title: Loss of FANCC function is associated with failure to inhibit late firing replication origins after DNA cross-linking.
abstract: Fanconi anemia (FA) cells are abnormally sensitive to DNA cross-linking agents with increased levels of apoptosis and chromosomal instability. Defects in eight FA complementation groups inhibit monoubiquitination of FANCD2, and subsequent recruitment of FANCD2 to DNA damage and S-phase-associated nuclear foci. The specific functional defect in repair or response to DNA damage in FA cells remains unknown. Damage-resistant DNA synthesis is present 2.5-5 h after cross-linker treatment of FANCC, FANCA and FANCD2-deficient cells. Analysis of the size distribution of labeled DNA replication strands revealed that diepoxybutane treatment suppressed labeling of early but not late-firing replicons in FANCC-deficient cells. In contrast, normal responses to ionizing radiation were observed in FANCC-deficient cells. Absence of this late S-phase response in FANCC-deficient cells leads to activation of secondary checkpoint responses.
authors.affiliation: Molecular and Cellular Biology Program, Fred Hutchinson Cancer Research Center and University of Washington, Seattle, WA, USA.
authors.forename: Randall A
authors.initials: RA
authors.lastname: Phelps
authors.forename: Helene
authors.initials: H
authors.lastname: Gingras
authors.forename: David M
authors.initials: DM
authors.lastname: Hockenbery
mesh_terms: D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D003432:Cross-Linking Reagents / Q000633:toxicity*; D004247:DNA / Q000187:drug effects; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair / Q000235:genetics; D004261:DNA Replication / Q000235:genetics*; D004852:Epoxy Compounds / Q000633:toxicity; D005199:Fanconi Anemia / Q000235:genetics*; D052217:Fanconi Anemia Complementation Group A Protein / Q000235:genetics / Q000502:physiology; D052218:Fanconi Anemia Complementation Group C Protein / Q000235:genetics / Q000502:physiology*; D052236:Fanconi Anemia Complementation Group D2 Protein / Q000235:genetics / Q000502:physiology; D006801:Humans; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000502:physiology; D018741:Replication Origin / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology; D016196:S Phase / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D003432:Cross-Linking Reagents; C068651:E6 protein, Human papillomavirus type 16; D004852:Epoxy Compounds; D052217:Fanconi Anemia Complementation Group A Protein; D052218:Fanconi Anemia Complementation Group C Protein; D052236:Fanconi Anemia Complementation Group D2 Protein; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; C007366:diepoxybutane; D004247:DNA