Homologous cell-derived oncogenes in avian carcinoma virus MH2 and murine sarcoma virus 3611

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Abstract
Retroviral oncogenes (v-onc) are derived from cellular genes (c-onc) which are highly conserved among different species. Retrovirus-transduced oncogenes are most commonly associated with the induction of haematopoietic tumours and sarcomas. The avian retrovirus Mill Hill no. 2 (MH2) was isolated from a spontaneous ovarian tumour of a chicken and is distinguished by the predominant induction of liver and kidney carcinomas in fowl. MH2 also induces transformation of fibroblasts, macrophages and epithelial cells in culture. The genome of MH2 contains two unrelated and independently expressed cell-derived oncogenes, v-mil and v-myc. Three other viral isolates among avian acute transforming retroviruses contain the v-myc oncogene, but only MH2 contains both v-myc and v-mil. Hence, some of the pathogenic specificities of MH2 may be due to the simultaneous expression of two oncogenes. The murine sarcoma virus 3611 (3611-MSV) isolated from a mouse carrying lung carcinoma and peritoneal tumours, induces fibrosarcomas in newborn mice and the transformation of fibroblasts and epithelial cells in culture. The oncogenic properties of 3611-MSV are due to the presence in its genome of a cell-derived oncogene termed v-raf. We report here that the two independently transduced oncogenes v-mil and v-raf are closely related and that they were apparently derived from homologous cellular genes of avian and mammalian species.