Acetylates histones, giving a specific tag for transcriptional activation (By similarity). Also acetylates non-histone proteins, like DDX21, FBL, IRF2, MAFG, NCOA3, POLR1E/PAF53 and FOXO1 (By similarity). Binds specifically to phosphorylated CREB and enhances its transcriptional activity toward cAMP-responsive genes. Acts as a coactivator of ALX1. Acts as a circadian transcriptional coactivator which enhances the activity of the circadian transcriptional activators: NPAS2-ARNTL/BMAL1 and CLOCK-ARNTL/BMAL1 heterodimers (By similarity). Acetylates PCNA; acetylation promotes removal of chromatin-bound PCNA and its degradation during nucleotide excision repair (NER) (By similarity). Acetylates POLR1E/PAF53, leading to decreased association of RNA polymerase I with the rDNA promoter region and coding region (By similarity). Acetylates DDX21, thereby inhibiting DDX21 helicase activity (By similarity). Acetylates FBL, preventing methylation of 'Gln-105' of histone H2A (H2AQ104me) (By similarity). Functions as a transcriptional coactivator for SMAD4 in the TGF-beta signaling pathway (By similarity). acetyl-CoA + L-lysyl-[histone] = CoA + H(+) + N(6)-acetyl-L-lysyl-[histone] acetyl-CoA + L-lysyl-[protein] = CoA + H(+) + N(6)-acetyl-L-lysyl-[protein] Found in a complex containing NCOA2; NCOA3; IKKA; IKKB and IKBKG. Probably part of a complex with HIF1A and EP300. Interacts with phosphorylated CREB1. Interacts with the C-terminal region of CITED4. The TAZ-type 1 domain interacts with HIF1A. Interacts with SRCAP, CARM1, ELF3, MLLT7/FOXO4, N4BP2, NCOA1, NCOA3, NCOA6, PCAF, DDX5, DDX17, PELP1, PML, SMAD1, SMAD2, SMAD3, SPIB, TRERF1 and ZCCHC12. Interacts with KLF1; the interaction results in acetylation and enhancement of transcriptional activity of KLF1. Interacts with DAXX; the interaction is dependent on CBP sumoylation and results in suppression of the transcriptional activity via recruitment of HDAC2 to DAXX. Interacts with MAF. Interacts with MTDH. Interacts with MAFG; the interaction acetylates MAFG in the basic region and stimulates NFE2 transcriptional activity through increasing its DNA-binding activity. Interacts with IRF2; the interaction acetylates IRF2 and regulates its activity on the H4 promoter. Interacts (via N-terminus) with SS18L1/CREST (via C-terminus) (By similarity). Interacts with IRF3 (when phosphorylated); forming the dsRNA-activated factor 1 (DRAF1), a complex which activates the transcription of the type I interferon genes (By similarity). Interacts with MECOM. Interacts with CITED1 (via C-terminus) Interacts with GATA1; the interaction results in acetylation and enhancement of transcriptional activity of GATA1. Interacts with FOXO1; the interaction acetylates FOXO1 and inhibits its transcriptional activity. Interacts with NPAS2, CLOCK and ARNTL/BMAL1. Interacts with ASF1A and ASF1B; this promotes histone acetylation. Interacts with acetylated TP53/p53 and with the acetylated histones H3 and H4. Interacts (via transactivation domain and C-terminus) with PCNA; the interaction occurs on chromatin in UV-irradiated damaged cells. Interacts with DHX9 (via N-terminus); this interaction mediates association with RNA polymerase II holoenzyme and stimulates CREB-dependent transcriptional activation (By similarity). Interacts with SMAD4; negatively regulated by ZBTB7A (By similarity). Forms a complex with KMT2A and CREB1 (By similarity). Interacts with DDX3X; this interaction may facilitate HNF4A acetylation (By similarity). Recruited to nuclear bodies by SS18L1/CREST. In the presence of ALX1 relocalizes from the cytoplasm to the nucleus. Expressed in hypothalamus and cortex. Up-regulated by IL-1 treatment. Methylation of the KIX domain by CARM1 blocks association with CREB. This results in the blockade of CREB signaling, and in activation of apoptotic response (By similarity). Phosphorylated by CHUK/IKKA at Ser-1383 and Ser-1387; these phosphorylations promote cell growth by switching the binding preference of CREBBP from TP53 to NF-kappa-B. Sumoylation negatively regulates transcriptional activity via the recruitment of DAAX.