Suppression of translation frameshift by upstream termination codon.

Retroviruses employ translation frameshift for gene expression. Translation frameshift takes place at the slippery heptanucleotide sequence on mRNA. A downstream stem-loop structure (and a pseudoknot formed by the stem-loop) enhances the level of ribosomal frameshifting. Here, we describe that an upstream termination codon suppresses the ribosomal frameshifting, leading to reduction in the expression of downstream genes.