Figure 3

Simplified view of the eukaryotic NMD process. After splicing, the nuclear EJC proteins deposit onto an mRNA. Once this mRNA reaches the cytoplasm, after the nuclear export, some nuclear EJC components dissociate and the cytoplasmic NMD proteins bind to the mRNA. During the first round of translation, NMD is triggered by the recognition of PTC upstream of the exon-exon junction and the EJC-associated NMD proteins. This PTC-containing mRNA can be degraded either from the 5′-end by the Xrn1-mediated 5′→3′ exonucleolytic decay, or from the 3′-end by deadenylation and exosome-mediated 3′→5′ exonucleolytic decay.