NCIt definition : Nonsense-Mediated Decay is the widely conserved process in eukaryotes whereby certain
alternatively spliced RNAs, some selenoprotein mRNAs, and nonsense or frame-shift
mutations that result in premature translation termination signal rapid mRNA degradation;
the mechanism that eliminates mRNAs with premature termination codons, reducing the
accumulation of deleterious proteins and their effects. NMD is initiated during translation
when hUpf proteins phosphorylated by SMG proteins cooperate with an exon-junction
complex to identify mRNAs with premature stop codons and mark the transcript for rapid
decay. Degrading mRNAs from both ends, NMD involves decapping, deadenylating, and
exonucleolytic activities.;