ID1

DNA-binding protein inhibitor ID-1 is a is_associated_with::protein that in humans is encoded by the ID1 is_associated_with::gene.

Function
The protein encoded by this gene is a helix-loop-helix (HLH) protein that can form heterodimers with members of the basic HLH family of is_associated_with::transcription factors. The encoded protein has no DNA binding activity and therefore can inhibit the DNA binding and transcriptional activation ability of basic HLH proteins with which it interacts. This protein may play a role in cell growth, senescence, and differentiation. Two transcript variants encoding different isoforms have been found for this gene.

Interactions
ID1 has been shown to interact weakly with is_associated_with::MyoD     but very tightly with ubiquitously expressed E proteins. E proteins heterodimerize with tissue restricted bHLH proteins such as Myod, NeuroD, etc. to form active transcription complexes so by sequestering E proteins, Id proteins can inhibit tissue restricted gene expression in multiple cell lineages using the same biochemical mechanism. Other interacting partners include is_associated_with::CASK.

Clinical significance
ID1 can be used to mark is_associated_with::endothelial progenitor cells which are critical to tumor growth and is_associated_with::angiogenesis. Targeting ID1 results in decreased tumor growth.