Characterization of flat revertants isolated from cells transformed by Abelson murine leukemia virus (Ab‐MuLV)

Transformed Fisher rat fibroblast cell lines by Abelson murine leukemia virus frequently revert to the normal phenotype in usual culture conditions. Molecular Biological analysis of thre revertant clones isolated from the transformants showed that their morphological reversions were due to inactivation of the v‐abl oncogene at multiple steps including transcription, translation or v‐abl protein kinase activity itself without any change in structural gene expression of helper virus. These findings suggest the existence of a specific mechanism(s) for elimination of the v‐abl oncogene by segregation, mutation, or gene rearrangement in these cells.