To explore transcriptional regulation in B cells at a global scale, we combined transcriptional reporters with CRISPR-Cas9 genomic screening in the DLBCL line SU-DHL-4.11 To optimize the experimental approach, we first labeled the B cell transcriptional coactivator OCAB with an mOrange-P2A (mO) reporter (Figure 1A). Here, POU2AF1 is linked to diffuse large B-cell lymphoma.