The surveillance mechanism of the spindle position checkpoint in yeast.
The spindle position checkpoint in Saccharomyces cerevisiae delays mitotic exit until the spindle has moved into the mother-bud neck, ensuring that each daughter cell inherits a nucleus. The small G protein Tem1p is critical in promoting mitotic exit and is concentrated at the spindle pole destined for the bud. The presumed nucleotide exchange factor for Tem1p, Lte1p, is concentrated in the bud. These findings suggested the hypothesis that movement of the spindle pole through the neck allows Tem1p to interact with Lte1p, promoting GTP loading of Tem1p and mitotic exit. However, we report that deletion of LTE1 had little effect on the timing of mitotic exit. We also examined several mutants in which some cells inappropriately exit mitosis even though the spindle is within the mother. In some of these cells, the spindle pole body did not interact with the bud or the neck before mitotic exit. Thus, some alternative mechanism must exist to coordinate mitotic exit with spindle position. In both wild-type and mutant cells, mitotic exit was preceded by loss of cytoplasmic microtubules from the neck. Thus, the spindle position checkpoint may monitor such interactions.
Adames
N R
NR
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA. nadames@cellbio.wustl.edu
Oberle
J R
JR
Cooper
J A
JA
D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology; D003593:Cytoplasm / Q000378:metabolism / Q000502:physiology; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors; D008868:Microtubule Proteins / Q000235:genetics / Q000502:physiology; D008870:Microtubules / Q000378:metabolism / Q000502:physiology; D008938:Mitosis / Q000502:physiology*; D016296:Mutagenesis; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D008941:Spindle Apparatus / Q000502:physiology*
C119117:BFA1 protein, S cerevisiae; C119683:BIM1 protein, S cerevisiae; C070351:BUB2 protein, S cerevisiae; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins; D020662:Guanine Nucleotide Exchange Factors; C089357:LTE1 protein, S cerevisiae; D008868:Microtubule Proteins; D029701:Saccharomyces cerevisiae Proteins