Analysis of Adh gene regulation in Drosophila: studies using somatic transformation.

We have used in vitro mutagenesis and somatic transformation [Sofer and Martin, 1987a; Martin et al., 1986] to investigate the role of cis-acting sequences in the control of alcohol dehydrogenase gene expression in larvae of Drosophila melanogaster. Two sets of experiments were carried out. In the first, a series of deletions were constructed in the region upstream of the proximal transcriptional start site. In the second, one or both introns were removed from within the structural gene. These constructs (on circular plasmids) were injected into Adh-null embryos and ADH activity was assayed in third instar larvae of the injected generation. The first set of experiments indicated that there are at least three distinct regulatory regions essential for larval activity located in the 5' flanking region of the gene. One, in an area that includes the TATA box, was found to be necessary but not sufficient for larval ADH activity. Two others, further upstream, seemed to have enhancer-like properties because their absence could be compensated by a second copy of the Adh gene on the same plasmid molecule. The second set of experiments showed that neither the tissue distribution nor amount of ADH activity was affected by the removal of one or both introns from the Adh gene.