FIG. 8.

EBV induces expression of the IRF-5 negative regulator IRF-4. (A) Western blot assay comparing the expression of IRF-5 with that of IRF-4 and IRF-3 in different B-cell lines. Lane 1, 293 cells transfected with V3 IRF-5. Lanes 2, 4, and 6, type III latently infected cell lines. Lane 3, EBNA2 deletion-containing P3HR-1 cells. Lane 5, type I latently infected cell line. β-Tubulin served as a control for protein loading. (B) Western blot assay showing the dependence of IRF-4 expression on EBV latency gene expression. EREB2-5 cells were deprived of β-estradiol and harvested at the time points noted. Four days after withdrawal, β-estradiol was added back into the medium at 1 μM and cells were grown for a further 1 day (−4/+1). The membrane was probed with anti-IRF-4 and LMP1 antibodies. β-Tubulin was used as a loading control. (C) LMP-1 regulates IRF-4 expression. 1852, a tetracycline-on LMP-1, type III cell line, was grown in medium without tetracycline for 5 days, and then tetracycline was added back to the medium (time zero). A Western blot of the cell extract was probed with anti-IRF-4 and LMP1 antibodies. β-Tubulin was used as a loading control. The results are representative of two experiments.