title: Claspin inhibition leads to fragile site expression.
abstract: Fragile sites are hot spots for sister chromatid exchanges, translocations, deletions, complex rearrangements, and gene amplification. It has been hypothesized that rearrangements at fragile sites derive from unreplicated regions resulting from stalled forks that escape the ATR replication checkpoint. In the present study, we investigated the role of the Claspin (CLSPN) gene, which codes for an adaptor protein in the ATR pathway, during DNA replication stress in human cells. We show that the inhibition of the CLSPN gene leads to both genome instability and fragile site expression. Following aphidicolin treatment, we found a transient increase of Claspin synthesis due to its requirement to checkpoint activation. However, Claspin synthesis decreased after a prolonged aphidicolin treatment. We propose that CLSPN modulation, following an extreme replication block, allows rare cells to escape checkpoint mechanisms and enter mitosis with a defect in genome assembly. Our observations provide the basis for a better understanding of cell cycle checkpoints deregulation in cancer.
authors.affiliation: Istituto di Tecnologie Biomediche, Consiglio Nazionale delle Ricerche, Segrate (Mi), Italy.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Focarelli
authors.forename: Samuela
authors.initials: S
authors.lastname: Soza
authors.forename: Linda
authors.initials: L
authors.lastname: Mannini
authors.forename: Marianna
authors.initials: M
authors.lastname: Paulis
authors.forename: Alessandra
authors.initials: A
authors.lastname: Montecucco
authors.forename: Antonio
authors.initials: A
authors.lastname: Musio
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors* / Q000235:genetics; D016590:Aphidicolin / Q000494:pharmacology; D015153:Blotting, Western; D002478:Cells, Cultured; D002869:Chromosome Aberrations; D043283:Chromosome Fragile Sites / Q000235:genetics*; D004261:DNA Replication; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008938:Mitosis
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C488158:CLSPN protein, human; D016590:Aphidicolin