FIG. 3.

Binding specificity of trans-acting factors for α and β 3′ UTRs. EMSA analyses were performed using in vitro-transcribed ³²P-labeled α-globin 3′ UTRs (A) and β-globin 3′ UTRs (B) incubated in MEL cell S-100 extract. Reactions were supplemented with defined quantities of unlabeled α- or β-mRNA 3′ UTR competitor. The composition of each reaction mixture is indicated above the autoradiograph, and the positions of the α and β complexes are shown on the left.