FIGURE 3.

Response of the BLV promoter to ectopically expressed DNA methyltransferases. Raji cells were transiently cotransfected using the DEAE-dextran procedure with 500 ng of pLTRwt-luc and increasing amounts (0, 50, 100, 250, 500, and 1000 ng of plasmid DNA) of the DNMT1, DNMT3A, and DNMT3B expression vectors (A, B, and C, respectively). To maintain the same amount of transfected DNA and avoid squelching artifacts, the different amounts of DNMT expression vector cotransfected were complemented to 1000 ng of DNA by using the empty vector. Luciferase activities measured in cell lysates 44 h after transfection were normalized to protein concentrations. The results are presented as histograms indicating the induction by DNMT1, DNMT3A, or DNMT3B with respect to the activity of the reporter construct in the absence of DNMT, which was assigned a value of 1. Means ± S.E. are indicated. A representative experiment of four independent transfections is shown. Nuclear extracts were prepared and analyzed by Western blot with an anti-c-Myc antibody to detect DNMT1, DNMT3A, and DNMT3B expression levels. These results are presented in parallel with the transfection results for each DNMT.