Tax-mediated inhibition of TGF-β–induced and Smad-induced transcription: a model.

(A) Tax inhibits Smad-dependent transcription by competing with Smad for binding to the coactivator CBP/p300. (B) Tax binds to CBP/p300 and leads to a change in conformation or stability of the Smad-CBP/p300 complex, thereby repressing Smad transactivation function.