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. May self-associate (By similarity). Interacts with GATA4, HES1 and HEYL (By similarity). Interacts with HDAC1, NCOR1 and SIN3A (By similarity). Interacts with ARNT and GATA6. Belongs to the HEY family.