In vitro binding of BCL6 to the BSE1 motifs.

(A) Sequence of the BCL6 exon 1 region in which the 4 deregulating mutations (in bold, underlined) were mapped. The corresponding murine sequence is also aligned to show the complete sequence identity between the 2 species. Boxed areas represent the 2 BCL6 binding motifs (BSE1A and BSE1B). Nonderegulating mutations are shown in gray. (B) BCL6 deregulating mutations abolish binding of BCL6 to its exon 1 sequences in vitro. EMSA was performed on Ly1 nuclear extracts using as probes the indicated oligonucleotides. The B6BS probe containing the BCL6 canonical binding site was used as a control.8 Arrows point to BCL6-containing complexes. Supershift analysis was performed using an anti-BCL6 (N71-1) antiserum that recognizes the N-terminus of the BCL6 protein.