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Spindle Assembly Checkpoint (spindle + assembly_checkpoint)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

SAC-ing mitotic errors: How the spindle assembly checkpoint (SAC) plays defense against chromosome mis-segregation

CYTOSKELETON, Issue 3 2005
Sheila Kadura
First page of article [source]

Cell cycle execution point analysis of ORC function and characterization of the checkpoint response to ORC inactivation in Saccharomyces cerevisiae

GENES TO CELLS, Issue 6 2006
Daniel G. Gibson
Chromosomal replication initiates through the assembly of a prereplicative complex (pre-RC) at individual replication origins in the G1-phase, followed by activation of these complexes in the S-phase. In Saccharomyces cerevisiae, the origin recognition complex (ORC) binds replication origins throughout the cell cycle and participates in pre-RC assembly. Whether the ORC plays an additional role subsequent to pre-RC assembly in replication initiation or any other essential cell cycle process is not clear. To study the function of the ORC during defined cell cycle periods, we performed cell cycle execution point analyses with strains containing a conditional mutation in the ORC1, ORC2 or ORC5 subunit of ORC. We found that the ORC is essential for replication initiation, but is dispensable for replication elongation or later cell cycle events. Defective initiation in ORC mutant cells results in incomplete replication and mitotic arrest enforced by the DNA damage and spindle assembly checkpoint pathways. The involvement of the spindle assembly checkpoint implies a defect in kinetochore-spindle attachment or sister chromatid cohesion due to incomplete replication and/or DNA damage. Remarkably, under semipermissive conditions for ORC1 function, the spindle checkpoint alone suffices to block proliferation, suggesting this checkpoint is highly sensitive to replication initiation defects. We discuss the potential significance of these overlapping checkpoints and the impact of our findings on previously postulated role(s) of ORCs in other cell cycle functions. [source]

Proteome analysis of apoptosis signaling by S -trityl- L -cysteine, a potent reversible inhibitor of human mitotic kinesin Eg5

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 2 2008
Frank Kozielski
Abstract Mitotic kinesins represent potential drug targets for anticancer chemotherapy. Inhibitors of different chemical classes have been identified that target human Eg5, a kinesin responsible for the establishment of the bipolar spindle. One potent Eg5 inhibitor is S -trityl- L -cysteine (STLC), which arrests cells in mitosis and exhibits tumor growth inhibition activity. However, the underlying mechanism of STLC action on the molecular level is unknown. Here, cells treated with STLC were blocked in mitosis through activation of the spindle assembly checkpoint as shown by the phosphorylated state of BubR1 and the accumulation of mitosis specific phosphorylation on histone H3 and aurora A kinase. Using live cell imaging, we observed prolonged mitotic arrest and subsequent cell death after incubation of GFP-,-tubulin HeLa cells with STLC. Activated caspase-9 occurred before cleavage of caspase-8 leading to the accumulation of the activated executioner caspase-3 suggesting that STLC induces apoptosis through the intrinsic apoptotic pathway. Proteome analysis following STLC treatment revealed 33 differentially regulated proteins of various cellular processes, 31 of which can be linked to apoptotic cell death. Interestingly, four identified proteins, chromobox protein homolog, RNA-binding Src associated in mitosis 68,kDa protein, stathmin, and translationally controlled tumor protein can be linked to mitotic and apoptotic processes. [source]

High expression of BUBR1 is one of the factors for inducing DNA aneuploidy and progression in gastric cancer

CANCER SCIENCE, Issue 3 2010
Koji Ando
(Cancer Sci 2010; 101: 639,645) Gastric cancers show high frequency of DNA aneuploidy, a phenotype of chromosomal instability. It is suggested that the abnormal spindle assembly checkpoint is involved in DNA aneuploidy, but the underlying mechanism is still unclear. We studied the mechanism by assessing the expression of BUBR1 in gastric cancer. The DNA ploidy patterns of 116 gastric cancer samples obtained from the Department of Surgery and Science at Kyushu University Hospital were analyzed. Of those, DNA aneuploidy was seen in 70 (60.3%) cases of gastric cancer. The expression of BUBR1 was studied by immunohistochemistry in 181 gastric cancer samples and by real-time RT-PCR in several gastric cancer cell lines. Ninety-one (50.3%) cases had high expression of BUBR1 and those cases correlated significantly with DNA aneuploidy (P < 0.05). Also high expression of BUBR1 cases had significant correlation with deep invasion, lymph node metastasis, liver metastasis, and poor prognosis. In gastric cancer cell lines, high expression of BUBR1 had a significant relationship with DNA aneuploidy (P < 0.05). Then, gastric cancer cell lines MKN-28 and SNU-1 were transfected with full-length BUBR1 to observe the significance of the change in BUBR1 expression. Enforced expression of BUBR1 resulted in changes to the ploidy pattern and high Ki-67 expression. Collectively, our clinical and in vitro data indicate that high expression of BUBR1 may be one of causative factors for the induction of DNA aneuploidy and progression of gastric cancer. [source]

A High-Content, Cell-Based Screen Identifies Micropolyin, A New Inhibitor of Microtubule Dynamics

CHEMICAL BIOLOGY & DRUG DESIGN, Issue 6 2009
Manu De Rycker
High-content cell-based screens provide a powerful tool to identify new chemicals that interfere with complex biological processes. Here, we describe the identification of a new inhibitor of microtubule dynamics (micropolyin) using a high-content screen. Integrated high-resolution imaging allowed for fast selection of hits and progression to target identification. Treatment of cells with micropolyin efficiently causes a pro-metaphase arrest, with abnormal spindle morphology and with the spindle assembly checkpoint activated. The arrest appears to result from interference of micropolyin with microtubule dynamics. We show in vitro that tubulin is indeed the target of micropolyin and that micropolyin inhibits microtubule polymerization. Our results demonstrate the power of high-content image- and cell-based screening approaches to identify potential new drug candidates. As our approach is unbiased, it should allow for discovery of new targets that may otherwise be overlooked. [source]