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Insect Biochem Mol Biol. 2002 Feb;32(2):121-32.

Isolation and characterization of novel mutations of the Broad-Complex, a key regulatory gene of ecdysone induction in Drosophila melanogaster.

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Laboratoire de Biologie du Développement, Institut Jacques-Monod, CNRS, Université Paris, 7-Denis Diderot et Université Paris, 6-P et M Curie 75251, Paris Cedex 05, France.


Seven new alleles of the Broad-Complex gene of Drosophila melanogaster, which encodes a family of four zinc finger protein isoforms BR-C Z1, Z2, Z3 and Z4, were generated by transposase-induced mobilization of a P[Zw] element inserted in either the first intron downstream from the P165 promoter or the exon encoding the Z2-specific zinc finger domain. They were characterized by genetic complementation tests, molecular mapping and cytogenetic analysis of their effect on ecdysone-induced puffing and BR-C proteins binding to polytene chromosomes. Four mutations that correspond to three overlapping deletions and one tandem insertion of the P[Zw] element are located in the intron. They provide evidence that regulatory elements essential for a correct expression of the BR-C Z2 and BR-C Z3 transcripts are located within the intron downstream from the P165 promoter. Three mutations correspond to internal deletions of the locus and exhibit a complete loss of all BR-C(+) genetic functions in the complementation and cytogenetic tests. They thus provide well characterized new amorphic reference alleles of the BR-C gene. The precise cytogenetic location of more than 300 binding sites of BR-C proteins on larval salivary gland polytene chromosomes was determined by immunostaining using specific antibodies. Sites were found in big ecdysone inducible puffs, constitutively active small puffs as well as interbands. A complete list of the major sites on all four salivary gland polytene chromosomes of BR-C(+) larvae is presented.

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