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. Author manuscript; available in PMC: 2009 Jun 20.
Published in final edited form as: Mol Cell. 2008 Jun 20;30(6):743–754. doi: 10.1016/j.molcel.2008.05.003

Fig. 7.

Fig. 7

A model for Prp22-catalyzed mRNA release. Prp22 interacts with intron RNA adjacent to the 3′ splice site in spliceosomes that are poised for the 2nd transesterification reaction. The U5 snRNP contributes RNA and protein contacts to configure the active site for step 2 catalysis. Concurrent with exon ligation, Prp22 is deposited on the mRNA downstream of the exon-exon junction. Bound to its target RNA, Prp22 helicase hydrolyzes ATP and moves in the 3′→5′ direction to disrupt contacts with the U5 snRNP, thereby liberating spliced mRNA from the residual spliceosome that still contains excised lariat-intron RNA.