ETO and Bcl-6 form a complex while bound to DNA. (A) EMSA of nuclear extract prepared from 293T cells cotransfected with myc-Bcl-6 and HA-ETO or by the corresponding empty vectors. Three micrograms nuclear extract was incubated with radiolabeled double-stranded Bcl-6 binding-site oligonucleotide (B6BS) or with the cyclin D2 oligonucleotides that contained the Bcl-6 consensus binding site. Lanes 1 and 16, free probe; lanes 2 and 15, empty vector; lanes 3 to 8 and 9 to 14, Bcl-6–ETO-DNA complex; lanes 4 and 10, 100 × wild-type unlabeled cold probe; lanes 5 and 11, 100 × mutated cold probe; lanes 6 and 12, 2 μg rabbit Bcl-6 antibody C19; lanes 7 and 13, 2 μg rabbit ETO antibody Ab1; lanes 8 and 14, 2 μg rabbit IgG.