Role of the ATFa/JNK2 complex in Jun activation

The ATFa proteins, which are members of the CREB/ATF family of transcriptio n factors, display quite versatile properties, We have previously shown tha t they interact with the adenovirus E1a oncoprotein, mediating part of its transcriptional activity and heterodimerize with the Jun, Fos or related tr anscription factors, thereby modulating their DNA-binding specificity, In t he present study, we report the sequence requirement of the N-terminal acti vation domain of ATFa and demonstrate the importance of specific threonine residues (Thr51 and Thr53) in addition to that of the metal-binding domain, in transcriptional activation processes. We also show that the N-terminal domain of ATFa which stably binds the Jun N-terminal kinase-2 (JNK2) (Bocco et al,, 1996), is not a substrate for this kinase in vivo but, instead, se rves as a JNK2-docking site for ATFa-associated partners like JunD, allowin g them to be phosphorylated by the bound kinase.