c-Jun activation of the DYNCRE3 site in the prodynorphin promoter

The DYNCRE3 site in the prodynorphin promoter is similar to both the AP-1 and cAMP-responsive element (CRE) consensus sequences. Because c-Jun is known to bind to both AP-1 and CRE sequences, we evaluated the potential role of this transcription factor at the DYNCRE3 site using transient transfection and gel mobility shift analyses. In PC12 cells, co-transfections of a chloramphenicol acetyl transferase (CAT) reporter gene containing the DYNCRE3 site and a c-Jun expression vector resulted in transcriptional activity 9-fold greater than control. Co-transfections with a mutant c-Jun protein lacking the transactivation domain resulted in a concentration-dependent decrease in transcriptional activity. Gel mobility shift analysis demonstrated the formation of a multi-component protein-DNA complex between an oligonucleotide centered on the DYNCRE3 site and nuclear extract from untreated and forskolin-stimulated PC12 cells. The upper band of this complex could be completely supershifted with the addition of a c-Jun specific antibody. These convergent data suggest that c-Jun is involved in transcriptional activation through the DYNCRE3 site.