FIG. 3.

Identification of a DNA-binding species which interact solely with the E2F elements within the c-myb promoter. Complexes formed with X50-7 nuclear extracts and radiolabeled E2F elements from the DHFR (A) and c-myb (B) promoters were analyzed by EMSA. Reaction mixtures were preincubated in the absence (None) or in the presence of a 100-fold excess of the indicated unlabeled competitor oligonucleotides. Positions of complexes a to e are indicated. DHFRwt, c-myc, c-myb, and CDC2, oligonucleotides corresponding to the E2F sites within the DHFR, c-myc, c-myb, and cdc2 promoters, respectively; E2F1-A and E2F1-B, oligonucleotides corresponding to the two E2F sites found in the E2F1 promoter; DHFRmut, mutant DHFR probe.