Dxo1 is a new type of eukaryotic enzyme with both decapping and 5′-3′ exoribonuclease activity

Rail1 is a component of the mRNA 5′-end quality-control mechanism in yeast. Structural, biochemical and functional studies of its homolog in Kluyveromyces lactis now reveal that the enzyme, dubbed Dxo1, has not only decapping but also 5′-3′ exonuclease activity, enabling it to single-handedly decap and degrade mRNAs from the 5′ end.