PLASMID RESCUE OF AN ONCOGENIC SEQUENCE CONTAINING A MOUSE MAMMARY-TUMOR VIRUS GENE

Plasmid rescue was performed on an oncogenically transformed cell line established by transfection of NIH/3T3 cells with normal mouse DNA and plasmids containing a murine leukemia virus long terminal repeat, and a selectable marker. One of the rescued plasmids contained newly acquired DNA 3,500 basepairs in length. This sequence was present in several extra copies in the parental cell line. It was also found to be transcribed. NIH/3T3 cells transfected with the rescued plasmid proved to be oncogenic in nude mice. The acquired sequence appeared to contain (part of) the long terminal repeat of mouse mammary tumor virus.