CHIP coactivates with EBNA2 and inhibits EBNALP and EBNA2 coactivation. (A) Schematic diagram of Flag-tagged CHIP and CHIP deletion or point mutant proteins, CHIPΔTPR, CHIPΔU, CHIPK₃₀A, and H₂₆₀Q. (B-C) CHIP inhibits EBNALP, but not EBNALPd45, coactivation with EBNA2 in BJAB cells. BJAB cells were transfected with 10 μg E2, FLP, or FLPd45, or 30 μg CHIP or CHIP mutant expression vectors, 5 μg LMP1p-Luciferase reporter plasmid, 2 μg β-gal control expression plasmid, or vector DNA to balance the amount of transfected DNA. Assays were done after 24 hours. (D) Relative expression levels of CHIP or CHIP mutant proteins after expression for 24 hours in BJAB cells. Flag-tagged CHIP proteins were detected by immune blot with M2 antibody. (E) EBV latency I Akata BL cells were transfected with 10 μg E2 and 10 μg FLP, FLPd10, FLPd34, or FLPd45 expression vector and after 48 hours immune blotted for LMP1 expression. CHIP(+) indicates an immune blot from cells that were also transfected with 30 μg CHIP expression plasmid.