MUTATIONAL ANALYSIS OF THE ROLE OF THE CARBOXY-TERMINAL REGION OF THEV-ERBB PROTEIN IN ERYTHROID CELL-TRANSFORMATION

The v-erbB protein encoded by the avian erythroblastosis virus AEV-H i s responsible for the transformation of fibroblasts and erythroblasts by this virus. Deletion of amino acids 961-1102, which lie carboxy ter minal to the kinase domain of the v-erbB protein, destroys the ability of the virus to transform erythroid cells without severely affecting fibroblast transformation. This region is termed the E-domain and has been postulated to contain a region important for erythroid cell trans formation. In-frame deletions of approximately 23 amino acids were int roduced throughout the E-domain in an attempt to locate a specific reg ion that was essential for erythroid cell transformation. Several of t he deletions gave rise to a partial transformed phenotype, although no single deletion that completely abolished erythroid cell transformati on was found. Interestingly, deletion of amino acids 1031-1055 resulte d in a superactivated v-erbB protein that was more active for erythroi d cell transformation than the wild-type AEV-H v-erbB protein. This in dicates that there is a negative regulatory region located within this region that normally partially suppresses the transforming activity o f the v-erbB protein for erythroid cells. These data suggest that the E-domain contains both negative and positive regulatory regions that f unction in erythroid cells, and complete deletion of the region is nec essary to abolish erythroid cell transformation.