Nucleoporin Nup153 docks the splicing machinery to the nuclear pore for efficient mRNA processing

Abstract

The nuclear pore complex (NPC), composed of proteins termed nucleoporins (Nups), intercalates the nuclear envelope, and is primarily involved in protein trafficking and mRNA export. At the nuclear basket, Nups have been associated with chromatin organization and postulated to function as transcriptional hubs, working in tandem with mRNA export machinery. However, little is known about the intermediate process of RNA splicing at the NPC. Here, we used BioID to screen for interactors of basket-Nups Nup153 and TPR and discovered the enrichment of splicing proteins across all spliceosome complexes (E, A, B, B*, P). The peripheral nature of the interaction between Nup153 and selected splicing components was confirmed by in-situ proximity ligation assay and STED microscopy. The presence of splicing components at the NPC, reduced upon splicing inhibition, is partly dependent on Nup153 and functionally correlated to the splicing of Nup153-bound genes. Assessed by DamID, Nup153-bound genes ([~]500) are characterized by multiple long introns with lower-than-average GC content. Positioned at the periphery but distinct from the neighbouring lamina-associated domain (LADs) in chromatin signatures and expression levels, these genes showed Nup153-dependent splicing defect, suggesting that splicing occurs at the NPC. Altogether, our data substantiates the gene gating theory bringing transcription and export, now accompanied by speckle-distant splicing events, at the level of the NPC.