Figure 1.

Inhibition of poly(A) site cleavage by CBC depletion. (A) An m⁷GpppG-capped pre-mRNA containing the L3 poly(A) site was incubated with increasing amounts of either a mock-depleted (lanes 1–4) or a CBC-depleted (lanes 5–8) HeLa cell nuclear extract in the presence of 3′ dATP. Products of the cleavage reaction were resolved on a denaturing 10% polyacrylamide gel. (B) An m⁷GpppG-capped precleaved RNA (extending only to the poly(A) cleavage site) containing the HIV-1 poly(A) site was incubated with increasing amounts of either mock-depleted (lanes 1–4) or CBC-depleted (lanes 5–8) HeLa cell nuclear extract in the presence of ATP. The reaction products were resolved on a denaturing 5% polyacrylamide gel.