FIGURE 3.

Dimerization of full-length CAPRI in cells requires the helix motif in the C-terminal tail. A, myc-CAPRI coimmunoprecipitates with GFP-CAPRI. Cos-7 cells were transfected to co-overexpress GFP-CAPRI (or GFP as control) with myc-CAPRI. Anti-GFP monoclonal antibody was used for immunoprecipitation (IP) and anti-CAPRI antibody for Western blotting (WB). B, mutation of the two leucines in the helix motif of the C-terminal tail of CAPRI abolishes the dimerization of full-length CAPRI. Cos-7 cells were transfected to co-overexpress GFP-CAPRI (of GFP as control) with myc-CAPRI or myc-SH-CAPRI. Anti-GFP antibody was used for immunoprecipitation and anti-CAPRI antibody for Western blotting. myc-SH-CAPRI protein failed to coimmunoprecipitate with GFP-CAPRI, whereas myc-CAPRI did. C, deletion of the C-terminal tail of CAPRI abolishes the dimerization of full-length CAPRI. HA-tagged CAPRI mutant with a 41-AA C-terminal deletion, HA-ΔcCAPRI, was co-overexpressed with GFP-CAPRI or GFP. Immunoprecipitation was performed using anti-GFP antibody, and blotting was done with anti-HA and GFP antibodies. HA-ΔcCAPRI failed to coimmunoprecipitate with GFP-CAPRI. The blots shown are representative of at least three independent experiments.