THE DROSOPHILA GENE ASTEROID ENCODES A NOVEL PROTEIN AND DISPLAYS DOSAGE-SENSITIVE INTERACTIONS WITH STAR AND EGFR

The asteroid gene of Drosophila was found to lie within 189 bp of Star . Asteroid cDNA clones were isolated and sequenced and a single putati ve open reading frame was identified that encodes a novel protein of 8 15 amino acids with a calculated molecular mass of 93 kilodaltons. Usi ng cDNA probes, asteroid transcripts were localized to the proliferati ve tissues of embryos and to the mitotically active tissue anterior to the morphogenetic furrow in eye imaginal discs. Ribonuclease protecti on assays identified a mutation of asteroid that acts as a dominant en hancer of Star mutations and also enhances the Ellipse mutation, Egfr( El). Based on these data, a model for asteroid gene function in EGF re ceptor signaling is presented.