New mechanistic insights into Prp22-mediated exon ligation and mRNA release

Dr. Cheng, Soo-Chen - September, 2025

The DExD/H-box RNA helicase Prp22 catalyzes mRNA release from the spliceosome, and has also been implicated in proofreading the 3’ splice site, preventing exon ligation of mutant pre-mRNAs. We unveil an unexpected role for Prp22 in promoting exon ligation of both wild-type and mutant pre-mRNAs by stabilizing Slu7’s association with the. Notably, ATP binding, rather than hydrolysis, by Prp22 inhibits exon ligation. Following exon ligation, Prp22-mediated ATP hydrolysis facilitates the dissociation of both Slu7 and mRNA. Remarkably, Prp22 and Cwc22, which bind the 3’- and 5’-exons respectively, remain associated with the released mRNA. We propose that Prp22 facilitates exon ligation by stabilizing Slu7 binding, with binding of ATP by Prp22 potentially destabilizing that interaction, thereby weakening contacts between the 5’-exon and the 3’ splice site to inhibit exon ligation. After exon ligation, Prp22-driven ATP hydrolysis induces a conformational change in Prp8 that disrupts its interdomain interactions, enabling mRNA release through the domain interfaces. These findings change the current view of splicing fidelity control and offer new mechanistic insights into Prp22-mediated mRNA release. The paper is recognized as Breakthrough Article by NAR.