Disappearance of the budding yeast Bub2-Bfa1 complex from the mother-bound spindle pole contributes to mitotic exit.

Budding yeast spindle position checkpoint is engaged by misoriented spindles and prevents mitotic exit by inhibiting the G protein Tem1 through the GTPase-activating protein (GAP) Bub2/Bfa1. Bub2 and Bfa1 are found on both duplicated spindle pole bodies until anaphase onset, when they disappear from the mother-bound spindle pole under unperturbed ...
conditions. In contrast, when spindles are misoriented they remain symmetrically localized at both SPBs. Thus, symmetric localization of Bub2/Bfa1 might lead to inhibition of Tem1, which is also present at SPBs. Consistent with this hypothesis, we show that a Bub2 version symmetrically localized on both SPBs throughout the cell cycle prevents mitotic exit in mutant backgrounds that partially impair it. This effect is Bfa1 dependent and can be suppressed by high Tem1 levels. Bub2 removal from the mother-bound SPB requires its GAP activity, which in contrast appears to be dispensable for Tem1 inhibition. Moreover, it correlates with the passage of one spindle pole through the bud neck because it needs septin ring formation and bud neck kinases.
Mesh Terms:
Alleles, Anaphase, CDC2 Protein Kinase, Cell Cycle Proteins, Cyclin B, Cyclin-Dependent Kinase Inhibitor Proteins, Cyclin-Dependent Kinases, Cytoskeletal Proteins, GTPase-Activating Proteins, Gene Expression Regulation, Fungal, Genes, Dominant, Guanine Nucleotide Exchange Factors, Methionine, Microtubule Proteins, Mitosis, Mitotic Spindle Apparatus, Models, Genetic, Monomeric GTP-Binding Proteins, Mutation, Pheromones, Protein Kinases, Protein Tyrosine Phosphatases, Protein-Serine-Threonine Kinases, Protein-Tyrosine Kinases, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
J. Cell Biol.
Date: Jan. 30, 2006
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