Normal and Transforming N-Terminal Variants of c-abl

V-abl was first described as the oncogene contained in Abelson murine leukemia virus (A-MuLV), a virus that transforms both lymphocytes and fibroblast lines. The v-abl gene product has a protein tyrosine kinase activity which is essential for the transforming capacity of the virus (Prywes et al. 1983). The normal cellular counterpart, the c-abl proto-oncogene, also encodes a protein with tyrosine kinase activity (Konopka and Witte 1985; Ben-Neriah et al. 1986a). In addition to capture by retroviruses, c-abl can be activated by chromosomal translocations, such as in human chronic myeloid leukemia. In this review we discuss the structure of the c-abl gene, the various transcripts it expresses, and how it is activated to become an oncogene.