Dr. Bryant proposes to continue his analysis of the lethal(1)discs large-1 (l(1)d.lg-1) locus, and oncogene of Drosophila melanogaster. Mutations in this locus cause neoplastic transformation of the imaginal tissue leading to an extended larval life and a block in pupariation. Other alleles allow normal imaginal growth but interfere with differentiation during metamorphosis. His initial genetic and molecular characterization of the locus has revealed the presence of at least three complementation groups and a complex pattern of expression of the l(1)d.lg-1 transcripts. Sequencing of partial cDNAs indicates that the locus encodes at least two different peptides, one of which appears to be transmembrane. Database homology searches have shown that the predicted l(1)d.lg-1 proteins contain the src homology region 3 or A-box. This amino acid motif has been found in several of the vertebrate oncogenes and can regulate the transforming ability of these proteins. Dr. Bryant plans to isolate full length cDNAs for the l(1)d.lg-1 transcripts to determine the sequence of the entire protein. He will also use these cDNAs to make minigene transformation constructs to correlate the genetic and molecular results. He will make antibodies to each of the predicted peptides to use for localization and biochemical characterization. Finally he will attempt to analyze the function of the A-box by sequencing this region from the pre-existing alleles of l(1)d.lg-1 and by creating specific alterations in this domain using in vitro mutagenesis. The results from these experiments should reveal how mutations in the l(1)d.lg-1 oncogene can cause neoplastic transformation and should help clarify the relationship of this gene to the vertebrate oncogenes. %%% This study will yield information about the regulation of a gene involved in growth control during development in Drosophila. This gene has homologies to mammalian genes involved in the transformation to malignant growth.
