A Notch-dependent transcriptional mechanism controls expression of temporal patterning factors in Drosophila medulla

In this work, we show that the expression of one temporal transcription factor(TTF), Sloppy-paired (Slp), in the Drosophila medulla TTF cascade, is regulated directly by two other TTFs and the Notch signaling pathway. We show that the previous TTF, Eyeless, another TTF Scro and Su(H)/NICD regulate the transcription of Slp through binding to two cis-regulatory elements in the slp locus. Slp expression is delayed when Notch signaling is lost or when cell cycle progression is blocked, which also cause loss of Notch signaling. Furthermore, we show that supplying Notch signaling can rescue the delayed Slp expression in cell-cycle arrested neuroblasts. Thus our work demonstrates that Notch signaling cooperates with TTFs to promote the progression of the TTF transcriptional cascade. Dam-ID sequencing to profile the binding sites of Su(H) and Ey