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Spindle checkpoint

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https://www.readbyqxmd.com/read/28634351/a-dynamical-model-for-activating-and-silencing-the-mitotic-checkpoint
#1
Richard Henze, Peter Dittrich, Bashar Ibrahim
The spindle assembly checkpoint (SAC) is an evolutionarily conserved mechanism, exclusively sensitive to the states of kinetochores attached to microtubules. During metaphase, the anaphase-promoting complex/cyclosome (APC/C) is inhibited by the SAC but it rapidly switches to its active form following proper attachment of the final spindle. It had been thought that APC/C activity is an all-or-nothing response, but recent findings have demonstrated that it switches steadily. In this study, we develop a detailed mathematical model that considers all 92 human kinetochores and all major proteins involved in SAC activation and silencing...
June 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28607478/precocious-centriole-disengagement-and-centrosome-fragmentation-induced-by-mitotic-delay
#2
Menuka Karki, Neda Keyhaninejad, Charles B Shuster
The spindle assembly checkpoint (SAC) delays mitotic progression until all sister chromatid pairs achieve bi-orientation, and while the SAC can maintain mitotic arrest for extended periods, moderate delays in mitotic progression have significant effects on the resulting daughter cells. Here we show that when retinal-pigmented epithelial (RPE1) cells experience mitotic delay, there is a time-dependent increase in centrosome fragmentation and centriole disengagement. While most cells with disengaged centrioles maintain spindle bipolarity, clustering of disengaged centrioles requires the kinesin-14, HSET...
June 13, 2017: Nature Communications
https://www.readbyqxmd.com/read/28604727/bub1-positions-mad1-close-to-knl1-melt-repeats-to-promote-checkpoint-signalling
#3
Gang Zhang, Thomas Kruse, Blanca López-Méndez, Kathrine Beck Sylvestersen, Dimitriya H Garvanska, Simone Schopper, Michael Lund Nielsen, Jakob Nilsson
Proper segregation of chromosomes depends on a functional spindle assembly checkpoint (SAC) and requires kinetochore localization of the Bub1 and Mad1/Mad2 checkpoint proteins. Several aspects of Mad1/Mad2 kinetochore recruitment in human cells are unclear and in particular the underlying direct interactions. Here we show that conserved domain 1 (CD1) in human Bub1 binds directly to Mad1 and a phosphorylation site exists in CD1 that stimulates Mad1 binding and SAC signalling. Importantly, fusion of minimal kinetochore-targeting Bub1 fragments to Mad1 bypasses the need for CD1, revealing that the main function of Bub1 is to position Mad1 close to KNL1 MELT repeats...
June 12, 2017: Nature Communications
https://www.readbyqxmd.com/read/28603453/centromeric-non-coding-transcription-opening-the-black-box-of-chromosomal-instability
#4
REVIEW
Rodrigo Cáceres-Gutiérrez, Luis A Herrera
In eukaryotes, mitosis is tightly regulated to avoid the generation of numerical chromosome aberrations, or aneuploidies. The aneuploid phenotype is a consequence of chromosomal instability (CIN), i.e., an enhanced rate of chromosome segregation errors, which is frequently found in cancer cells and is associated with tumor aggressiveness and increased tumor cell survival potential. To avoid the generation of aneuploidies, cells rely on the spindle assembly checkpoint (SAC), a widely conserved mechanism that protects the genome against this type of error...
June 2017: Current Genomics
https://www.readbyqxmd.com/read/28600783/kinetochore-malfunction-in-human-pathologies
#5
Bas de Wolf, Geert J P L Kops
The cell cycle culminates in mitosis with the purpose of dividing the cell's DNA content equally over two daughter cells. Error-free segregation relies on correct connections between chromosomes and spindle microtubules. Kinetochores are complex multi-protein assemblies that mediate these connections and are the platforms for attachment-error-correction and spindle assembly checkpoint signaling. Proper kinetochore function is therefore key in preventing aneuploidization. Mutations in genes encoding kinetochore proteins are associated with several severe developmental disorders associated with microcephaly, and kinetochore defects contribute to chromosomal instability in certain cancers...
2017: Advances in Experimental Medicine and Biology
https://www.readbyqxmd.com/read/28590163/merotelic-kinetochore-attachment-in-oocyte-meiosis-ii-causes-sister-chromatids-segregation-errors-in-aged-mice
#6
Jin-Mei Cheng, Jian Li, Ji-Xin Tang, Xiao-Xia Hao, Zhi-Peng Wang, Tie-Cheng Sun, Xiu-Xia Wang, Yan Zhang, Su-Ren Chen, Yi-Xun Liu
Mammalian oocyte chromosomes undergo two meiotic divisions to generate haploid gametes. The frequency of chromosome segregation errors during meiosis I increase with age. However, little attention has been paid to the question of how aging affects sister chromatid segregation during oocyte meiosis II. More importantly, how aneuploid metaphase II (MII) oocytes from aged mice evade the spindle assembly checkpoint (SAC) mechanism to complete later meiosis II to form aneuploid embryos remains unknown. Here, we report that MII oocytes from naturally aged mice exhibited substantial errors in chromosome arrangement and configuration compared with young MII oocytes...
June 7, 2017: Cell Cycle
https://www.readbyqxmd.com/read/28582586/tension-sensors-reveal-how-the-kinetochore-shares-its-load
#7
REVIEW
Edward D Salmon, Kerry Bloom
At metaphase in mitotic cells, pulling forces at the kinetochore-microtubule interface create tension by stretching the centromeric chromatin between oppositely oriented sister kinetochores. This tension is important for stabilizing the end-on kinetochore microtubule attachment required for proper bi-orientation of sister chromosomes as well as for satisfaction of the Spindle Assembly Checkpoint and entry into anaphase. How force is coupled by proteins to kinetochore microtubules and resisted by centromere stretch is becoming better understood as many of the proteins involved have been identified...
June 5, 2017: BioEssays: News and Reviews in Molecular, Cellular and Developmental Biology
https://www.readbyqxmd.com/read/28567704/fission-yeast-ctf1-a-cleavage-and-polyadenylation-factor-subunit-is-required-for-the-maintenance-of-genomic-integrity
#8
Amit Sonkar, Sachin Gaurav, Shakil Ahmed
Accurate segregation of chromosome during mitosis requires the coordinated action of several cell cycle checkpoints that monitor replication of the genome and the attachment of sister chromatids to the mitotic spindle apparatus. Here we have characterized the fission yeast Ctf1, an ortholog of S. cerevisiae Rna15 in the maintenance of genomic integrity. The ctf1 is nonessential for the cell survival and its deletion strain exhibit cold sensitivity. The ctf1 deleted cells exhibit genetic interaction with spindle checkpoint protein Mad2 and Bub1...
May 31, 2017: Molecular Genetics and Genomics: MGG
https://www.readbyqxmd.com/read/28566455/correction-for-nakano-et-al-rad51-dependent-aberrant-chromosome-structures-at-telomeres-and-ribosomal-dna-activate-the-spindle-assembly-checkpoint
#9
Akemi Nakano, Kenta Masuda, Taisuke Hiromoto, Katsunori Takahashi, Yoshitake Matsumoto, Ahmed G K Habib, Ahmed G G Darwish, Masashi Yukawa, Eiko Tsuchiya, Masaru Ueno
No abstract text is available yet for this article.
June 15, 2017: Molecular and Cellular Biology
https://www.readbyqxmd.com/read/28562161/pp2a-b56%C3%AE-is-required-for-an-efficient-spindle-assembly-checkpoint
#10
Prajakta Varadkar, Fatima Abbasi, Kazuyo Takeda, Jade J Dyson, Brent McCright
The Spindle Assembly Checkpoint (SAC) is part of a complex feedback system designed to ensure that cells do not proceed through mitosis unless all chromosomal kinetochores have attached to spindle microtubules. The formation of the kinetochore complex and the implementation of the SAC are regulated by multiple kinases and phosphatases. BubR1 is a phosphoprotein that is part of the Cdc20 containing mitotic checkpoint complex that inhibits the APC/C so that Cyclin B1 and Securin are not degraded, thus preventing cells going into anaphase...
May 31, 2017: Cell Cycle
https://www.readbyqxmd.com/read/28561035/inner-centromere-localization-of-the-cpc-maintains-centromere-cohesion-and-allows-mitotic-checkpoint-silencing
#11
Rutger C C Hengeveld, Martijn J M Vromans, Mathijs Vleugel, Michael A Hadders, Susanne M A Lens
Faithful chromosome segregation during mitosis requires that the kinetochores of all sister chromatids become stably connected to microtubules derived from opposite spindle poles. How stable chromosome bi-orientation is accomplished and coordinated with anaphase onset remains incompletely understood. Here we show that stable chromosome bi-orientation requires inner centromere localization of the non-enzymatic subunits of the chromosomal passenger complex (CPC) to maintain centromeric cohesion. Precise inner centromere localization of the CPC appears less relevant for Aurora B-dependent resolution of erroneous kinetochore-microtubule (KT-MT) attachments and for the stabilization of bi-oriented KT-MT attachments once sister chromatid cohesion is preserved via knock-down of WAPL...
May 31, 2017: Nature Communications
https://www.readbyqxmd.com/read/28553959/biallelic-trip13-mutations-predispose-to-wilms-tumor-and-chromosome-missegregation
#12
Shawn Yost, Bas de Wolf, Sandra Hanks, Anna Zachariou, Chiara Marcozzi, Matthew Clarke, Richarda M de Voer, Banafsheh Etemad, Esther Uijttewaal, Emma Ramsay, Harriet Wylie, Anna Elliott, Susan Picton, Audrey Smith, Sarah Smithson, Sheila Seal, Elise Ruark, Gunnar Houge, Jonathon Pines, Geert J P L Kops, Nazneen Rahman
Through exome sequencing, we identified six individuals with biallelic loss-of-function mutations in TRIP13. All six developed Wilms tumor. Constitutional mosaic aneuploidies, microcephaly, developmental delay and seizures, which are features of mosaic variegated aneuploidy (MVA) syndrome, were more variably present. Through functional studies, we show that TRIP13-mutant patient cells have no detectable TRIP13 and have substantial impairment of the spindle assembly checkpoint (SAC), leading to a high rate of chromosome missegregation...
May 29, 2017: Nature Genetics
https://www.readbyqxmd.com/read/28553202/a-systematic-rnai-screen-reveals-a-novel-role-of-a-spindle-assembly-checkpoint-protein-bugz-in-synaptic-transmission-in-c-elegans
#13
Mei Han, Wenjuan Zou, Hao Chang, Yong Yu, Haining Zhang, Shitian Li, Hankui Cheng, Guifeng Wei, Yan Chen, Valerie Reinke, Tao Xu, Lijun Kang
Synaptic vesicles (SV) store various neurotransmitters that are released at the synapse. The molecular mechanisms of biogenesis, exocytosis, and endocytosis for SV, however, remain largely elusive. In this study, using Complex Object Parametric Analysis and Sorter (COPAS) to monitor the fluorescence of synapto-pHluorin (SpH), we performed a whole-genome RNAi screen in C. elegans to identify novel genetic modulators in SV cycling. One hundred seventy six genes that up-regulating SpH fluorescence and 96 genes that down-regulating SpH fluorescence were identified after multi-round screen...
2017: Frontiers in Molecular Neuroscience
https://www.readbyqxmd.com/read/28550769/mk-8776-a-novel-chk1-inhibitor-exhibits-an-improved-radiosensitizing-effect-compared-to-ucn-01-by-exacerbating-radiation-induced-aberrant-mitosis
#14
Motofumi Suzuki, Tohru Yamamori, Tomoki Bo, Yuri Sakai, Osamu Inanami
Checkpoint kinase 1 (Chk1) is an evolutionarily conserved serine/threonine kinase that plays an important role in G2/M checkpoint signaling. Here, we evaluate the radiosensitizing effects of a novel selective Chk1 inhibitor MK-8776, comparing its efficacy with a first-generation Chk1 inhibitor UCN-01, and attempt to elucidate the mechanism of radiosensitization. In a clonogenic survival assay, MK-8776 demonstrated a more pronounced radiosensitizing effect than UCN-01, with lower cytotoxicity. Importantly, radiosensitization by MK-8776 can be achieved at doses as low as 2...
May 24, 2017: Translational Oncology
https://www.readbyqxmd.com/read/28544703/high-ubiquitin-specific-protease-44-expression-induces-dna-aneuploidy-and-provides-independent-prognostic-information-in-gastric-cancer
#15
Sho Nishimura, Eiji Oki, Koji Ando, Makoto Iimori, Yu Nakaji, Yuichiro Nakashima, Hiroshi Saeki, Yoshinao Oda, Yoshihiko Maehara
Chromosomal instability (CIN), characterized by aneuploidy, is a major molecular subtype of gastric cancer. The deubiquitinase USP44 is an important regulator of APC activation in the spindle checkpoint and leads to proper chromosome separation to prevent aneuploidy. Aberrant expression of USP44 leads CIN in cells; however, the correlation between USP44 and DNA aneuploidy in gastric cancer is largely unknown. We analyzed USP44 expression in 207 patients with gastric cancer by immunohistochemistry and found that the proportion of USP44 expression was higher in gastric cancer tumors (mean, 39...
June 2017: Cancer Medicine
https://www.readbyqxmd.com/read/28539402/spindle-assembly-checkpoint-signaling-and-sister-chromatid-cohesion-are-disrupted-by-hpv-e6-mediated-transformation
#16
Hazheen K Shirnekhi, Erin P Kelley, Jennifer G DeLuca, Jacob A Herman
Aneuploidy, a condition that results from unequal partitioning of chromosomes during mitosis, is a hallmark of many cancers, including those caused by human papillomaviruses (HPVs). E6 and E7 are the primary transforming proteins in HPV that drive tumor progression. In this study, we stably expressed E6 and E7 in non-cancerous RPE1 cells and analyzed the specific mitotic defects that contribute to aneuploidy in each cell line. We find that E6-expression results in multiple chromosomes associated with one or both spindle poles, causing a significant mitotic delay...
May 24, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28539250/target-residence-time-guided-optimization-on-ttk-kinase-results-in-inhibitors-with-potent-anti-proliferative-activity
#17
Joost C M Uitdehaag, Jos de Man, Nicole Willemsen-Seegers, Martine B W Prinsen, Marion A A Libouban, Jan Gerard Sterrenburg, Joeri J P de Wit, Judith R F de Vetter, Jeroen A D M de Roos, Rogier C Buijsman, Guido J R Zaman
The protein kinase threonine tyrosine kinase (TTK; also known as Mps1) is a critical component of the spindle assembly checkpoint and a promising drug target for the treatment of aggressive cancers, such as triple negative breast cancer. While the first TTK inhibitors have entered clinical trials, little is known about how the inhibition of TTK with small-molecule compounds affects cellular activity. We studied the selective TTK inhibitor NTRC 0066-0, which was developed in our own laboratory, together with 11 TTK inhibitors developed by other companies, including Mps-BAY2b, BAY 1161909, BAY 1217389 (Bayer), TC-Mps1-12 (Shionogi), and MPI-0479605 (Myrexis)...
May 21, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28536121/spindle-assembly-checkpoint-satisfaction-occurs-via-end-on-but-not-lateral-attachments-under-tension
#18
Jonathan Kuhn, Sophie Dumont
To ensure accurate chromosome segregation, the spindle assembly checkpoint (SAC) prevents anaphase until all kinetochores attach to the spindle. What signals the SAC monitors remains unclear. We do not know the contributions of different microtubule attachment features or tension from biorientation to SAC satisfaction nor how these possible cues change during attachment. In this study, we quantify concurrent Mad1 intensity and report on SAC silencing, real-time attachment geometry, occupancy, and tension at individual mammalian kinetochores...
June 5, 2017: Journal of Cell Biology
https://www.readbyqxmd.com/read/28516917/maternal-age-dependent-apc-c-mediated-decrease-in-securin-causes-premature-sister-chromatid-separation-in-meiosis-ii
#19
Ibtissem Nabti, Rosanna Grimes, Hema Sarna, Petros Marangos, John Carroll
Sister chromatid attachment during meiosis II (MII) is maintained by securin-mediated inhibition of separase. In maternal ageing, oocytes show increased inter-sister kinetochore distance and premature sister chromatid separation (PSCS), suggesting aberrant separase activity. Here, we find that MII oocytes from aged mice have less securin than oocytes from young mice and that this reduction is mediated by increased destruction by the anaphase promoting complex/cyclosome (APC/C) during meiosis I (MI) exit. Inhibition of the spindle assembly checkpoint (SAC) kinase, Mps1, during MI exit in young oocytes replicates this phenotype...
May 18, 2017: Nature Communications
https://www.readbyqxmd.com/read/28512144/tog-tubulin-binding-specificity-promotes-microtubule-dynamics-and-mitotic-spindle-formation
#20
Amy E Byrnes, Kevin C Slep
XMAP215, CLASP, and Crescerin use arrayed tubulin-binding tumor overexpressed gene (TOG) domains to modulate microtubule dynamics. We hypothesized that TOGs have distinct architectures and tubulin-binding properties that underlie each family's ability to promote microtubule polymerization or pause. As a model, we investigated the pentameric TOG array of a Drosophila melanogaster XMAP215 member, Msps. We found that Msps TOGs have distinct architectures that bind either free or polymerized tubulin, and that a polarized array drives microtubule polymerization...
June 5, 2017: Journal of Cell Biology
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