GROWTH-STATE-DEPENDENT RADIATION-INDUCED EXPRESSION OF THE PROTOONCOGENE C-FOS IN NIH 3T3 CELLS

Expression of the proto-oncogene c-fos in response to ionizing radiati on has been observed in some but not all cell lines tested. Here we re port on delayed, transient c-fos expression in NIH 3T3 cells induced b y Co-60 gamma rays in the dose range 2-5 Gy, Induction of c-fos was si gnificantly increased in cells irradiated in the density-arrested quie scent state compared to irradiation in the exponential growth phase, T he enhancement correlated with the transition to quiescence as measure d by the proliferation markers, proliferating cell nuclear antigen and bromodeoxyuridine. The observation of growth-state-dependent expressi on of c-fos after irradiation might indicate a functional relationship between c-fos and growth control in the DNA damage response, e.g. a p otential role of c-fos in the control of replicative proteins. (C) 199 6 by Radiation Research Society