Related Experiment Video
Updated: Jun 27, 2026
10:24
Two- and Three-Dimensional Live Cell Imaging of DNA Damage Response Proteins
Published on: September 28, 2012
Bir1 is required for the tension checkpoint.
Michelle M Shimogawa1, Per O Widlund, Michael Riffle
1Department of Biochemistry, University of Washington, Seattle, WA 98195-7350, USA.
Molecular Biology of the Cell
|December 6, 2008
Summary
The chromosomal passenger protein Bir1 is essential for the tension checkpoint in Saccharomyces cerevisiae. Bir1 ensures proper localization of Ipl1, enabling kinetochore detachment and cell cycle progression.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- The Saccharomyces cerevisiae tension checkpoint ensures proper chromosome segregation.
- Chromosomal passenger proteins, including Ipl1 (Aurora B), Sli15 (INCENP), and Bir1, play roles in this checkpoint.
- The specific function of Bir1 in the tension checkpoint has been debated.
Purpose of the Study:
- To investigate the role of Bir1 in the Saccharomyces cerevisiae tension checkpoint.
- To characterize a novel temperature-sensitive mutant of Bir1 (bir1-107).
Main Methods:
- Isolation and characterization of the bir1-107 temperature-sensitive mutant.
- Analysis of biorientation, tension checkpoint response, and kinetochore detachment.
- Localization studies of chromosomal passenger proteins using microscopy.
Main Results:
- The bir1-107 mutant exhibits biorientation defects, impaired checkpoint response to lack of tension, and failure in kinetochore detachment.
- Disruption of Bir1 localization leads to aberrant Ipl1 localization.
- Chromosomal passengers localize between kinetochores under tension and are removed upon tension establishment.
Conclusions:
- Bir1 is crucial for proper Ipl1 localization and kinetochore detachment, fulfilling a key checkpoint role.
- Tension establishment triggers the removal of Ipl1, Bir1, and Sli15 from kinetochores, allowing checkpoint satisfaction.
Related Concept Videos
02:19The Spindle Assembly Checkpoint
The spindle assembly checkpoint is a molecular surveillance mechanism ensuring the fidelity of chromosome segregation during anaphase. The checkpoint monitors the completion of all the prerequisite steps before chromosome segregation to determine whether the segregation process should proceed or be delayed.
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
02:19The Spindle Assembly Checkpoint
The spindle assembly checkpoint is a molecular surveillance mechanism ensuring the fidelity of chromosome segregation during anaphase. The checkpoint monitors the completion of all the prerequisite steps before chromosome segregation to determine whether the segregation process should proceed or be delayed.
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
01:26Tension Response at Adherens Junctions
The adherens junctions that anchor cells together are multi-protein complexes that dynamically adapt to mechanical stimuli such as tensile forces and shear stress. Mechanosensory proteins in these junctions can sense such mechanical stimuli and undergo a shift in their conformation, resulting in an altered function — a process called mechanotransduction.
α-Catenin as a Mechanosensory Protein
The α-catenin of adherens junctions is an allosteric protein with three VH (vinculin homology) domains...
α-Catenin as a Mechanosensory Protein
The α-catenin of adherens junctions is an allosteric protein with three VH (vinculin homology) domains...
01:23Negative Regulator Molecules
Positive regulators allow a cell to advance through cell cycle checkpoints. Negative regulators have an equally important role as they terminate a cell’s progression through the cell cycle—or pause it—until the cell meets specific criteria.
01:28The Cell Cycle Control System
The cell cycle regulation directs how a cell proceeds from one phase to the next and begins mitosis. The cell cycle control system includes intracellular regulatory molecules and external triggers. They provide "stop" or "advance" signals and operate at specific cell cycle stages termed checkpoints to ensure that a particular process is completed before the cell advances to the next phase.
Cyclins and cyclin-dependent kinases (Cdks) are the primary cell cycle regulators and function at the cell...
Cyclins and cyclin-dependent kinases (Cdks) are the primary cell cycle regulators and function at the cell...
02:11The Cell Cycle Control System
The cell cycle is an organized set of events that leads the cell to divide into two daughter cells, each containing chromosomes identical to the parent cell. It is the cell cycle that leads to the formation of an entire organism from a single-cell zygote. Besides, cell division also functions in the renewal or repair of tissues in adult multicellular eukaryotes. For example, in the bone marrow, the stem cells divide to form new blood cells. Although essential for several functions, cell...