Ig/EBP-1: a ubiquitously expressed immunoglobulin enhancer binding protein that is similar to C/EBP and heterodimerizes with C/EBP.

We report the isolation and characterization of cDNA clones that encode a protein with the same DNA binding specificity as the immunoglobulin heavy chain enhancer binding protein E (μEBP-E). We call the gene encoding this protein Ig/EBP-1. A fusion protein encoded by the cDNA binds specifically to μEBP-E-binding sites (E sites) in both the IgH enhancer and the V H 1 promoter. Sequence analysis reveals that Ig/EBP-1 is a member of the «basic-zipper» family of DNA-binding proteins that are characterized by basic regions and heptad repeats of leucine residues. Among known family members, Ig/EBP-1 demonstrates highest homology to C/EBP throughout the DNA-binding domain and leucine repeat region