Transforming capacities of avian erythroblastosis virus mutants deleted in the erbA or erbB oncogenes.

Mutants of avian erythroblastosis virus (AEV) were constructed by deleting large nucleotide segments in each of the viral oncogenes termed v-erbA and v-erbB. Mutants in erbA (erbA -B +) retained the ability to transform fibroblasts in vitro, and these cells exhibited most of the transformation characteristics that typify wild-type AEV-transformed fibroblasts. In addition, the mutants induced small erythroid colonies upon infection of bone marrow cells in culture. Chickens inoculated with erbA -B + virus or with erbA -B +-transformed cells developed sarcomas or atypical erythroid leukemias. The erythroid cells transformed in vivo or in vitro by the erbA -B + viruses appeared not to be as tightly blocked in differentiation as wild-type transformed cells. In contrast, fibroblasts infected with the erbA +B - mutant resembled normal cells in all transformation parameters tested, and no bone marrow cell transformation was observed with the mutant. The results indicate that the main transforming properties of AEV are encoded in erbB and that its effects are enhanced by erbA.