FIG. 8.
The spacer sequence contributes to the IL-15 virus-inducible reporter activity. (A) The 128/Luc construct with the native spacer sequence is activated about 10-fold when cotransfected with IRF-1, p50, and p65 expression plasmids into the p19 cells. However, when the spacer sequence was removed in 128/Luc, no reporter activity was observed in a similar experiment. Replacement of the native spacer sequence with an irrelevant sequence with the same number of nucleotides in the 126/Luc construct did not increase the promoter activity of this construct when it was cotransfected with IRF-1, p50, and p65 expression plasmids. This indicates the importance of the spacer sequence in the activity of the virus-inducible region. (B) The spacer sequence forms a DNA-protein complex with p19 cell extracts. Total cell extracts were prepared and used in an EMSA with the spacer as a probe (CTGTTAGCTGGGGTT). The arrow indicates the position of the DNA-protein complex. The spacer unlabeled probe was added at 50× excess, as indicated in this figure.