A screening assay for the detection of NF-kappaB-dependent gene induction using the destabilized variant of the reporter protein enhanced green fluorescent protein (d2EGFP) is used for assessing the biological effects of accelerated heavy ions as a model of space environmental radiation conditions. The time course of d2EGFP expression and therefore of activation of NF-kappaB-dependent gene expression was measured after treatment with TNFA or after heavy-ion exposure using flow cytometry. The reported experiments clearly show that accelerated argon ions (95 MeV/nucleon, LET 230 keV/microm) induce the NF-kappaB pathway at low particle densities (1-2 particle hits per nucleus), which result in as few as 5-50 induced DSBs per cell.