Multiple screening approaches identify novel transcription factor binding partners for Eyes absent. Trevor L. Davis^1,2, Ilaria Rebay^1,2. 1) Committee on Development, Regeneration, and Stem Cell Biology, University of Chicago, Chicago, IL; 2) Ben May Department for Cancer Research, University of Chicago, Chicago, IL.

   A long-standing question in developmental biology is how transcription factors direct different outcomes of gene expression depending on context. One way these proteins activities change is through binding to different co-factors to create multi-protein complexes that uniquely affect transcription. In Drosophila, four transcription factors known as the retinal determination (RD) network control eye development, but little is known about how these proteins cooperate with others during development. To investigate transcriptional complex behavior in vivo, we study the RD transactivator Eyes absent (Eya). Loss of Eya or its co-activator, Sine oculis (So), abolishes retinal development, while their misexpression creates ectopic eyes. However, both proteins bind co-activators and So also functions in repressive complexes with Groucho, raising the possibility that both activation and repression by Eya-So are essential for eye development. Because additional proteins likely regulate these behaviors, we performed a yeast two-hybrid screen for novel Eya interactors. This approach identified putative Eya-binding transcription factors that we find are required for eye development. To assess which interactions are relevant in vivo, we asked whether knockdown of candidates modified the eya^RNAi reduced-eye phenotype. We hypothesized that genes whose knockdown suppressed this phenotype inhibit transcriptional activation by Eya, while those that enhanced it promote Eya-mediated gene expression. To test these ideas, we asked if Eyas ability to induce ectopic transcription was increased by expressing RNAi transgenes that suppressed eya^RNAi and vice versa. Based on these data, we selected putative co-repressors and co-activators that may regulate Eyas transcriptional function. Future work will test whether these complexes contain So and characterize the developmental processes and target loci that are controlled by Eya-candidate interactions.