resa ◽  
Wei Wang ◽  
Michael D. Blower
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Aurora B ◽  
Nucleic Acid Binding ◽  
Mitotic Chromosomes ◽  
Nuclear Envelope Breakdown ◽  
Binding Domains ◽  
Chromosome Alignment ◽  
Rna Complexes

During mitosis, the genome is transformed from a decondensed, transcriptionally active state to a highly condensed, transcriptionally inactive state. Mitotic chromosome reorganization is marked by the general attenuation of transcription on chromosome arms, yet how the cell regulates nuclear and chromatin-associated RNAs after chromosome condensation and nuclear envelope breakdown is unknown. SAF-A/hnRNPU is an abundant nuclear protein with RNA-to-DNA tethering activity, coordinated by two spatially distinct nucleic acid–binding domains. Here we show that RNA is evicted from prophase chromosomes through Aurora-B–dependent phosphorylation of the SAF-A DNA-binding domain; failure to execute this pathway leads to accumulation of SAF-A–RNA complexes on mitotic chromosomes, defects in metaphase chromosome alignment, and elevated rates of chromosome missegregation in anaphase. This work reveals a role for Aurora-B in removing chromatin-associated RNAs during prophase and demonstrates that Aurora-B–dependent relocalization of SAF-A during cell division contributes to the fidelity of chromosome segregation.

scholarly journals Prophase removal of chromosome-associated RNAs facilitates anaphase chromosome segregation

2019 ◽  
Author(s):  
Judith A. Sharp ◽  
Wei Wang ◽  
Michael D. Blower
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Nuclear Protein ◽  
Aurora B ◽  
Dna Binding Domain ◽  
Nucleic Acid Binding ◽  
Mitotic Chromosomes ◽  
Nuclear Envelope Breakdown ◽  
Binding Domains

AbstractDuring mitosis, the genome is transformed from a decondensed, transcriptionally active state to a highly condensed, transcriptionally inactive state. Mitotic chromosome reorganization is marked by the general attenuation of transcription on chromosome arms, yet how the cell regulates nuclear and chromatin-associated RNAs after chromosome condensation and nuclear envelope breakdown is unknown. SAF-A/hnRNPU is an abundant nuclear protein with RNA-to-DNA tethering activity, coordinated by two spatially distinct nucleic acid binding domains. Here we show that RNA is evicted from prophase chromosomes through Aurora-B-dependent phosphorylation of the SAF-A DNA-binding domain; failure to execute this pathway leads to accumulation of SAF-A:RNA complexes on mitotic chromosomes and elevated rates of anaphase segregation defects. This work reveals a role for Aurora-B in removing chromatin-associated RNAs during prophase, and demonstrates that Aurora-B dependent relocalization of SAF-A during cell division contributes to the fidelity of chromosome segregation.

scholarly journals DUSP7 Regulates the Activity of ERK2 to Promote Proper Chromosome Alignment During Cell Division

2020 ◽  
Author(s):  
Xiao Guo ◽  
Yenni A. Garcia ◽  
Ivan Ramirez ◽  
Erick F. Velasquez ◽  
Lucy W. Gao ◽  
...  
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Human Cell ◽  
Mitotic Chromosome ◽  
Marked Decrease ◽  
Metaphase Plate ◽  
Chromosome Congression ◽  
Dual Specificity ◽  
Chromosome Alignment ◽  
Chemical Inhibition

SUMMARYHuman cell division is a highly regulated process that relies on the accurate capture and movement of chromosomes to the metaphase plate. Errors in the fidelity of chromosome congression and alignment can lead to improper chromosome segregation, which is correlated with aneuploidy and tumorigenesis. Here we show that the dual specificity phosphatase DUSP7 is important for regulating chromosome alignment. DUSP7 bound to ERK2 and regulated the abundance of active phospho-ERK2 through its phosphatase activity. Overexpression of DUSP7, but not catalytic dead mutants, led to a marked decrease in phopho-ERK2 and mitotic chromosome misalignment, while knockdown of DUSP7 also led to defective chromosome congression that resulted in a prolonged mitosis. Consistently, chemical inhibition of the MEK kinase that phosphorylates ERK2 or ERK2 itself led to chromosome alignment defects. Our results support a model where MEK phosphorylation and DUSP7 dephosphorylation regulate the levels of active phospho-ERK2 to promote proper cell division.

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.

scholarly journals Differential requirement for Bub1 and Bub3 in regulation of meiotic versus mitotic chromosome segregation

2020 ◽  
Vol 219 (4) ◽  
Author(s):  
Gisela Cairo ◽  
Anne M. MacKenzie ◽  
Soni Lacefield
Keyword(s):  
Chromosome Segregation ◽  
Protein Phosphatase ◽  
Mitotic Chromosome ◽  
Budding Yeast ◽  
Meiotic Chromosome ◽  
Protein Phosphatase 1 ◽  
Aurora B ◽  
Chromosome Missegregation ◽  
Anaphase Onset ◽  
Spindle Microtubules

Accurate chromosome segregation depends on the proper attachment of kinetochores to spindle microtubules before anaphase onset. The Ipl1/Aurora B kinase corrects improper attachments by phosphorylating kinetochore components and so releasing aberrant kinetochore–microtubule interactions. The localization of Ipl1 to kinetochores in budding yeast depends upon multiple pathways, including the Bub1–Bub3 pathway. We show here that in meiosis, Bub3 is crucial for correction of attachment errors. Depletion of Bub3 results in reduced levels of kinetochore-localized Ipl1 and concomitant massive chromosome missegregation caused by incorrect chromosome–spindle attachments. Depletion of Bub3 also results in shorter metaphase I and metaphase II due to premature localization of protein phosphatase 1 (PP1) to kinetochores, which antagonizes Ipl1-mediated phosphorylation. We propose a new role for the Bub1–Bub3 pathway in maintaining the balance between kinetochore localization of Ipl1 and PP1, a balance that is essential for accurate meiotic chromosome segregation and timely anaphase onset.

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 Bub1, Sgo1, and Mps1 mediate a distinct pathway for chromosome biorientation in budding yeast

2011 ◽  
Vol 22 (9) ◽  
pp. 1473-1485 ◽  
Author(s):  
Zuzana Storchová ◽  
Justin S. Becker ◽  
Nicolas Talarek ◽  
Sandra Kögelsberger ◽  
David Pellman
Keyword(s):  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Budding Yeast ◽  
Spindle Pole ◽  
Growth Defect ◽  
Aurora B ◽  
Mitotic Kinase ◽  
Sister Chromatids ◽  
Chromosome Alignment ◽  
Chromosomal Passenger

The conserved mitotic kinase Bub1 performs multiple functions that are only partially characterized. Besides its role in the spindle assembly checkpoint and chromosome alignment, Bub1 is crucial for the kinetochore recruitment of multiple proteins, among them Sgo1. Both Bub1 and Sgo1 are dispensable for growth of haploid and diploid budding yeast, but they become essential in cells with higher ploidy. We find that overexpression of SGO1 partially corrects the chromosome segregation defect of bub1Δ haploid cells and restores viability to bub1Δ tetraploid cells. Using an unbiased high-copy suppressor screen, we identified two members of the chromosomal passenger complex (CPC), BIR1 (survivin) and SLI15 (INCENP, inner centromere protein), as suppressors of the growth defect of both bub1Δ and sgo1Δ tetraploids, suggesting that these mutants die due to defects in chromosome biorientation. Overexpression of BIR1 or SLI15 also complements the benomyl sensitivity of haploid bub1Δ and sgo1Δ cells. Mutants lacking SGO1 fail to biorient sister chromatids attached to the same spindle pole (syntelic attachment) after nocodazole treatment. Moreover, the sgo1Δ cells accumulate syntelic attachments in unperturbed mitoses, a defect that is partially corrected by BIR1 or SLI15 overexpression. We show that in budding yeast neither Bub1 nor Sgo1 is required for CPC localization or affects Aurora B activity. Instead we identify Sgo1 as a possible partner of Mps1, a mitotic kinase suggested to have an Aurora B–independent function in establishment of biorientation. We found that Sgo1 overexpression rescues defects caused by metaphase inactivation of Mps1 and that Mps1 is required for Sgo1 localization to the kinetochore. We propose that Bub1, Sgo1, and Mps1 facilitate chromosome biorientation independently of the Aurora B–mediated pathway at the budding yeast kinetochore and that both pathways are required for the efficient turnover of syntelic attachments.

scholarly journals Aurora A kinase phosphorylates Hec1 to regulate metaphase kinetochore–microtubule dynamics

2017 ◽  
Vol 217 (1) ◽  
pp. 163-177 ◽  
Author(s):  
Keith F. DeLuca ◽  
Amanda Meppelink ◽  
Amanda J. Broad ◽  
Jeanne E. Mick ◽  
Olve B. Peersen ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Microtubule Dynamics ◽  
Aurora B ◽  
Aurora A Kinase ◽  
Aurora A ◽  
Tail Domain ◽  
Mitotic Chromosomes ◽  
Metaphase Chromosomes ◽  
Mitotic Kinases ◽  
Microtubule Attachment

Precise regulation of kinetochore–microtubule attachments is essential for successful chromosome segregation. Central to this regulation is Aurora B kinase, which phosphorylates kinetochore substrates to promote microtubule turnover. A critical target of Aurora B is the N-terminal “tail” domain of Hec1, which is a component of the NDC80 complex, a force-transducing link between kinetochores and microtubules. Although Aurora B is regarded as the “master regulator” of kinetochore–microtubule attachment, other mitotic kinases likely contribute to Hec1 phosphorylation. In this study, we demonstrate that Aurora A kinase regulates kinetochore–microtubule dynamics of metaphase chromosomes, and we identify Hec1 S69, a previously uncharacterized phosphorylation target site in the Hec1 tail, as a critical Aurora A substrate for this regulation. Additionally, we demonstrate that Aurora A kinase associates with inner centromere protein (INCENP) during mitosis and that INCENP is competent to drive accumulation of the kinase to the centromere region of mitotic chromosomes. These findings reveal that both Aurora A and B contribute to kinetochore–microtubule attachment dynamics, and they uncover an unexpected role for Aurora A in late mitosis.

scholarly journals Whole-proteome genetic analysis of dependencies in assembly of a vertebrate kinetochore

2015 ◽  
Vol 211 (6) ◽  
pp. 1141-1156 ◽  
Author(s):  
Itaru Samejima ◽  
Christos Spanos ◽  
Flavia de Lima Alves ◽  
Tetsuya Hori ◽  
Marinela Perpelescu ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Protein Complexes ◽  
Interacting Proteins ◽  
Quantitative Mass Spectrometry ◽  
Mitotic Chromosomes ◽  
Microtubule Binding ◽  
Checkpoint Signaling ◽  
Ndc80 Complex ◽  
Stable Association

Kinetochores orchestrate mitotic chromosome segregation. Here, we use quantitative mass spectrometry of mitotic chromosomes isolated from a comprehensive set of chicken DT40 mutants to examine the dependencies of 93 confirmed and putative kinetochore proteins for stable association with chromosomes. Clustering and network analysis reveal both known and unexpected aspects of coordinated behavior for members of kinetochore protein complexes. Surprisingly, CENP-T depends on CENP-N for chromosome localization. The Ndc80 complex exhibits robust correlations with all other complexes in a “core” kinetochore network. Ndc80 associated with CENP-T interacts with a cohort of Rod, zw10, and zwilch (RZZ)–interacting proteins that includes Spindly, Mad1, and CENP-E. This complex may coordinate microtubule binding with checkpoint signaling. Ndc80 associated with CENP-C forms the KMN (Knl1, Mis12, Ndc80) network and may be the microtubule-binding “workhorse” of the kinetochore. Our data also suggest that CENP-O and CENP-R may regulate the size of the inner kinetochore without influencing the assembly of the outer kinetochore.

scholarly journals Contribution of hCAP-D2, a Non-SMC Subunit of Condensin I, to Chromosome and Chromosomal Protein Dynamics during Mitosis

2005 ◽  
Vol 25 (2) ◽  
pp. 740-750 ◽  
Author(s):  
Erwan Watrin ◽  
Vincent Legagneux
Keyword(s):  
Rna Interference ◽  
Mitotic Spindle ◽  
Topoisomerase Ii ◽  
Mitotic Chromosome ◽  
Chromosomal Protein ◽  
Structural Components ◽  
Mitotic Chromosomes ◽  
Sister Chromatids ◽  
Chromosome Alignment ◽  
Structural Maintenance Of Chromosomes

ABSTRACT Condensins are heteropentameric complexes that were first identified as structural components of mitotic chromosomes. They are composed of two SMC (structural maintenance of chromosomes) and three non-SMC subunits. Condensins play a role in the resolution and segregation of sister chromatids during mitosis, as well as in some aspects of mitotic chromosome assembly. Two distinct condensin complexes, condensin I and condensin II, which differ only in their non-SMC subunits, exist. Here, we used an RNA interference approach to deplete hCAP-D2, a non-SMC subunit of condensin I, in HeLa cells. We found that the association of hCAP-H, another non-SMC subunit of condensin I, with mitotic chromosomes depends on the presence of hCAP-D2. Moreover, chromatid axes, as defined by topoisomerase II and hCAP-E localization, are disorganized in the absence of hCAP-D2, and the resolution and segregation of sister chromatids are impaired. In addition, hCAP-D2 depletion affects chromosome alignment in metaphase and delays entry into anaphase. This suggests that condensin I is involved in the correct attachment between chromosome kinetochores and microtubules of the mitotic spindle. These results are discussed relative to the effects of depleting both condensin complexes.

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