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. 2003 Sep;77(17):9590–9612. doi: 10.1128/JVI.77.17.9590-9612.2003

FIG. 3.

FIG. 3.

Exogenously introduced C/EBPα triggers endogenous RTA protein expression in PEL cells. (A to C) Control double-stain IFA showing lack of background expression of either Flag epitope or the endogenous RTA protein in BCBL1 cells transfected with empty CMV-Flag vector DNA as detected with anti-Flag MAb (A) (rhodamine [red]) or anti-RTA PAb (B) (FITC [green]). (C) DAPI nuclear staining (blue) showing all cells in the same field. (D to F) Expression of Flag-C/EBPα protein (D) (red) in transfected BCBL1 cells induces expression of endogenous RTA protein in the same cells as detected with anti-RTA PAb (E) (green). (F) Merged image. (G to I) Expression of Flag-RAP protein in transfected BCBL1 cells (G) (red) fails to induce endogenous RTA protein expression (H) (green). (I) DAPI (blue) showing the whole cell population. (J to L) Expression of Flag-RAP protein (J) (red) in C/EBPα plus Flag-RAP cotransfected BCBL1 cells and induction of RTA (K) (green) in the same cells. (L) Merged image. Note that spontaneous background RTA expression occurs in approximately 1% of untreated BCBL1 cells.