Abstract
The spindle pole body (SPB) in Saccharomyces cerevisiae functions to nucleate and organize spindle microtubules, and it is embedded in the nuclear envelope throughout the yeast life cycle. However, the mechanism of membrane insertion of the SPB has not been elucidated. Ndc1p is an integral membrane protein that localizes to SPBs, and it is required for insertion of the SPB into the nuclear envelope during SPB duplication. To better understand the function of Ndc1p, we performed a dosage suppressor screen using the ndc1-39 temperature-sensitive allele. We identified an essential SPB component, Nbp1p. NBP1 shows genetic interactions with several SPB genes in addition to NDC1, and two-hybrid analysis revealed that Nbp1p binds to Ndc1p. Furthermore, Nbp1p is in the Mps2p-Bbp1p complex in the SPB. Immunoelectron microscopy confirmed that Nbp1p localizes to the SPB, suggesting a function at this location. Consistent with this hypothesis, nbp1-td (a degron allele) cells fail in SPB duplication upon depletion of Nbp1p. Importantly, these cells exhibit a "dead" SPB phenotype, similar to cells mutant in MPS2, NDC1, or BBP1. These results demonstrate that Nbp1p is a SPB component that acts in SPB duplication at the point of SPB insertion into the nuclear envelope.
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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Alleles
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Calmodulin-Binding Proteins
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Carrier Proteins / analysis
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Cell Cycle / genetics
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Cell Cycle Proteins / analysis
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism*
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Cell Membrane / metabolism
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Cytoskeletal Proteins
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DNA-Binding Proteins / analysis
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Genes, Essential
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Genes, Fungal
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Membrane Proteins / metabolism*
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Microtubule Proteins / metabolism
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Microtubules / chemistry
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Microtubules / genetics
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Microtubules / metabolism
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Mitosis / genetics
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Nuclear Envelope / metabolism
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Nuclear Pore Complex Proteins
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Nuclear Proteins / metabolism*
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Saccharomyces cerevisiae / chemistry
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae / ultrastructure
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Saccharomyces cerevisiae Proteins / analysis
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
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Spindle Apparatus / chemistry
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Spindle Apparatus / genetics
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Spindle Apparatus / metabolism*
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Two-Hybrid System Techniques
Substances
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BBP1 protein, S cerevisiae
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Calmodulin-Binding Proteins
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Carrier Proteins
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Cell Cycle Proteins
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Cytoskeletal Proteins
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DNA-Binding Proteins
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MPS2 protein, S cerevisiae
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Membrane Proteins
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Microtubule Proteins
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NBP1 protein, S cerevisiae
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NDC1 protein, S cerevisiae
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Nuclear Pore Complex Proteins
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Nuclear Proteins
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SPC110 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins