A novel programed frameshift expresses the POL3 gene of retrotransposon Ty3 of yeast: Frameshifting without tRNA slippage

摘要

Most retroviruses and retrotransposons express their gene as a translational fusion to the upstream gene, often involving translational frameshifting. We describe here an unusual translational frameshift event occurring between the and genes of the retrotransposon Ty3 of yeast. A +1 frameshift occurs within the sequence GCG AGU U (shown as codons of ), encoding alanine-valine (GCG A GUU). Unlike other programed translational frameshifts described, this event does not require tRNA slippage between cognate or near-cognate codons in the mRNA. Two features distal to the GCG codon stimulate frameshifting. The low availability of the tRNA specific for the “hungry” serine codon, AGU, induces a translational pause required for frameshifting. A sequence of 12 nt distal to the AGU codon (termed the Ty3. “context”) also stimulates the event.