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, 46 (1), 9-16

When a Ribosome Encounters a Premature Termination Codon


When a Ribosome Encounters a Premature Termination Codon

Jungwook Hwang et al. BMB Rep.


In mammalian cells, aberrant transcripts harboring a premature termination codon (PTC) can be generated by abnormal or inefficient biogenesis of mRNAs or by somatic mutation. Truncated polypeptides synthesized from these aberrant transcripts could be toxic to normal cellular functions. However, mammalian cells have evolved sophisticated mechanisms for monitoring the quality of mRNAs. The faulty transcripts harboring PTC are subject to nonsense-mediated mRNA decay (NMD), nonsense-mediated translational repression (NMTR), nonsense-associated alternative splicing (NAS), or nonsense-mediated transcriptional gene silencing (NMTGS). In this review, we briefly outline the molecular characteristics of each pathway and suggest mRNA quality control mechanisms as a means to regulate normal gene expression.


Fig. 1.
Fig. 1.. Simplified view of mammalian gene expression. Gene expression cascades of normal mRNAs (left) and PTC-containing mRNAs targeted for NMD (right) are depicted. The details are described in the text.
Fig. 2.
Fig. 2.. Different fates of PTC-containing mRNAs.

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