Figure 7.

Model for CGS1 exon 1-mediated post-transcriptional regulation. When the cellular concentration of AdoMet is high, translation of CGS1 mRNA is temporarily arrested when the A site of the ribosome resides at the Ser-94 codon of CGS1. The MTO1 region in the nascent polypeptide acts within the ribosomal exit tunnel to cause translation elongation arrest. Following the translation arrest, mRNA degradation occurs upstream of the stalled ribosome, resulting in production of the 5′-truncated RNA species. The ribonuclease (Pacman) responsible for the mRNA degradation remains to be identified.