Binding to X is necessary for the cytoplasmic localization of P. (A) Schematic representation of FLAG-fused deletion mutants of BDV P. F, FLAG. (B) Subcellular localization of BDV P mutants in the presence of wild-type X. X and P expression plasmids were cotransfected into OL cells in the ratio of 5:1 (0.5:0.1 μg) on eight-well chamber slides. Panels: a, pcPf and pcX; b, pcP'f and pcX; and c, pcP-Δ1 and pcX. (C) Immunoprecipitation of BDV P and X. Lanes: 1, pcX alone, 2, pcPf and pcX; 3, pcP'f and pcX; 4, pcPf-Δ1 and pcX. The cell lysates transfected with P mutant and X expression plasmids (ratio, 1:1 [3:3 μg]) were immunoprecipitated with anti-FLAG antibody, and coprecipitants were detected with anti-X antibody.