title: USP7 counteracts SCFbetaTrCP- but not APCCdh1-mediated proteolysis of Claspin.
abstract: Claspin is an adaptor protein that facilitates the ataxia telangiectasia and Rad3-related (ATR)-mediated phosphorylation and activation of Chk1, a key effector kinase in the DNA damage response. Efficient termination of Chk1 signaling in mitosis and during checkpoint recovery requires SCF(betaTrCP)-dependent destruction of Claspin. Here, we identify the deubiquitylating enzyme ubiquitin-specific protease 7 (USP7) as a novel regulator of Claspin stability. Claspin and USP7 interact in vivo, and USP7 is required to maintain steady-state levels of Claspin. Furthermore, USP7-mediated deubiquitylation markedly prolongs the half-life of Claspin, which in turn increases the magnitude and duration of Chk1 phosphorylation in response to genotoxic stress. Finally, we find that in addition to the M phase-specific, SCF(betaTrCP)-mediated degradation, Claspin is destabilized by the anaphase-promoting complex (APC) and thus remains unstable in G1. Importantly, we demonstrate that USP7 specifically opposes the SCF(betaTrCP)- but not APC(Cdh1)-mediated degradation of Claspin. Thus, Claspin turnover is controlled by multiple ubiquitylation and deubiquitylation activities, which together provide a flexible means to regulate the ATR-Chk1 pathway.
authors.affiliation: Institute of Cancer Biology and Centre for Genotoxic Stress Research, Danish Cancer Society, DK-2100 Copenhagen, Denmark.
authors.forename: Helene
authors.initials: H
authors.lastname: Faustrup
authors.forename: Simon
authors.initials: S
authors.lastname: Bekker-Jensen
authors.forename: Jiri
authors.initials: J
authors.lastname: Bartek
authors.forename: Jiri
authors.initials: J
authors.lastname: Lukas
authors.forename: Niels
authors.initials: N
authors.lastname: Mailand
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D064173:Anaphase-Promoting Complex-Cyclosome; D002460:Cell Line; D000071877:Checkpoint Kinase 1; D004249:DNA Damage; D016193:G1 Phase; D006801:Humans; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism / Q000502:physiology*; D013379:Substrate Specificity; D043222:Ubiquitin Thiolesterase / Q000378:metabolism / Q000502:physiology*; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism / Q000502:physiology*; D000076084:Ubiquitin-Specific Peptidase 7; D054875:Ubiquitination / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C488158:CLSPN protein, human; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044843:SKP Cullin F-Box Protein Ligases; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C464569:USP7 protein, human; D043222:Ubiquitin Thiolesterase; D000076084:Ubiquitin-Specific Peptidase 7