IN-VITRO TRANSFORMING CAPACITIES OF MOUSE C-JUN-JUND CHIMERIC GENES

Among the murine Jun family of transcription factors, c-Jun and JunD a re closely-related proteins with similar dimerization, DNA binding and transactivating properties. However, when expressed from a self-repli cating retroviral RCAS vector, c-jun, but not junD, transforms chick e mbryo fibroblasts. We attempted to map the regions of c-jun which are important for transformation by constructing hybrids between c-jun and junD. Using common restriction sites, we prepared six different chime ric molecules. All of these c-jun:junD hybrids code for transactivator s of AP1-containing promoters. An N-terminal segment of 79 amino acids of c-Jun converts JunD into a strong transforming protein, while othe r segments of c-Jun contribute to a lesser extent. Contrary to what ha s been reported with rat embryo fibroblasts, a c-Jun derivative with s erines substituted by alanines in positions 63 and 73 still transforms CEFs efficiently.