Transcriptional activity of Ig reporter constructs.

(A) Transfection of Namalwa and Raji (positive control) and L1236 (HD cell line) with the wild-type promoter-driven luciferase reporters (μET1) and the mutant promoter-driven reporters (μET1m). (B) The same cell lines as in panel A were transfected for control with luciferase reporters containing the intact tk-promoter (tk.luc, −109 to +52) or a truncated version of this promoter (pTATA, −38 to +52). (C) Transfection of Namalwa, Raji, and L1236 cell lines with wild-type (4 × wt) or mutant (4 × mut) octamer-dependent Ig reporter constructs. (D) Schematic representation of the reporter constructs used. Wild-type octamer motifs in the Ig promoter or synthetic promoter are indicated as filled circles, mutant octamer motifs are shown as open circles. Details about the reporter constructs can be found in Laumen and colleagues12 (for μET1.luc and μET1m.luc) or Pfisterer and coworkers22 (for 4 × wt and 4 × mut). All transfections were independently repeated minimally 3 times and in all cases a tk-driven renilla-luciferase reporter was cotransfected to correct for differences in transfection efficiencies. Relative activity is shown and the cotransfections with empty expression vectors were arbitrarily set to 1.