INTERACTIONS OF DROSOPHILA ULTRABITHORAX REGULATORY REGIONS WITH NATIVE AND FOREIGN PROMOTERS

The Ultrabithorax (Ubx) gene of the Drosophila bithorax complex is req uired to specify parasegments 5 and 6. Two P-element ''enhancer traps' ' have been recovered within the locus that contain the bacterial lacZ gene under the control of the P-element promoter. The P insertion tha t is closer to the Ubx promoter expresses lacZ in a pattern similar to that of the normal Ubx gene, but also in parasegment 4 during embryon ic development. Two deletions have been recovered that remove the norm al Ubx promoter plus several kilobases on either side, but retain the lacZ reporter gene. The lacZ patterns from the deletion derivatives cl osely match the normal pattern of Ubx expression in late embryos and i maginal discs. The lacZ genes in the deletion derivatives are also neg atively regulated by Ubx and activated in trans by Contrabithorax muta tions, again like the normal Ubx gene. Thus, the deleted regions, incl uding several kilobases around the Ubx promoter, are not required for long range interactions with Ubx regulatory regions. The deletion deri vatives also stimulate transvection, a pairing-dependent interaction w ith the Ubx promoter on the homologous chromosome.