FIG. 4.
A 265-bp region from the Mtv-1 LTR is sufficient as an enhancer in Ba/F3 cells. (A) Ba/F3 cells were transfected without added reporter plasmid DNA (mock) or with the enhancer test plasmid pGL2-Pro or pGL2-Pro carrying the Mtv-1 regions indicated cloned into the unique BamHI and SalI sites 3′ of the promoter-reporter cassette. Cells were harvested and lysed, and luciferase activity was determined. Results are expressed as relative light units and represent the arithmetic means ± standard deviations from at least three parallel experiments with two different DNA preparations. PSV40, SV40 promoter (solid square). The NFI (solid oval) and MAF (open oval) sites are shown. (B) The DNA sequence of the Mtv-1 LTR region (8) from positions −1025 to −761 is presented below the graph. Established NFI and MAF binding sites (14) are shown by dashed and solid ovals, respectively.