Figure 2.

Binding of the 3′-UTR is competed by cold 3′-UTR RNA. In this experiment 20 ng GST–αCP₂ was incubated with 15 000 c.p.m. (15 pmol) of radiolabeled RNA. Cold RNA, at the indicated fold excess, was added just prior to incubation with the radiolabeled probe and the reaction mixture kept on ice for 30 min prior to electrophoresis on a 6% native gel. The addition of cold 3′-UTR in excess competed with binding of the radiolabeled probe (lanes 2–6). Addition of 100-fold excess of an unrelated sequence (lane 7) had no effect on binding, indicating a specific interaction of GST–αCP₂ with the 3′-UTR.