Abstract
Aphysical and functional link between the nuclear pore complex (NPC) and the spindle checkpoint machinery has been established in the yeast Saccharomyces cerevisiae. We show that two proteins required for the execution of the spindle checkpoint, Mad1p and Mad2p, reside predominantly at the NPC throughout the cell cycle. There they are associated with a subcomplex of nucleoporins containing Nup53p, Nup170p, and Nup157p. The association of the Mad1p-Mad2p complex with the NPC requires Mad1p and is mediated in part by Nup53p. On activation of the spindle checkpoint, we detect changes in the interactions between these proteins, including the release of Mad2p (but not Mad1p) from the NPC and the accumulation of Mad2p at kinetochores. Accompanying these events is the Nup53p-dependent hyperphosphorylation of Mad1p. On the basis of these results and genetic analysis of double mutants, we propose a model in which Mad1p bound to a Nup53p-containing complex sequesters Mad2p at the NPC until its release by activation of the spindle checkpoint. Furthermore, we show that the association of Mad1p with the NPC is not passive and that it plays a role in nuclear transport.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Antimetabolites / pharmacology
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Benomyl / pharmacology
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Biological Transport, Active
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Calcium-Binding Proteins / drug effects
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Calcium-Binding Proteins / genetics
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Calcium-Binding Proteins / metabolism
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Carrier Proteins*
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Cell Cycle Proteins
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Cell Nucleus / genetics
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Cell Nucleus / physiology
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Deoxyglucose / pharmacology
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Fungal Proteins / drug effects
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Fungal Proteins / genetics
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Fungal Proteins / metabolism
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Gene Deletion
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Genes, Reporter
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Kinetochores / physiology
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Mad2 Proteins
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Mating Factor
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Mitosis
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Models, Genetic
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Nocodazole / pharmacology
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Nuclear Pore / metabolism
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Nuclear Pore / physiology*
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Nuclear Pore Complex Proteins / chemistry
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Nuclear Pore Complex Proteins / genetics
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Nuclear Pore Complex Proteins / metabolism*
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Peptides / pharmacology
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Phosphoproteins / drug effects
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Phosphoproteins / genetics
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Phosphoproteins / metabolism
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Phosphorylation
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Repressor Proteins / drug effects
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Repressor Proteins / genetics
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Repressor Proteins / metabolism
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Saccharomyces cerevisiae / cytology
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Saccharomyces cerevisiae / genetics*
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Saccharomyces cerevisiae / physiology
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
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Sodium Azide / pharmacology
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Spindle Apparatus / physiology*
Substances
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Antimetabolites
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Calcium-Binding Proteins
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Carrier Proteins
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Cell Cycle Proteins
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Fungal Proteins
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MAD1 protein, S cerevisiae
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MAD2 protein, S cerevisiae
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Mad2 Proteins
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Nuclear Pore Complex Proteins
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Nuclear Proteins
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Peptides
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Phosphoproteins
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Repressor Proteins
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Saccharomyces cerevisiae Proteins
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Mating Factor
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Sodium Azide
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Deoxyglucose
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Nocodazole
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Benomyl