EBV vPK regulates expression of ZEBRA in BLs and LCLs. (A and B) HH514-16 (A) and CLIX-FZ (B) BL cells were transfected with empty vector (EV) or pFLAG-vPK, treated with NaB (A) or doxycycline (B) after 24 h, harvested at the indicated times posttreatment, and immunoblotted with antibodies against ZEBRA, FLAG, and β-actin. Numbers represent relative amounts of ZEBRA after normalizing to β-actin (A) or the ratio between endogenous ZEBRA (lower-molecular-mass band) and doxycycline-induced FLAG-ZEBRA (higher-molecular-mass band) (B). (C) LCL was transfected with empty vector plus pLIX-FZ (encoding doxycycline-inducible BZLF1) or pFLAG-vPK and pLIX-FZ, exposed to doxycycline after 24 h, and harvested at indicated times posttreatment for immunoblotting with antibodies against ZEBRA or FLAG. Numbers reflect the ratio between endogenous ZEBRA and doxycycline-inducible FLAG-ZEBRA. (D and E) HH514-16 (D) and CLIX-FZ (E) cells were transfected with scrambled siRNA or si-BGLF4, treated with NaB (D) or doxycycline (E) after 8 h, and harvested at the indicated times after treatment for immunoblotting with antibodies against ZEBRA, β-actin, and FLAG. Top rows of numbers indicate relative amounts of ZEBRA protein normalized to β-actin (D) or the ratio between endogenous ZEBRA (lower-molecular-mass band) and doxycycline-induced FLAG-ZEBRA (higher-molecular-mass band) (E). Bottom rows of numbers represent relative amounts of vPK after normalization to β-actin (D) or FLAG-ZEBRA (E). All experiments were performed at least twice.