title: Dual mode of degradation of Cdc25 A phosphatase.
abstract: The Cdc25 dual-specificity phosphatases control progression through the eukaryotic cell division cycle by activating cyclin-dependent kinases. Cdc25 A regulates entry into S-phase by dephosphorylating Cdk2, it cooperates with activated oncogenes in inducing transformation and is overexpressed in several human tumors. DNA damage or DNA replication blocks induce phosphorylation of Cdc25 A and its subsequent degradation via the ubiquitin-proteasome pathway. Here we have investigated the regulation of Cdc25 A in the cell cycle. We found that Cdc25 A degradation during mitotic exit and in early G(1) is mediated by the anaphase-promoting complex or cyclosome (APC/C)(Cdh1) ligase, and that a KEN-box motif in the N-terminus of the protein is required for its targeted degradation. Interestingly, the KEN-box mutated protein remains unstable in interphase and upon ionizing radiation exposure. Moreover, SCF (Skp1/Cullin/F-box) inactivation using an interfering Cul1 mutant accumulates and stabilizes Cdc25 A. The presence of Cul1 and Skp1 in Cdc25 A immunocomplexes suggests a direct involvement of SCF in Cdc25 A degradation during interphase. We propose that a dual mechanism of regulated degradation allows for fine tuning of Cdc25 A abundance in response to cell environment.
authors.affiliation: European Institute of Oncology, 435 Via Ripamonti, I-20141 Milan, Italy. mdonzell@ieo.it
authors.forename: Maddalena
authors.initials: M
authors.lastname: Donzelli
authors.forename: Massimo
authors.initials: M
authors.lastname: Squatrito
authors.forename: Dvora
authors.initials: D
authors.lastname: Ganoth
authors.forename: Avram
authors.initials: A
authors.lastname: Hershko
authors.forename: Michele
authors.initials: M
authors.lastname: Pagano
authors.forename: Giulio F
authors.initials: GF
authors.lastname: Draetta
mesh_terms: D020816:Amino Acid Motifs; D064173:Anaphase-Promoting Complex-Cyclosome; D064199:Cdc20 Proteins; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D008025:Ligases / Q000378:metabolism*; D046911:Macromolecular Substances; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin / Q000378:metabolism; D043743:Ubiquitin-Protein Ligase Complexes; D020687:cdc25 Phosphatases / Q000378:metabolism*
chemical_list: C577495:CDC20 protein, S cerevisiae; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; D046911:Macromolecular Substances; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; C517004:CDC25A protein, human; D020687:cdc25 Phosphatases; D008025:Ligases