Abstract
In this study we demonstrate that the Deg1 degradation signal of the transcriptional repressor Matalpha2 confers compartment-specific turnover to a reporter protein. Rapid degradation of a Deg1-containing fusion protein is observed only when the reporter is efficiently imported into the nucleus. In contrast, a reporter that is constantly exported from the nucleus exhibits an extended half-life. Furthermore, nuclear import functions are crucial for both Deg1-induced degradation as well as for the turnover of the endogenous Matalpha2 protein. The conjugation of ubiquitin to a Deg1-containing reporter protein is abrogated in mutants affected in nuclear import. Obviously, the Deg1 signal initiates rapid proteolysis within the nucleoplasm, whereas in the cytosol it mediates turnover via a slower pathway. In both pathways the ubiquitin-conjugating enzymes Ubc6p/Ubc7p play a pivotal role. These observations imply that both the cellular targeting of a substrate and the compartment-specific activity of components of the ubiquitin-proteasome system define the half-life of naturally short-lived proteins.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Carrier Proteins / metabolism
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Cell Nucleus / metabolism*
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Cytoplasm / metabolism
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Escherichia coli / metabolism
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Fungal Proteins / metabolism*
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Genes, Reporter
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Green Fluorescent Proteins
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Homeodomain Proteins / metabolism*
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Intramolecular Transferases
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Kinetics
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Ligases / metabolism
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Luminescent Proteins / metabolism
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Membrane Proteins / metabolism
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Microscopy, Fluorescence
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Mutation
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Plasmids / metabolism
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Precipitin Tests
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Protein Transport
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Recombinant Fusion Proteins / metabolism
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Repressor Proteins / metabolism*
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Saccharomyces cerevisiae / metabolism
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Saccharomyces cerevisiae Proteins*
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Time Factors
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Transcription, Genetic
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Ubiquitin-Conjugating Enzymes*
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Ubiquitins / metabolism*
Substances
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CUE1 protein, S cerevisiae
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Carrier Proteins
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Fungal Proteins
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Homeodomain Proteins
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Luminescent Proteins
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MATA2 protein, S cerevisiae
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Membrane Proteins
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Recombinant Fusion Proteins
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Repressor Proteins
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Saccharomyces cerevisiae Proteins
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Ubiquitins
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Green Fluorescent Proteins
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UBC6 protein, S cerevisiae
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UBE2J1 protein, human
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UBE2L3 protein, human
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Ubiquitin-Conjugating Enzymes
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Intramolecular Transferases
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DEG1 protein, S cerevisiae
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Ligases