Fig 8.

Model for the nuclear retention of unspliced RNAs through the interaction between pre-EJC and the spliceosome. Pre-EJC (Y14, MAG-1, eIF4AIII, and UAP56) is recruited onto introns that are committed to be spliced with the help of the IBP160 and PRP19 complex. Pre-EJC interacts with the spliceosome through U2 snRNP, and this interaction is recognized by one or more factors that anchor the complex in the nucleus. After removing all introns to be spliced, the spliceosomes release, and at the same time, the pre-EJCs translocate onto exon junctions as EJCs. Here, nuclear retention through pre-EJC is cancelled, and the fully spliced mRNA is exported by the nuclear export receptor TAP/NXF-1.