CREB mediates transactivation by E1A 243R of the PCNA promoter. (A) Experimental design and schematic diagram of the G5PCNA-CAT reporter plasmid and GAL4-fusion protein constructs. G5PCNA-CAT (33) has five tandem GAL4 DNA-binding sites located upstream of the PCNA basal promoter (sequences from −47 to +62) linked to a CAT reporter. GAL4-ATF-1, GAL4-CREB, or GAL4-DBD were cotransfected into HeLa cells with either pCMV12S.FS or pCMV12S. A representative experiment shown in B and C displays an average of three independent transfections performed in duplicate, with SD indicated. Transient expression assays with human 293 cells were carried out with GAL4-ATF-1, GAL4-CREB, or GAL4-DBD and the G5PCNA-CAT reporter. (D) An average of two independent experiments carried out in duplicate, with SD noted.