Regulation of AP-1 Activity by Adenovirus E1A: Dissection of Dimers Containing Jun, Fos, and ATF/CREB Members
The proteins encoded by early region 1 A (E1A) of human adenoviruses (Ad) modulate the expression of both adenovirus genes and various host cell genes. A putative role for preexisting activator protein (AP-1) in conserved region 3 (CR3)-dependent transactivation was suggested by a study performed in HeLa cells. Since CR1 is required for both 243R-E1 A-dependent regulation of cJun/AP-1 and E1A-induced cell transformation, cJun may have a crucial role in adenovirus transformation. Enhancement of the cJun transactivation function by E1A, thus, does not lead to activation of genes controlled by cJun/cJun or cJun/cFos, but appears to lead to constitutive expression of genes controlled by cJun/ATF-2 and possibly other cJun-containing dimers. Regulation of AP-1 activity by adenovirus E1A is a complex process because multiple AP-1 components are affected and different E1A domains, which can elicit opposite effects, are involved.