Abstract

The Broad-Complex (BR-C) is essential for metamorphosis in Drosophila melanogaster. This locus is coextensive with the 2B5 ecdysone-responsive early puff and is necessary for puffing and transcription of many subsequently activated late genes in the developing salivary gland. Mapping of 31 cDNA clones indicates that approximately 100 kb of the genome is devoted to the synthesis of many BR-C RNAs. Sequence analyses of these cDNA clones show that the BR-C encodes a family of related proteins characterized by a common core amino-terminal domain fused to alternate carboxy domains each containing a pair of zinc fingers. Most proteins also contain domains rich in distinctive amino acids located between the common core and zinc finger regions. BR-C mutant alleles resulting from chromosomal rearrangements at 2B5 are associated with deletions of 5'-untranslated sequences, separation of the core coding domain from the downstream zinc finger domains, or a P element insertional disruption of a zinc finger coding sequence. We infer that the BR-C directly regulates late gene expression by specifying the synthesis of a family of proteins with DNA binding potential.