title: Correlations between radiation-induced double strand breaks and cell cycle checkpoints in X-irradiated NIH/3T3 fibroblasts.
abstract: BACKGROUND
  To better understand the relationship between the formation of radiation-induced DNA double strand breaks (DSB) and cell cycle checkpoint activation, studies were conducted in the NIH/3T3 fibroblast cell line in order to establish correlations between the temporal appearance of gamma-H2AX foci (a DSB) and the expression of the cell cycle regulatory proteins, the cyclins, and their cyclin kinase inhibitor, p21.
  
  
  METHODS
  Immunocytochemistry was used to determine the expression of cyclin E, A, B1, p21, and the generation of DSB in NIH/3T3 cells exposed to 2 or 4 Gy X-irradiation.
  
  
  CONCLUSIONS
  The data suggest that the G1/S- and S-phase delay (cyclin E and cyclin A protein levels) are dependent on the dose of radiation while the G2/M (cyclin B1 protein levels) delay is dependent on the quantity of DSB sustained by the irradiated cell.
authors.affiliation: Department of Physics, East Carolina University, Greenville, North Carolina, USA. cariveau@sri.org
authors.forename: Mickael J
authors.initials: MJ
authors.lastname: Cariveaua
authors.forename: Gerhard W
authors.initials: GW
authors.lastname: Kalmus
authors.forename: Roberta M
authors.initials: RM
authors.lastname: Johnke
authors.forename: Ron R
authors.initials: RR
authors.lastname: Allison
authors.forename: Mark
authors.initials: M
authors.lastname: Evans
authors.forename: Donald
authors.initials: D
authors.lastname: Holbert
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000528:radiation effects*; D019925:Cyclin A / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D019927:Cyclin E / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004249:DNA Damage / Q000528:radiation effects*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D006657:Histones / Q000378:metabolism; D007124:Immunoenzyme Techniques; D051379:Mice; D041681:NIH 3T3 Cells; D014965:X-Rays
chemical_list: C534699:CCNB1 protein, human; C534700:Ccnb1 protein, mouse; D019925:Cyclin A; D019926:Cyclin B; D056744:Cyclin B1; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; C468783:H2AX protein, human; D006657:Histones