title: Polo-like kinase-1 controls proteasome-dependent degradation of Claspin during checkpoint recovery.
abstract: DNA-damage checkpoints maintain genomic integrity by mediating a cell-cycle delay in response to genotoxic stress or stalled replication forks. In response to damage, the checkpoint kinase ATR phosphorylates and activates its effector kinase Chk1 in a process that critically depends on Claspin . However, it is not known how exactly this kinase cascade is silenced. Here we demonstrate that the abundance of Claspin is regulated through proteasomal degradation. In response to DNA damage, Claspin is transiently stabilized, and its expression depends on Chk1 kinase activity. In addition, we show that Claspin is degraded upon mitotic entry, a process that depends on the beta-TrCP-SCF ubiquitin ligase and Polo-like kinase-1 (Plk1). We demonstrate that Claspin interacts with both beta-TrCP and Plk1 and that inactivation of these components or the beta-TrCP recognition motif in Claspin prevents its mitotic degradation. Interestingly, expression of a nondegradable Claspin mutant inhibits recovery from a DNA-damage-induced checkpoint arrest. Thus, we conclude that Claspin levels are tightly regulated, both during unperturbed cell cycles and after DNA damage. Moreover, our data demonstrate that the degradation of Claspin at the onset of mitosis is an essential step for the recovery of a cell from a DNA-damage-induced cell-cycle arrest.
authors.affiliation: Unidad de Investigación, Hospital Universitario de Canarias, Ofra s/n, La Cuesta, 38320 Tenerife, Spain.
authors.forename: Ivan
authors.initials: I
authors.lastname: Mamely
authors.forename: Marcel Atm
authors.initials: MA
authors.lastname: van Vugt
authors.forename: Veronique A J
authors.initials: VA
authors.lastname: Smits
authors.forename: Jennifer I
authors.initials: JI
authors.lastname: Semple
authors.forename: Bennie
authors.initials: B
authors.lastname: Lemmens
authors.forename: Anastassis
authors.initials: A
authors.lastname: Perrakis
authors.forename: René H
authors.initials: RH
authors.lastname: Medema
authors.forename: Raimundo
authors.initials: R
authors.lastname: Freire
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D000071877:Checkpoint Kinase 1; D004249:DNA Damage; D006801:Humans; D009154:Mutation; D046988:Proteasome Endopeptidase Complex / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D044844:beta-Transducin Repeat-Containing Proteins / Q000378:metabolism; D000097869:Polo-Like Kinase 1
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D000071877:Checkpoint Kinase 1; D046988:Proteasome Endopeptidase Complex; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D044844:beta-Transducin Repeat-Containing Proteins; D000097869:Polo-Like Kinase 1; C488158:CLSPN protein, human; C576597:ATR protein, human; C000605867:CHEK1 protein, human