Selective induction of murine oncornavirus gene expression in somatic cell hybrids between mouse peritoneal macrophages and SV-40-transformed human cells

Somatic cell hybrids of BALB c and C57BL 6 mouse peritoneal macrophages and human Lesch-Nyhan fibroblasts transformed by infection with simian virus 40 have been examined by radioimmunoassay for synthesis of the viral envelope and major core proteins of the murine endogenous type-C oncornavirus. Little or no detectable viral proteins (approximately 1 ng/mg of protein) were present in extracts of the parental cells. In contrast, hybrid clones of BALB c cells containing human chromosome 7 with the simian virus 40 genome synthesized extremely high concentrations of the murine type-C virus core protein (210 to 6000 ng/mg) and also the envelope glycoprotein (83 to 250 ng/mg). The highest concentrations were in cells containing human chromosomes 5 and 11 in addition to 7. There was little or no change in the concentration of viral proteins in the C57BL 6-human cell hybrids. These results suggest that human-cell gene products can be active in the induction of the murine oncornavirus genome.