Transformation with subgenomic fragments of feline sarcoma virus proviral DNA

Murine fibroblasts can be transformed by subgenomic fragments of feline sarcoma virus (FeSV) proviral DNA generated by BamH-I digestion of DNA of Snyder-Theilen FeSV and FeLV-infected mink cells. The efficiency of transformation of NIH 3T3 cells by BamH-I-treated FeSV proviral DNA was the same as that of untreated FeSV DNA. Focus-forming virus could not be rescued from the BamH-I-digested FeSV DNA-transformed cells. However, DNA from these transformed cells was able to induce transformation in secondary transfection experiments. Analysis of the DNAs from two BamH-I-digested FeSV DNA-transformed clones showed that the transformants contained only the 5′ two-thirds of the FeSV provirus. Cells transformed by subgenomic fragments of FeSV DNA produce the 85,000-dalton gag-x protein, but do not express FOCMA. These experiments support the notion that the gag-x protein plays an active role in maintenance of the transformed phenotype.