SNIP1 is smad nuclear interacting protein that contains a forkhead-associated （FHA） domain and acts as a nuclear inhibitor of CBP/p300. SNIP1 is an inhibitor of the TGF-beta signal transduction pathway and is significant in suppressing transcriptional activation dependent on the co-activators CBP and p300. Inhibition of NF-kappa B activity is a function of the N-terminal domain of SNIP1 and involves competition of SNIP1 and the NF-kappa B subunit， RelA/p65， for binding to p300， similar to the mechanism of inhibition of Smad signaling by SNIP1.
