Figure 1

Proteasome inhibitors inhibit the growth of BRCA1- but not BRCA2-deficient cells. (a) Knockdown of BRCA1, but not BRCA2, sensitizes MDA-MB-231 (left), HeLa (middle) and U2OS (right) cells to a proteasome inhibitor bortezomib. Cell viability was measured in 96-well plates using CellTitre-Blue reagent to detect viable cells after 4 days of incubation with indicated doses of bortezomib. All treatments were performed in four replicas (N=4). (b) Same as (a) with two independent siRNAs for BRCA1 and BRCA2 in HeLa cells; N=4. (c) Western blot showing that the level of cleaved PARP (cPARP) correlates with efficiency of BRCA1 depletion at the mRNA level (d) and cell viability (b). (d) qRT-PCR demonstrating the efficiency of BRCA1 knockdown for two siRNAs in HeLa cells. (e) Experimental scheme for inducing genetic deletion of Brca1 in mouse ES cells. (f) Loss of murine Brca1 (mBrca1) sensitizes mouse ES cells to bortezomib, which is rescued by the expression of human BRCA1 (hBRCA1); N=3. (g) Western blot demonstrating siRNA-mediated knockdown of BRCA1/2 and induction of apoptosis measured by the amount of cPARP in HeLa cells treated with indicated doses of bortezomib for 20 h. (h) Similar to BRCA1, depletion of BARD1 (siBARD1), but not RNF8 (siRNF8), sensitizes HeLa cells to bortezomib; N=2. Error bars in (a, b, d, f, and h) indicate S.D. RNAiMAX, effect of the Lipofectamine RNAiMAX reagent on the expression of BRCA1; siBRCA1, siRNAs targeting BRCA1; siControl, non-targeting negative control siRNA