FIG. 5.

Anti-αCP antibodies bind the mRNP β complex. ³²P-labeled β 3′ UTR was incubated in MEL cell S-100 extract in the absence (lanes 1 and 2) or presence (lanes 3 to 5) of anti-αCP antibodies, and the reactions were resolved on a nondenaturing polyacrylamide gel. FF1 and FF3 denote rabbit antisera raised against αCP-1 and αCP-2 isoforms, respectively. The reaction shown in lane 2 was supplemented with homodeoxyribopoly(C) to verify the position of the β complex. The composition of each reaction is indicated at the top of the gel, and the positions of the native and supershifted β complexes are given on the left.