Isolation of a murine retrovirus with a temperature-sensitive src gene.

A murine retrovirus containing the src gene of avian sarcoma virus ts LA31A was generated. In contrast to the avian sarcoma virus, our recombinant murine retrovirus can efficiently infect mammalian cells. Transformation of NIH3T3 cells by the recombinant murine retrovirus is temperature sensitive. At the permissive temperature of 34 degrees, cells form foci of rounded cells. At the nonpermissive temperature of 39 degrees, the infected cells remain flat and exhibit contact inhibition. No disease was observed following infection of newborn NFS/n mice with the ts mutant virus. In contrast, infection of newborn NFS/n mice with a recombinant murine retrovirus containing the wild-type src gene causes fibrosarcomas and hepatosplenomegaly.