FIG. 3.

AU/A-rich sequences surrounding the core upstream element contribute to the strength of the μs poly(A) signal. The AAUAAA core upstream element and proximal downstream GU/U-rich element are shown in uppercase letters, and the CA cleavage site is shown in bold. The nucleotides that are changed from the wild-type sequence are underlined. In pA1, the changes are due to the restriction site used for cloning. In pA2, the entire sequence surrounding AAUAAA has been changed. The pA/splice expression ratios are compiled from at least two S1 nuclease analyses of two independent transfections in HepG2 cells.