Enables Notch binding activity. Involved in negative regulation of Notch signaling pathway and positive regulation of Notch signaling pathway. Predicted to be active in nucleolus. Is expressed in several structures, including Malpighian tubule primordium; anal pad primordium; embryonic/larval midgut primordium; gut section; and larval somatic muscle cell. Orthologous to human NLE1 (notchless homolog 1).