scholarly journals Counteraction between Astrin-PP1 and Cyclin-B-CDK1 pathways protects chromosome-microtubule attachments independent of biorientation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xinhong Song ◽  
Duccio Conti ◽  
Roshan L. Shrestha ◽  
Dominique Braun ◽  
Viji M. Draviam
Keyword(s):  
Chromosomal Instability ◽  
Rnai Screen ◽  
Cyclin B ◽  
Macromolecular Structure ◽  
Aurora B ◽  
Unique Role ◽  
Chromosome Missegregation ◽  
Spindle Poles ◽  
Microtubule Attachment

AbstractDefects in chromosome-microtubule attachment can cause chromosomal instability (CIN), frequently associated with infertility and aggressive cancers. Chromosome-microtubule attachment is mediated by a large macromolecular structure, the kinetochore. Sister kinetochores of each chromosome are pulled by microtubules from opposing spindle-poles, a state called biorientation which prevents chromosome missegregation. Kinetochore-microtubule attachments that lack the opposing-pull are detached by Aurora-B/Ipl1. It is unclear how mono-oriented attachments that precede biorientation are spared despite the lack of opposing-pull. Using an RNAi-screen, we uncover a unique role for the Astrin-SKAP complex in protecting mono-oriented attachments. We provide evidence of domains in the microtubule-end associated protein that sense changes specific to end-on kinetochore-microtubule attachments and assemble an outer-kinetochore crescent to stabilise attachments. We find that Astrin-PP1 and Cyclin-B-CDK1 pathways counteract each other to preserve mono-oriented attachments. Thus, CIN prevention pathways are not only surveying attachment defects but also actively recognising and stabilising mature attachments independent of biorientation.

scholarly journals Cells protect chromosome-microtubule attachments, independent of biorientation, using an Astrin-PP1 and CyclinB-CDK1 feedback loop

2020 ◽  
Author(s):  
Duccio Conti ◽  
Xinhong Song ◽  
Roshan L. Shrestha ◽  
Dominique Braun ◽  
Viji M Draviam
Keyword(s):  
Chromosomal Instability ◽  
Feedback Loop ◽  
Cyclin B ◽  
Macromolecular Structure ◽  
Aurora B ◽  
Unique Role ◽  
Spindle Poles ◽  
Microtubule Attachment ◽  
Segregation Of Chromosomes

Defects in chromosome-microtubule attachment can cause chromosomal instability, associated with infertility and aggressive cancers. Chromosome-microtubule attachment is mediated by a large macromolecular structure, the kinetochore. Kinetochore pairs are bioriented and pulled by microtubules from opposing spindle poles to ensure the equal segregation of chromosomes. Kinetochore-microtubule attachments lacking opposing-pull are detached by Aurora-B/Ipl1; yet, how mono-oriented attachments that are a prerequisite for biorientation, but lacking opposing-pull are spared is unclear. Using an RNAi-mediated screen, we uncover a unique role for the Astrin-SKAP complex in protecting mono-oriented attachments. We provide the first evidence for how a microtubule-end associated protein senses outer-kinetochore changes specific to end-on attachments and assembles into an outer kinetochore crescent to stabilise mature attachments. We find that Astrin-PP1 and Cyclin-B-CDK1 activities counteract each other to preserve mono-oriented attachments. Thus, cells are not only surveying chromosome-microtubule attachment errors, but they are also actively sensing and stabilising mature attachments independent of biorientation.

scholarly journals Aurora B kinase activity is regulated by SET/TAF1 on Sgo2 at the inner centromere

2019 ◽  
Vol 218 (10) ◽  
pp. 3223-3236 ◽  
Author(s):  
Yuichiro Asai ◽  
Koh Fukuchi ◽  
Yuji Tanno ◽  
Saki Koitabashi-Kiyozuka ◽  
Tatsuyuki Kiyozuka ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Chromosomal Instability ◽  
Kinase Activity ◽  
Fine Tuning ◽  
Aurora B ◽  
The Novel ◽  
Aurora B Kinase ◽  
Microtubule Attachment ◽  
Molecular Events

The accurate regulation of phosphorylation at the kinetochore is essential for establishing chromosome bi-orientation. Phosphorylation of kinetochore proteins by the Aurora B kinase destabilizes improper kinetochore–microtubule attachments, whereas the phosphatase PP2A has a counteracting role. Imbalanced phosphoregulation leads to error-prone chromosome segregation and aneuploidy, a hallmark of cancer cells. However, little is known about the molecular events that control the balance of phosphorylation at the kinetochore. Here, we show that localization of SET/TAF1, an oncogene product, to centromeres maintains Aurora B kinase activity by inhibiting PP2A, thereby correcting erroneous kinetochore–microtubule attachment. SET localizes at the inner centromere by interacting directly with shugoshin 2, with SET levels declining at increased distances between kinetochore pairs, leading to establishment of chromosome bi-orientation. Moreover, SET overexpression induces chromosomal instability by disrupting kinetochore–microtubule attachment. Thus, our findings reveal the novel role of SET in fine-tuning the phosphorylation level at the kinetochore by balancing the activities of Aurora B and PP2A.

scholarly journals Aurora B switches relative strength between kinetochore–microtubule attachment modes to promote error correction

2018 ◽  
Author(s):  
Harinath Doodhi ◽  
Taciana Kasciukovic ◽  
Lesley Clayton ◽  
Tomoyuki U. Tanaka
Keyword(s):  
Error Correction ◽  
Chromosome Segregation ◽  
Relative Strength ◽  
Lateral Side ◽  
Aurora B ◽  
Spindle Poles ◽  
Microtubule Attachment ◽  
Attachment Strength ◽  
Dam1 Complex

AbstractFor proper chromosome segregation, sister kinetochores must interact with microtubules from opposite spindle poles; this is called bi-orientation. To establish bi-orientation prior to chromosome segregation, any aberrant kinetochore–microtubule interaction must be resolved (error correction) by Aurora B kinase that phosphorylates outer kinetochore components. Aurora B differentially regulates kinetochore attachment to the microtubule plus end and its lateral side (end-on and lateral attachment, respectively). However, it is still not fully understood how kinetochore–microtubule interactions are exchanged during error correction. Here we reconstituted the kinetochore–microtubule interface of budding yeast in vitro by attaching the Ndc80 complexes (Ndc80C) to nanobeads. These Ndc80C–nanobeads recapitulated in vitro the lateral and end-on attachments of authentic kinetochores, on dynamic microtubules loaded with the Dam1 complex. This in vitro assay enabled the direct comparison of lateral and end-on attachment strength and showed that Dam1 phosphorylation by Aurora B makes the end-on attachment weaker than the lateral attachment. We suggest that the Dam1 phosphorylation weakens interaction with the Ndc80 complex, disrupts the end-on attachment and promotes the exchange to a new lateral attachment, leading to error correction. Our study reveals a fundamental mechanism of error correction for establishment of bi-orientation.

scholarly journals The wages of CIN

2008 ◽  
Vol 180 (4) ◽  
pp. 661-663 ◽  
Author(s):  
Karen W. Yuen ◽  
Arshad Desai
Keyword(s):  
Cancer Cells ◽  
Solid Tumors ◽  
Chromosomal Instability ◽  
Chromosome Instability ◽  
Spindle Checkpoint ◽  
Human Cells ◽  
Normal Cells ◽  
Chromosome Missegregation ◽  
Cell Biol ◽  
The Relationship

Aneuploidy and chromosome instability (CIN) are hallmarks of the majority of solid tumors, but the relationship between them is not well understood. In this issue, Thompson and Compton (Thompson, S.L., and D.A. Compton. 2008. Examining the link between chromosomal instability and aneuploidy in human cells. J. Cell. Biol. 180:665–672) investigate the mechanism of CIN in cancer cells and find that CIN arises primarily from defective kinetochore–spindle attachments that evade detection by the spindle checkpoint and persist into anaphase. They also explore the consequences of artificially elevating chromosome missegregation in otherwise karyotypically normal cells. Their finding that induced aneuploidy is rapidly selected against suggests that the persistence of aneuploid cells in tumors requires not only chromosome missegregation but also additional, as yet poorly defined events.

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 Centromere-localized Aurora B kinase is required for the fidelity of chromosome segregation

2019 ◽  
Vol 219 (2) ◽  
Author(s):  
Cai Liang ◽  
Zhenlei Zhang ◽  
Qinfu Chen ◽  
Haiyan Yan ◽  
Miao Zhang ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Essential Role ◽  
Spindle Assembly Checkpoint ◽  
Histone H3 ◽  
Spindle Assembly ◽  
Aurora B ◽  
Aurora B Kinase ◽  
Chromosome Missegregation ◽  
Proper Timing ◽  
Segregation Of Chromosomes

Aurora B kinase plays an essential role in chromosome bi-orientation, which is a prerequisite for equal segregation of chromosomes during mitosis. However, it remains largely unclear whether centromere-localized Aurora B is required for faithful chromosome segregation. Here we show that histone H3 Thr-3 phosphorylation (H3pT3) and H2A Thr-120 phosphorylation (H2ApT120) can independently recruit Aurora B. Disrupting H3pT3-mediated localization of Aurora B at the inner centromere impedes the decline in H2ApT120 during metaphase and causes H2ApT120-dependent accumulation of Aurora B at the kinetochore-proximal centromere. Consequently, silencing of the spindle assembly checkpoint (SAC) is delayed, whereas the fidelity of chromosome segregation is negligibly affected. Further eliminating an H2ApT120-dependent pool of Aurora B restores proper timing for SAC silencing but increases chromosome missegregation. Our data indicate that H2ApT120-mediated localization of Aurora B compensates for the loss of an H3pT3-dependent pool of Aurora B to correct improper kinetochore–microtubule attachments. This study provides important insights into how centromeric Aurora B regulates SAC and kinetochore attachment to microtubules to ensure error-free chromosome segregation.

scholarly journals The cGAS/STING/TBK1/IRF3 innate immunity pathway maintains chromosomal stability through regulation of p21 levels

2020 ◽  
Vol 52 (4) ◽  
pp. 643-657 ◽  
Author(s):  
Abdul Basit ◽  
Min-Guk Cho ◽  
Eui-Yun Kim ◽  
Dohyeong Kwon ◽  
Suk-Jo Kang ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Adverse Effects ◽  
Cancer Cells ◽  
Chromosomal Instability ◽  
Interferon Regulatory Factor ◽  
Mitotic Arrest ◽  
Regulatory Factor ◽  
Chromosome Missegregation ◽  
Sting Pathway ◽  
Innate Immunity Pathway

Abstract Chromosomal instability (CIN) in cancer cells has been reported to activate the cGAS–STING innate immunity pathway via micronuclei formation, thus affecting tumor immunity and tumor progression. However, adverse effects of the cGAS/STING pathway as they relate to CIN have not yet been investigated. We addressed this issue using knockdown and add-back approaches to analyze each component of the cGAS/STING/TBK1/IRF3 pathway, and we monitored the extent of CIN by measuring micronuclei formation after release from nocodazole-induced mitotic arrest. Interestingly, knockdown of cGAS (cyclic GMP-AMP synthase) along with induction of mitotic arrest in HeLa and U2OS cancer cells clearly resulted in increased micronuclei formation and chromosome missegregation. Knockdown of STING (stimulator of interferon genes), TBK1 (TANK-binding kinase-1), or IRF3 (interferon regulatory factor-3) also resulted in increased micronuclei formation. Moreover, transfection with cGAMP, the product of cGAS enzymatic activity, as well as add-back of cGAS WT (but not catalytic-dead mutant cGAS), or WT or constitutively active STING (but not an inactive STING mutant) rescued the micronuclei phenotype, demonstrating that all components of the cGAS/STING/TBK1/IRF3 pathway play a role in preventing CIN. Moreover, p21 levels were decreased in cGAS-, STING-, TBK1-, and IRF3-knockdown cells, which was accompanied by the precocious G2/M transition of cells and the enhanced micronuclei phenotype. Overexpression of p21 or inhibition of CDK1 in cGAS-depleted cells reduced micronuclei formation and abrogated the precocious G2/M transition, indicating that the decrease in p21 and the subsequent precocious G2/M transition is the main mechanism underlying the induction of CIN through disruption of cGAS/STING signaling.

scholarly journals The Opposing Functions of Protein Kinases and Phosphatases in Chromosome Bipolar Attachment

2019 ◽  
Vol 20 (24) ◽  
pp. 6182 ◽  
Author(s):  
Delaney Sherwin ◽  
Yanchang Wang
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Protein Phosphatase ◽  
Spindle Assembly Checkpoint ◽  
Model Organism ◽  
Eukaryotic Cells ◽  
Genome Integrity ◽  
Chromosome Missegregation ◽  
Spindle Poles ◽  
Mitosis And Meiosis

Accurate chromosome segregation during cell division is essential to maintain genome integrity in all eukaryotic cells, and chromosome missegregation leads to aneuploidy and therefore represents a hallmark of many cancers. Accurate segregation requires sister kinetochores to attach to microtubules emanating from opposite spindle poles, known as bipolar attachment or biorientation. Recent studies have uncovered several mechanisms critical to chromosome bipolar attachment. First, a mechanism exists to ensure that the conformation of sister centromeres is biased toward bipolar attachment. Second, the phosphorylation of some kinetochore proteins destabilizes kinetochore attachment to facilitate error correction, but a protein phosphatase reverses this phosphorylation. Moreover, the activity of the spindle assembly checkpoint is regulated by kinases and phosphatases at the kinetochore, and this checkpoint prevents anaphase entry in response to faulty kinetochore attachment. The fine-tuned kinase/phosphatase balance at kinetochores is crucial for faithful chromosome segregation during both mitosis and meiosis. Here, we discuss the function and regulation of protein phosphatases in the establishment of chromosome bipolar attachment with a focus on the model organism budding yeast.

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