Expression of the ASV src gene in hybrids between normal and virally transformed cells: specific suppression occurs in some hybrids but not others.

Somatic cell hybrids have been made between clones of rat cells transformed by avian sarcoma virus and rat or mouse cells that are untransformed. Intraspecies hybrids were either predominantly morphologically normal or predominantly transformed, some clones that formed transformed intraspecies hybrids yielding normal interspecies hybrids. Untransformed hybrids usually showed no detectable alteration in the structure or location of the integrated provirus, but viral RNA and pp60src kinase activities were much reduced. No decrease in viral gene expression was seen in transformed hybrids. Thus hybrid suppression of viral transformation, mediated in trans by the untransformed parent, is a specific event that depends on both untransformed and transformed parental parameters.