Gaussia princeps luciferase-based complementation assay and data analysis [normalized luminescence ratio (NLR)] were performed according to Cassonnet et al. (74). Human 293T cells were plated in a 96-well plate with 2 × 104 cells per well and transfected the next day with 100 ng of each plasmid using the jetPRIME reagent (Polyplus-transfection). Luciferase signals were read 24 hours after transfection. NLR was calculated by dividing the luciferase value of the two chimeric partners by the sum of the luciferase values of each chimeric partner mixed with the other free Gaussia luciferase domain. Results were expressed as fold increase with respect to the reference (wt full-length P), which was set to 1.