title: Caffeine stabilizes Cdc25 independently of Rad3 in Schizosaccharomyces pombe contributing to checkpoint override.
abstract: Cdc25 is required for Cdc2 dephosphorylation and is thus essential for cell cycle progression. Checkpoint activation requires dual inhibition of Cdc25 and Cdc2 in a Rad3-dependent manner. Caffeine is believed to override activation of the replication and DNA damage checkpoints by inhibiting Rad3-related proteins in both Schizosaccharomyces pombe and mammalian cells. In this study, we have investigated the impact of caffeine on Cdc25 stability, cell cycle progression and checkpoint override. Caffeine induced Cdc25 accumulation in S. pombe independently of Rad3. Caffeine delayed cell cycle progression under normal conditions but advanced mitosis in cells treated with replication inhibitors and DNA-damaging agents. In the absence of Cdc25, caffeine inhibited cell cycle progression even in the presence of hydroxyurea or phleomycin. Caffeine induces Cdc25 accumulation in S. pombe by suppressing its degradation independently of Rad3. The induction of Cdc25 accumulation was not associated with accelerated progression through mitosis, but rather with delayed progression through cytokinesis. Caffeine-induced Cdc25 accumulation appears to underlie its ability to override cell cycle checkpoints. The impact of Cdc25 accumulation on cell cycle progression is attenuated by Srk1 and Mad2. Together our findings suggest that caffeine overrides checkpoint enforcement by inducing the inappropriate nuclear localization of Cdc25.
authors.affiliation: Department of Chemistry and Molecular Biology, Lundberg Laboratory, University of Gothenburg, Box 462, SE-405 30, Göteborg, Sweden.
authors.forename: John P
authors.initials: JP
authors.lastname: Alao
authors.forename: Johanna J
authors.initials: JJ
authors.lastname: Sjölander
authors.forename: Juliane
authors.initials: J
authors.lastname: Baar
authors.forename: Nejla
authors.initials: N
authors.lastname: Özbaki-Yagan
authors.forename: Bianca
authors.initials: B
authors.lastname: Kakoschky
authors.forename: Per
authors.initials: P
authors.lastname: Sunnerhagen
mesh_terms: D002110:Caffeine / Q000378:metabolism*; D002453:Cell Cycle; D064447:Checkpoint Kinase 2 / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D055550:Protein Stability / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D012568:Schizosaccharomyces / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism*
chemical_list: D029702:Schizosaccharomyces pombe Proteins; D002110:Caffeine; D064447:Checkpoint Kinase 2; C456840:rad3 protein, S pombe; C570820:Cdc25 protein, S pombe; D010749:Phosphoprotein Phosphatases