Figure 2.

rCBC restores poly(A) site cleavage efficiency to a CBC-depleted HeLa cell nuclear extract. Uncapped (pppG, lanes 1 and 8) or capped (m⁷GpppG, lanes 2–7 and 9–14) pre-mRNAs containing the L3 poly(A) site were incubated in mock-depleted (lanes 1–7) or CBC-depleted (lanes 8–14) HeLa cell nuclear extract in the presence of 3′ dATP. The extracts were supplemented with the indicated amount of recombinant CBC (lanes 5–7 and 12–14). The reaction products were resolved on a denaturing 10% polyacrylamide gel.