The N-terminal transactivation domain of ATF2 is a target for the co-operative activation of the c-jun promoter by p300 and 12S E1A

The adenovirus EIA proteins activate the c-jun promoter through two Jun/ATF -binding sites, jun1 and jun2. P300, a transcriptional coactivator of sever al AP1 and ATF transcription factors has been postulated to play a role in this activation, Here,,ve present evidence that p300 can control c-jun tran scription by acting as a cofactor for ATF2: (1) Over-expression of p300 mas found to stimulate c-jun transcription both in the presence and absence of EIA. (2) Like E1A, p300 activates the c-jun promoter through the jun1 and jun2 elements and preferentially activates the N-terminal domain of ATF2. ( 3) Co-immunoprecipitation assays of crude cell extracts indicate that endog enous p300/CBP(-like) proteins and ATF2 proteins are present in a multiprot ein complex that can bind specifically to the jun2 element, We further demo nstrate that the Stress-Activated-Protein-Kinase (SAPK) target sites of ATF 2, Thr69 and Thr71 are not required for the formation of the p300/CBP-ATF2 multiprotein complex. These data indicate that E1A does not inhibit all tra nscription activation functions of p300, and, in fact, cooperates with p300 in the activation of the ATF2 N-terminus.