The CBP co-activator is a histone acetyltransferase

THE CBP protein acts as a transcriptional adaptor for many different transcription factors by directly contacting DNA-bound activators 1–7 . One mechanism by which CBP is thought to stimulate transcription is by recruiting the histone acetyltransferase (HAT) P/CAF to the promoter 8 . Here we show that CBP has intrinsic HAT activity. The HAT domain of CBP is adjacent to the binding site for the transcriptional activator El A. Although E1A displaces P/CAF from CBP, it does not disrupt the CBP-associated HAT activity. Thus E1A carries HAT activity when com-plexed with CBP. Targeting CBP-associated HAT activity to specific promoters may therefore be a mechanism by which E1A acts as a transcriptional activator.