FOXP1 binds in the proximity of the TSS of PRDM1, IRF4, and XBP1. (A) Tracks showing locations of FOXP1 ChIP-seq peaks in the proximity of the TSS of the PRDM1, IRF4, and XBP1 genes in OCI-Ly7 and 3 other DLBCL cell lines. Called peaks are indicated by black bars above the tracks. (B) ChIP with an antibody against FOXP1 in the DLBCL cell lines OCI-LY7, OCI-LY3, and OCI-LY10, followed by quantitative PCR for regions in the proximity of the PRDM1, XBP1, and IRF4 genes in which FOXP1 ChIP-seq peaks were observed in multiple cell lines (regions are indicated in panel A by red bars above the tracks). Hemoglobin beta (HBB) was taken along as a negative control region. Means ± SEM of at least 3 independent experiments are shown. For all sites analyzed, significant differences were observed between FOXP1 and IgG immunoprecipitation (IP). Significant differences for FOXP1 binding between a specific region and the control region (HBB) are indicated (t test, *P < .05; **P < .01). Primers are listed in supplemental Table 1. (C) A luciferase-reporter construct driven by the PRDM1 promoter was cotransfected in HEK293T cells with a renilla expression vector and increasing (left) or fixed amounts (right) of a FOXP1 expressing vector (FOXP1), or with the empty control vector (ctrl). Values were corrected for renilla luminescence (transfection efficiency) and normalized to expression in control-transduced cells. Means ± SD of a representative experiment of 2 independent experiments performed in triplicate (left), or the means ± SEM of 5 independent experiments (right), are shown.