FIG. 3.

Activation of the BaLCV and RhLCV Qp promoters is IRF dependent. (A) The dependence of the BaLCV and RhLCV Qp promoters on the IRF binding site QRE-2, which is essential for EBV Qp function, was evaluated by an hGH reporter gene assay with EBV-negative Louckes BL cells. Promoter activity is presented as the ratio of hGH expression achieved from a wild-type promoter sequence (Qp) to that achieved from the respective LCV Qp in which the IRF binding site had been mutated (mtQp). (B) The BaLCV and RhLCV Qp promoters require IRF expression for activation. MEFs nullizygous for IRF-1 and IRF-2 were cotransfected with a Qp or mtQp hGH reporter plasmid and either an empty expression vector (pSG5) or the IRF-2 expression vector pSG.IRF-2. Promoter activity was measured by radioimmunoassay of hGH expression. The data shown are from a representative experiment in which all transfections were done in triplicate and hGH values were corrected for transfection efficiency. The 5′ and 3′ coordinates of the promoter DNA in each reporter plasmid were −143 to +75 relative to the EBV Qp transcription start site. Error bars indicate standard deviations.