Figure 2.

Prp43 Has Distinct Binding Sites on Preribosomal RNA

Shown is predicted secondary structure of regions of yeast 18S (A) and 25S rRNA (B–E), modified from Piekna-Przybylska et al. (2007). The binding sites of Prp43 are marked in gray. A boxed “M” represents a site of 2′-O-methylation in the rRNA, and large numbers indicate the corresponding snoRNA. Small numbers represent the position of the indicated residue in 18S or 25S. In (C), part of the 25S structure is excised at “a” and shown below the main model, as it projects into the background. The major binding site for Prp43 in 18S is located in helix 44 (A), close to the dimethylation sites of Dim1 (${\mathrm{m}}_2^6$A${\mathrm{m}}_2^6$A) and cleavage site D (the 3′ end of the 18S rRNA). In 25S, Prp43 binds between helices 39 and 40 (B), between helices 23 and 24 (C), over helix 34 (D), and along helix 83 (E).