Courtesy of Jens Lykke-Andersen
A post-splicing complex deposited upstream of each exon-exon junction tags mRNAs for nuclear export and mRNA surveillance. The pre-mRNA is coated with hnRNP proteins. The Spliceosome deposits an exon-exon junction complex that promotes nuclear export by interaction with TAP and mRNA surveillance by interaction with hUpf proteins.
Throughout the journey from gene to protein, RNAs are encrusted with proteins that splice and dice sequences and inevitably regulate the processing and features of the final product. These nuclear sequence shufflings are implicated increasingly in mechanisms such as RNA-export to the cytoplasm, and nonsense-mediated decay (NMD), which detects and degrades RNAs with premature termination codons (PTCs). The role of splicing in export, however, remained largely unclear. Perhaps even more puzzling, NMD machinery in the cytoplasm needs to distinguish PTCs from legitimate stop codons. This suggested to some that mRNA can remember where its introns were after it leaves ...
