Abstract
Cullin-4 forms a scaffold for multiple ubiquitin ligases. In Schizosaccharomyces pombe, the Cullin-4 homologue (Pcu4) physically associates with Ddb1 and the COP9 signalosome (CSN). One target of this complex is Spd1. Spd1 regulates ribonucleotide reductase (RNR) activity. Spd1 degradation during S phase, or following DNA damage of G2 cells, results in the nuclear export of the small RNR subunit. We demonstrate that Cdt2, an unstable WD40 protein, is a regulatory subunit of Pcu4-Ddb1-CSN ubiquitin ligase. cdt2 deletion stabilises Spd1 and prevents relocalisation of the small RNR subunit from the nucleus to the cytoplasm. cdt2+ is periodically transcribed by the Cdc10/DSC1 transcription factor during S phase and transiently transcribed following DNA damage of G2 cells, corresponding to Spd1 degradation profiles. Cdt2 co-precipitates with Spd1, and Cdt2 overexpression results in constitutive Spd1 degradation. We propose that Cdt2 incorporation into the Pcu4-Ddb1-CSN complex prompts Spd1 targeting and subsequent degradation and that Cdt2 is a WD40 repeat adaptor protein for Cullin-4-based ubiquitin ligase.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing / genetics
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Adaptor Proteins, Signal Transducing / metabolism*
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COP9 Signalosome Complex
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Cell Cycle / physiology
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism*
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Cullin Proteins / genetics
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Cullin Proteins / metabolism
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DNA Damage
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Enzyme Activation
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Humans
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Multiprotein Complexes / genetics
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Multiprotein Complexes / metabolism*
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Peptide Hydrolases / genetics
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Peptide Hydrolases / metabolism*
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Protein Subunits / genetics
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Protein Subunits / metabolism
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Schizosaccharomyces / genetics
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Schizosaccharomyces / physiology
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Schizosaccharomyces pombe Proteins / genetics
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Schizosaccharomyces pombe Proteins / metabolism*
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Transcription, Genetic
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Transcriptional Activation*
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Ubiquitin-Protein Ligase Complexes / genetics
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Ubiquitin-Protein Ligase Complexes / metabolism*
Substances
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Adaptor Proteins, Signal Transducing
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Cdt2 protein, S pombe
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Cell Cycle Proteins
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Cullin Proteins
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DNA-Binding Proteins
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Ddb1 protein, S pombe
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Multiprotein Complexes
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Protein Subunits
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Schizosaccharomyces pombe Proteins
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Spd1 protein, S pombe
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Ubiquitin-Protein Ligase Complexes
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Peptide Hydrolases
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COP9 Signalosome Complex