TCL1 (T cell leukemia 1), MTCP1 and TCL1b belong to the TCL1 proto-oncogene family, and their products are involved in Akt activation during embryonic development, T cell leukemias, prolymphocytic leukemias and B cell lymphomas (1-3). The Akt association domain of TCL1 binds with the PH domain of Akt. The formation of an oligomeric TCL-Akt complex is required for TCL1 coactivator function and results in phosphorylation and activation of Akt . Furthermore, functional analysis indicates that the interaction between TCL1 and Akt promotes translocation of Akt to the nucleus (4-6). These findings are supported by the crystal structure of TCL1, which suggests that TCL1 may participate in molecular transport (7).