Acetylates histones; giving a specific tag for transcriptional activation. Also acetylates non-histone proteins; like NCOA3 and FOXO1. 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. Acetylates PCNA; acetylation promotes removal of chromatin-bound PCNA and its degradation during nucleotide excision repair (NER) (PubMed:24939902). {ECO:0000269|PubMed:11154691; ECO:0000269|PubMed:12738767; ECO:0000269|PubMed:12929931; ECO:0000269|PubMed:14645221; ECO:0000269|PubMed:24939902; ECO:0000269|PubMed:9707565}.