Abstract
The yeast transcription factor GAL4 is widely used in Drosophila genetics to misexpress genes that are under control of the yeast upstream activator sequence (UAS). Here we show that high levels of GAL4 change the expression of many Drosophila genes in a UAS-independent manner, including genes that encode components of important signaling pathways. We find that at least part of the genomic response to GAL4 appears to be caused by effects of GAL4 on stress and immune response pathways. Finally, using the transcription factor Senseless as an example, we demonstrate how an interaction between GAL4 and a GAL4-driven protein can impede the use of the GAL4/UAS system in experiments aimed at determining the transcriptional response to a misexpressed gene.
