Immunogen sequence: MFRDFGEPGP SSGNGGGYGG PAQPPAAAQA AQQKFHLVPS INTMSGSQEL QWMVQPHFLG PSSYPRPLTY PQYSPPQPRP GVIRALGPPP GVRRRPCEQI. The v-Fos oncogene was initially detected in two independent murine osteosarcoma virus isolates and an avian nephroblastoma