Virus-specific DNA sequences in mouse and rat cells transformed by the Harvey and Moloney murine sarcoma viruses detected by in situ hybridization

The [3H]DNA product of the murine sarcoma-leukemia virus (MSV(MLV)) and viral 60–70 S [3H]RNA was annealed with cytological preparations of mouse and rat cells transformed by the Harvey and Moloney strains of MSV. With viral [3H]DNA as cytological probe, these in situ hybridization measurements detected from 25 to 30 autoradiographic grains per interphase nucleus of transformed cells and 1 to 3 grains per nucleus of uninfected rat and mouse cells. With viral 60–70 S [3H]RNA of lower specific radioactivity as cytological probe, 12 grains per transformed cell nucleus were detected. These findings indicate that transformation of cells with MSV(MLV) produces a several-fold increase in the content of some virus-specific DNA sequences. Virus-specific sequences in transformed mouse cells were localized in the chromocenters of interphase nuclei.