Transformation of NIH/3T3 mouse cells by DNA of Rous sarcoma virus

Abstract

NIH/3T3 mouse cells were transformed by integrated and unintegrated DNAs of Rous sarcoma virus (RSV)-infected chicken cells without production of progeny virus. In addition, DNA of the replication-defective Bryan high titer strain of RSV transformed NIH/3T3 cells, indicating that transformation of NIH/3T3 cells by RSV DNA did not require virus replication. The efficiency of transformation of NIH/3T3 cells by RSV DNA was similar to the efficiency of transformation of these cells by murine sarcoma virus DNA and to the efficiency of transfection of chicken embryo fibroblasts by RSV DNA. NIH/3T3 cells transformed by RSV DNA were morphologically similar to cells transformed by virus infection and were capable of anchorage-independent growth in soft agar. Stable inheritance of intact RSV genomes by RSV DNA-transformed NIH/3T3 cells was demonstrated by rescue of virus from these cells after fusion with chicken embryo fibroblasts and by transfection assays of the DNAs of RSV DNA-transformed NIH/3T3 cells on chicken embryo fibroblasts. Analysis of the DNAs of RSV DNA-transformed NIH/3T3 cells by restriction endonuclease digestion and nucleic acid hybridization indicated that RSV genomes were linked to cellular DNA sequences. It therefore appeared that transformation of NIH/3T3 cells by RSV DNA occurred by direct integration and stable expression of the donor DNA, rather than by production of extracellular progeny virus and secondary virus infection, as was previously shown to be required for transformation of chicken embryo fibroblasts by RSV DNA.