Differential regulation of JunB and JunD by adenovirus type 5 and 12 E1A proteins.

The genes of the Jun family encode components of the TPA-inducible transcription factor AP-1. These genes are induced by a wide variety of extracellular stimuli, such as growth factors, phorbol esters and activators of protein kinase A. We have previously shown that the adenovirus type 5 E1A protein (E1A5) induces c-jun and junB expression in a number of different cell types. In this paper we show that the third member of the Jun family, junD, is also strongly induced by E1A5. Multiple sequences in the junB and junD promoters are responsible for the effects of E1A5. By contrast, adenovirus type 12 E1A (E1A12), like retinoic acid (RA), strongly induces c-jun expression, while expression of junB and junD is not altered. Interestingly, E1A12 expression leads to complete differentiation of P19 EC cells, comparable to the effect of RA on these cells, while E1A5-expressing cells are only partially differentiated.