Sa. Strobel et al., COMPLEMENTARY SETS OF NONCANONICAL BASE-PAIRS MEDIATE RNA HELIX PACKING IN THE GROUP INTRON ACTIVE-SITE, Nature structural biology, 5(1), 1998, pp. 60-66
Helix packing is critical for RNA tertiary structure formation, althou
gh the rules for helix-helix association within structured RNAs are la
rgely unknown. Docking of the substrate helix into the active site of
the Tetrahymena group I ribozyme provides a model system to study this
question, Using a novel chemogenetic method to analyze RNA structure
in atomic detail, we report that complementary sets of noncanonical ba
se pairs (a G.U wobble pair and two consecutively stacked sheared A.A
pairs) create an RNA helix packing motif that is essential for 5'-spli
ce site selection in the group I intron. This is likely to be a genera
l motif for helix-helix interaction within the tertiary structures of
many large RNAs.