Fig. 3. Grp/DChk1 is phosphorylated in S2 cells in response to HU or IR. Western-blot analysis of Grp/DChk1 of S2 cells treated with 10 mM HU during 15 hours or with 150 Gy IR followed by 2 hours recovery. Grp/DChk1 was detected as a slower migrating protein in S2 cells treated with HU (A, lane 2) or treated with IR (B, lane 2) compared with untreated S2 cells (A,B, lanes 1,3). A shift in mobility of Grp/DChk1 was not detected in S2 cells treated with HU or IR and calf-intestine alkaline phosphatase (CIP; A,B, lane 4). In both A and B, CP190 protein levels were detected as a loading control.