CREB-binding protein and p300/CBP-associated factor are transcriptional coactivators of the p53 tumor suppressor protein.

The structurally related transcriptional coactivators p300 and CBP possess histone acetyltransferase activity and associate with P/CAF, which is also a histone acetyltransferase. CBP and p300 have properties of tumor suppressor proteins; their interaction with P/CAF is disrupted by the adenoviral E1A oncoprotein, and the genes encoding CBP and p300 are mutated in human cancer. We observed a physical interaction between the transactivation domain of the p53 tumor suppressor protein and CBP. Furthermore, CBP and P/CAF enhanced the ability of p53 to activate expression of the endogenous p21(cip1/waf1) gene, whereas E1A and dominant negative CBP mutants suppressed p53-dependent p21(cip1/waf1) expression. These studies link two tumor suppressor families and provide a framework for understanding the molecular mechanism by which p53 activates transcription.