Tcl1 enhances Akt1 kinase activity. Endogenous Akt1 was immunoprecipitated from 293 cells transfected with the indicated constructs. Kinase activity was determined by using GSK3-β-GST fusion protein as a substrate. Each reaction was terminated after 0, 4, 10, and 30 min. Amounts of Akt (upper panels) and phospho-GSK3-β (lower panels) were determined by Western blotting with rabbit anti-Akt antibody and anti-phospho-GSK3-β antibody, respectively. (A) Akt1 was immunoprecipitated from TCL1-transfected cells with a anti-Tcl1 antibody (Left) or vector-transfected cells with anti-Akt antibody (Right). (B) Same lysates as in A, but immunoprecipitations were carried out with an anti-Akt antibody only. (C) Lysates of thymus from a TCL1-transgenic mouse (2) (left two lanes) or a wild-type mouse (right two lanes) were immunoprecipitated with anti-Akt antibody. For immunoprecipitation of Akt, we used anti-PKBα/Akt1 clone 7 antibody, anti-Akt/PKB rabbit polyclonal antibody, or anti-Akt antibody included with Akt kinase assay kit, with consistent results.