SUPPRESSOR OF HAIRLESS-INDEPENDENT EVENTS IN NOTCH SIGNALING IMPLY NOVEL PATHWAY ELEMENTS

The Notch (N) pathway defines an evolutionarily conserved cell signali ng mechanism that governs cell fate choices through local cell interac tions. The ankyrin repeat region of the Notch receptor is essential fo r signaling and has been implicated in the interactions between Notch and two intracellular elements of the pathway: Deltex (Dx) and Suppres sor of Hairless (Su(H)). Here we examine directly the function of the Notch cdc10/ankyrin repeats (ANK repeats) by transgenic and biochemica l analysis. We present evidence implicating the ANK repeats in the reg ulation of Notch signaling through homotypic interactions. In vivo exp ression of the Notch ANK repeats reveals a cell nonautonomous effect a nd elicits mutant phenotypes that indicate the existence of novel down stream events in Notch signaling. These signaling activities are indep endent of the known effector Su(H) and suggest the existence of yet un identified Notch pathway components.