ID1
ID1, or inhibitor of DNA binding 1, is a member of the ID protein family. ID proteins are small basic helix-loop-helix (bHLH) proteins that lack a complete basic DNA-binding domain, which makes them unable to bind DNA directly. They function as dominant negative regulators of bHLH transcription factors, interfering with differentiation programs by sequestering E proteins such as E12 and E47, thereby preventing formation of functional bHLH heterodimers. ID1 is expressed in various tissues during development and reactivated in adult tissues in response to growth factors and oncogenic signals. It promotes cell proliferation and inhibits differentiation, contributing to maintenance of progenitor or stem cell states in multiple lineages including neural, hematopoietic, and muscle lineages. Its expression is regulated by signaling pathways such as BMP, VEGF, Notch, and Wnt, and by oncogenic pathways in cancer cells.
In development, ID1 helps regulate patterning and timing of differentiation. In cancer, ID1 overexpression is associated
ID1 belongs to a small family of ID proteins (ID1–ID4) characterized by a conserved HLH motif but