Fig. 5.

USP20, but not USP33, deubiquitinates Tax. (A) Tax coimmunoprecipitates with USP20 but not USP33. The indicated plasmids were transfected into HEK293T cells and immunoprecipitated using anti-HA for HA-USP20 (USP20; lanes 3 and 4) or HA-USP33 (USP33; lanes 5 and 6). The immunoprecipitates were blotted and probed with anti-USP20 or anti-USP33. The coimmunoprecipitated Flag-Tax was verified by immunoblotting with anti-Flag. WCE, whole-cell extract. (B) Flag-Tax and HA-Ub as indicated were cotransfected into HEK293T cells with USP20 (lane 3) or USP33 (lane 4). Immunoprecipitation was performed with anti-Flag (top panels). Ubiquitinated Tax (lanes 2, 3, and 4; top panel) was detected using anti-HA in immunoblotting of anti-Flag immunoprecipitates. The amount of ubiquitinated Tax was reduced by the cotransfection of USP20 (lane 3). Amounts of Tax, USP20, USP33, and actin in the whole-cell lysates (WCE) are verified in the bottom panels by immunoblotting.