DEFECTIVE INDUCTION OF STRESS-ACTIVATED PROTEIN-KINASE ACTIVITY IN ATAXIA-TELANGIECTASIA CELLS EXPOSED TO IONIZING-RADIATION

The activity of stress-activated protein (SAP) kinase is stimulated by diverse agents such as tumor necrosis factor, UV Light, and protein s ynthesis inhibitors. The present study demonstrates that ionizing radi ation (IR) exposure is also associated with the induction of SAP kinas e activity. Cells derived from patients with ataxia-telangiectasia (A- T) are characterized by hypersensitivity to IR. In this study, we demo nstrate that IR-induced activation of SAP kinase is defective in A-T c ells. In contrast, exposure of A-T cells to UV light or anisomycin res ults in the induction of SAP kinase activity. These findings indicate that IR-induced signals involved in SAP kinase activation are defectiv e in A-T cells.