The mouse gene that encodes the delta transcription factor has been cloned and characterized. This gene spans 23 kb and is composed of five exons and four introns. The first exon consists of a long (431 bp), (C+G)-rich, untranslated segment and a 679-bp coding segment, which specifies the unusual tracts of consecutive acidic residues and histidines and the long alanine-glycine stretches. The sequence that encodes the four zinc-finger motifs of this protein is interrupted by two introns. Nuclease protection experiments revealed a major transcriptional start point and several additional start points distributed over a 28-bp segment. Transfection experiments with 5' and 3' deletion mutants localized the promoter to a (C+G)-rich region that is < 700 bp upstream and no more than 32 bp downstream of the major start point. An especially critical promoter element lies between -58 and -18 and contains a high-affinity Sp1 binding site, as demonstrated by electrophoretic mobility-shift experiments with nuclear extract and recombinant Sp1 proteins. Several striking similarities between the delta gene and genes encoding other transcription factors and regulatory proteins are noted and discussed with respect to their possible biological significance.