Rad9, Rad17, TopBP1 and Claspin Play Essential Roles in Heat-Induced Activation of ATR Kinase and Heat Tolerance
Figure 5
Caffeine suppressed heat-induced phosphorylation at Chk1 Ser345 and Chk2 Thr68 and enhanced heat cytotoxicity.
A. Western blot. HeLa cells were cultured at 42.5°C for 1 hour in the presence or absence of 12 mM caffeine. RI: relative intensity compared to the sample of 42.5°C for 60 minutes. B. Clonogenic survival of heat-treated HeLa cells in the presence or absence of 12 mM caffeine. C. Apoptosis. HeLa cells were cultured at 42.5°C for 2 hours and at 37°C for 12 hours in the presence or absence of 12 mM caffeine. *p = 0.0019 (Student's t test). D. Clonogenic survival of WT DT40 cells cultured at 45°C for the indicated time in the presence or absence of 2 mM caffeine. E. Apoptosis. WT DT40 cells were cultured at 45°C for 60 minutes and at 39.5°C for 60 minutes in the presence or absence of 2 mM caffeine. *p = 0.0014 (Student's t test).