Complementation of transforming domains in E1a/myc chimaeras

The myc oncogene is functionally similar to adenovirus E1a in its ability to collaborate with activated ras oncogenes to transform primary fibroblasts. The transforming functions of E1a and myc have been mapped to two distinct regions in each protein. I investigated the functional similarities between E1a and myc by constructing E1a/myc chimaeras to discover whether the individual transforming domains of E1a could complement individual myc-transforming domains. Transformation assays in rat embryo fibroblasts demonstrated that the N-terminal transforming domain of E1a (CR1) could complement the C-terminal transforming domain of myc in cis, and that the reciprocal chimaera (N-terminal myc/C-terminal E1a) was also active. Chimaeras constructed using domains from transformation-defective mutants of either E1a or myc were inactive, indicating that both E1a and myc domains contribute to function. These experiments suggest that transformation by myc and E1a may involve interactions with common substrates.