Exploration of the efficacy of the GAL4/UAS method of transgene expression in Drosophila melanogaster.

Developed in 1993, the GAL4/UAS system is a popular tool used to express transgenes in the fruit fly Drosophila melanogaster, with increasing success in zebrafish and mice. Despite the success of GAL4/UAS in many areas of research, studies have also shown that GAL4 expression in D. melanogaster is not entirely without effect. GAL4 is a yeast transcription factor that binds to an upstream activating sequence (UAS) which is attached to the promoter of a gene of interest (a UAS transgene) via recombinant DNA methods. GAL4 can be expressed tissue or stage specifically, driving expression of the UAS transgene. Additionally, the UAS transgene can be over-expressed or downregulated. Previously a GAL4/UAS strategy was used to study the effect of downregulating ribosomal protein gene expression on life span. GAL4 expression was used to activate a UAS transgene that targeted specific ribosomal proteins via the silencing mechanism of RNAi. As a control for the effect of using GAL4 to drive expression of a transgene, the same experiment included a UAS transgene that targeted GAL4 itself. While downregulation of the ribosomal proteins did in fact show life span extension (relative to a non transgenic background strain), surprisingly, so did the GAL4/UAS RNAi line. Experiments have shown that the expression of RNAi itself has little to no effect on lifespan, so we hypothesize that the GAL4/UAS system itself may in fact prolong lifespan. Here we discuss the effects of the GAL4/UAS system on lifespan in Drosophila melanogaster.