FIGURE 7.

The Prp24-S283Y substitution rescues the lethal U4–G14U/U6-A62G mutation at higher temperatures. (A) Crystal structure (PDB: 4n0t) of the interface between Prp24 RRM3 (in cyan) and the “top” of the U6 RNA telestem, visualized with PyMOL (http://www.pymol.org/). The hydrogen bond between the hydroxyl group of serine 283 and N3 of A91 is shown as a dotted line, as are hydrogen bonds in the A40–A91 base pair. (B) Serial dilutions of isolates of yeast strain JEB100 that contain the indicated alleles of the U4, U6, and PRP24 genes were grown on YEPD medium at the indicated temperatures. Mutant residues are boxed. (S) serine; (Y) tyrosine.