title: Transactivation of Schizosaccharomyces pombe cdt2+ stimulates a Pcu4-Ddb1-CSN ubiquitin ligase.
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.
authors.affiliation: Genome Damage and Stability Centre, University of Sussex, Brighton, UK.
authors.forename: Cong
authors.initials: C
authors.lastname: Liu
authors.forename: Marius
authors.initials: M
authors.lastname: Poitelea
authors.forename: Adam
authors.initials: A
authors.lastname: Watson
authors.forename: Shu-hei
authors.initials: SH
authors.lastname: Yoshida
authors.forename: Chikashi
authors.initials: C
authors.lastname: Shimoda
authors.forename: Christian
authors.initials: C
authors.lastname: Holmberg
authors.forename: Olaf
authors.initials: O
authors.lastname: Nielsen
authors.forename: Antony M
authors.initials: AM
authors.lastname: Carr
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000075686:COP9 Signalosome Complex; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics / Q000502:physiology; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C506543:Cdt2 protein, S pombe; D018797:Cell Cycle Proteins; D044842:Cullin Proteins; D004268:DNA-Binding Proteins; C500125:Ddb1 protein, S pombe; D046912:Multiprotein Complexes; D021122:Protein Subunits; D029702:Schizosaccharomyces pombe Proteins; C102445:Spd1 protein, S pombe; D043743:Ubiquitin-Protein Ligase Complexes; D010447:Peptide Hydrolases; D000075686:COP9 Signalosome Complex