EMSA comparing nuclear extracts from B lymphocytes and PC lines for specific binding to exon 1 of the human PRDM1 gene. (A) Schematic representation of the fragment used as probe and the competitive fragments for EMSA. A fragment corresponding to the entire exon 1 (+ 1/+ 104) was used as probe. Three cold fragments, divisions of exon 1 (+ 1/+ 27), (+ 28/+ 59), (+ 60/+ 104), were used for competition experiments. (B) EMSA with probe (+ 1/+ 104) and nuclear extracts from human PC lines: U266 (myeloma), NCI-H929 (myeloma), RPMI-8226 (myeloma); from human B-cell lines: Daudi (Burkitt lymphoma), Raji (Burkitt lymphoma), Ramos (Burkitt lymphoma), NALM-6 (pre-B-cell leukemia); or from the epithelial cell line: HEp-2 (laryngeal carcinoma). Lane marked as free probe was nuclear-extract–free. (C) Competition experiments using the probe (+ 1/+ 104) and Daudi nuclear extracts. (Lane 1) Probe-free. (Lanes 2,3) Probe with nuclear extract without and with Zn⁺⁺ (0.5 mM) in the binding buffer, respectively. Competition assays with the corresponding cold fragments (100 ×) are shown: (lane 4) + 1/+ 27; (lane 5) + 28/+ 59; and (lane 6) + 60/+ 104.