Structure of an aberrant spliceosome intermediate on its way to disassembly

Intron removal during pre-mRNA splicing is of extraordinary complexity and its disruption causes a vast number of genetic diseases in humans. While key steps of the canonical spliceosome cycle have been revealed by combined structure-function analyses, structural information on an aberrant spliceosome committed to discard is not available. Here, we report the cryo-EM structure of a B state spliceosome intermediate primed for disassembly. We identify the DEAH-box helicase – G patch protein pair (Gih35-Gpl1) to maintain catalytic dormancy with Gpl1 recognizing a remodeled active site of the spliceosome due to a single-nucleotide insertion at the 3' end of the 5' exon. Remodeling is communicated to the spliceosome surface and the Ntr1 complex is recruited. Our data pave the way for a targeted analysis of spliceosome-associated quality control. Overall design: Detailed analysis of Ctr1-deficient and WT strains using high throughput poly(A)+ RNA sequencing. RNAseq of RNA-IP experiemnts of Nrl1-NTP_Prp43-6xFlag S. pombe strains (2 biological repliactes), RNA-IP of no-tag control strain (negative control) and total RNA sequencing