E(y)1, a component of the transcription initiation complex, is required for Notch signaling activation in Drosophila. Gengqiang Xie, Dongyu Jia, Wu-Min Deng. Department of Biological Science, Florida State University, Tallahassee, FL, 32306.

   The Notch signaling pathway plays pivotal roles in a variety of developmental events, including cell differentiation, proliferation and apoptosis in multiple metazoan tissues. Dysregulation of this pathway has been linked to several inherited genetic diseases and cancer. In a large-scale RNAi screen for genes involved in follicle-cell differentiation and cell-cycle switches, we identified that e(y)1 is required for the Notch-dependent mitotic-to-endocycle transition in follicle cells at stage 6/7 of oogenesis. We further show, by monitoring the reporters of Notch activity, that E(y)1 positively regulates the Notch signaling pathway both in follicle cells and in the wing imaginal development. E(y)1 has been shown to be a component of transcription factor TFIID complex and/or SAGA histone acetyltransferase complex, suggesting an important function for gene transcriptional regulation. As expected, epistatic analysis indicates that E(y)1 acts in the level of the Notch transcription factor complex. We are currently investigating the mechanism by which E(y)1 regulates the Notch signaling pathway at the transcriptional level.