A HOMEODOMAIN POINT MUTATION OF THE DROSOPHILA-PROBOSCIPEDIA PROTEIN PROVOKES EYE LOSS INDEPENDENTLY OF HOMEOTIC FUNCTION

The Drosophila homeotic gene proboscipedia (pb: HoxA2/B2 homolog) is r equired for adult mouthparts development. Ectopic PB protein expressio n from a transgenic Hsp70-pb minigene (HSPB) results in transformation of adult antennae to maxillary palps. In contrast, most tissues appea r refractory to PB-induced effects. To study the basis of homeotic tis sue specificity we are isolating and studying mutations that modify do minant HSPB-induced phenotypes. One HSPB point mutation (Arg5 of the h omeodomain to His) removes homeotic activity in the mouthparts and ant ennae, but provokes a dose-sensitive eye loss. We show that eye loss c an be induced by PB proteins that no longer effectively bind to DNA. T he dose-sensitive eye:Loss thus appears to be mediated by specific, co ntext-dependent protein-protein interactions. (C) 1997 Elsevier Scienc e Ireland Ltd.