Reversion of Murine Sarcoma Virus Transformed Mouse Cells: Variants without a Rescuable Sarcoma Virus

Murine sarcoma virus transformed mouse 3T3 cells, which are negative for murine leukemia virus and which yield sarcoma virus after superinfection with murine leukenmia virus, spotaneously give rise to flat variants front which murine sarcoma virus can no longer be rescued. The revertants support leukemia viruis growth and show an enhanced sensitivity to murine sarcoma superinfection and, like normal cells, do not release RNA-dependent DNA polymerase activity. Because revertants could be obtained with high frequency from progeny of single transformed cells, each cell that containts the sarconma virus genome seems to have the capacity to suppress or eliminate an RNA tumor virus native to its species of origin.