Transcriptional regulator that plays a central role in Notch signaling, a signaling pathway involved in cell-cell communication that regulates a broad spectrum of cell-fate determinations. Acts as a transcriptional repressor when it is not associated with Notch proteins. When associated with some NICD product of Notch proteins (Notch intracellular domain), it acts as a transcriptional activator that activates transcription of Notch target genes (By similarity). Required for the transcriptional activation of ESR1, suggesting that it is required during primary neurogenesis in embryos. Binds to the oxygen responsive element of COX4I2 and activates its transcription under hypoxia conditions (4% oxygen) (By similarity). Interacts with activated Notch proteins (By similarity). Forms a ternary complex with nrarp and the intracellular domain (NICD) of notch1. Interacts with rita1, leading to nuclear export, prevent the interaction between rbpj and NICD product and subsequent down-regulation of the Notch signaling pathway. Mainly nuclear, upon interaction with rita1, translocates to the cytoplasm, down-regulating the Notch signaling pathway. Belongs to the Su(H) family.