A notch-independent activity of suppressor of hairless is required for normal mechanoreceptor physiology

Suppressor of Hairless [Su(H)]/Lag-1/RBP-J kappa /CBF1 is the only known tr ansducing transcription factor for Notch receptor signaling. Here, we show that Su(H) has three distinct functions in the development of external mech anosensory organs in Drosophila: Notch-dependent transcriptional activation and a novel autorepression function, both of which direct cell fate decisi ons, and a novel auto-activation function required for normal socket cell d ifferentiation. This third phase of activity, the first known Notch-indepen dent activation function for Su(H) in development, depends on a cell type-s pecific autoregulatory enhancer that is active throughout adult life and is required for proper mechanoreception. These results establish a direct lin k between a broadly deployed cell signaling pathway and an essential physio logical function of the nervous system.