FIG. 5.

A positive element for lens-preferred expression. Induction of a heterologous (TK) promoter by the composite UB.ZPE element, containing the MARE and Pax6 binding sites (−245 to −152). The results of transfection of pTKCAT and UB.ZPE.TKCAT into NIH 3T3 cells and N/N1003A cells are shown. The CAT activity of UB.ZPE.TKCAT relative to that of parent pTKCAT in the same experiment is shown for each cell type. The composite UB.ZPE positive element is illustrated below. Boxes show major footprinted regions: UB is footprinted in fibroblasts which do not support ζ expression, while ZPE is footprinted in lens-derived cells which do allow expression (38). The position of the MARE/Nrl binding site is shown. The ZPE is the binding site for canonical Pax6.