Figure 4
From: Suppression of BRCA1 sensitizes cells to proteasome inhibitors
Suppression of 53BP1 inhibits apoptosis in BRCA1-depleted cells after bortezomib treatment. (a) FACS analysis of cell cycle distribution of HeLa cells transfected with siRNAs shown above and drug treatment marked on the right. Note that a combination of siBRCA1 and bortezomib treatments leads to a reduced proportion of cells at the G1 phase and increase at the G2/M phase, whereas a concomitant depletion of 53BP1 restores cell cycle distribution to the level of controls. The G2/M fraction is marked with a frame. (b) FACS analysis of HeLa cells stained for Annexin V. Annexin V-positive fraction is marked with brackets. Cells were transfected with siRNAs as indicated above and treated with bortezomib as shown on the right. Note that the Annexin V-positive fraction of BRCA1-depleted cells is increasing in a dose-dependent manner after bortezomib treatment, but greatly reduced upon depletion of 53BP1. (c) Western blot showing that knockdown of 53BP1 inhibits apoptosis in BRCA1-depleted cells after bortezomib treatment. The bar graph below shows quantification of cleaved PARP (cPARP) level normalized to the average of β-actin and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) protein levels. (d) Western blot showing inhibition of RB1 phosphorylation in siBRCA1 and bortezomib-treated cells after depletion of 53BP1
