Figure 1.
Secondary structural folds for (A) the major spliceosome U2–U6 snRNA complex in its three-helix conformation (note: Ψ modifications replaced by U in the transcribed samples used in these experiments), and folds proposed for (B) the human U12–U6atac snRNA complex; (C) the Arabidopsis minor spliceosome U12–U6atac snRNA complex that maintains five base pairs between the catalytic triad and ISL bulge; and (D) alternate fold for the Arabidopsis snRNA complex (proposed here) that maintains the AY·C (where Y is a pyrimidine) motif seen in human U6 snRNA and proposed for the human U6atac ISL. Lines denoting Watson–Crick base pairs and dots denoting G·U pairs are those proposed in the publications.