Figure 5.

Depurination of rRNA by monomeric and complexed pokeweed antiviral protein (PAP). Isolated ribosomes of pokeweed and lysate of rabbit reticulocytes were incubated with monomeric or complexed PAP (5 nm) or buffer alone (–PAP). rRNA was isolated and primer extension analysis was performed using two end‐labelled primers, one annealing downstream of the expected depurination site (Dep’n) and the other annealing downstream of the 5′ end of 28S rRNA. cDNA products were separated on a 7 m urea/6% acrylamide gel, and extension patterns were visualized with a phosphorimager. –rRNA indicates extension reactions without rRNA template. The percentage depurination was estimated by the densitometry of band intensities of the Dep’n cDNA product relative to the 28S ribosomal cDNA product. Values represent means ± standard error for three independent experiments.