In budding yeast, most cytoplasmic mRNA turnover is initiated by deadenylation 1. These messages are then either decapped and subject to 5′ → 3′ decay 2,3 or degraded by the cytoplasmic exosome 4.

In eukaryotes, the decapping machinery is highly conserved and plays an essential role in controlling mRNA stability, a key step in the regulation of gene expression. Yet, the role of mRNA decapping ...