FIG. 3.

The 3′ region upstream of exon 6B makes pre-mRNA responsive to PTB. (A) Schematic representation of the Glo-βTm pre-mRNA used in in vitro splicing experiments. The intronic region upstream of exon 6B containing the BP, PY, and 3′ 6B fragments is shown. (B) In vitro splicing of the Glo-βTm pre-mRNA. Splicing experiments were performed as in Fig. 2B, with mock-depleted extracts (lane 1) and PTB-immunodepleted nuclear extracts (lanes 2 to 5) in the absence (lane 2) or in the presence of 0.05, 0.1, and 0.2 μg of recombinant PTB1 (lanes 3 to 5, respectively) for 90 min.