FIG. 4.

Analysis of K1 promoter activity in BCBL-1 cells. (A) K1 promoter activity in the context of latent KSHV infection was measured by transfections of the K1 promoter constructs in BCBL-1 B cells. Transfection efficiencies were normalized by using a plasmid expressing β-galactosidase. Cells were left untreated and harvested 48 h posttransfection. Luciferase activity was measured for each construct and normalized to β-galactosidase activity. Activity of each promoter construct is represented as fold activation over the pGL2-Basic vector control. (B) Each of the K1 promoter constructs was cotransfected with a pcDNA3-Orf50 expression plasmid into BCBL-1 cells. Luciferase activities were measured and normalized as described above. Activity of each promoter construct is represented as fold activation over the pcDNA3 vector control. (C) The effects of TPA induction on the K1 promoter were tested by performing the same transfections described for panel A but treating cells with TPA to induce the KSHV lytic cycle or DMSO (negative control). Activity of each promoter construct is represented as fold activation over the DMSO control.