Base-pairing interactions between substrate RNA and H/ACA guide RNA modulate the kinetics of pseudouridylation, but not the affinity of substrate binding by H/ACA small nucleolar ribonucleoproteins

Competitive in vitro pseudouridylation of 3′ substrate wild-type. An excess (250 nM) of nonradioactive 3′ substrate G7 insert was incubated with 50 nM reconstituted snR34 H/ACA snoRNP for 3 min before 250 nM [³H-C5] uridine-labeled 3′ substrate wild-type was introduced to the reaction (black circles). As a control, 250 nM [³H-C5] uridine-labeled 3′ substrate wild-type was incubated with 50 nM reconstituted snR34 H/ACA snoRNP in the absence of 3′substrate G7 insert (gray squares). Mean and standard deviation of duplicate reactions are shown.