Glue protein genes in Drosophila virilis: their organization, developmental control of transcription and specific mRNA degradation.

The gene Lgp-1, which is localized in the intermoult puff 16A of D. virilis polytene chromosomes, encodes the major larval glue protein Igp-1. The gene consists of two exons interrupted by a short intron. In the 5' flanking region of Lgp-1, we find putative ecdysone receptor binding sites and two proximal conserved sequence motifs which are possibly involved in gene regulation. The amino acid sequence deduced from the DNA sequence reveals a relationship to the 68C glue protein family of D. melanogaster. The size of the Lgp-1 transcripts decreases in late third instar larvae concomitantly with their disappearance. This is caused by deadenylation followed by distinct nucleolytic attacks in the 3' untranslated region. Preliminary data suggest the presence of another glue protein gene in the 16A puff region which is related to the Lgp-1 gene.