CBP and P300 bind to the CREB via a domain known as KIX [1]. The KIX domain of CBP also binds to transactivation domains of other nuclear factors including Myb and Jun.

1: Solution structure of the KIX domain of CBP bound to the transactivation domain of CREB: a model for activator:coactivator interactions. Radhakrishnan I, Perez-Alvarado GC, Parker D, Dyson HJ, Montminy MR, Wright PE; Cell 1997;91:741-752. PMID:9413984