FIG. 3.

Activation of the vIRF promoter 3′-end deletion mutant and TATA element site-directed mutant. (A) Schematic diagram of the vIRF promoter and two mutant constructs. The vIRF promoter deletion mutant lacked part of the putative vIRF lytic promoter sequence but retained all of the latent promoter sequence. The TATA box was located between the minor and major transcript start sites. In the vIRF promoter TATA mutant, TATATA was changed to TAGCTC. (B) Relative luciferase activity of the vIRF promoter deletion mutant and the TATA element mutant compared with the wild-type promoter. Neither mutant construct was responsive to TPA induction. Note that the vIRF promoter still had low activity in the latent phase (uninduced). The wild-type vIRF promoter and the two mutant promoter constructs were transfected into BCBL-1 cells that were not induced or were induced with TPA immediately after transfection. Cells were harvested 48 h later and assayed for luciferase activity. Luciferase activity values were normalized by cotransfecting an internal control plasmid (pCMV-β-Gal). Activities were expressed relative to the wild-type promoter activity induced by TPA, which was defined as 100%. The average of duplicate experiments (with standard deviation [error bar]) is represented.