title: DNA cross-linker-induced G2/M arrest in group C Fanconi anemia lymphoblasts reflects normal checkpoint function.
abstract: Cells from individuals with Fanconi anemia (FA) arrest excessively in the G2/M cell cycle compartment after exposure to low doses of DNA cross-linking agents. The relationship of this abnormality to the fundamental genetic defect in such cells is unknown, but many investigators have speculated that the various FA genes directly regulate cell cycle checkpoints. We tested the hypothesis that the protein encoded by the FA group C complementing gene (FAC) functions to control a cell cycle checkpoint and that cells from group C patients (FA[C]) have abnormalities of cell cycle regulation directly related to the genetic mutation. We found that retroviral transduction of FA(C) lymphoblasts with wild-type FAC cDNA resulted in normalization of the cell cycle response to low-dose mitomycin C (MMC). However, when DNA damage was quantified in terms of cytogenetic damage or cellular cytotoxicity, we found similar degrees of G2/M arrest in response to equitoxic amounts of MMC in FA(C) cells as well as in normal lymphoblasts. Similar results were obtained using isogenic pairs of uncorrected, FAC- or mock-corrected (neo only) FA(C) cell lines. To test the function of other checkpoints we examined the effects of hydroxyurea (HU) and ionizing radiation on cell cycle kinetics of FA(C) and normal lymphoblasts as well as with isogenic pairs of uncorrected, FAC-corrected, or mock-corrected FA(C) cell lines. In all cases the cell cycle response of FA(C) and normal lymphoblasts to these two agents were identical. Based on these studies we conclude that the aberrant G2/M arrest that typifies the response of FA(C) cells to low doses of cross-linking agents does not represent an abnormal cell cycle response but instead represents a normal cellular response to the excessive DNA damage that results in FA(C) cells following exposure to low doses of cross-linking agents.
authors.affiliation: Division of Hematology and Medical Oncology, Department of Medicine, Oregon Health Sciences University, Portland, OR, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Heinrich
authors.forename: M E
authors.initials: ME
authors.lastname: Hoatlin
authors.forename: A J
authors.initials: AJ
authors.lastname: Zigler
authors.forename: K V
authors.initials: KV
authors.lastname: Silvey
authors.forename: A C
authors.initials: AC
authors.lastname: Bakke
authors.forename: W W
authors.initials: WW
authors.lastname: Keeble
authors.forename: Y
authors.initials: Y
authors.lastname: Zhi
authors.forename: C A
authors.initials: CA
authors.lastname: Reifsteck
authors.forename: M
authors.initials: M
authors.lastname: Grompe
authors.forename: M G
authors.initials: MG
authors.lastname: Brown
authors.forename: R E
authors.initials: RE
authors.lastname: Magenis
authors.forename: S B
authors.initials: SB
authors.lastname: Olson
authors.forename: G C
authors.initials: GC
authors.lastname: Bagby
mesh_terms: D002110:Caffeine / Q000494:pharmacology*; D002461:Cell Line, Transformed; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004247:DNA / Q000187:drug effects* / Q000528:radiation effects; D004249:DNA Damage / Q000187:drug effects* / Q000528:radiation effects; D018076:DNA, Complementary / Q000235:genetics; D005199:Fanconi Anemia / Q000235:genetics / Q000473:pathology*; D016195:G2 Phase / Q000187:drug effects* / Q000528:radiation effects; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology*; D008214:Lymphocytes / Q000187:drug effects* / Q000473:pathology / Q000528:radiation effects; D008677:Metaphase / Q000187:drug effects* / Q000528:radiation effects; D016685:Mitomycin / Q000494:pharmacology*; D014162:Transfection
chemical_list: D003432:Cross-Linking Reagents; D018076:DNA, Complementary; D002110:Caffeine; D016685:Mitomycin; D004247:DNA; D006918:Hydroxyurea