| Abstract: | Oncogenic forms of the Abl and Src tyrosine kinases trigger the destruction of the Abi proteins, a family of Abl-interacting proteins that antagonize the oncogenic potential of Abl after overexpression in fibroblasts. The destruction of the Abi proteins requires tyrosine kinase activity and is dependent on the ubiquitin–proteasome pathway. We show that degradation of the Abi proteins occurs through a Ras-independent pathway. Significantly, expression of the Abi proteins is lost in cell lines and bone marrow cells isolated from patients with aggressive Bcr–Abl-positive leukemias. These findings suggest that loss of Abi proteins may be a component in the progression of Bcr–Abl-positive leukemias and identify a novel pathway linking activated nonreceptor protein tyrosine kinases to the destruction of specific target proteins through the ubiquitin–proteasome pathway. |
