A144E TACI preassembles in 293T cells but the IC domains failed to cluster both at baseline and following ligand stimulation. (A) Self-association of WT and A144E mTACI in 293T transfectants. (B-C) FRET analysis of 293T cells cotransfected with CFP-tagged WT mTACI and YFP-tagged WT mTACI, A144E mTACI, or CD40 control in the absence of ligand (B), and following addition of ZZ-APRIL, BAFF, or BAFF-60mer (C). Similar results were obtained in 3 experiments.