Efficient transformation of chicken embryo fibroblasts by c-Jun requires structural modification in coding and noncoding sequences.

To assess the transforming capability of the c-Jun protein, we introduced the chicken c-jun proto-oncogene into a replication competent avian retroviral expression vector (RCAS). Overexpression of c-Jun leads to transformation of CEFs with an efficienty that is 15- to 25-fold less than that seen for v-Jun. There are four structural difference between v-Jun and c-Jun. To determine the relative contribution that each of these structural differences between v-Jun and c-Jun has on oncogenic activity, several deletion and substitution mutants were constructed.