FIG. 3.

Proteins which associate with TCFβ1 phosphorylate GST–c-Jun in vitro. Bacterially expressed GST fusion proteins of full-length TCFβ1 (residues 1 to 301), the activation domain of TCFβ1 (residues 1 to 144), or the DNA binding domain of TCFβ1 (residues 145 to 301) were incubated with cell lysates from unactivated (−) Jurkat cells (left panel) or Jurkat cells activated (+) with anti-CD3 plus anti-CD28 (left panel) or were incubated with activated recombinant JNK2 (a kind gift from M. Karin) (right panel). The proteins associated with GST-TCFβ1 were immobilized on glutathione-agarose beads. GST–c-Jun was subsequently added to the kinase reaction mixture, and the phosphorylated proteins were resolved on SDS-polyacrylamide gels and analyzed by autoradiography.