BSAP represses PRDM1 through the binding site onto the exon 1. (A) Schematic representation showing the construction of reporter plasmids containing the putative minimal promoter of PRDM1 (pGL3-PRDM1) or with the mutated BSAP-binding site (pGL3-PRDM1-BSAPmut). (B) Daudi cells were transiently transfected with the pGL3-PRDM1 or pGL3-PRDM1-BSAPmut luciferase reporters. Relative luciferase activity was normalized to pGL3-PRDM1. Error bars represent SEM from at least 4 experiments. (C) HEK293 cells were transiently cotransfected with the pGL3-PRDM1 luciferase reporter and with the empty pIRES2-GFP or pBSAP-IRES2-GFP expression vectors. The relative luciferase activity from the empty pIRES2-GFP was used as 100%. Error bars represents SEM from at least 4 experiments. (D) A Western blot from cotransfected HEK293 cells (without endogenous BSAP expression) and Daudi cell as control of endogenous BSAP expression is shown. A total of 105 and 106 of HEK293 and Daudi cells per well were loaded, respectively.