Downstream effector of Notch signaling which may be required for cardiovascular development. Transcriptional repressor which binds preferentially to the canonical E box sequence 5'-CACGTG-3'. Represses transcription by the cardiac transcriptional activators GATA4 and GATA6. Self-associates. Interacts with GATA4, GATA6, HES1, HEY1 and HEY2. Interacts with HDAC1, NCOR1 and SIN3A. Belongs to the HEY family.