FIG. 5.

U1A binding between the downstream GU-rich regions inhibits secretory poly(A) site expression in vivo. Luciferase constructs containing the wild-type secretory poly(A) site from position 1790 to 2085 or that containing single (mut ds1 and mut ds2) or double mutations (mut ds12) in the downstream U1A binding sites were transfected into HeLa cells, and luciferase activity was measured 24 h later. Bars represent the mean of triplicates ± SE. Activity was expressed as a percentage of the wild type (wt).