The G2-phase decatenation checkpoint is defective in Werner syndrome cells.
It has been proposed that cells monitor chromatid catenation status after DNA replication and inhibit progression into mitosis until chromatids are correctly decatenated by topoisomerase II (TopoII). Studies in yeast have suggested that TopoII may interact with RecQ helicases during this process. Using ICRF187, a TopoII catalytic inhibitor that prevents chromatid decatenation without producing DNA strand breaks, we demonstrated that cells deficient of WRN, a human RecQ helicase, displayed a defect in decatenation checkpoint activation, which was corrected by ectopic expression of wild-type WRN. We also provide evidence that BRCA1 is phosphorylated in an ATR-dependent manner in response to decatenation checkpoint activation and that this phosphorylation is not detectable in Werner syndrome cells. Furthermore, ICRF187 treatment resulted in coimmunoprecipitation of WRN and TopoII. Finally, we demonstrated that override of the decatenation checkpoint resulted in enhanced chromosomal damage and apoptosis only in the absence of WRN, but not in normal cells. Our findings suggest that WRN plays a role in the activation of G(2) decatenation checkpoint and that the abortive function of this pathway itself does not appear to be sufficient to cause genomic instability but rather predisposes to genomic instability and apoptotic cell death in the absence of other "caretaker" genes, such as WRN.
Franchitto
Annapaola
A
CNRS UPR2169 Instabilité Génétique et Cancer, Institut Gustave Roussy, 94805 Villejuif, France. franchitto@igr.fr
Oshima
Junko
J
Pichierri
Pietro
P
D017209:Apoptosis; D019313:BRCA1 Protein / Q000378:metabolism; D002478:Cells, Cultured / Q000166:cytology / Q000201:enzymology; D004249:DNA Damage; D004265:DNA Helicases / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D005090:Exodeoxyribonucleases; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D016195:G2 Phase / Q000235:genetics / Q000502:physiology*; D018816:Genes, cdc; D006801:Humans; D009154:Mutation; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011929:Razoxane / Q000494:pharmacology; D053484:RecQ Helicases; D059005:Topoisomerase II Inhibitors; D014898:Werner Syndrome / Q000201:enzymology / Q000473:pathology*; D000071657:Werner Syndrome Helicase
D019313:BRCA1 Protein; D059005:Topoisomerase II Inhibitors; D011929:Razoxane; D005090:Exodeoxyribonucleases; D004265:DNA Helicases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase