| Siah 1 binds and regulates the function of Numb . ^^^ We report that Siah 1 interacts directly with and promotes the degradation of the cell fate regulator Numb . ^^^ Siah 1 mediated Numb degradation leads to redistribution of endogenous cell surface Notch to the cytoplasm and nucleus and to augmented Notch regulated transcriptional activity . ^^^ These data imply that through its ability to target Numb for degradation , Siah 1 can act as a key regulator of Numb related activities , including Notch signaling . . ^^^ |