FBJ murine osteosarcoma virus: identification and molecular cloning of biologically active proviral DNA

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Abstract
A 12.0-kilobase (kb) EcoRi restriction fragment containing FBJ murine osteosarcoma virus (FBJ-MSV) proviral DNA was identified in FBJ-MSV-transformed nonproducer rat cells and molecularly cloned in bacteriophage Charon 30 (.lambda.FBJ-1). A 5.8-kb HindIII fragment containing the entire FBJ-MSV proviral DNA was isolated from .lambda.FBJ-1 and subsequently subcloned in plasmid pBR322 (pFBJ-2). The DNA from recombinant plasmid pFBJ-2 was able to induce morphological transformation of rat fibroblasts in tissue culture. Transfected cells contained the p55 and p39 antigens specific for cells transformed by FBJ-MSV. The organization of the FBJ-MSV provirus was analyzed by restriction endonuclease mapping, and a region of nonhomology with the helper virus was delineated. Sequences specific for this region (presumably the viral fos gene) were subcloned and used as a probe to identify related sequences present in the normal genomes of cells from a variety of mammalian species (cellular fos). A single-size (3.4 kb long)class of RNA hybridizing to the viral fos probe was identified in FBJ-MSV-transformed cells.