Fig. 4
From: Genome annotation for clinical genomic diagnostics: strengths and weaknesses
The nonsense-mediated decay (NMD) pathway. Under normal cellular circumstances, exon–exon junction complexes (EJCs) that are in place after splicing are removed by the ribosome during the first round of translation. However, when a transcript contains a premature termination codon (PTC), perhaps as a result of an single-nucleotide variant (SNV), indel or inclusion of an out-of-frame exon upstream of one or more EJCs, these EJCs remain in place because the ribosome complex disassociates at the premature stop codon and thus cannot remove the downstream EJC. This triggers the NMD pathway, and the transcript is degraded