The CCC Proline Codon Preceding a Stop Codon Modulates Translation Termination in Eukaryotes Depending on the Molecular Context

In bacteria, glycine and proline codons, located upstream of stop codons, suppress translation termination. However, the effects of those codons in eukaryotes have not been systematically investigated. In this study, we demonstrate that preceding stop codon CCC codon of proline suppresses translation termination in eukaryotes during the synthesis of long protein. Conversely, during the synthesis of short peptide, a upstream proline codon stimulates the formation of termination complexes. Furthermore, we investigated the role of poly(A)-binding protein (PABP), a key regulator of eukaryotic translation termination associated with the poly(A) tail of mRNA, in modulation of translation termination by the 5' context of stop codons. Our findings reveal that during the synthesis of short peptides PABP reduces dependence of translation termination on the 5' stop codon contexts and promotes translation termination independently of the 5' stop codon context during the synthesis of long proteins.