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Oncogene. 2000 Nov 20;19(49):5643-50.

Regulation of cell death by the Abl tyrosine kinase.

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Department of Biology and the Cancer Center, University of California, San Diego, La Jolla, California, CA 92093-0322, USA.


The c-abl proto-oncogene encodes a protein tyrosine kinase that is distributed in the nucleus and the cytoplasm of proliferating cells. In the nucleus, c-Abl activity is negatively regulated by the retinoblastoma protein (RB) and positively regulated by DNA damage signals. Activation of the c-Abl kinase by DNA damage requires the function of ATM, which regulates cell cycle checkpoint, DNA repair and apoptosis in response to DNA damage. Cells lacking c-Abl can activate cell cycle checkpoints and DNA repair, but show defects in apoptosis. The apoptosis defect of c-Abl deficient cells is correlated with a defect in the induction and activation of p73, which is a functional homologue of the p53 tumor suppressor protein and has pro-apoptotic activity. The inhibition of c-Abl by RB is consistent with RB's ability to block apoptosis; while the activation of c-Abl by ATM is consistent with ATM's ability to activate cell death. The oncogenic Bcr-Abl tyrosine kinase is a potent inhibitor of apoptosis, and it is retained exclusively in the cytoplasm of transformed cells. Interestingly, when Bcr-Abl is trapped inside of the nucleus through a combined disruption of its cytoplasmic retention and its nuclear export, this oncogenic Abl kinase induces apoptosis. Taken together, the current results support a role for the nuclear c-Abl tyrosine kinase in the regulation of apoptosis. Whether the cytoplasmic c-Abl kinase can actively inhibit apoptosis remains to be determined; however, a deliberate retention of c-Abl in the cytoplasm could potentially contribute to the attenuation of apoptosis response.

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