Molecular characterization of Drosophila gene encoding G₀ α subunit Homolog

A Drosophila melanogaster gene (dgo) encoding a G protein α subunit has been isolated by screening genomic and adult head cDNA libraries using bovine transduction α subunit cDNA as probe. The gene, which maps to 47A on the second chromosome, encodes two proteins which are both 354 amino acids long but differ in seven amino acids in the amino-terminal region. The 81% identical to that of a rat G₀ α subunit. Analysis of genomic clones revealed that there are eight coding exons and that the putative transcripts for the two proteins differ in the 5'-noncoding regions and the first coding exons but share the remaining six coding exons. The arrangement of two different 5'-noncoding regions on the gene suggests that two different promoters regulate the expression of the transcripts encoding the two proteins. RNA blot analysis detected three transcripts: a 3.9-kilobase (kb) transcript found at all stages of development; a 5.4-kb transcript present predominantly in adult heads; and a 3.4-kb transcript present only in adult bodies. In situ hybridizations of a cDNA probe to adult tissue sections showed that the gene is expressed abundantly in neuronal cell bodes in the brain, optic lobe, and thoracic ganglia.