Transcriptional repressor. Binds DNA on N-box motifs: 5'-CACNAG-3'. Plays a role in the patterning of tissue boundaries. Promotes floor plate development and prechordal plate development. Required for lens development as early as the stage of lens field formation, partly through regulation of gene expression of the cell cycle inhibitor cdknx/p27(xic1). A role in neural crest development is disputed. Transcription repression requires formation of a complex with a corepressor protein of the Groucho/TLE family. Binds DNA in the form of a heterodimer with the bHLH protein hey1/hrt1. Interacts (via Orange domain) with id3 (via HLH domain) (By similarity). Interacts with the bHLH protein hes6; this interaction may inhibit the transcriptional repressor activity. Shows a complex and dynamic expression pattern in developing embryos. In neurulae, expressed in the presumptive floor plate, the anterior part of the prechordal plate and in the anterior neural border. In tailbud embryos, expressed in various neuroectoderm derivatives and in the mesoderm, where expression is limited to the presomitic mesoderm (PSM) and pronephros. In the PSM, expressed in an anterior stripe prior to the formation of each somite. Expression in the presumptive neural crest is disputed. Expressed both maternally and zygotically. Shows lower zygotic expression than hes4-B/hairy2b. By Notch-signaling. Acts in a complex regulatory loop with other bHLH proteins. Has a particular type of basic domain (presence of a helix-interrupting proline) that binds to the N-box (CACNAG), rather than the canonical E-box (CANNTG). The C-terminal WRPW motif is a transcriptional repression domain necessary for the interaction with Groucho/TLE family members, transcriptional corepressors recruited to specific target DNA by Hairy-related proteins. Multiple papers report expression in the developing neural crest and a role in neural crest formation. However, PubMed:17724611 reports differences between the duplicated hes4 gene products and shows that hes4-B/hairy2b but not hes4-A/hairy2a has a role in neural crest formation, and that hes4-B/hairy2b but not hes4-A/hairy2a is expressed in the presumptive neural crest. Probable intron retention at N-terminus and possible frameshift and contaminating sequence at C-terminus.