Abstract
Recruitment of Mad1-Mad2 complexes to unattached kinetochores is a central event in spindle checkpoint signaling. Despite its importance, the mechanism that recruits Mad1-Mad2 to kinetochores is unclear. In this paper, we show that MAD-1 interacts with BUB-1 in Caenorhabditis elegans. Mutagenesis identified specific residues in a segment of the MAD-1 coiled coil that mediate the BUB-1 interaction. In addition to unattached kinetochores, MAD-1 localized between separating meiotic chromosomes and to the nuclear periphery. Mutations in the MAD-1 coiled coil that selectively disrupt interaction with BUB-1 eliminated MAD-1 localization to unattached kinetochores and between meiotic chromosomes, both of which require BUB-1, and abrogated checkpoint signaling. The identified MAD-1 coiled-coil segment interacted with a C-terminal region of BUB-1 that contains its kinase domain, and mutations in this region prevented MAD-1 kinetochore targeting independently of kinase activity. These results delineate an interaction between BUB-1 and MAD-1 that targets MAD-1-MAD-2 complexes to kinetochores and is essential for spindle checkpoint signaling.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Anaphase / physiology
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Animals
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Binding Sites
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Caenorhabditis elegans / cytology*
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Caenorhabditis elegans / genetics
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Caenorhabditis elegans / metabolism
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Caenorhabditis elegans Proteins / genetics
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Caenorhabditis elegans Proteins / metabolism
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Caenorhabditis elegans Proteins / physiology*
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism
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Cell Cycle Proteins / physiology*
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Chromosomes / metabolism
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Kinetochores / metabolism*
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Kinetochores / physiology
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M Phase Cell Cycle Checkpoints*
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Mad2 Proteins / genetics
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Mad2 Proteins / metabolism
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Mad2 Proteins / physiology
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Meiosis / physiology
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Models, Biological
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Mutagenesis
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Nuclear Proteins / physiology*
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Protein Serine-Threonine Kinases / physiology
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Protein Structure, Tertiary
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Signal Transduction
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Two-Hybrid System Techniques
Substances
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Caenorhabditis elegans Proteins
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Cell Cycle Proteins
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MDF-1 protein, C elegans
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Mad2 Proteins
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Nuclear Proteins
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Protein Serine-Threonine Kinases
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bub-1 protein, C elegans