NMD: a multifaceted response to premature translational termination.

Although most mRNA molecules derived from protein-coding genes are destined to be translated into functional polypeptides, some are eliminated by cellular quality control pathways that collectively perform the task of mRNA surveillance. In the nonsense-mediated decay (NMD) pathway premature translation termination promotes the recruitment of a set of factors that destabilize a targeted mRNA. The same factors also seem to have key roles in repressing the translation of the mRNA, dissociating its terminating ribosome and messenger ribonucleoproteins (mRNPs), promoting the degradation of its truncated polypeptide product and possibly even feeding back to the site of transcription to interfere with splicing of the primary transcript.