A function of CBP as a transcriptional co-activator during Dpp signalling

CBP/p300 is a transcriptional co-activator that is recruited to enhancers b y various DNA-binding proteins, including proteins whose activity is contro lled by extracellular signals. Here, we report that Drosophila CBP loss-of- function mutants show specific defects which mimic those seen in mutants th at lack the extracellular signal Dpp or its effector Mad. Furthermore, we f ind that CEP loss severely compromises the ability of Dpp target enhancers to respond to endogenous or exogenous Dpp, Finally, we show that CBP binds to the C-terminal domain of Mad. Our results provide evidence that CBP func tions as a co-activator during Dpp signalling, and they suggest that Mad ma y recruit CBP to effect the transcriptional activation of Dpp-responsive ge nes during development.