scholarly journals Loss of spindle assembly checkpoint–mediated inhibition of Cdc20 promotes tumorigenesis in mice

2009 ◽  
Vol 185 (6) ◽  
pp. 983-994 ◽  
Author(s):  
Min Li ◽  
Xiao Fang ◽  
Zhubo Wei ◽  
J. Philippe York ◽  
Pumin Zhang
Keyword(s):  
Dna Damage ◽  
Genomic Instability ◽  
Genome Stability ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Cellular Mechanism ◽  
Late Gestation ◽  
Dna Damage Checkpoint ◽  
Chromosome Missegregation ◽  
Sister Chromatids

Genomic instability is a hallmark of human cancers. Spindle assembly checkpoint (SAC) is a critical cellular mechanism that prevents chromosome missegregation and therefore aneuploidy by blocking premature separation of sister chromatids. Thus, SAC, much like the DNA damage checkpoint, is essential for genome stability. In this study, we report the generation and analysis of mice carrying a Cdc20 allele in which three residues critical for the interaction with Mad2 were mutated to alanine. The mutant Cdc20 protein (AAA-Cdc20) is no longer inhibited by Mad2 in response to SAC activation, leading to the dysfunction of SAC and aneuploidy. The dysfunction could not be rescued by the additional expression of another Cdc20 inhibitor, BubR1. Furthermore, we found that Cdc20AAA/AAA mice died at late gestation, but Cdc20+/AAA mice were viable. Importantly, Cdc20+/AAA mice developed spontaneous tumors at highly accelerated rates, indicating that the SAC-mediated inhibition of Cdc20 is an important tumor-suppressing mechanism.

scholarly journals The Fission Yeast Crb2/Chk1 Pathway Coordinates the DNA Damage and Spindle Checkpoint in Response to Replication Stress Induced by Topoisomerase I Inhibitor

2005 ◽  
Vol 25 (17) ◽  
pp. 7889-7899 ◽  
Author(s):  
Ada Collura ◽  
Joel Blaisonneau ◽  
Giuseppe Baldacci ◽  
Stefania Francesconi
Keyword(s):  
Dna Damage ◽  
Fission Yeast ◽  
Topoisomerase I ◽  
Genome Stability ◽  
Cell Cycle Progression ◽  
Spindle Assembly Checkpoint ◽  
Genetic Material ◽  
Spindle Checkpoint ◽  
Dna Damage Checkpoint ◽  
Replicative Stress

ABSTRACT Living organisms experience constant threats that challenge their genome stability. The DNA damage checkpoint pathway coordinates cell cycle progression with DNA repair when DNA is damaged, thus ensuring faithful transmission of the genome. The spindle assembly checkpoint inhibits chromosome segregation until all chromosomes are properly attached to the spindle, ensuring accurate partition of the genetic material. Both the DNA damage and spindle checkpoint pathways participate in genome integrity. However, no clear connection between these two pathways has been described. Here, we analyze mutants in the BRCT domains of fission yeast Crb2, which mediates Chk1 activation, and provide evidence for a novel function of the Chk1 pathway. When the Crb2 mutants experience damaged replication forks upon inhibition of the religation activity of topoisomerase I, the Chk1 DNA damage pathway induces sustained activation of the spindle checkpoint, which in turn delays metaphase-to-anaphase transition in a Mad2-dependent fashion. This new pathway enhances cell survival and genome stability when cells undergo replicative stress in the absence of a proficient G2/M DNA damage checkpoint.

scholarly journals The copy-number and varied strengths of MELT motifs in Spc105 balance the strength and responsiveness the Spindle Assembly Checkpoint

2020 ◽  
Author(s):  
Babhrubahan Roy ◽  
Simon JY Han ◽  
Adrienne N. Fontan ◽  
Ajit P. Joglekar
Keyword(s):  
Chromosome Segregation ◽  
Copy Number ◽  
Genome Stability ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Evolutionary Trend ◽  
Binding Affinities ◽  
Chromosome Missegregation ◽  
Anaphase Onset ◽  
Maintain Genome Stability

SummaryThe Spindle Assembly Checkpoint (SAC) maintains genome stability while enabling timely anaphase onset. To maintain genome stability, the SAC must be strong so that it delays cell division even if one chromosome is unattached, but for timely anaphase onset, it must be responsive to silencing mechanisms. How it meets these potentially antagonistic requirements is unclear. Here we show that the balance between SAC strength and responsiveness is determined by the number of ‘MELT’ motifs in the kinetochore protein Spc105/KNL1 and their Bub3-Bub1 binding affinities. Spc105/KNL1 must contain many strong MELT motifs to prevent chromosome missegregation, but not too many, because this delays SAC silencing and anaphase onset. We demonstrate this by constructing a Spc105 variant that trades SAC responsiveness for significantly improved chromosome segregation accuracy. We propose that the necessity of balancing SAC strength with responsiveness drives the evolutionary trend of MELT motif number amplification and degeneration of their functionally optimal amino acid sequence.

scholarly journals The copy-number and varied strengths of MELT motifs in Spc105 balance the strength and responsiveness of the spindle assembly checkpoint

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Babhrubahan Roy ◽  
Simon JY Han ◽  
Adrienne Nicole Fontan ◽  
Ajit P Joglekar
Keyword(s):  
Chromosome Segregation ◽  
Copy Number ◽  
Genome Stability ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Evolutionary Trend ◽  
Binding Affinities ◽  
Chromosome Missegregation ◽  
Anaphase Onset ◽  
Maintain Genome Stability

During mitosis, the Spindle Assembly Checkpoint (SAC) maintains genome stability while also ensuring timely anaphase onset. To maintain genome stability, the SAC must be strong to delay anaphase even if just one chromosome is unattached, but for timely anaphase onset, it must promptly respond to silencing mechanisms. How the SAC meets these potentially antagonistic requirements is unclear. Here we show that the balance between SAC strength and responsiveness is determined by the number of ‘MELT’ motifs in the kinetochore protein Spc105/KNL1 and their Bub3-Bub1 binding affinities. Many strong MELT motifs per Spc105/KNL1 minimize chromosome missegregation, but too many delay anaphase onset. We demonstrate this by constructing a Spc105 variant that trades SAC responsiveness for much more accurate chromosome segregation. We propose that the necessity of balancing SAC strength and responsiveness drives the dual evolutionary trend of the amplification of MELT motif number, but degeneration of their functionally optimal amino acid sequence.

scholarly journals Mitotic Errors Promote Genomic Instability and Leukemia in a Novel Mouse Model of Fanconi Anemia

2021 ◽  
Vol 11 ◽  
Author(s):  
Donna M. Edwards ◽  
Dana K. Mitchell ◽  
Zahi Abdul-Sater ◽  
Ka-Kui Chan ◽  
Zejin Sun ◽  
...  
Keyword(s):  
Dna Damage ◽  
Genomic Instability ◽  
Fanconi Anemia ◽  
Spindle Assembly Checkpoint ◽  
Dna Damage Repair ◽  
Spindle Assembly ◽  
Dependent Manner ◽  
Damage Repair

Fanconi anemia (FA) is a disease of genomic instability and cancer. In addition to DNA damage repair, FA pathway proteins are now known to be critical for maintaining faithful chromosome segregation during mitosis. While impaired DNA damage repair has been studied extensively in FA-associated carcinogenesis in vivo, the oncogenic contribution of mitotic abnormalities secondary to FA pathway deficiency remains incompletely understood. To examine the role of mitotic dysregulation in FA pathway deficient malignancies, we genetically exacerbated the baseline mitotic defect in Fancc-/- mice by introducing heterozygosity of the key spindle assembly checkpoint regulator Mad2. Fancc-/-;Mad2+/- mice were viable, but died from acute myeloid leukemia (AML), thus recapitulating the high risk of myeloid malignancies in FA patients better than Fancc-/-mice. We utilized hematopoietic stem cell transplantation to propagate Fancc-/-; Mad2+/- AML in irradiated healthy mice to model FANCC-deficient AMLs arising in the non-FA population. Compared to cells from Fancc-/- mice, those from Fancc-/-;Mad2+/- mice demonstrated an increase in mitotic errors but equivalent DNA cross-linker hypersensitivity, indicating that the cancer phenotype of Fancc-/-;Mad2+/- mice results from error-prone cell division and not exacerbation of the DNA damage repair defect. We found that FANCC enhances targeting of endogenous MAD2 to prometaphase kinetochores, suggesting a mechanism for how FANCC-dependent regulation of the spindle assembly checkpoint prevents chromosome mis-segregation. Whole-exome sequencing revealed similarities between human FA-associated myelodysplastic syndrome (MDS)/AML and the AML that developed in Fancc-/-; Mad2+/- mice. Together, these data illuminate the role of mitotic dysregulation in FA-pathway deficient malignancies in vivo, show how FANCC adjusts the spindle assembly checkpoint rheostat by regulating MAD2 kinetochore targeting in cell cycle-dependent manner, and establish two new mouse models for preclinical studies of AML.

scholarly journals Saccharomyces cerevisiae BUB2 Prevents Mitotic Exit in Response to Both Spindle and Kinetochore Damage

Genetics ◽  
2000 ◽  
Vol 156 (2) ◽  
pp. 489-500
Author(s):  
Rajesh Krishnan ◽  
Faith Pangilinan ◽  
Catherine Lee ◽  
Forrest Spencer
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Damage ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Exit ◽  
Dna Damage Checkpoint ◽  
Yeast Two Hybrid ◽  
Continuous Presence ◽  
Two Hybrid

Abstract The spindle assembly checkpoint-mediated mitotic arrest depends on proteins that signal the presence of one or more unattached kinetochores and prevents the onset of anaphase in the presence of kinetochore or spindle damage. In the presence of either damage, bub2 cells initiate a preanaphase delay but do not maintain it. Inappropriate sister chromatid separation in nocodazole-treated bub2 cells is prevented when mitotic exit is blocked using a conditional tem1c mutant, indicating that the preanaphase failure in bub2 cells is a consequence of events downstream of TEM1 in the mitotic exit pathway. Using a conditional bub2tsd mutant, we demonstrate that the continuous presence of Bub2 protein is required for maintaining spindle damage-induced arrest. BUB2 is not required to maintain a DNA damage checkpoint arrest, revealing a specificity for spindle assembly checkpoint function. In a yeast two-hybrid assay and in vitro, Bub2 protein interacts with the septin protein Cdc3, which is essential for cytokinesis. These data support the view that the spindle assembly checkpoint encompasses regulation of distinct mitotic steps, including a MAD2-directed block to anaphase initiation and a BUB2-directed block to TEM1-dependent exit.

scholarly journals Eukaryotic clamp loaders and unloaders in the maintenance of genome stability

2020 ◽  
Vol 52 (12) ◽  
pp. 1948-1958
Author(s):  
Kyoo-young Lee ◽  
Su Hyung Park
Keyword(s):  
Dna Damage ◽  
Genomic Instability ◽  
Genome Stability ◽  
Critical Role ◽  
Nuclear Antigen ◽  
Checkpoint Activation ◽  
Sliding Clamp ◽  
Clamp Loaders ◽  
Factor C

AbstractEukaryotic sliding clamp proliferating cell nuclear antigen (PCNA) plays a critical role as a processivity factor for DNA polymerases and as a binding and acting platform for many proteins. The ring-shaped PCNA homotrimer and the DNA damage checkpoint clamp 9-1-1 are loaded onto DNA by clamp loaders. PCNA can be loaded by the pentameric replication factor C (RFC) complex and the CTF18-RFC-like complex (RLC) in vitro. In cells, each complex loads PCNA for different purposes; RFC-loaded PCNA is essential for DNA replication, while CTF18-RLC-loaded PCNA participates in cohesion establishment and checkpoint activation. After completing its tasks, PCNA is unloaded by ATAD5 (Elg1 in yeast)-RLC. The 9-1-1 clamp is loaded at DNA damage sites by RAD17 (Rad24 in yeast)-RLC. All five RFC complex components, but none of the three large subunits of RLC, CTF18, ATAD5, or RAD17, are essential for cell survival; however, deficiency of the three RLC proteins leads to genomic instability. In this review, we describe recent findings that contribute to the understanding of the basic roles of the RFC complex and RLCs and how genomic instability due to deficiency of the three RLCs is linked to the molecular and cellular activity of RLC, particularly focusing on ATAD5 (Elg1).

The mitosis-regulating and protein-protein interaction activities of Astrin are controlled by Aurora-A-induced phosphorylation

2014 ◽  
Vol 307 (5) ◽  
pp. C466-C478 ◽  
Author(s):  
Shao-Chih Chiu ◽  
Jo-Mei Maureen Chen ◽  
Tong-You Wade Wei ◽  
Tai-Shan Cheng ◽  
Ya-Hui Candice Wang ◽  
...  
Keyword(s):  
Regulatory Networks ◽  
Spindle Assembly Checkpoint ◽  
Morphological Changes ◽  
Spindle Assembly ◽  
Aurora A ◽  
Protein Protein Interaction ◽  
Daughter Cells ◽  
Sister Chromatids ◽  
Complicated Process ◽  
Spindle Stability

Cells display dramatic morphological changes in mitosis, where numerous factors form regulatory networks to orchestrate the complicated process, resulting in extreme fidelity of the segregation of duplicated chromosomes into two daughter cells. Astrin regulates several aspects of mitosis, such as maintaining the cohesion of sister chromatids by inactivating Separase and stabilizing spindle, aligning and segregating chromosomes, and silencing spindle assembly checkpoint by interacting with Src kinase-associated phosphoprotein (SKAP) and cytoplasmic linker-associated protein-1α (CLASP-1α). To understand how Astrin is regulated in mitosis, we report here that Astrin acts as a mitotic phosphoprotein, and Aurora-A phosphorylates Astrin at Ser115. The phosphorylation-deficient mutant Astrin S115A abnormally activates spindle assembly checkpoint and delays mitosis progression, decreases spindle stability, and induces chromosome misalignment. Mechanistic analyses reveal that Astrin phosphorylation mimicking mutant S115D, instead of S115A, binds and induces ubiquitination and degradation of securin, which sequentially activates Separase, an enzyme required for the separation of sister chromatids. Moreover, S115A fails to bind mitosis regulators, including SKAP and CLASP-1α, which results in the mitotic defects observed in Astrin S115A-transfected cells. In conclusion, Aurora-A phosphorylates Astrin and guides the binding of Astrin to its cellular partners, which ensures proper progression of mitosis.

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