Figure 12.

Ability of multimerized HS7 site B motifs to confer PU.1 stimulation to a TK minimal promoter. NIH3T3 cells were transiently cotransfected with 500 ng of either pTK, or p(Bwt)₃TK or p(BmutPU.1)₃TK and with increasing amounts (0, 100, 250 and 500 ng) of the PU.1 expression vector, pJ6-PU.1. To maintain the same amount of transfected DNA and to avoid squelching artifacts, the different amounts of PU.1 expression vector cotransfected were complemented to 500 ng of DNA by using the empty pJ6 vector. Luciferase activities were measured in cell lysates 44 h after transfection and were normalized with respect to protein concentrations of the lysates. Results are presented as histograms indicating the induction by PU.1 (in fold) with respect to the activity of each TK reporter construct in the absence of PU.1, which was assigned a value of 1. Means of triplicate samples and standard errors of the means are shown. An experiment representative of three independent transfections performed with at least two different DNA preparations is shown.