LMP1 sequestration of TRAF3 requires the major LMP1 cytoplasmic domain TRAF-binding site. (A) A schematic of the CTAR1 cytoplasmic region of LMP1, indicating its 3 TRAF-binding motifs. The SUB2 LMP1 molecule has the indicated mutation in the first of these motifs. (B) CD40 immunoprecipitations (IP) as in prior figures, from whole-cell lysates (WCL) of parent CH12.LX cells or transfected subclones expressing WT or SUB2 LMP1 molecules, induced to express LMP1 as in Figure 4. A representative western blot of 3 similar experiments is shown. (C) Relative CD40-associated TRAF3 levels (presented as mean values ± SE from 3 independent experiments as above), with CD40-associated TRAF3 levels in parent CH12.LX cells set at 1. A 1-way ANOVA was used to analyze results for statistical significance, and the adjusted P value was calculated using Sidak’s multiple comparison test (*P < .0001, **P = .001).