Acts as a transcriptional activator: mediates transcriptional activation by binding to E box-containing promoter consensus core sequences 5'-CANNTG-3'. Associates with the p300/CBP transcription coactivator complex to stimulates transcription of the secretin gene as well as the gene encoding the cyclin-dependent kinase inhibitor p21Cip1. Contributes to the regulation of several cell differentiation pathways, like those that promote the formation of early retinal ganglion cells, inner ear sensory neurons, granule cells forming either the cerebellum or the dentate gyrus cell layer of the hippocampus, endocrine islet cells of the pancreas and enteroendocrine cells of the small intestine. Together with PAX6 or SIX3, is required for the regulation of amacrine cell fate specification. Also required for dendrite morphogenesis and maintenance in the cerebellar cortex. Associates with chromatin to enhancer regulatory elements in genes encoding key transcriptional regulators of neurogenesis. Interacts (via helix-loop-helix motif domain) with EP300 (via C-terminus). Heterodimer with TCF3/E47; the heterodimer is inhibited in presence of ID2, but not NR0B2, to E- box element. Efficient DNA-binding requires dimerization with another bHLH protein. Interacts with RREB1. Interacts with EP300; the interaction is inhibited by NR0B2. Interacts with TCF3; the interaction is inhibited by ID2. Note: This description may include information from UniProtKB.