FIG. 7.

Primer extension analysis of the 3′SS used in pNS20/74 and by endogenous α- and β-tubulin. (A) Twenty micrograms of cellular RNA and primers specific for pNS20/74. The entire reaction product was loaded, and the gel was exposed to a phosphorimager screen for 60 h. (B) Ten micrograms of RNA and primers specific for α-tubulin and β-tubulin. Half the reaction product was loaded, and the gel was exposed to a phosphorimager screen for 15 h. One major product was seen in each analysis. (C) Schematic depiction of possible primer extension products. The expected lengths include the 39 nt of the miniexon which are added during the trans-splicing reaction.