Figure 11.

Multimerized copies of the HS7 sites B and C confer Oct-1 and Oct-2 down-regulation to a heterologous minimal promoter. NIH3T3 cells were transiently cotransfected with 500 ng of the pTK, p(Bwt)₃TK, p(BmutOct)₃TK, p(Cwt)₃TK or p(CmutOct)₃TK reporter construct and with increasing amounts (0, 100 and 500 ng) of either pCG-Oct-1 (A) or pCG-Oct-2 (B). To maintain the same amount of transfected DNA and to avoid squelching artifacts, the different amounts of Oct-1/Oct-2 expression vectors cotransfected were complemented to 500 ng of DNA by using the empty pCG 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 luciferase activity of each reporter construct in the absence of ectopically expressed Oct-1 or Oct-2, which was arbitrarily assigned a value of 100% of activity. The down-regulation of the TK promoter constructs by Oct-1 (A) and Oct-2 (B) is also indicated (in fold). 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.