IG S-GAMMA-SPECIFIC DNA-BINDING PROTEIN SNAP IS RELATED TO THE HELIX-LOOP-HELIX TRANSCRIPTION FACTOR E47

SNAP, a DNA-binding protein, is specific for the S-gamma switch region s, Two E-2 box consensus binding motifs are located within the SNAP re cognition site, Direct- and competition-binding analyses demonstrate t hat a truncated form of the E47 transcription factor, E47S, is capable of specific interactions with the SNAP binding motif. The methylation interference pattern for E47S binding on the pl.S(gamma)3.A.1 probe w as similar to that previously obtained for SNAP binding activity and w as also related to that found for E47S on the mu E5 probe, The interac tion of purified E47S with the SNAP recognition motif was cooperative and formed complexes which migrated more slowly than the E47S homodime r complex. SNAP is distinguished from full-length E47 homodimers, foun d in BCF-1, by its migration position in the gel shift assay, differen ces in the competition-binding results and its unique reactivity with anti-E47 antibodies, SNAP is related to E47 as judged by a similar met hylation interference pattern on S(gamma)3 A site DNA and by its react ivity with anti-E47 mAb, The anti-E47 antibodies block SNAP binding to its cognate site, whereas anti-E47 antibodies supershift E47 homodime rs bound to the mu E5 recognition site, Thus, SNAP may be a heteroolig omeric species containing E47 or highly related proteins.