FIG. 2.

Mutations of pNL4-3 used in this study. The sequence of exon 2 is shown in uppercase letters, and the surrounding intron sequences are shown in lowercase letters. The location of the changes in sequence for each of the mutants is shown. The predicted ΔG⁰₃₇ in kcal/mol for the eight base pairs of U1 snRNA binding to wild-type and mutated 5′ss D2 was calculated by the method described by Serra and Turner (24).