Ubiquitylation Regulates Interactions of Astral Microtubules with the Cleavage Apparatus

Correct positioning of the mitotic spindle relative to the cleavage apparatus is crucial for successful mitosis. In budding yeast, the Adenomatous Polyposis Coli-related protein Kar9, yeast EB1, and Myo2, a type V myosin, mediate positioning of the mitotic spindle close to the septin-anchored cleava...

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Bibliographic Details
Published in:Current biology 2010-07, Vol.20 (14), p.1233-1243
Main Authors: Kammerer, Daniel, Stevermann, Lea, Liakopoulos, Dimitris
Format: Article
Language:English
Subjects:
CELLBIO
Cytokinesis - physiology
Microscopy, Fluorescence
Microtubule-Associated Proteins - metabolism
Microtubules - metabolism
Microtubules - physiology
Mitosis - physiology
Models, Biological
Myosin Heavy Chains - metabolism
Myosin Type V - metabolism
Nuclear Proteins - metabolism
Phosphorylation
Saccharomyces cerevisiae
Saccharomyces cerevisiae Proteins - metabolism
Spindle Apparatus - physiology
Ubiquitination
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Summary:Correct positioning of the mitotic spindle relative to the cleavage apparatus is crucial for successful mitosis. In budding yeast, the Adenomatous Polyposis Coli-related protein Kar9, yeast EB1, and Myo2, a type V myosin, mediate positioning of the mitotic spindle close to the septin-anchored cleavage apparatus at the bud neck. We find that Kar9 is ubiquitylated and degraded by the proteasome. Ubiquitylation requires the ubiquitin-conjugating enzymes Ubc1 and Ubc4 and phosphorylation of Kar9 by yeast Cdk1. Importantly, Kar9 ubiquitylation and degradation depend on an intact cleavage apparatus. Kar9 is stabilized in septin mutant cells or cells lacking the bud neck formin Bnr1, but not in the bud formin Bni1 or the actomyosin ring. Transport of Kar9 to the bud neck by Myo2 is also required for Kar9 degradation. Abrogation of Kar9 phosphorylation and ubiquitylation increases interactions of astral microtubules (aMTs) with the bud neck and causes spindle mispositioning. Photoconversion experiments showed that Kar9 association with aMTs is stable. We propose that ubiquitylation controls interactions of aMTs with the cleavage apparatus through localized disassembly of Kar9 complexes. [Display omitted] ► Ubiquitylation of APC-related Kar9 regulates spindle positioning in budding yeast ► Ubc1, Ubc4, and Cdk1 phosphorylation are required for Kar9 ubiquitylation ► Ubiquitylation and degradation require an intact cleavage apparatus ► Ubiquitylation may control microtubule interactions with the cleavage apparatus
ISSN:0960-9822
1879-0445
DOI:10.1016/j.cub.2010.05.064