p300/CBP knockdown desensitizes cells to C107, and TSA pretreatment sensitizes cells to C107. A) Cos7 cells stably expressing p300/CBP shRNA or empty vector control (as described in Figure 2) were transfected with Histac, followed by imaging and treatment with 20 μM C107 at time zero (p < 0.05 after 25 min for p300 shRNA and CBP shRNA versus empty vector). B) Wild-type Cos7 cells transfected with Histac were pretreated with 1 μM TSA or ethanol control for 1 h, followed by imaging and treatment with 20 μM C107 or DMSO control at time zero, with TSA or ethanol remaining throughout (p < 0.05 after 30 min for C107 treatment of TSA pretreated versus EtOH pretreated). C) Cos7 cells stably expressing p300/CBP shRNA or empty vector control, transfected with Histac, were pretreated with 1 μM TSA for 1 h, followed by imaging and treatment with 20 μM C107 at time zero. D) Cos7 cells stably expressing p300/CBP shRNA or empty vector control were transfected with Histac, followed by imaging and treatment with 1 μM TSA at time zero.