A role for proto-oncogenes in the regulation and modulation of cell proliferation1,2 has been suggested by the findings that the B-chain of platelet-derived growth factor (PDGF) is encoded by the proto-oncogene sis3-7 and that the erb-B oncogene product is a truncated form of the epidermal growth factor (EGF) receptor8-10. Furthermore, the product of the proto-oncogene fms (c-fms) may be related or identical to the receptor for macrophage colony-stimulating factor (CSF-1)11. v-fms is the transforming gene of the McDonough strain of feline sarcoma virus (SM-FeSV) 12,13 and belongs to the family of src-related oncogenes which have tyrosine-specific kinase activity. Furthermore, nucleo-tide sequence analysis of the v-fms gene product revealed topologi-cal properties of a cell-surface receptor protein14. To elucidate the features involved in the conversion of a normal cell-surface receptor gene into an oncogenic one, we have now determined the complete nucleotide sequence of a human c-fms complementary DNA. The 972-amino-acid c-fms protein has an extracellular domain, a membrane-spanning region, and a cytoplasmic tyrosine protein kinase domain. Comparison of the feline v-fms and human c-fms sequences reveals that the proteins share extensive homology but have different carboxyl termini.
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