FIGURE 4.

PP4R4 is a cytoplasmic regulatory subunit for PP4c. A, localization of PP4R4 by indirect immunofluorescence. Vero cells were transfected with HA-tagged constructs as indicated; 24 h post transfection, cells were fixed, permeabilized, and stained with anti-HA antibody, as described under “Experimental Procedures.” B, model depicting multiple PP4c-containing stable complexes. PP4R1, PP4R2-PP4R3, and PP4R4 are all specific interactors for PP4c. α4-CCT interacts with both PP2Ac and PP4c. Although PP2A A-PP2A B′δ exhibits a stronger affinity for PP2Ac, these proteins also weakly interact with PP4c.