The incorporation of the 21st amino acid, selenocysteine (Sec), occurs on mRNAs that
harbor in-frame stop codons because the Sec-tRNA Sec recognizes a UGA codon. This sets
up an intriguing interplay between translation elongation, translation termination and the
complex machinery that marks mRNAs that contain premature termination codons for
degradation, leading to nonsense mediated mRNA decay (NMD). In this review we discuss
the intricate and complex relationship between this key quality control mechanism and the …