Tax-1 and Gβ2 interaction domains. (A) Schematic representation of the Gβ2 subunit and deletion mutants. Gβ consists of an amino-terminal α-helical segment followed by 7-repeat bladelike structures called WD repeats. (B) HEK 293T cells were transfected with EYFP-Gβ2 (Fl), EYFP-Gβ2 (aa 1-100), EYFP-Gβ2 (aa 101-200), EYFP-Gβ2 (aa 201-340), and HTLV-1Tax expression constructs, as indicated. Forty-eight hours after transfection, cells were lysed and protein expression was verified by immunoblotting using anti-GFP and anti–Tax-1–specific antibodies. Lysates were immunoprecipitated with a GFP-specific antibody. Immunoprecipitated proteins were analyzed by SDS-PAGE and immunoblotting using an anti–Tax-1 antibody. (C) Schematic representation HTLV-1 Tax deletion mutants. Deleted regions are indicated by the wide V-like symbols. (D) HEK 293T cells were transfected with EGFP-TD55, EGFP-TD99, EGFP-TD150, EGFP-TD254, and Flag-Gβ2–expressing constructs, as indicated. Forty-eight hours after transfection, cells were lysed and protein expression was verified by immunoblotting using anti–Flag M2 and anti–GFP-specific antibodies. Lysates were immunoprecipitated with M2 Flag–specific antibody. Immunoprecipitated proteins were analyzed by SDS-PAGE and immunoblotting with anti–GFP antibody. Arrows indicate immunoprecipitated protein bands.