NFAT and AP-1 signaling pathways are responsible for HBZ-mediated inhibition of IFN-γ production. (A-C) Effects of wild-type and mutant sHBZ on (A) an NFAT-Luc reporter, (B) an AP-1-Luc reporter, and (C) the IFN-γ promoter. (D) The suppressive effect of sHBZ mutants on IFN-γ production from primary mouse CD4 T cells. Retroviruses expressing wild-type and mutated HBZ were transduced to primary mouse CD4 T cells, stimulated with PMA and ionomycin, and stained. (E) ChIP assay of the NFAT and AP-1 binding sites of IFN-γ promoter. sHBZ-expressing Jurkat cells were stimulated with PMA and ionomycin, and ChIP assay was performed using anti-NFATc2 or anti–c-Jun antibodies. The IFN-γ promoter (−302 to −137) was amplified by real-time PCR. The data from stimulated empty-transfected Jurkat cells were used as a reference. Representative data (mean ± SD) from 2 or 3 independent experiments are shown. N.D. indicates not detected.