FIG. 3.

USF1 and USF2 activate the class I promoter. HeLa cells were cotransfected with 10 μg of -400CAT class I reporter construct (Fig. 1) and 3 μg of the vector control, pSG5, or the indicated USF expression plasmids. Representative maps of the expressed USF sequences and deleted regions are given on the left-hand side of the figure: upstream regulatory region (USR), binding region (BR), and HLH-Z interaction domain (HLH-LZ). Numbers in parentheses refer to deleted amino acids. Basal -400CAT activity (cotransfected with pSG5) is shown at the top of each panel. (A) The ability of USF1 and derivative truncations to trans-activate MHC class I promoter expression. (B) The ability of USF2 and truncated derivatives to activate class I expression. Data are expressed as relative percentages of acetylation normalized to the transfection control, pSV2LUC. Error bars indicate standard errors.