Abl Interactor 2 (ABI2)

Sequence analysis predicted that the 401-amino acid ABI2 protein is 65% identical to the Abi1 mouse protein and 70% identical to the frog Xlan4 protein. ABI2 possesses a basic N terminus with homology to a homeodomain protein; a central serine-rich region; 3 PEST sequences, which are implicated in susceptibility to protein degradation; several proline-rich stretches; and an acidic C terminus with multiple phosphorylation sites and an SH3 domain. Binding and mutational analyses showed that the interaction between the N-terminal proline-rich stretch of ABI2 and the ABL1 SH3 domain is highly specific, but that the ABI2 SH3 domain also binds to a proline-rich stretch downstream of the nuclear localization signal in the ABL1 C terminus. Immunoblot and autoradiographic analyses indicated that ABI2 is phosphorylated by ABL1.