Bortezomib transiently repressed the expression of HR genes at the transcriptional level. (A) MM cell lines were treated with 2.5nM bortezomib and harvested at the indicated times. FANCD2, RAD-51, BRCA1, and BRCA2 mRNA levels were determined by qRT-PCR. Data quantification was carried out by the 2^−ΔΔCt method. (B-C) MM1S cells transfected with a pSGG_prom vector (SwitchGear genomics) that contains an approximately 3-kb fragment of the human promoter for BRAC1, BRAC2, FANCD2, RAD51, or GAPDH (control) cloned into the MCS and fused to a luciferase reporter gene. Transfected cells were treated with a nonlethal dose(s) of bortezomib alone (B), the NF-κB inhibitor SN50 (C), or vehicle control (CNT) for 24 hours and then assayed for their luciferase activity. Signal was read out on a luminometer.