HUMAN P300 PROTEIN IS A COACTIVATOR FOR THE TRANSCRIPTION FACTOR MYOD

Human p300 protein is a cellular target of adenoviral E1A oncoprotein and a potential transcriptional coactivator. Both p300 and Rb family p rotein-binding regions of E1A are required for the repression of muscl e gene expression, which is regulated by MyoD family transactivators, This implies that p300 is involved in MyoD-dependent transactivation, We show that the repression of MyoD mediated E box (MyoD consensus) re porter activity by E1A is correlated with its interaction with p300, i ndicating that p300 participates in MyoD-dependent transactivation, In addition, p300 is able to interact both in vivo and in vitro with Myo D through a portion at the carboxyl-terminal cysteine/histidine-rich d omain and associates with the components of the basal transcriptional complex through its two separate transactivation domains at the amino and carboxyl termini, Consistent with its role as a coactivator, p300 potentiates MyoD-activated transcription.