Oct1, Oct2, and BOB.1 transcription factors interact with the octamer motifs in Ig regulatory elements of immunoglobulin-producing Burkitt lymphoma cell lines. (A) Maps of the IgH and histone H2B showing the location of primers used for ChIP analysis. Oct indicates octamer motif; CDR3, complementarity determining region 3; intE, internal enhancer; and LCR, locus control region. Primer locations are depicted by arrows. (B) Binding of Oct1, Oct2, and BOB.1/OBF.1 to IgH regulatory regions of B-JAB and Namalwa cell lines was detected by chromatin immunoprecipitation (ChIP) assays. Primers specific for the histone H2B promoter were used as positive control. Negative controls were chromatin immunoprecipitated with anti-PLC-γ1 antibody as well as samples to which no antibody was added (No Ab). DNA purified from the lysates incubated without antibody was used as input control (Input). Amplification products were detected by ethidium bromide staining on agarose gel. All experiments were performed at least in triplicate. prom indicates promoter; and Int Enh, internal enhancer.