Differential kinetochore requirements for establishment and maintenance of the spindle checkpoint are dependent on the mechanism of checkpoint activation in Saccharomyces cerevisiae.
The spindle checkpoint in the yeast Saccharomyces cerevisiae is an intracellular signal transduction pathway comprised of two branches that inhibit two different mitotic transitions in cells treated with benzimidazole drugs such as nocodazole. The kinetochore is an integral component of the MAD2 branch of the spindle checkpoint pathway. Current models propose that the kinetochore is required for both the establishment and maintenance of the spindle checkpoint but a role for the kinetochore in the maintenance of spindle checkpoint in yeast has never been directly tested. We used a temperature sensitive ndc10-1 mutant to inactivate kinetochores before and after arresting cells in mitosis to determine the role of kinetochores in the establishment and maintenance of the spindle checkpoint. We show that both establishment and maintenance requires kinetochore function in response to spindle damage induced by benzimidazole drugs. Excess expression of the Mps1 protein kinase causes wild type cells and ndc10-1 cells to arrest in mitosis. Unlike the spindle checkpoint arrest activated by benzimidazoles, this arrest can be maintained independently of kinetochores. The arrest induced by excess Mps1p is independent of BUB2. Therefore, mitotic arrest induced by excess Mps1p expression is due to the action of the MAD2 branch of the spindle checkpoint pathway and excess Mps1p acts downstream of the kinetochore.
Poddar
Atasi
A
Department of Biochemistry and Molecular Genetics, University of Virginia Medical Center, Charlottesville, Virginia 229083-0733, USA.
Daniel
Jewel A
JA
Daum
John R
JR
Burke
Daniel J
DJ
D002352:Carrier Proteins / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D018386:Kinetochores / Q000502:physiology*; D064246:Mad2 Proteins; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D015739:Nocodazole / Q000494:pharmacology; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism*
C070351:BUB2 protein, S cerevisiae; C081071:CBF2 protein, S cerevisiae; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C577695:MAD2 protein, S cerevisiae; D064246:Mad2 Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; C093416:MPS1 protein, S cerevisiae; D015739:Nocodazole