THE STONED LOCUS OF DROSOPHILA-MELANOGASTER PRODUCES A DICISTRONIC TRANSCRIPT AND ENCODES 2 DISTINCT POLYPEPTIDES

The stoned gene of Drosophila melanogaster is required for normal neur onal function in both adult and larva. We have identified DNA sequence s that lie within a genetic region that is known to include the stoned gene and that also reveal restriction site variations in two stoned l ethal mutants. This genomic region contains a single transcription uni t coding for an similar to 8.4 kb transcript. The transcript is prefer entially expressed in the head of adult flies. The isolation and seque ncing of cDNA and genomic clones reveals that stoned appears to encode a dicistronic mRNA, although the possible existence of other forms of mRNA cannot be excluded. Antibody cross-reactivity shows that two pro teins are translated from the stoned locus in vivo. Both open reading frames (ORFs) encode novel proteins. The protein encoded by the first ORF contains four tandemly repeated motifs, and one domain of the prot ein encoded by the second ORF shows similarity to a family of proteins (AP50s) associated with clathrin assembly protein complexes.