| This led to the identification of the neurogenic basic helix loop helix transcription factor , NeuroD 1 , as a target of Rb action . ^^^ Rb and to a lesser extent p 107 , but not p 130 , enhance NeuroD 1 dependent transcription , and this activity appears to depend on direct protein interactions between the Rb pocket and the helix loop helix domain of NeuroD 1 . ^^^ In vivo , NeuroD is found in a complex that includes Rb and also the orphan nuclear receptor NGFI B , which mediates corticotropin releasing hormone activation of POMC transcription . ^^^ The formation of a similar complex in vitro requires the presence of Rb as a bridge between NeuroD and NGFI B . ^^^ |