FIG. 6.

Inhibition of STAT6 expression contributes to reactivation of KSHV lytic replicaton. (A) Stress-induced RTA expression in PEL cells is correlated with inhibition of STAT6 expression. PEL cells (BC3 and BCBL1) and KSHV-negative BJAB cells were individually subjected to treatment with hypoxia (1% O₂ or 100 μM CoCl₂) or TPA and sodium butyrate (NaBu) (20 ng/ml and 1.5 mM, respectively) for 18 h. Cell lysates were subjected to immunoblotting against STAT6, RTA, and GAPDH. The relative density (RD) of RTA was quantified and is shown at the bottom. (B and C) STAT6 knockdown enhances the expression of RTA. PEL BC3 cells (parent, shSTAT6, or shCtrl) were subjected to treatment with TPA and NaB (20 ng/ml and 1.5 mM, respectively) for various times (0, 12, or 24 h). Cell lysates were subjected to the immunoblotting assay as in panel A, or the treated cells were fixed and subjected to an immunofluorescence assay with anti-RTA and DAPI (4′,6-diamidino-2-phenylindole) staining. The numbers shown in the figure indicate the percentages of RTA-positive cells.