(A) Rescue of the impact of miRNAs on ABT888 sensitivity. MDAMB231 cells were transfected with control miRNA or indicated miRNA mimics with or without target gene cDNAs (lacking MREs) and treated with vehicle or ABT888, before viability assay by ATP quantification. Expression of each target protein is examined by immune blot. (B and C) Expression of miRNAs and target transcripts in synchronized cells. MDAMB231 (B) or MCF10A (C) cells were synchronized with mimosine and the relative amount of miR-1255b, miR-193b*, and miR-148b* or BRCA1, BRCA2, and RAD51 mRNA for G1- or S-phase was determined by qRT-PCR (normalized to RNU1 or GAPDH, respectively). Mean ± SD of three independent experiments is shown and statistical significance is indicated by *(p<0.05). (D–F) Impact of inhibiting miRNAs on targets in G1 cells. MDAMB231 cells were transfected with control ANT or ANTs for miR-1255b, miR-193b*, and miR-148b* as a single (D) or a combination (F). Subsequently, the cells were synchronized with mimosine and BRCA1, BRCA2, and RAD51 mRNA was assessed by qRT-PCR (normalized to GAPDH) in the G1 and/or S-phase (D and F). Cell lysates from G1 cells were analyzed by immunblot for BRCA1, BRCA2, and RAD51 (E). Images were quantified by ImageJ software and the mean ± SD of three independent experiments is shown, * indicates p<0.05.